Primitive Archer

Main Discussion Area => Bows => Topic started by: DC on November 01, 2018, 09:55:29 am

Title: Bow design and development
Post by: DC on November 01, 2018, 09:55:29 am
I was waiting for my turn at the range the other night and was looking at the bows. Not counting the compounds every bow there(except mine) was a FG recurve.( I can be a little slow sometimes ;D ;D) Ignoring the FG part all the designs were deflexed recurves. Not one FG longbow and I know they made them when I was a kid. This got me thinking that somewhere in the past bow making companies must have done a lot of testing of various designs and all decided to make basically the same design. There must be a lot of data squirrelled away on the effect of various tests. Does anyone have access to any of this stuff? I realise that FG data won't be directly transferable to wood but a good design is a good design.
Title: Re: Bow design and development
Post by: Badger on November 01, 2018, 10:18:48 am
  That is an interesting question you are asking. Surprisingly little good data has been generated from bow making companies. They found designs that seem to get them up in the 90% of what is possible range and settled in. For the most part little details about things that can have small effects on performance have been ignored or have failed to be isolated. Some computer modeling programs available now seem to be making design a little easier as building hundreds of bows to test small things is not practical.
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 10:36:31 am
I guess they aren't huge companies like GM that can afford to have a "Skunk Works" department constantly fiddling with stuff.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 12:33:59 pm
I have a feeling that a design that will please the masses,,is what you see,,
it is hard to apply alot of what you see to a wood bow,, just a differet beast,,Marc makes some deflex recurves and you can see that works,, but alot of great designs have been used for centuries as well,, that are not deflexed,,etc etc,,
the deflex may be the best design for fiberglass in general,, not sure about that,, maybe the most" popular "  right now,, alot of Native style bows were reflexed in the handle,, so something about that worked for them,,and thats how they made a living,, (-P
Title: Re: Bow design and development
Post by: JNystrom on November 01, 2018, 12:56:19 pm
I see the point of view is "what is the most accurate and fast arrow launching tool on open ground while standing in FITA position". Maybe a reflex-deflex is the best design for that. Or like said earlier it just pleases the masses. If you look at maybe the golden era of target archery, men shot a 6 feet longbow.

On my opinion the best bow design is the one that suits the purpose best. I wouldn't go hunting or shooting from horse back with a 6 foot longbow.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 01:24:03 pm
good point, what is best for the purpose at hand,, could vary quite a bit,,
Title: Re: Bow design and development
Post by: Stick Bender on November 01, 2018, 01:58:49 pm
I think the claim to fame for the D/R bow is it can be pulled to full longer draws in a shorter package as compared to long bows , there is a ton of info on the long bows as you described by bowyers that are still making them particularly the guys making HH type or ASL type bows the D/R design in the FG world is generally considered a Hybrid type bow not a true static recurve & with modern material there just as fast or faster then static recurves ,I think Fred Bear spent most of his life trying to perfect the deflexed design the D/R design can be incredibly fast and accurate design ,I'm not sure how the FG data would be applicable to natural material designs the taper rates will be genraly more shallow and the material used capable of much higher stresses & mass properties , I think the reason you see similar designs is because of trial and error they just work it's hard to improve on history , another plus for the D/R design is the stack free FDC in a short package ! Just my 2 cents but I love the design because it's performance & feel !
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 02:22:16 pm
One thing that strikes me as odd is that FG will bend further and take more strain(correct me if I'm wrong) and yet any FG bow I saw(I searched a bit), even "long bows" have a deflexed handle which reduces strain. Makes me think that there is another advantage to deflexed handles.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 02:33:55 pm
like stick bender said,, stack free full draw curve,,
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 02:43:00 pm
Missed that, sorry. trying to read too fast. I would have thought that the stack-free part would come from the reflex rather than the deflex. I can see low stack being more than a comfort thing too. If you have a maximum draw of 40# and you can remove the stack portion it leaves room for the whole F/D curve to hump up, sorta. Do you have a theory why the deflex would contribute to low stack?
Title: Re: Bow design and development
Post by: Stick Bender on November 01, 2018, 02:43:28 pm
Well there are probably many reasons that could be covered over a dozen threads on the topic by far smarter people then me ,but from a lay mans practical point one of my hunting bows Is a 60 in deflexed angular design it will not stack tell past 32 in. If I where pulling the same length strait long bow to my 31 in. Draw it would stack like crazy ,so DFC is much better with deflexing in the center & & reflexing the mid limb & tips allows a better string angle as opposed to a non deflexed design enhancing performance & that applies to any material used I would think ,great topic Don. Here is a FDC done by a friend of mine on that bow !
Title: Re: Bow design and development
Post by: PatM on November 01, 2018, 03:21:30 pm
Deflex also more reliably eliminates shock and vibration.

 There's still plenty of glass bows of other design out there.  Your local scene just doesn't use them.
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 03:33:18 pm
SB-deflexed angular? What is the angular? And DFC? Sorry.
PatM-I didn't look real hard, just did a bit of surfing some the major manufacturers. It's hard enough getting around the compounds let alone finding info on traditional bows.
Title: Re: Bow design and development
Post by: Stick Bender on November 01, 2018, 03:46:45 pm
If you deflex the center enough the strung profile becomes angular but with any design there are trade offs ,I just built a 64 in. of the same design it had great  performance but there is a point where the deflex is so great  that your brace height becomes so high that performance balances out ,I think the design performs best in shorter bows even with heavy arrows, I have been religiously playing with the design for a year and it's always about making another to find out what's best...lol a lot of little hidden quirks in the design but great bows ! It's like any thing with this bow making you just have to build and find out what works best at your draw & weight & materials !
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 03:47:42 pm
full draw curve   fdc

I am working on a sinew recurve now,, but the handle is gonna be straigt or reflexed,, I just dont think I can get the tips to come forward enough with deflex in the handle,, but maybe I should try it on the next one,, )P( )P(
Title: Re: Bow design and development
Post by: Halfbow on November 01, 2018, 03:58:22 pm
I'm with DC here. Reflex should decrease stack, deflex should increase it.

In general. the higher the early draw weight, the less stack a bow should have. Said another way, the closer the weight at partial draw is to the full draw weight, the less stack. This is almost by definition, as a bow that stacks can be described as a bow with a partial draw weight that's considerably less than its full draw weight.

To illustrate:

(https://horsebackarchery.files.wordpress.com/2012/11/force-curve1.jpg?w=584&h=437)

(Pic from https://horsebackarchery.wordpress.com/2012/11/04/bow-mechanics-energy-storage/ (https://horsebackarchery.wordpress.com/2012/11/04/bow-mechanics-energy-storage/) I hope they don't mind)

The farther the tips are in front of the handle, the higher the early draw weight, because the bow is already more stressed at brace. This means that the farther the tips are in front of the handle, the less stack. So reflex, whether in the handle, through the limbs, or in recurves at the ends, should reduce stack. (Of course this is not the only factor, but it's a big one. String angle matters too.) Conversely, deflex makes a bow less stressed at brace, and thus should decrease early draw weight, and thus will increase stack. Reflex/deflex bows balance two factors to get pleasantly straight draw curves.

Deflex is useful for materials like wood because it reduces strain. It allows for recurved limbs and the beneficial string angle that comes with them without stressing the wood too much. But if your materials can take more stress, it seems to me that more reflex would result in more energy storage, smoother draw, and more speed.

If you look at the draw curves of highly reflexed bows, they're excellent. Better than the curve you posted Stick Bender.

These bows which are not deflexed in the handle:

(http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows_files/image002.jpg)

have a draw curve like:

(http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows_files/image008.jpg)

(Bows and data from http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm))

However the deflex part of deflex/reflex bows has a lot of other benefits. Less vibration (though highly reflexed vibration free bows are possible, just finicky to get right). They're less effected by sloppy releases. And highly reflexed bows are difficult to string and require more care to make sure they stay well aligned. I think that's the real answer to why companies don't usually make highly reflexed modern material bows.
Title: Re: Bow design and development
Post by: Stick Bender on November 01, 2018, 03:59:08 pm
Do it Brad you might be surprised I'm going to be sending you a highly natural reflexed  osage stave shortly when I can get to the post office in a couple weeks I cut 2 years ago that would be perfect for the designed or one of your native bows !
Title: Re: Bow design and development
Post by: leonwood on November 01, 2018, 04:05:26 pm
My last five selfbows have been deflexed reflex/recurve bows. The first one I made just shot so extremely smooth and really fast that I had to try a few more. Now I am not a calculations kind of guy. I just grab a stave and start building totally by feel with a general design in my head. But the deflex reflex bows are my best shooters for sure. Almost no handshock, no set and really fast. So I am guessing those fg bow designers sure knew what they where doing when they started designing rd bows!
Title: Re: Bow design and development
Post by: Halfbow on November 01, 2018, 04:22:10 pm
Leonwood, there is absolutely no doubt that reflex/deflex bows are excellent, both in performance and in shooting characteristics. They are likely legitimately the best design for many people. But when you say they're really fast, I'm curious what you're comparing them to. It's a claim I hear a lot, but I expect many people's impressions come after comparing them to longbows, and not highly reflexed bows. Have you tried a highly reflexed bow? (Not an attack, just curious. I haven't tried any extreme examples myself.)

If you read that article I linked about the Turkish bows (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm)) I think you'll be impressed by the performance. All three of those bows pictured are made of natural materials and are toying with 200fps at 10 grains per pound.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 04:23:29 pm
well its got me thinking for sure,, sure wont hurt to try one,, (--)
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 04:26:47 pm
halfbow you are right,, 170fps seems fast till ,, well 200 fps,,,and like we talk about all the time,, its not all about speed,,
but it is very interesting to see what certain designs will do,, my hunting bow is slow by most standards,, but I shoot it very well,, but if I had a faster bow I shot as well,, I would shoot that,, etc etc etc,,
Title: Re: Bow design and development
Post by: Halfbow on November 01, 2018, 04:34:12 pm
Absolutely, I'm not trying to put speed on a pedestal. It's smart to be more concerned about other things, and that's why I say reflex/deflex is such a great design. :) My point here was really just to say, deflex doesn't reduce stack.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 01, 2018, 04:59:57 pm
wow, I really didnt understand that,,  :)
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 05:33:34 pm
I'm with DC here. In general. the higher the early draw weight, the less stack a bow should have. Said another way, the closer the weight at partial draw is to the full draw weight, the less stack. This is almost by definition, as a bow that stacks can be described as a bow with a partial draw weight that's considerably less than its full draw weight.
I'm not sure if this is semantics or not but I kinda thought it was the other way around. It sounds to me that you're saying that a bow with high early draw weight won't stack. Correct me if I'm wrong :). I think that if you have a bow that doesn't stack it will have a fatter F/D. If the bow doesn't stack it allows you to make the bow heavier. It may sound like we're saying the same thing but my cause is your effect and vice versa.
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 05:43:16 pm
I'm a little different. I put speed on a pedestal ;D ;D. Cast has been the measure of a bow for thousands of years. (I think, I wasn't there for all of them) It isn't the complete measure of a bow, though. If a super fast bow is so shocky that it's unshootable it's not much use. Or if it sprays arrows all over the shed. It is a major part of most of the good things and it's the easiest to measure though.
Title: Re: Bow design and development
Post by: Halfbow on November 01, 2018, 05:49:08 pm
Hm I think it is semantics. I am indeed saying a bow with high early draw weight won't stack (with some qualifications, but that's the gist of it). A fat f/d curve shows that the bow has a high early draw weight. So to saying a bow has high early draw weight is the same statement as saying a bow has a fat f/d curve.

These are all just descriptions. Fat f/d curve, high early draw weight, non-stacking. All equivalent descriptions, and you can say them in any order you like. A bow that stacks less will have a fatter f/d curve. A bow with a fatter f/d curve will stack less. It works fine either way.

Let me know if I misunderstood you. :)
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 06:40:59 pm
I think we're on the same page. :D
Title: Re: Bow design and development
Post by: Badger on November 01, 2018, 09:29:32 pm
 This was an experiential bow I built several years ago. In the pic the bow was knocked down to about 28# so the lady could shoot it in the 50# class. She did get a record with it. But on this bow I tried out some theories. It had about 12" reflex to start, and 12" static hooks as well as a very short working limb area. the theory was that the short working limbs would keep it stable at brace and prevent it from vibrating and loosing power at the end of the power stroke. It worked extremely well but the wood broke down badly within a dozen shots and the performance fell off to nothing extraordinary. One the first shot it was well over the 200 fps mark, I think about 208 if I remember correctly each shot continued to drop off as did the bow weight. It leveled off after about a dozen shots to 38# starting at 50#. I made 2 of these, this was the slightly lighter of the two.
Title: Re: Bow design and development
Post by: DC on November 01, 2018, 09:46:35 pm
Do you think that if you had let the hooks work a bit it would have been unstable?
Title: Re: Bow design and development
Post by: Badger on November 01, 2018, 10:45:21 pm
  i think it would have been unstable and defeated the whole purpose of a rigid limb test. I call these hinge bows. I n the pic it is not as clear because I tillered it down for a lday to shoot so it has a bit more working limb than when originally made.
Title: Re: Bow design and development
Post by: Stick Bender on November 02, 2018, 04:19:54 am
Nice looking bow Steve , I can only speak to bows I have made myself but there is always pro's & con's to every design but the D/R  bow has a lot to offer in a mild shooting fast hunting bow , but Don what is it you where after info wise in comparing natural to glass ? I think Brad said it best there 2 different beast ?
Title: Re: Bow design and development
Post by: PatM on November 02, 2018, 05:08:01 am
Leonwood, there is absolutely no doubt that reflex/deflex bows are excellent, both in performance and in shooting characteristics. They are likely legitimately the best design for many people. But when you say they're really fast, I'm curious what you're comparing them to. It's a claim I hear a lot, but I expect many people's impressions come after comparing them to longbows, and not highly reflexed bows. Have you tried a highly reflexed bow? (Not an attack, just curious. I haven't tried any extreme examples myself.)

If you read that article I linked about the Turkish bows (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm)) I think you'll be impressed by the performance. All three of those bows pictured are made of natural materials and are toying with 200fps at 10 grains per pound.

 Are they that close to 200 at 10 grains per pound?
Title: Re: Bow design and development
Post by: Del the cat on November 02, 2018, 05:44:20 am
I think there is some confusion/mixing up of design and materials in this thread.
Horn sinew composites are the shape they are because it suits the materials.
Modern D/R shaped bows (F/G Carbon etc) (spits on floor) are basically down to Clarence N Hickman's work in the 50's
D/R designs in wood/boo are toned down versions of the above tailored to suit the materials, and yes they'll give better F/D curves but only when the design and draw weight matches the material.
Del
Title: Re: Bow design and development
Post by: leonwood on November 02, 2018, 06:08:47 am
Leonwood, there is absolutely no doubt that reflex/deflex bows are excellent, both in performance and in shooting characteristics. They are likely legitimately the best design for many people. But when you say they're really fast, I'm curious what you're comparing them to. It's a claim I hear a lot, but I expect many people's impressions come after comparing them to longbows, and not highly reflexed bows. Have you tried a highly reflexed bow? (Not an attack, just curious. I haven't tried any extreme examples myself.)

If you read that article I linked about the Turkish bows (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm)) I think you'll be impressed by the performance. All three of those bows pictured are made of natural materials and are toying with 200fps at 10 grains per pound.

First of all, I am in no way suggesting that highly reflexed bows are not good at all! I sure have made several highly reflexed bows and they where definitely the fastest bows I ever made. However I found that they break down in speed over a year or so and lack the extreme smoothness of highly deflexed bows. This is especially true for longbows. (My recurves usually shoot smoother due to string angle etc)
Now most of my rd bows shoot 175+ and some even in the 180ties. The highly reflexed recurves I made shoot 192 and one even 195 but they did drop down to 185 after a few 100 shots. My first few reflex/deflex bows still have the exact same poundage as the had when I made them and had thousands of shots over the last two years.

Now over here we al shoot either target or 3D courses so accuracy is favourable above extreem speed, the reflex/deflex gives me really good accuracy, no handshock, and if done correctly also more then enough speed. Another important aspect of the deflex is that because of the lower strain at brace, the bow still shoots the same after long hours of brace time, this really helps for 3D competitions which can take all day.
Title: Re: Bow design and development
Post by: Stick Bender on November 02, 2018, 07:08:53 am
Lol Del he mentioned the FG in the original post thats the reason I mentioned it , Im glad he didnt say carbon , you would need a spit tune  >:D
Title: Re: Bow design and development
Post by: DC on November 02, 2018, 11:11:37 am
but Don what is it you where after info wise in comparing natural to glass ? I think Brad said it best there 2 different beast ?
I wasn't really comparing the material, it's the design(RD) that most bows seem to be now. I was hoping that there might be so info available from the manufacturers development that might explain why it works so nice. Unfortunately I'm a "Why" person and while a lot of people will accept some pretty vague explanations as to why things work I can't do that. Things like "It's the string angle" leave me wanting more. I want to know why the string angle does what it does. I just grabbed string angle as an example, it may or may not have much to do with this. There must be a reason why they chose the deflex angle they did. Possibly they did it by trial and error and even they don't know the real reason.
   I have a theory that has to do with the lever length of a limb. The actual lever length of a straight bow gets shorter as the limb bends. Reflex and recurves minimise or reverse this so the actual lever length can get longer as the limb bends(or straightens) as you draw it. I've made models that show this and it's not a lot but the difference is there. Sorry, I'm rambling :)

PS Modified to separate my theory from the rest of my rambling :-[ :-[
Title: Re: Bow design and development
Post by: Halfbow on November 02, 2018, 11:20:36 am
Badger, wow that sounds like quite a bow you made there. Props on making one like that which failed gradually rather than explosively. What was it made of? As I'm sure you're aware, your design theories there have a lot in common with the Turkish bows I talked about. Tiny working areas and long rigid levers.

Are they that close to 200 at 10 grains per pound?

Yes, according to that article. They got quite scientific with it, you can read all about their methodology. With lighter arrows they got as fast as 357fps, and have several reasons to think in better conditions the bows could have shot faster. Computationally this means (given good arrows) they're creeping up on the historical Turkish flight record of 930 yards.

First of all, I am in no way suggesting that highly reflexed bows are not good at all! I sure have made several highly reflexed bows and they where definitely the fastest bows I ever made. However I found that they break down in speed over a year or so and lack the extreme smoothness of highly deflexed bows. This is especially true for longbows. (My recurves usually shoot smoother due to string angle etc)
Now most of my rd bows shoot 175+ and some even in the 180ties. The highly reflexed recurves I made shoot 192 and one even 195 but they did drop down to 185 after a few 100 shots. My first few reflex/deflex bows still have the exact same poundage as the had when I made them and had thousands of shots over the last two years.

Now over here we al shoot either target or 3D courses so accuracy is favourable above extreem speed, the reflex/deflex gives me really good accuracy, no handshock, and if done correctly also more then enough speed. Another important aspect of the deflex is that because of the lower strain at brace, the bow still shoots the same after long hours of brace time, this really helps for 3D competitions which can take all day.

Sounds like we are in complete agreement then. :)

I think there is some confusion/mixing up of design and materials in this thread.
Horn sinew composites are the shape they are because it suits the materials.

I would look at this a little bit differently. Of course design will differ for different materials. Just as materials can be quite different from each other, ideal designs for materials can be quite different from others. If you start with a certain material as an unchangeable given, and set out to arrange that material in to the best arrow shooting device you can, you will eventually arrive at your favorite design for that material. And if you start out with different materials, you will arrive at different favorite designs.

I don't think this is what people were up to when they developed the Asiatic composites. Material wasn't an unchangeable given. They weren't suffering from a lack of wood (or bamboo) and were forced to figure out how to make do with mostly sinew and horn. Their unchangeable givens were concepts. Concepts like, all other things being equal, light limbs shoot faster. Short limbs are lighter. Reflex reduces stack and increases speed. Etc. Then they went out and figured out which materials would allow them to take those concepts to whatever extreme they could make possible. And it resulted in the hardest shooting bows the world had ever seen. With these bows (and horses) they overran pretty much anyone who stood against them, from the ancient Romans to the medieval Europeans, and made the largest continuous land empire in history.

So with the original question being, "why so many modern reflex/deflex bows?", I'm adding to that, saying that I'd be curious to see more modern companies taking these proven concepts to whatever extreme they can with whatever modern materials they can.

I'm all about traditional bow making, and that comes from my interest in history. But I'm also curious... what could a modern materials bow reflexed like this do?
(http://mandarinmansion.com/images/kaman/crab-bow.jpg)

I'd love to see.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 02, 2018, 11:21:11 am
I think the bow bow badger posted is good example,, if that bow were fiberglass it would not break down and woould be shooting the same,with the wood bows,, the breaking down of the wood adds an extra challenge to the design,,,the fiberglass will hold up to many more design ideas,, so a great design on a fibergass bow,, might break down a wood bow quickly,, so makes it hard to apply the fiberglass ideas,,,, some things are universal,,but the fiberglass and wood are just too far apart in what can be done with each,,  (-_) I think as a starting point,, a great design for a wood bow,, will work nicely for a fiberglass bow,, but not the other way around,,
Halfbow,, nice post, I would like to see that too,,  :)

also do you think that the Turkish flight record is due to better archers or design,,???
Title: Re: Bow design and development
Post by: Bayou Ben on November 02, 2018, 03:14:32 pm
Some good points being made here.  I'll start by saying I have no desire to ever work with FG, but when the FG guys talk design on the other site I listen.  Some of those guys are very meticulous on recording FDC's, as well as other things like string tension at brace. 

One trend that I noticed in FG bows are forward handle r/d designs.  Many individuals are building them, and some of the performance numbers are pretty good, high  190's and 200's w/ 10gpp, all while being forgiving, stable, and accurate.   So if FG doesn't take set and break down like wood, why would a mild r/d forward handle FG bow perform better than most other FG designs?  I don't know the answer to that, but it makes me consider that string angle has a lot more to do with efficiency than we realize. 

It seems that a forward handle design would have more benefit for an all wood bow than it would for FG.  I'm currently working on a bow that is applying and testing this concept.  My thought is that the forward handle will allow more draw while giving better string angle and less stack farther out in the draw.  We'll see how it goes....

Ritchie (Stick Bender) refers to this bow as angular.  I'm not sure about the terminology.

 
Title: Re: Bow design and development
Post by: bradsmith2010 on November 02, 2018, 04:17:37 pm
its over my head now ,, but I listening,,  (=)
Title: Re: Bow design and development
Post by: Stick Bender on November 02, 2018, 04:40:54 pm
When I saw your design Ben I instantly recognized it & it's some thing I thought about doing with maple/osage/sinew,  I'm glad some body is trying it in wood ,I say angular meaning the braced profile of these bows similar to Egyptian  composite bows , I'm not really a technical bowyer but after building a few of these & testing them I came to intuitive ideas about them ,I think maintaining the string angle threw out the draw is a huge plus ,but also the high limb return speed is huge ,I discovered that by accident when I made a 64 in version expecting it to shoot heavy arrows fast when the opposite happened it shot lighter arrows better, I look at this design as the lower limbs doing the majority of the work with the mids assisting and helping to maintain the angle coupled to the rigid tips ,the power lam in my bows extend about 3 in. Beyond the fades  , I'm curious about your power lam length in your bow , Im very interested in your bow please post about it when your done I think another hidden feature with these bows is because of the curvatures of the limbs they end up with more working limb in a shorter foot print ,I think it would make a great bow in wood might take some trial and error but that's half the fun !
Title: Re: Bow design and development
Post by: Halfbow on November 03, 2018, 01:10:18 am
Wow I tried a very similar looking bow once.

(https://i.imgur.com/IQcML7W.jpg)

(The back is up in the pic)

I planned to eventually add siyahs. Unfortunately mine was a failure before it even got to bend, just because of a stupid mistake on my part. Hope you have better luck with yours! Seems to me that the design could make a great bow.

But I'm not sure I follow how a handle that bulges out on the back of the bow would improve string angle much. I just liked the idea because it seemed like it would fit the hand better than a similar shape bulging out the belly.

There must be a reason why they chose the deflex angle they did. Possibly they did it by trial and error and even they don't know the real reason. I have a theory that this has to do with the lever length of a limb. The actual lever length of a straight bow gets shorter as the limb bends. Reflex and recurves minimise or reverse this so the actual lever length can get longer as the limb bends(or straightens) as you draw it.

I'm not sure if this is what you meant, but you've got me thinking. If you take a bow with strongly recurved tips, hold it vertically, and draw it, then as the main part of the limbs bends to become more horizontal,  the recurved tips are doing the opposite, becoming more vertical.  This keeps the nocks far away from the handle on the vertical plane, giving you more leverage. The two parts of the limb trade off the job throughout the draw. That's cool. I've never thought of it that way before. However, that would be just as true for a reflexed recurve as it would be for a deflexed recurve.

also do you think that the Turkish flight record is due to better archers or design,,???

Better design. Unless archers back then were better than a quick drawing instant release shooting machine. :)
Title: Re: Bow design and development
Post by: PatM on November 03, 2018, 05:38:46 am
  But  "simpler" modern designs greatly exceeded the Turkish records.

 The Turkish data from Adam K doesn't really show a 200 fps 10gr/p trend.
Title: Re: Bow design and development
Post by: Bayou Ben on November 03, 2018, 08:31:23 am
Half bow, my thought behind forward handle and string angle is as you draw the bow back your string angle increases.  If you put let’s say an inch of handle up front as opposed to the belly and you pull your bow back to 28” then you would have the same angle as pulling a traditional belly handle bow 27”.  Not that big of a difference it seems, but it’s definitely something.  And in that same example, a wooden bow has the benefit of less stress, as equivalent to only pulling a belly handle bow 27”.  Those 2 coupled together should result in a less stressed belly with more energy storage.   
A FG bow doesn’t benefit from less stress since it has no memory, so it leads me to believe the string angle on those last few inches are more than insignificant.  Plus on most FG bows with big risers, they are putting closer to 1.5” up front. 
We’ll see though.   These are just unproven thoughts in my head at this point. 
Title: Re: Bow design and development
Post by: DC on November 03, 2018, 08:52:07 am
However, that would be just as true for a reflexed recurve as it would be for a deflexed recurve.



Yes it would. I didn't mean to tie that in with the deflex stuff. I little punctuation may have sorted that out ;)

PS I went back and sort of straightened it out
Title: Re: Bow design and development
Post by: Stick Bender on November 03, 2018, 10:40:03 am
Ben how long is your riser & power lam ?
Title: Re: Bow design and development
Post by: Bayou Ben on November 03, 2018, 11:38:34 am
The riser is what I normally consider a powerlam.  Just bamboo/riser/maple/osage.  It’s 10.5”.  Bow is 62 ntn, so I needed more working limb that’s why I made the riser or powerlam a little shorter than my others.
Title: Re: Bow design and development
Post by: Halfbow on November 03, 2018, 06:54:06 pm
Half bow, my thought behind forward handle and string angle is as you draw the bow back your string angle increases.  If you put let’s say an inch of handle up front as opposed to the belly and you pull your bow back to 28” then you would have the same angle as pulling a traditional belly handle bow 27”.  Not that big of a difference it seems, but it’s definitely something.  And in that same example, a wooden bow has the benefit of less stress, as equivalent to only pulling a belly handle bow 27”.  Those 2 coupled together should result in a less stressed belly with more energy storage.   
A FG bow doesn’t benefit from less stress since it has no memory, so it leads me to believe the string angle on those last few inches are more than insignificant.  Plus on most FG bows with big risers, they are putting closer to 1.5” up front. 
We’ll see though.   These are just unproven thoughts in my head at this point. 

Yes, I'm with you. It will indeed make the string angle that of a 1" shorter draw. But... if you're willing to come with me on a bit of a silly thought experiment here. If all else is equal, say if you were to take an already made bow and saw the handle buldge off the belly and stick it to the back (assume you find a way to do that which doesn't compromise the integrity of the construction). Now your bow's handle has been moved forward an inch, and everything else is untouched.

You have made the bow safer. Drawing to 29" will strain the bow as much as drawing to 28" used to. But it will also make the bow weaker at any given draw length. Drawing to 28" will get you the same poundage as drawing to 27" used to. Also, without changing anything about how the limbs are bending or the length of the string, you have changed your brace height from say 7" to 8". So to get the same length power stroke, you would have to draw it one inch farther anyway. But if you drew to 28" before moving the handle, and to 28" after, you'd find that you'd ended up with a bow with a lighter draw weight and a shorter power stroke.

Maybe you don't want it to be weaker, so you add some thin belly lams to get the poundage back up to where it was. And maybe you don't want a higher brace height so you lengthen the string a bit. You end up with a bow with the same draw weight, brace height, and power stroke length as the original. But for what trade off? Well the most obvious one is that your limbs are heavier now. Also, when you lengthened the string, you let the limbs bend less at brace. So I think you would find that your bow has less string tension at brace than it did in its original form, which means the f/d curve would be less fat than it was originally, which means more stack, and less stored energy. I think moving the handle forward will have near identical effects to deflexing a bow. All the same pluses and minuses.

If you're after good string angle (which I agree is important), wouldn't recurves help a lot more?

But  "simpler" modern designs greatly exceeded the Turkish records.

The Turkish data from Adam K doesn't really show a 200 fps 10gr/p trend.

Modern bows use modern materials. And not just modern bow materials, but modern strings, carbon arrows, etc. This gives an advantage. And also innovations like center shot. This is kind of my point.

So yes, the old Turkish records have been soundly beaten. But even so, I think "greatly exceeded" is a bit of an exaggeration. Setting aside compound bows, the Turk's numbers aren't exactly laughable. And when compared to our attempts at primitive material bows, they're amazing. As far as I'm aware, a modern attempt at a primitive materials bow has yet to beat the old flight records. Generally the primitive bows we are happy to call impressive today are shooting a fraction of the distance.

We are not the inheritors of 100 generations of unbroken bow making knowledge living in a society where you start learning archery as a toddler and live and die by the bow. Our connection to that knowledge got damaged when warfare moved on from archery. Even our attempts at faithfully recreating asiatic composite bows fail to live up to their antique counterparts. However, modern materials have helped us a lot. But it seems to me like we achieved a convenient, easy to maintain, and long lasting modern bow which also preformed admirably, and (mostly) stopped there. When we might have the ability to take performance who knows how much further. I see few people trying to take it in the direction I'm curious to to see.

I'm not holding up Turkish bows as the greatest design possible or anything. With modern knowledge and science we can point out improvements. But I think the asiatic composites were on to something. They were chasing some universal concepts that I think are simply true. I could talk about many examples, but just to pick one: the more reflex, the more energy a bow will store at the same draw weight. I really don't see any way around that. If anyone is finding that adding reflex is causing worse performance, the issue is probably with the materials. Wood will obviously fail or break down in such high stress designs. Perhaps fiberglass isn't good for the job either. If tests show that fiberglass bows are slower when bent that far (I haven't actually seen these results, but it seems plausible to me), then fiberglass has some kind of internal friction or some inefficiency when bent so extremely. That's not an argument against the high reflex concept, that's just an argument that fiberglass is not the ideal material for the ideal fast bow.

Maybe no material in the universe can spring back from extreme bends as well as horn and sinew. That would be interesting to know in itself. I'd enjoy it if there were true. Go nature. That would indeed suggest that the old asiatic composites got nearly all the performance out of highly reflexed bows as ever could be. But if anyone were to suggest that, I'd be immediately skeptical. Nature is amazing, but modern material science is too. There's got to be some material or combination of materials that can bend that much, store that much energy, and be lighter/spring back faster. And it's hard to imagine how such a bow wouldn't be breaking records in its category.
Title: Re: Bow design and development
Post by: DC on November 03, 2018, 07:38:24 pm
I redid the experiment I mentioned back a bit. The first two pictures show the setup. Two 30" limbs, same taper, one straight and one I heat treated some reflex into. Two slots cut into the 2x4, one straight and one at an angle to make deflex. A bunch of nails 1" apart so I can pull the "bow" 1" and then mark it. This is a half bow. Don't feel that i need the other half.
  I put a limb in the slot and adjusted the string length for equal brace height. Then I marked the tip. Moved the string down one nail and marked the tip again. Repeat 27 times. Then I measured the lever length from the base of the limb to the first mark and again to the last mark.
  The second picture is the results. Line "B" (I screwed up the labeling, sue me ;D)is the straight limb in the straight slot. Lever length is 28 1/8" at brace and 27 3/16" at FD.
Line "A" is the reflexed limb in the straight slot. Lever length is 28" at brace and 27 3/4" at FD
Line "C" is reflexed limb in the deflexed slot. Lever length is 27 1/2" at brace and 28" at FD
The lever length is shorter a full draw on the straight limb. The lever length is about the same on the straight handled reflex limb. The deflex reflex lever length is longer at full draw. It's not a big difference but there is 5% dif between the best and worst.
Title: Re: Bow design and development
Post by: Badger on November 03, 2018, 07:57:48 pm
    There is a lot you can do with horn and sinew that you simply cannot do with wood. With regular hunting arrow weights the horn sinew bows are not all that much better than well made wood bows but with light flight arrows and short bows they can excel even though not many shooters today are getting the distances that are possible a few are getting some pretty impressive distances. The record shot by the sultan has been called in question and I myself am not convinced it was a real shot. But we do know it was very possible.
Title: Re: Bow design and development
Post by: Stick Bender on November 03, 2018, 08:06:45 pm
Asiatic composite bows have awesome performance with the highly reflexed design & there's guys around here making them with great performance but a lot of the old ones where in the 100 lb plus class the old adage if you want the bow to go faster pull it farther or make it heavier with the right design apply's  I don't think modern materials would have a issue taking the stresses of that much reflex & I know there are guys making them but never really saw any performance stats on them ,like you said maybe not the best design for the material , I think what's not discussed a lot with design is consistency & durability and the horn composite bows certainly have it , I think every material has it's idealized design the trick is finding it , I think chasing speed can be over rated ,I have some very fast bows but don't like some of them the way they shoot the bow to me has to be smooth drawing user friendly ,accurate ,durable type bow for me to like it , I think one size or one material or one design doesn't fit all , it seems to me from bows I have built there is always trade offs in design !
Title: Re: Bow design and development
Post by: Del the cat on November 04, 2018, 01:34:54 am
@ DC
Nice experiment,write up and pics... thanks for posting :)
Del
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 09:15:05 am
Thanks Del, I was thinking about it last night and I'm wondering if leverage has anything to do with performance. It crossed my mind that because you're using the same lever to store the energy as you are to harvest the energy there might not be a gain.
Title: Re: Bow design and development
Post by: Del the cat on November 04, 2018, 10:10:34 am
Thanks Del, I was thinking about it last night and I'm wondering if leverage has anything to do with performance. It crossed my mind that because you're using the same lever to store the energy as you are to harvest the energy there might not be a gain.
Even if it's the same lever there may be a gain if the variation is F/D curves gives a smoother acceleration to the arrow... even if the area under the curve is the same, maybe slight changes give a smoother more efficient power delivery and leave less in the bow.
I like your word "Harvest" ... they may have the same energy stored, but the D/R presumably harvests it better :)
Del
Title: Re: Bow design and development
Post by: Badger on November 04, 2018, 10:34:52 am
   In recent years I have kind of gotten away from the maximum speed thing but it does still fascinate me. At some point when you reach the higher levels perfection of execution starts to play in more significantly. I was trying to find this list I made several years ago that attempted to isolate all the ways we could store more energy, all the things that rob energy and all the things that improve efficiency.

   Energy losses are for the most part confined to hysteresis and vibration or distortion of the limbs. 
   Energy storage is for the most part a product of geometry.

   Adding length to the bow is the easiest way to increase energy storage but not always a very efficient method. Adding reflex and curves to increase tension and lower string angles are probably a more efficient method but also carry a risk of added vibration. This is where we tend to experiment the most and get a lot of mixed results. The more curves in a bow limb the more complicated it gets. Every inch of the limb responds to its particular string angle relationship throughout the draw. Some of the forward handle bows or heavily deflexed bows with curves at the ends do a good job of keeping string angles low throughout most of the draw but also require a lot of working limb which gives the bow more opportunity to distort or vibrate toward the end of the power stroke. Reducing outer limb mass cuts back on the momentum the limbs carry and gives the arrow a little more control over the bow limbs.

     I think what is most fascinating is how we can try different strategies, not just different designs but strategies that have to be executed through designs. My favorite strategies involve limiting the amount of working limb as much as possible reducing opportunity for vibration. This carries a higher risk of set and hysteresis so it often requires wider working limb areas and flawless tillering in those areas. It also lends it self well to more conservative designs not using as much curve in the limbs or excessive reflex.

      My favorite method which I have never come close to perfecting and I think in the long run will prove out to be the most effective involves limb tapers matched to the curves in the bow which will allow for the limb to uncoil kind of the same way a fly line uncoils when cast. This is where the last part of the limb to uncoil is toward the tips. I still believe this design would allow for more working limb with less vibration and be more efficient. It would also allow bigger curves and more net reflex.

      Hysteresis in our bows is almost entirely a product of set and is one of our biggest losses. All we can do here is keep set low by using dry wood and making sure we have enough working limb and wide enough limbs along with flawless tillering.   
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 10:51:42 am
I'm jumping from pillar to post here but do you think it matters when the arrow reaches maximum acceleration? Is it better for the arrow to get a big kick at the begining and then "coast" or is a nice smooth increase in acceleration with the big kick at the end better? I'm thinking about the positive effect of early draw weight here. Also compound bows have that funny F/D curve and they are fast. I have no idea how a person could use this info in a selfbow but it is info. :D
Title: Re: Bow design and development
Post by: Del the cat on November 04, 2018, 11:05:48 am
I'm jumping from pillar to post here but do you think it matters when the arrow reaches maximum acceleration? Is it better for the arrow to get a big kick at the begining and then "coast" or is a nice smooth increase in acceleration with the big kick at the end better? I'm thinking about the positive effect of early draw weight here. Also compound bows have that funny F/D curve and they are fast. I have no idea how a person could use this info in a selfbow but it is info. :D
Think of two identical dragsters on the track, one with an experienced driver and one with a rookie ... which would you bet on?
Too much kick up the pants wastes a lot of energy flexing the arrow more than necessary. The smoother acceleration curve is more efficient... a regular bow doesn't coast the arrow, it is accelerating through the whole power stroke, but the rate of acceleration is decreasing.
So at the start you have the most force, but the arrow also has most inertia being stationary.
A compound gets the arrow moving and increases the acceleration as the arrow speeds up ... back to the dragster analogy.
Note I've prob' take a bit of a liberty with some of the terms I use but it's the idea I'm try to express rather than an exact analysis.
Del
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 11:13:41 am
Thanks Del, that was my gut feeling. I wonder if you had a compound that stored the same amount of energy as a self bow if it would still be faster.
Title: Re: Bow design and development
Post by: Badger on November 04, 2018, 11:30:29 am
    A compound isn't really a true bow.
Title: Re: Bow design and development
Post by: Del the cat on November 04, 2018, 11:50:50 am
Thanks Del, that was my gut feeling. I wonder if you had a compound that stored the same amount of energy as a self bow if it would still be faster.
I'd guess yes as the limbs would travel a shorter distance so would be quicker and the acceleration would be smoother, prob have a longer draw too with a few extra inches of low weight hold off (or whatever it's called )
But I think we need to stop thinking and have a beer instead ;)
Del
Title: Re: Bow design and development
Post by: Del the cat on November 04, 2018, 11:52:05 am
    A compound isn't really a true bow.
  ;D Yup, I ain't arguing with that
Del
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 12:21:09 pm
It's just after breakfast here. But I guess beer is the breakfast of champions ;D ;D
Title: Re: Bow design and development
Post by: bradsmith2010 on November 04, 2018, 12:39:32 pm
DC,, could you explain to me in simple terms, ,what you think your experiment shows,, Im a bit confused,, )P(
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 01:32:03 pm
I'll try :) On page 164 of TBB4 baker talks a little about leverage. When I read this a few years ago it stuck in my mind the more leverage is faster. I'm going to read it again. Anyway with this more leverage thing in my brain one day I was thinking about why recurves didn't have as much stack. it occurred to me that as the bow was drawn the recurve would stick out effectively making the lever(limb) longer. If you don't know a lever is measured from the fulcrum(handle) to the point of effort(string nock). It doesn't matter what shape the limb is between those points, the lever is always measured in a straight line between those two point. I realised that with a straight bow as the limb bent the lever would get shorter and it does, by around an inch or so at full draw. I had to set up my experiment to check the recurved bow. I found that with the recurved bow the limb kind of stayed the same. While I was at it I tried an deflex/reflex bow and it gained length.
This length change is a gradual thing and depends on the amount of deflex/reflex/recurve so it varies.
With this in mind and the leverage=good in mind I put 2+2 together and came up with maybe 3.5. I'm not quite sure how it all fits together but I feel that the extra leverage at full draw can't be a bad thing. This must tie in with string angle somehow and one may just be the result of the other. Until someone can explain(in simple terms :D) the how and why string angle and leverage actually affect energy storage and delivery I'm just as ignorant as ever. I just thought I would show my results in case it jogged some physicists brain. There has to be someone out there that can explain this stuff.
Hope that helps, if not I'll try again :D
Title: Re: Bow design and development
Post by: bradsmith2010 on November 04, 2018, 01:40:10 pm
yes thank you I understand,,the reflex deflex is longer at full draw,,and could be part of its shooting advantage,, (R 
Title: Re: Bow design and development
Post by: Halfbow on November 04, 2018, 02:01:15 pm
First let me say, I love this convo. This is the stuff I find fascinating.

There is a lot you can do with horn and sinew that you simply cannot do with wood. With regular hunting arrow weights the horn sinew bows are not all that much better than well made wood bows but with light flight arrows and short bows they can excel even though not many shooters today are getting the distances that are possible a few are getting some pretty impressive distances.
I agree. Except from what I've seen, short bows seem to do well with both heavy and light arrows. But indeed the drawbacks of horn and sinew (higher density and such) may start to catch up with it in lower draw weights. Though I theorize that something else is skewing the results here. Many people are making these comparatively light horn bows to look like the warbows and heavy flight bows of the past. With the higher density of sinew and horn, you have to be really careful what you do with them. The profile of a heavy horn bow can make for an unideal light horn bow ...that still preforms comparably with top tier wood bows.

The record shot by the sultan has been called in question and I myself am not convinced it was a real shot. But we do know it was very possible.

I've been frustrated by the lack of info I could find online about this. Most sources I found seem to accept it as historical fact, but details are scarce. I certainly haven't found anything very academic. If you could point me to that, or to the controversy about it, I'd be interested to read.



DC, fantastic test. When you started talking about lever length, I started trying to picture what kind of line the tips of various bows would draw in the air. I failed.  :P Then you posted that test! It's a clever way to test it, That could be really useful for trying to figure out ideal limb shapes for energy storage for various designs. I may have to try to recreate it some time, because I want to know about like 100 different variations. XD

The deflex won here, which is interesting. I'm curious how that holds up with different limb shapes and different amounts of recurve. But it made it occur to me that a bow with most of the working area near the handle, with a stiffer mid and outer limb, will have a profile more like a deflex bow. So extreme mollegabets and bows with smaller working areas and stiffer outer limbs, like Badger is talking about, are getting some of the geometrical advantage of a deflexed handle without necessarily actually having deflex.

I'm still trying to wrap my head around it fully, but I'm wondering if the more important measurement isn't something different than the lever length. I'm more tempted to measure the distance of the tip to the middle line. The line which the arrow will be along. It seems like that will have more to do with the leverage the string has on the limb. Like marked in red:

(https://i.imgur.com/z3Hv4R8.jpg)

Or on recurves, measure from where the string lifts off. As before then, your bow is effectively shorter. Here is an extreme example to illustrate the point:

(https://i.imgur.com/8rYSvJS.jpg)

Here's a silly extreme example just to illustrate why I think this may be the more important measurement:

(https://i.imgur.com/8gjThnN.jpg)

Imagine that's a tiny bow being drawn to 24". This bow would clearly be a nightmare to try to draw further. The string has no leverage anymore. Much stack. Yet the lever length is about as fine as it ever was. The distance from the middle line tells you more.

I have more to say about force draw curves, but I'm out of time so it will have to wait till later!
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 02:18:12 pm
I've done a test and marked where the string lifted off as the point of effort. It really makes a big difference. There are so many combo's of stuff that I just did the three easy ones. I wondered if anyone was going to mention using string lift off. I haven't done it with these limbs but I did it with a ridiculous amount of reflex the last time. At brace the string hit the limb about the middle. There was 4-5" of lever length change. It would have never been stable so I just put it aside.
I have to do some more but I have to make better limbs. These were just 1/8" panelling and took a lot of set.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 04, 2018, 04:43:54 pm
nice (f)
Title: Re: Bow design and development
Post by: willie on November 04, 2018, 05:14:09 pm
DC,
acceleration can be had at a steady rate, ie , where velocity can be increasing at an incremental amount that doesn't change. acceleration can also be had at an increasing or decreasing  rate. the rate of acceleration can be decreasing while the velocity of the arrow is increasing.

Code: [Select]
https://sites.google.com/site/technicalarchery/technical-discussions-1/arrow/accel%20vs%20time.png?attredirects=0
Code: [Select]
https://sites.google.com/site/technicalarchery/technical-discussions-1/arrow/velocity%20vs%20time.png?attredirects=0
that being said, I will agree with Del that smoothness counts for a lot. I can't help but think that if a limb profile was developed that shot an arrow better than those used by most olympic recurve shooters, there would be much more variety in what is seen used in those matches. I am surprised by how similar most of those bows are.
If more speed or range is desired, it seems to me that staying within the design and upping the draw weight, draw length and arrow weight would be the place to look for an increase in performance
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 06:21:34 pm
Hey Willie. I can't help but think that with something as high profile as the Olympics at stake that these factories must have a Skunk Works somewhere and like you say it's surprising how similar these bows are. Does the Olympics put any limits or restrictions on the bows? Maybe they are the best they can be or maybe the changes just aren't obvious.
I'm kind of stuck when it comes to draw weight. Just can't seem to pull much more than 40#. So When I started chasing speed I decided on 40# and 28" as my limits.
Title: Re: Bow design and development
Post by: willie on November 04, 2018, 06:57:46 pm
I dunno about a skunkworks, but there are a few  top line manufactures  seem to dominate the market. Since accuracy is the primary driver of what flies and what doesn't, and these are repudiately the the best shooters in the world doing the "testing", the typical design would seem to be a good departure point for making improvements.
It would be an interesting to see if there are arbitrary restrictions that influence designs, but I am not the guy to ask, just a curious observer. I do notice that a lot of the interchangeable limbs offered seem to keep a decent width in the outer limb.

https://www.ocf.berkeley.edu/~archery/wp-content/uploads/docs/recurve-fundamentals.pdf
Title: Re: Bow design and development
Post by: DC on November 04, 2018, 07:25:08 pm
I got this from the link you posted

Quote
For a cantilever spring, however, the DFC is non-linear, as both the
force and the differential force both increase as the deflection increases.

Can you explain this for me? I think this is something I have wanted to know ever since I started bending sticks
Title: Re: Bow design and development
Post by: loon on November 04, 2018, 11:37:01 pm
As the cantilever spring is bent, both the force and the rate of increase of the force (the differential) increases. So, the force increases at a faster rate as it is bent, that just means that it stacks, while the coil spring doesn't stack, at least as quickly.
Title: Re: Bow design and development
Post by: Badger on November 04, 2018, 11:48:07 pm
  A bow limb gains very little weight because of bending it. The vast majority of the weight is gained because the string angles get higher and leverage is reduced.
Title: Re: Bow design and development
Post by: Bayou Ben on November 05, 2018, 08:56:06 am
"My favorite method which I have never come close to perfecting and I think in the long run will prove out to be the most effective involves limb tapers matched to the curves in the bow which will allow for the limb to uncoil kind of the same way a fly line uncoils when cast. This is where the last part of the limb to uncoil is toward the tips. I still believe this design would allow for more working limb with less vibration and be more efficient. It would also allow bigger curves and more net reflex. "

Steve, so if I'm following you, on the case of a r/d bow, you would have more taper in the deflex area and less taper towards the reflexed tip area?

Title: Re: Bow design and development
Post by: Halfbow on November 05, 2018, 09:09:56 am
I can't help but think that if a limb profile was developed that shot an arrow better than those used by most olympic recurve shooters, there would be much more variety in what is seen used in those matches. I am surprised by how similar most of those bows are.
If more speed or range is desired, it seems to me that staying within the design and upping the draw weight, draw length and arrow weight would be the place to look for an increase in performance
I think you guys just have more faith in the world than me. It's easy for me to imagine it being more of a cultural thing. Like perhaps what was once innovation has calcified in to fashion, and there's just not much of a market for new and different. Then the incentive for companies would be toward incremental improvements. Just enough for the marketing team to sell each year. Also, (correct me if I'm wrong) isn't there a high degree of interchangeability between these bows? Swapping limbs and risers and such? If so, that would really stifle innovation in the interest of remaining compatible. But as you say, accuracy is of utmost importance for Olympic archers, and I fully believe that they've just about perfected that aspect. So, again, there may not be a lot of demand to try new and different.

https://www.ocf.berkeley.edu/~archery/wp-content/uploads/docs/recurve-fundamentals.pdf
That article was a good read on the points it covered, but I thought a few things were curiously omitted. Made me feel vindicated. Most notably... How're they going to not talk about the angle the limbs come off the riser? And the overall reflex or deflex? The distance the handle is in front of or behind the tips when unbraced. They just seem to start with the assumption that the industry has it perfect. Almost like it didn't occur to them that it's a variable they can play with. Maybe the industry does have it dialed in already, but their failure to mention it makes me think maybe they don't.

A bow limb gains very little weight because of bending it. The vast majority of the weight is gained because the string angles get higher and leverage is reduced.

I agree that string angle's contribution to draw weight is important and probably often underappreciated, but I think saying that bending causes "very little" weight gain has got to be overstating it. That would mean a reflexed bow's string tension at brace would be very marginally increased over a deflexed bow's, all else being equal. But in my experience, I wouldn't describe the difference as marginal.


Which is a nice segue in to... reflex. I will explain how I think of it. Probably this will be old news to some of you, but I haven't seen it explained quite this way before. Tell me if I'm way off base.

(This example is simplified to show the concept. And it will leave aside limitations of material, and efficiency issues. Don't take it as an indication that I'm unaware of these things, or that I don't think they're of utmost importance in design. But I also think understanding concepts is important, and distilling them in thought experiments is helpful. I'm picturing a modern material for the sake of this discussion anyway.)

Imagine 3 bows. All the same length, all circular tiller, and all 50lbs at 28". These bows look nearly identical. In use, their profile is identical. And in terms of nearly everything that article was concerned about, they are identical. They're all stable. They all have the same unideal string angles.

But these bows are really different. When you unstring them.

Bow A is deflexed, bow B is straight, and bow C is highly reflexed.

(https://i.imgur.com/WS8TKHx.jpg)

Let's call bows 0% bent when unbraced and 100% bent when at full draw. So I ask, how bent are these bows at brace?

I'm too lazy to try to measure my picture, so I will make up some numbers that seem reasonable to me. Bow A is about 10% bent at brace, B is 50%, and C is 80%.

(https://i.imgur.com/GTtZgz8.jpg)
(https://i.imgur.com/hIkdWEX.jpg)
(https://i.imgur.com/MliguE0.jpg)

So at brace, bow A barely has anywhere to be. Its position of perfect comfort is only like an inch away. It's feeling pretty good about things. The string isn't holding it back much. String tension will be low. Pluck it and get a low note, if anything.

Meanwhile, bow C is very far away from its unbraced profile, and is furiously trying to return to it. The straight string is holding back ~80% of the bow's might. The tension in the string is very high. Pluck it and hear a high note.

Bow B is in between.

So when drawing bow A you are making it move 90% its range of motion. From the bow's perspective, its state at brace is entirely different from its state at full draw. The bow is pretty comfy at brace, and furious at full draw:

(https://i.imgur.com/PrI2zPG.jpg)

Drawing bow C is only moves it 20% of its range of motion. The motion during the draw is not a huge change of state for this bow. It's furious at brace and still furious at full draw:

(https://i.imgur.com/aoFSCbu.jpg)

But they're all 50lbs at 28". So what does this mean in use?

For bow A, I picture getting ready to draw it, putting my fingers on the string, and finding it very easy to pull back. I'm like, "What is this? A kid's bow?" But the weight ramps up and by the time I'm at full draw, it's transformed to be much more difficult. In other words, bow A stacks a lot. It's f/d curve is hollow. It's not storing much energy.

For bow C I picture putting my fingers on the string, starting to draw, and immediately finding the string digging menacingly in to my fingers, resisting me. I think, "What is this? A war bow? Can I even fully draw a bow this heavy?" But then I continue and by the time I'm at full draw... surprisingly the last few inches felt not much more difficult than the first few. This is a smooth draw. It's f/d curve is full. It's storing far more energy.

Bow B, of course, will be in between.

Lots of talk about reflex gets caught up in geometry, but overall reflex or deflex isn't something you can see in a braced bow. Reflexed and deflexed bows can have just about any braced geometry you want.

So, that's how I think of it. I hope that's helpful.
Title: Re: Bow design and development
Post by: DC on November 05, 2018, 09:52:49 am
OK I have to draw back and think a bit. Aaall be baack :D
Title: Re: Bow design and development
Post by: Badger on November 05, 2018, 11:56:53 am
Good examples Half, Take example C for instance. With all that reflex it would have a very high early draw weight. But the geometry isn't such that would allow for a gradual build up of weight so it would simply need to be tillered down in weight which would put that reflex far beyond the point of deminishing returns.
Title: Re: Bow design and development
Post by: PatM on November 05, 2018, 11:58:36 am
Pretty sure Olympic rules demand one style of bow. 
Title: Re: Bow design and development
Post by: BowEd on November 05, 2018, 12:02:23 pm
A pic of fdc and what Halfbow is talking about DC on a highly reflexed bow.Note how easy to draw bow per inch is midway compared to beginning and end which are basically the same each the first and last 2 inches of draw.
(https://i.imgur.com/UVmhd5M.jpg)
Title: Re: Bow design and development
Post by: Badger on November 05, 2018, 12:38:37 pm
   Ed, what kind of profile does this bow have? I think the profile has to be able to support the reflex.
Title: Re: Bow design and development
Post by: BowEd on November 05, 2018, 01:25:14 pm
So do I Steve.Resting profile shows it supports it very well.Resting 11" reflex before bracing.Shot and used 6 hours later 9.25" just unbraced.Returns back to 11" in a matter of 2-3 hours.Bow is 1.25" wide at fades not knowing exactly what profile your referring to.The fdc numbers will be close to the same 6 hours later also.
Title: Re: Bow design and development
Post by: Badger on November 05, 2018, 01:27:41 pm
Thats not what I am talking about Ed, what I am talking about is does the braced profile of the bow compliment the reflex with it's geometry?
Title: Re: Bow design and development
Post by: BowEd on November 05, 2018, 01:32:39 pm
OK I see.It does.You want a picture of the braced profile?Geometry??Give me a break!!Just spit balling here because nothing is stated but do you mean length of working limbs?If so 12 to 14 inches or there abouts.If any more info or pictures is needed just ask because I really don't see how a braced picture will mean anything to what Halfbow is stating to DC about.The unbraced resting profile after shooting is what counts for midrange smoothness of draw on a reflexed bow.
Title: Re: Bow design and development
Post by: Stick Bender on November 05, 2018, 01:44:15 pm
 Awesome FDC on that bow Ed !!
Title: Re: Bow design and development
Post by: Badger on November 05, 2018, 03:19:49 pm
ED, on the pic that Half posted it is a straight limbed bow. It is going to build weight a lot more linear than a bow with some curves or syhas. I don't think a straight limbed bow can compliment that much reflex. I know your bow has some curves LOL.
Title: Re: Bow design and development
Post by: BowEd on November 05, 2018, 04:00:32 pm
I would agree with that Steve.Half bow showed 3 examples of bows for DC though.Straight limbed one is just 1.The difference in area of draw weight accumulation throughout the draw is what he meant to show.
DC...I shoot with guys shooting FG bows all year here.Many here are not recurved extremely at all but just plain old D/R straight limbed long bows.They've been making their bows for decades and have tried recurves and their tips are not set back very far above the handle.They are into take down bows now.Changing the angles of attatchment of limbs on their risers for more or less poundage from their limbs.Course they are'nt all that concerned about performance but mostly hunting and accuracy and from shooting with them their bows are very good.At least they shoot very good for me.Just as good if not better than those sold by companies.I know at any time if I want to start making FG bows they would be right there to point the way.
I think the D/R design is a superb type design for a wooden bow.
Title: Re: Bow design and development
Post by: Bob Barnes on November 05, 2018, 05:36:52 pm
halfbow- thanks for the information... it is something that will be good to think about.  Have you ever made the 3 bows in your drawing to do a FDC on each for comparison?  Testing the 3 for speed, smoothness, and stability would be fun too. 
Ed- I hope you and Steve get on the same page so that you can help me understand this better.  I know some of your bows look more like the "C" bow and they were great shooters at MoJam.
This is good stuff! :OK
Title: Re: Bow design and development
Post by: bradsmith2010 on November 05, 2018, 05:46:27 pm
Ed what I want to know,, is did that deer feel the thump of that full draw curve... :)
Title: Re: Bow design and development
Post by: Stick Bender on November 06, 2018, 01:12:28 am
Ed thanks for posting that I know you have built atleast 7 or 8 predecessors to that bow that I know of , Bob made a good point we need actual bows to see the results of theory in action because its been my exsperience it doesent always play out the way you think when you build the bow !
Title: Re: Bow design and development
Post by: Halfbow on November 06, 2018, 03:11:28 am
halfbow- thanks for the information... it is something that will be good to think about.  Have you ever made the 3 bows in your drawing to do a FDC on each for comparison?  Testing the 3 for speed, smoothness, and stability would be fun too.
Sadly no. Maybe one day I will find the time to make a more toned down version of this in wood. It would be fascinating. But it would be quite a test of skill to get 3 bows with different unbraced profiles to bend to the same shape and draw weight!
Title: Re: Bow design and development
Post by: DC on November 06, 2018, 10:19:25 am
The more I look at this design the more I think that the Wilcox Duoflex is kind of the pinnacle of the design. Does anyone have any pictures of one? Any more info than TBB? I did a google search and there doesn't seem to be much. I'm particularly interested in an unbraced side profile view and how many lams of whatever it was made of.
Title: Re: Bow design and development
Post by: Badger on November 06, 2018, 11:35:50 am
When I first started building bows I was unknowingly building the duoflex bows. I was using 3 lams. They are great shooters. But the bottom line is if you are using wood to build bows the first consideration has to be saying within the material limits of wood which really limits your options. You can build some outlandish aggressive profiles that will be decent shooters but if you have exceeded the limits of wood it won't be any better than a much more moderate design. I can get 100% ratio of stored energy to draw force using as little as 3" reflex. If deflexed out of the handle and recurved to gain the reflex you can max out a wood bow design as long as it is properly executed and doesn't take set. Horn and sinew of course as well as fiberglass are different animals but will still max out at just about the same place. Using wood to duplicate horn sinew or fiberglass is an exercise in futility.
Title: Re: Bow design and development
Post by: Halfbow on November 06, 2018, 11:46:39 am
The more I look at this design the more I think that the Wilcox Duoflex is kind of the pinnacle of the design. Does anyone have any pictures of one? Any more info than TBB? I did a google search and there doesn't seem to be much. I'm particularly interested in an unbraced side profile view and how many lams of whatever it was made of.
There are some unbraced pictures on this site in German. http://www.broadheads.de/docs/bowdocs/Willcox_Duoflex.html (http://www.broadheads.de/docs/bowdocs/Willcox_Duoflex.html) It was made of aluminum?? Was that common?

But I agree, this profile in the correct dimensions can't be too far off from an ideal design for wood. The bow I have in mind to make next will have a lot in common with that.
Title: Re: Bow design and development
Post by: PatM on November 06, 2018, 11:53:06 am
Originally they were Osage and Hickory and I've read that some had a middle lam of Beech.
Title: Re: Bow design and development
Post by: Badger on November 06, 2018, 12:26:41 pm
Originally they were Osage and Hickory and I've read that some had a middle lam of Beech.

   Mine were maple, walnut and rosewood belly. I got a big junk of it from someone at the airlines who bought it before it became illegal.
Title: Re: Bow design and development
Post by: DC on November 06, 2018, 12:30:52 pm
I know that it's pushing the limits but I thought if I could see an original Duoflex I could back off a bit and give it a shot. I want to see where the string hits the limb at brace. 
I've seen the German site and Google translates it quite well. I wasn't sure if the aluminum one would have the same profile or not if it's the only picture I can find it will do. The fact that they made some of aluminum makes me think that they realised they were pushing the wood.
Osage I got, Hickory may be tough to get. All the shovel handles seem to be Ash or no name overseas wood. Maybe Bamboo. Maybe Bamboo Yew. That's always been a good combo.
Thanks for the info ;)
Steve maple walnut and rosewood? If you were to try it again would you use the same wood?
Title: Re: Bow design and development
Post by: Badger on November 06, 2018, 12:40:36 pm
I know that it's pushing the limits but I thought if I could see an original Duoflex I could back off a bit and give it a shot. I want to see where the string hits the limb at brace. 
I've seen the German site and Google translates it quite well. I wasn't sure if the aluminum one would have the same profile or not if it's the only picture I can find it will do. The fact that they made some of aluminum makes me think that they realised they were pushing the wood.
Osage I got, Hickory may be tough to get. All the shovel handles seem to be Ash or no name overseas wood. Maybe Bamboo. Maybe Bamboo Yew. That's always been a good combo.
Thanks for the info ;)
Steve maple walnut and rosewood? If you were to try it again would you use the same wood?

    I have done a few very similar since then and i usually go with hickory or maple back and osage belly. Anything for the core. The only difference is I don't let my recurves work. The duoflex was a pretty fast bow but not any better than bows you see posted here all the time. I think it cast about 180 yards with 10 grains which is decent but not a barn burner. The original ones I built I had no idea what I was doing but got lucky, I think they were in the upper 40#'s. I used 3 each 1/8" laminations and tapered the width for about 2/3 of the bow. The curves were flexing. I think I used about 1 3/4 wide.
Title: Re: Bow design and development
Post by: Bayou Ben on November 06, 2018, 12:55:40 pm
Marc tried one out about 10 years ago......http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
Title: Re: Bow design and development
Post by: Stick Bender on November 06, 2018, 01:05:17 pm
There is also a nice D/R lam bow build in TBB4 that could easily could be modified I thought about building that one modified, using hickory for the back it's a pretty simple quick build ,maybe I will build that one in a FH design over winter ,I have all the lams for it lying around or I could grind them , Steve mentioned this before about lam bows the first one is always a prototype , but if I was chasing speed in a all natural bows I would go horn/composite there are guys here and other places making some screamers , maybe it's just me but most of the wood bows I have made that where fast always broke down speed wise after about 500 arrows with the exception of bamboo baked ones ! I'm not saying I can't make consistent wood bows just the ones in the 180s fps or above .it's hard for me keeping them there after many arrows !
Title: Re: Bow design and development
Post by: DC on November 06, 2018, 01:23:10 pm
I'm probably not testing mine long enough. I like making bows more than shooting them and make too many to put a lot of arrows through them. So what seems like a very good bow to me may break down after more arrows. I'll have to keep that in mind.
Title: Re: Bow design and development
Post by: Badger on November 06, 2018, 01:32:34 pm
Stick, 180 is not shabby at all for a wood bow. If I can get one to settle in at about 184 I am extremely happy. I am happy with anything over 180.
Title: Re: Bow design and development
Post by: Stick Bender on November 06, 2018, 01:39:03 pm
Don ,I have a long draw 31 in. so that adds fps but probably contributes to break down in wood bows to ,if I make bows in the 170 fps range they stay consistent it seems, so I might be under building the fast ones, I built a slightly reflexed BBH that shoots the low 170s consistently  and I have well over 1000 arrows threw it & it stays put even after long stringing !
Title: Re: Bow design and development
Post by: Stick Bender on November 06, 2018, 01:52:53 pm
Steve I would be more then happy with consistent 180s in a wood bow after 500 arrows, I'm not there yet with wood , but I'm curious if a multi lam bow like in TBB 4 might hold it's profile better with the multi glue lines in the lams at longer draws & be more durable ? I guess there is only one way to find out !
Title: Re: Bow design and development
Post by: Bayou Ben on November 06, 2018, 02:42:35 pm
Ritchie, that bow in TBB4 is skirting the line of what an all wood bow can do IMO.  I wouldn't veer from that recipe called out, unless it's to increase the working limb.  That bow is osage/osage/bamboo and has tip wedges of 12", a power lam/riser of 16" and is 66" ntn.  Do the math; there's not much working limb.  There's less than 1" deflex and a good amount of reflex.  I've tried it with other woods and they have failed miserably, and the bows didn't like much my 29.5" draw.  I've since dialed it back, and I've had much better luck. 
 
I do like how I can bend multiple lams without heat though, and they hold their shape quite well.       
Title: Re: Bow design and development
Post by: Stick Bender on November 06, 2018, 02:57:40 pm
Thanks Ben good to know , do your remember where it failed (where the weak areas) working limb ?
Title: Re: Bow design and development
Post by: Bayou Ben on November 06, 2018, 03:07:54 pm
Yeah most of these see a lot of stress mid limb.  Leaving it full width past mid limb should help. 
Title: Re: Bow design and development
Post by: Stick Bender on November 07, 2018, 01:24:05 am
Im waiting for your results on your latest, I was thinking I have the sled for the supper lam now the power lam & wedges combined in one lam it would simplify things a bit , also thinking quad lam maple/osage maybe 66in. ? Im just not sure on the tapper rate given the other design is shallow so Im waiting on you pionering....lol
Title: Re: Bow design and development
Post by: Halfbow on November 07, 2018, 05:44:04 am
Good examples Half, Take example C for instance. With all that reflex it would have a very high early draw weight. But the geometry isn't such that would allow for a gradual build up of weight so it would simply need to be tillered down in weight which would put that reflex far beyond the point of deminishing returns.

I'm not sure what you mean here. We know it's 50lbs at full draw, and you say it would have a high early draw weight. What would you expect the f/d curve to do between the high early draw weight and 50? I'm not sure where the need for tillering it down comes in.

The profile certainly isn't ideal. Add some good recurves and it will store a lot more energy. But that's true for all 3 bows.
Title: Re: Bow design and development
Post by: Badger on November 07, 2018, 09:11:41 am
Half, if you tillered the bow out to look like the other bows in the pic I think it would loose most of the high early draw weight long before you reached full draw. It would end up flmsy and unstable and if you did manage to get shots out of it the efficiency would be poor because the limbs would be too thin and prone to distortion. If it was tillered out like a horn bow with short working limbs all that would change except wood won't tolerate the short working limbs.
Title: Re: Bow design and development
Post by: Halfbow on November 07, 2018, 11:54:02 am
Yeah I certainly wasn't picturing wood for this thought experiment. Even with the full limb working evenly, you'd need an impressive material to take as much bend as bow C without breaking down quickly. But not an unrealistic one. As you know, materials that bendy exist. I was imagining a modern material, since we are discussing why modern bows are so uniform. If I were to try to make this a real life experiment with wood, the reflex would be way way toned down.

Given the set up (that all bows are 50lbs) we can immediately know that when unbraced, bow A is much stiffer than bow C. Bow C has lighter and more flexible limbs. But once they're all braced, bow C is stiffest. By which I mean, it's the hardest to get to bend farther.

I'm not understanding where a lack of stability would come in. There are no recurves to be pulled out of line. (I liked the way the paper linked by willie talked about this) With a recurve, because the tips point away from you, the string tension will have an amplifying effect on any sideways deviation. This pulls things out of line and encourages twist. But with a long bow profile like we're talking about, the string has a correcting effect. If any part of the bow gets a funny idea and wants to step out of line, the string will pull it right back in. And it will correct extra hard on bow C, due to the high string tension.

One type of stability that I could imagine being different is.. it may be more sensitive to where you hold the bow. Put your hand lower and the lower limb will bend more, higher and the higher limb will bend more. I could see bow A being less sensitive to inconsistency there.

I think we probably just need a real life experiment.  :)
Title: Re: Bow design and development
Post by: Badger on November 07, 2018, 11:57:23 am
Half, one of the big challenges that modern longbows face when adding over 3" reflex is that they become unstable at brace. They will rock back and forth. Reducing working limb is the only way to counter it. Wood bows are the same way if they have too much working limb and reflex.
Title: Re: Bow design and development
Post by: DC on November 07, 2018, 12:07:34 pm
I'm thinking that any time the tips are in front of the handle(fulcrum) you can have a tendency for twist. The self correcting doesn't take place until after the tips pass the handle. But even then if your limb wants to twist, say due to uneven thickness, the tips will still amplify the twist. Had this happen the other day. The tip was starting to twist at about half draw. The limb felt a little thicker on one side and a couple of scrapes later, no problem. That was actually the first time I'm managed to fix a twist that way. 
Title: Re: Bow design and development
Post by: Halfbow on November 07, 2018, 12:17:13 pm
Half, one of the big challenges that modern longbows face when adding over 3" reflex is that they become unstable at brace. They will rock back and forth. Reducing working limb is the only way to counter it. Wood bows are the same way if they have too much working limb and reflex.
Ok so if I'm understanding you right, it sounds like do mean the second kind of stability I mentioned. Where the top and bottom limb will too easily trade off bending more? If so, then I'm on board.

I must admit, I am unfamiliar with this being a major concern for modern longbows, but that's interesting. I'd have expected a handle that makes it clear where to hold the bow would be an effective counter for that, but I guess it's a bigger problem than I imagined.

In that case, what would you think of this thought experiment if I had used an extreme holmegaaurd-type design, to the point of them all being hinge bows?

I'm thinking that any time the tips are in front of the handle(fulcrum) you can have a tendency for twist. The self correcting doesn't take place until after the tips pass the handle. But even then if your limb wants to twist, say due to uneven thickness, the tips will still amplify the twist. Had this happen the other day. The tip was starting to twist at about half draw. The limb felt a little thicker on one side and a couple of scrapes later, no problem. That was actually the first time I'm managed to fix a twist that way. 

DC, I think you would find the effect you're talking about is a function of the bow's shape in use. Meaning, the bow's shape at any point from brace through full draw. In regard to twist, bow C is a very stable shape from brace through draw, same as the other 2 bows. You would only see that kind of unstability manifest when trying to string bow C. That bow would be a bear to string (as is any extreme reflex bow). But once you got it, I think you'd be golden in that regard.
Title: Re: Bow design and development
Post by: Stick Bender on November 07, 2018, 12:54:29 pm
Steve I don't know what modern long bow strait ? Your referring to if it's strait type with reflex I don't know but the moderen D/R long bow has no issue with limb rocking as described , if there was a issue as described I think it would be related to design,material or taper rate , about 3 in. in front of the handle is max that I have gone do to increasing brace height  ?
Title: Re: Bow design and development
Post by: willie on November 07, 2018, 03:56:59 pm
I got this from the link you posted

Quote
For a cantilever spring, however, the DFC is non-linear, as both the
force and the differential force both increase as the deflection increases.

Can you explain this for me? I think this is something I have wanted to know ever since I started bending sticks

I think what they are trying to say in a fancy way, is that the the cantilever will stack. take a look at the bottom sketch that halfbow  posted in reply 65 for an extreme example.


Title: Re: Bow design and development
Post by: willie on November 07, 2018, 04:08:30 pm
... How're they going to not talk about the angle the limbs come off the riser? And the overall reflex or deflex? The distance the handle is in front of or behind the tips when unbraced. They just seem to start with the assumption that the industry has it perfect. Almost like it didn't occur to them that it's a variable they can play with. Maybe the industry does have it dialed in already, but their failure to mention it makes me think maybe they don't.

Halfbow,
I hope Don doesn't mind me posting a link to a project I started last winter. I have asked myself similar questions, but more to do with arrows for flight shooting.

http://www.primitivearcher.com/smf/index.php/topic,62820.0.html

edit: fixed link, maybe.  look for "shooting fixture" in the flight section
Title: Re: Bow design and development
Post by: Halfbow on November 07, 2018, 06:37:11 pm
Willie, that fixture looks great. I know you were mostly focused on arrows, but did you get any impressions about different setups for bows?
Title: Re: Bow design and development
Post by: BowEd on November 08, 2018, 10:37:38 am
Halfbow.....To tiller out a bow such as C that you showed it would be like tillering a wildcat.Linear and lateral stability would be an issue especially more so if the bow was very narrow.More width can help with stabilizing.I've been there and done that and it can be done.Quite frustrating really with no added benefit but still very unstable as Badger stated even after tillering it stable.In fact the bow will stack at the end of the draw.Not a desirable thing at least for me.A bow such as C should have retro bent tips pointing straight down the last 6" in the profile you've shown.
A boat shape type profile with the reflex mostly on the outer half of bow and left a bit stiffish will be much easier.With not so much up close reflex to tiller coming from the fades but if reflex is in fades more so should be put in the outer half of limbs yet.
More reflex can be put on the last 6" of these bows here too with a bit more benefit but this profile is easier for me to brace with just a primitive stringer the way it is without the use of tepeliks.They are still very stable bows.The extra reflex on the outer limbs puts more pressure or strain closer to the handle which is flatter profiled which helps stabilize the limbs better.Making static recurves have the same effect of pressure on a self bow.As with most bows the most power on profiled bows like this comes from the innerlimbs to midlimb as it was'nt reflexed on the inner limbs that much to begin with and so it is more stable then.A hard almost impossible trick to do with wood alone bows with over 6 inches of resting tillered out reflex.
Different degrees of reflex here with the background one to tiller yet but when done will show the gradual increase over the other two in front.
(https://i.imgur.com/yrZTBG7.jpg)


Title: Re: Bow design and development
Post by: Badger on November 08, 2018, 11:37:56 am
Good one Ed! Nice photo!
Title: Re: Bow design and development
Post by: Bayou Ben on November 08, 2018, 12:36:03 pm
Many good points to ponder Ed.  And those bows are sweet!
Title: Re: Bow design and development
Post by: Halfbow on November 08, 2018, 04:18:20 pm
Ed those are some wonderful looking bows you've got there. I admire your skill, and I fully respect that you guys have experience with extremely reflexed bows, and I do not. The most extreme bow I've ever made ended up with a little over 6" of reflex and was 60" long. Not so extreme. So I'm not telling you guys you're wrong, I'm just looking to understand better. I'm reading your post closely.

To tiller out a bow such as C that you showed it would be like tillering a wildcat.Linear and lateral stability would be an issue especially more so if the bow was very narrow.I've been there and done that and it an be done.

Tillering bow C would be a nightmare, for sure. I can't imagine the process of even just getting it to brace. I had enough trouble getting my bow to brace. The fact that people can tiller a bow like bow C without computer controlled machines producing nearly full draw ready limbs straight off the factory floor... it's amazing that you say it's possible.

The difficulty of tillering makes sense to me, because a huge part of the tillering process has to happen while the tips are beyond the handle, and are pointing away from the direction the string wants to pull them, leading to intense lateral instability.

Quite frustrating really with no added benefit but still very unstable as Badger stated even after tillering it stable.

If I'm understanding you right, this is where you lose me a little bit. If we picture bow C on a tillering tree, once you get to the stage where you can finally pull those tips down past the handle (which would be when you've tillered it like 60% of the way to full draw (A)), then I imagine things become much easier and much more stable. I am very familiar with this transition from the reflexed bows I have made. In the tillering tree, while the tips are above the handle, the bow is doing all kinds of weird things and desperately wanting to flip. After the tips are below, ahh sigh of relief, things are in control now. From that transition point on, the farther you draw it, the more stable it becomes. That's the point that I'd expect a reflexed non-recurved bow to start behaving more like a sane bow. I hope I'm understanding you right, but I think you're telling me this isn't the case with bow C. You're telling me it would remain unstable even after the tips are past the handle and pointing down. I'm having a hard time understanding why that would be.

In fact the bow would stack at the end of the draw then.A  bow such as C should have retro bent tips pointing straight down the last 6" in the profile you've shown.

I'm not sure what you mean by tips pointing straight down. If you mean that a bow like C would automatically come out whip tillered, I'd have to disagree. If it came out whip tillered, then I'd just say whoever tillered it did it wrong. They should've left more material on the outer limbs. It's perfectly possible to have bow C come out to the circular full draw profile I've drawn.

I do agree that bow C would stack more than many recurved bows. Recurves, of course, add a lot more energy storage. But I think C would stack less than A and B, which was the point of the exercise. To distill out the effect of reflex without muddying the water with extra variables like recurves.

But sure. Add recurves to all 3 bows and they'll all stack less, and bow C will still stack less than the other two. I'd imagine that something like bow C with big recurves would start getting in to levels of energy storage that would make compound bows start worrying about competition. But that would be crazy unstable.

My expectation would be this: for bows with recurves, especially recurves that are extreme enough to point away from the belly side at brace (a.k.a. string contact somewhere along the limb), more string tension means less lateral stability. To a high degree. The string is trying hard to pull that recurve out of line. So for recurves, the more reflex the less stable in use.

Conversely, for a bow with no recurves, I wouldn't expect increased string tension to have nearly the same effect destabilizing effects in use. It will have some destabilizing effects, just because of the general increased tension everywhere. Like if I imagine limbs that are nearly as thick as they are wide, then yeah, there will be problems. But I wouldn't expect it to be too much for a reasonably wide limb. And to take that farther, if bow C were to taper in width like a modern fg recurve, with very wide and thin limbs staying quite wide and thin all the way to the tips.. I have a hard time imagining lateral problems. Perhaps my expectations just drastically underestimate the forces involved?

But in short, I'd expect recurves to have an extremely destabilizing effect on a high tension bow. However, I do see that shortening the working area will have a stabilizing effect. I'm with you guys there. But I'd think you'd only really need to do that to counter the destabilization from recruves. In addition, you can shorten the working area without recurves.

But every extremely reflexed bow I've ever seen has had some form of recurve. If the tips aren't pointing away from the belly at brace (string contact), then they're pretty damn close to being in line with the string. This makes sense because people are chasing that power. But it also means it makes sense that people have this association of more reflex = a bow with less lateral stability to a high degree. If you know of or have made any extremely reflexed bows with no recurve, I'd love to see them and to know more about them and how they failed.

A boat shape type profile with the reflex mostly on the outer half of bow will be much easier.With not so much up close reflex to tiller coming from the fades but if reflex is in fades more so should be put in the outer half of limbs yet.
More reflex can be put on the last 6" of these bows here too with a bit more benefit but this profile is easier for me to brace with just a primitive stringer the way it is without the use of tepeliks.They are still very stable bows.The extra reflex on the outer limbs puts more pressure or strain closer to the handle which is stiff which helps stabilize the limbs better.Making static recurves have the same effect of pressure on a self bow.

I fully understand you here and my expectations agree. :) It's interesting to note that it would be possible to make a bow that had your boat shape when unbraced, but had a perfectly circular tiller (identical to bow C) at full draw. What would your thoughts on that be?

Again, I respect your experience with this, I'm just contrasting my expectations with what you're saying in hopes that I can understand better. I'm actually wondering if our thoughts on this are as different as they seem to be.
Title: Re: Bow design and development
Post by: PatM on November 08, 2018, 04:24:25 pm
You'll hear of cases where strung reflexed bows have reversed themselves despite the tips being past the handle.

 With the built up stresses the bow is looking for the tiniest bit of weakness to one side and that can  be almost totally unapparent.
Title: Re: Bow design and development
Post by: Halfbow on November 08, 2018, 04:28:59 pm
Yes, on recurved bows. I've battled the effect myself. Once a bow flipped on me so hard it jammed my wrist, just from holding the handle while it happened. Scary stuff. But I've never heard of a bow without recurves unstringing itself, unless a nock broke or something. I don't understand how that could happen without some kind of total collapse of the material.
Title: Re: Bow design and development
Post by: Badger on November 08, 2018, 04:40:38 pm
Half, bows with a long static reflexed outer limb will flip in a heartbeat if they have some reflex. The low string angle for a long section of the limb creates a huge amount of stress.
Title: Re: Bow design and development
Post by: Halfbow on November 08, 2018, 04:49:13 pm
Ah, yeah, I mean terms get fuzzy here. When you say reflexed outer limb, I assume you mean it has some curve. It's that curve away from the string (at brace and after) that I'm suggesting really makes a flip more likely. Low string angles, however they are achieved, also help encourage it for sure.
Title: Re: Bow design and development
Post by: Badger on November 08, 2018, 05:01:16 pm
Not necessarily and curve just a kink in the limb a little past mid limb will do it. I stay away from those and prefer long sweeping gently curves.
Title: Re: Bow design and development
Post by: Halfbow on November 08, 2018, 05:03:37 pm
Yeah, a better way for me to say it would be: any concavity to the back of the bow at brace makes a flip much more likely.
Title: Re: Bow design and development
Post by: BowEd on November 08, 2018, 05:45:39 pm
Whenever the recurves I made have their tips aligned I have no problems of it twisting.This is at brace and full draw.They don't neccassarily have to look that way at rest yet either but it is preferrable.
The reflexed area on the outer limbs should be closer to not farther from the string at brace for good stability and lower stacking.
Making these type bows takes patience amoondo compared to a self bow.Extreme power and tension to deal with.As said it looks for the weakest point fold.
That's good you got one to settle with 6" of reflex.What reflex did you start with before tillering?
Making bows like ones shown takes me as much time planning on paper as constructing it,it seems.The best materials used is a must.
Title: Re: Bow design and development
Post by: Badger on November 08, 2018, 05:56:38 pm
  A recurve just aacts like a heavier shorter bow until you draw it out. If the outer limb has about 10" of straight limb pointing straight out almost parallel with the string that is when the forces get crazy and unstable. I have never seen a way to stabilize them without curving them.
Title: Re: Bow design and development
Post by: BowEd on November 08, 2018, 06:36:43 pm
Yes I would have to agree.Shooting a bow should be a fun & safe experience.Each of us has our own degree of fun I guess.There's a lot more safer ways to have fun.
Title: Re: Bow design and development
Post by: Halfbow on November 08, 2018, 06:41:55 pm
Ed - I don't remember how much reflex my bow started with. I shortened the siyahs at some point in the process, so it's hard to say.
(https://i.imgur.com/wUBbLBY.jpg)
You can maybe see the reflexed angle the (straight) limbs originally came off the handle, but after set that reflex is pretty much gone. I made a thread about it not too long ago. The one called Bamboo Asiatic horse bow, if you're curious to see more. And yeah there's no doubt that stable highly reflexed and recurved bows are possible. My lowly example certainly is very stable. I'm a big proponent of that, and was never meaning to suggest otherwise. But it did take some fine tuning to get it there. I was just suggesting that the recurve would increase tendencies toward instability, amplifying alignment issues when compared to not having it.

Badger - You touch on an interesting point there, that string contact has a stabilizing effect... up until the one unlucky time the string misses the limb and it flips. But yes I agree, 10" on the end nearly parallel to the string will be very unstable. But you're not going to get that unless the back of the limb has some concavity before the straight section. (Unless your brace height is next to nothing or your bow super long) So I maintain that concavity on the back (convexity on the belly) increases likelyhood of flipping. This is what I was meaning on in my long post up there when I said, "But every extremely reflexed bow I've ever seen has had some form of recurve. If the tips aren't pointing away from the belly at brace (string contact), then they're pretty damn close to being in line with the string."

You're making me realize that by "recurve" I've just been meaning any concavity of the back/convexity of the belly at brace. Whether in a working section, or stiff, or angled siyahs, or just at the tips, or through most of the limb. I was calling all those things recurves. Probably wasn't using the word quite right. ><
Title: Re: Bow design and development
Post by: BowEd on November 08, 2018, 07:07:05 pm
Yes I remember that bow now.Using the power fibers of bamboo on the belly.Very articulate joints made also.A very well crafted durable bow.A lot of thought went into the making of that bow.I would'nt call it a lowly bow at all.We don't see many like that.You made alignment of limbs a no problem project as a 5 piece bow.I'm sure it shoots very well for you.
Recurves do have tendencies to be more unstable than your regular straight gently curving self bow.It's the nature of the beast,but for those who like them it's what it is.
Title: Re: Bow design and development
Post by: Badger on November 08, 2018, 07:29:45 pm
  I don't think recurves are unstable at all, I hope I didn't give that impression. Like any design they have to be done right.
Title: Re: Bow design and development
Post by: BowEd on November 08, 2018, 09:46:47 pm
By unstable I mean a bit more work to make is all.
Title: Re: Bow design and development
Post by: Bayou Ben on November 09, 2018, 07:51:52 am
To illustrate Steve's point, this one flipped twice on me at low brace with all of that limb touching the string.  Very unstable.

The second pic is at full brace and it's much more stable.  Almost no part of the limb is touching the string.
Title: Re: Bow design and development
Post by: Badger on November 09, 2018, 09:24:42 am
Ben, that is exactly what I was talking about. That particular one looks like it might stabilize with a slightly higher brace but any straighter than that just doesn't work.
Title: Re: Bow design and development
Post by: BowEd on November 09, 2018, 09:59:14 am
Good illustration Ben.A picture is worth a thousand words as they say.I can see why by those pics.
To add here....A higher brace height is needed especially on those Egyption angular bows so they don't invert when the string slams home from release from what I've seen.
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 10:01:01 am
Flipped on release or drawing? Do you have an unbraced picture? How much reflex does it have? Sorry for all the questions but I wouldn't have thought that was unstable. I must be missing something. You sure got my attention ;D
Title: Re: Bow design and development
Post by: Bayou Ben on November 09, 2018, 10:49:28 am
DC, that's the same bow I'm working on in my tiller help thread.  It flipped or reverse strung itself the 1st time right after I braced it and the string was a little off center, and the 2nd time when I was putting the bow on tree and the string touched the cradle.  Just that little bit of sideways/lateral force caused it to reverse string itself.  But that was all while it was at low brace (~4", 1st pic of previous post) and the string was contacting a large portion of the limb.  Now at full brace it's a lot more stable (the 2nd pic of my previous post).
 
Title: Re: Bow design and development
Post by: Badger on November 09, 2018, 10:53:38 am
Ben, you did a pretty good job on that one keeping the limbs tiller rounded, you do have a slight kink near mid limb, that same design with the outer limb straight and slightly more reflex in the kink makes for a very unstable bow.
Title: Re: Bow design and development
Post by: Halfbow on November 09, 2018, 10:55:50 am
Good example Ben (and nice looking bow). Just want to point out that it was my point too. :)
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 11:09:59 am
Is this one going to be a problem? I started it a few years ago and got it too thin so it sat in the corner of shame until last week when I put a belly lam on it. I thought it would make a good tillering exercise. It's only an inch wide. I've been having trouble getting it to bend(it's flipping) but I thought it was just string alignment. I've been doing minor heating the correct that. haven't trid it today.
Title: Re: Bow design and development
Post by: Stick Bender on November 09, 2018, 11:10:09 am
Looks awsome Ben what target draw weight are you shooting for ?
Title: Re: Bow design and development
Post by: Badger on November 09, 2018, 11:15:56 am
Is this one going to be a problem? I started it a few years ago and got it too thin so it sat in the corner of shame until last week when I put a belly lam on it. I thought it would make a good tillering exercise. It's only an inch wide. I've been having trouble getting it to bend(it's flipping) but I thought it was just string alignment. I've been doing minor heating the correct that. haven't trid it today.

   I think you will need to get more bend in the inner limb, as much as you can get. I also think it is too narrow but the profile you have is doable.
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 11:27:57 am
I knew it was too narrow. Not much I can do about that. Would making it a bendy handle help or hurt. I think I remember reading something here that bendy handles aren't good for stability. Might be dreaming. I just thought it would be fun to test myself. It can always go back in the corner ;D
Title: Re: Bow design and development
Post by: Badger on November 09, 2018, 11:40:12 am
   I would lower the draw weight to 35#, I don't think that profile would suit a bend handle very well.
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 12:00:21 pm
Will do. Sorry about sidetracking the thread.
Title: Re: Bow design and development
Post by: Bayou Ben on November 09, 2018, 12:25:14 pm
Will do. Sorry about sidetracking the thread.
It's your thread....sidetrack away...

Looks awsome Ben what target draw weight are you shooting for ?

Anything over 50# I'll be happy with.  Going to see how set is going further out in the tiller before deciding for sure though.
Title: Re: Bow design and development
Post by: Halfbow on November 09, 2018, 02:02:20 pm
DC, I'm pretty sure this thread got a bit sidetracked a long time ago. XD That may be partially my fault. Sorry for that.



But because I'm afraid I was being confusing earlier, let me clarify what I was saying.

When I said, "But every extremely reflexed bow I've ever seen has had some form of recurve. If the tips aren't pointing away from the belly at brace (string contact), then they're pretty damn close to being in line with the string." Recurve may not have been the word I was looking for. I meant any concavity of the back/convexity of the belly at brace. In other words, the profile bending away from the direction the material is being pulled. I feel like there should be a word for this!

To illustrate:

(https://i.imgur.com/1X9ea6y.jpg)

So Ben, your bow (at the low brace in this pic) is an example of the sort of profile I was talking about being less stable originally, and this is what I meant by being in line with the string.

Looking at a different profile, bows with recurved tips will usually show both convex and concave sections of the back, like so:

(https://i.imgur.com/FdWarAp.jpg)

And bows with a kink/siyahs/whatever have the concave sections too, whether working or not. All kinds of weird things are possible:

(https://i.imgur.com/uE8VPhc.jpg)

But all these bows have at least one area where the back is concave at brace. I'm suggesting that this concavity makes flips much more likely in reflexed bows. It decreases string angle at the ends, and gives initial twist more leverage to twist more, in a sense.

As opposed to:

(https://i.imgur.com/LL3OBnk.jpg)

There is no area of that back that is concave, every part of the limb is going in the direction that it's being pulled. And nowhere is the limb close to running along the string. Given reasonably wide limbs, I'd expect this bow to be in negligible danger of flipping, no matter how much tension the string is under. It's hard to picture these limbs twisting in a way necessary to flip.

I wanted to use "recurve" to describe this concept, but I guess that implies that it's near the tips and curvy. I think it would be useful if we had a general word for concavity of the back at brace. Anyone with me?
Title: Re: Bow design and development
Post by: PatM on November 09, 2018, 02:32:36 pm
It's called reflex....  It's just concentrated more in one spot.  There is definitely a bit of a blurred ,line between reflex and recurves when it's a scenario like that above.  Back in the day they called it a semi-recurve.

 A reflexed bow strung up really can still flip around if it's narrow.  Your statement of reasonable width limbs can be the difference maker.

 A reflexed narrow longbow is rather prone to reversing unless care is taken. 
Title: Re: Bow design and development
Post by: Halfbow on November 09, 2018, 02:36:33 pm
Reflex isn't the word. We agree that bow C is reflexed right? But it has no concavity of the back at brace. Reflex can become convex at brace.

Edit: For a reflexed longbow to flip, the limbs (while constrained by the string) have to bend sideways to the same degree you want them to bend toward the belly. This isn't out of the question on something like an out of alignment elb where the string doesn't track over the handle. Because it's a bow that's not far off from being as thick as it is wide (so it can bend to the side about as easily as it can bend toward the belly), and it has small string angles. This is pretty far from how I picture bow C being. I think we agree here, but I don't want the effect of a limb that's considerably wider than it is thick to be minimized. On a longbow, I think the effect would be profound without the width being extreme.

Concavity of the back at brace opens up another mechanism by which a flip can happen. Twist. Twisting a long bow won't change it's effective profile much, but twisting a recurve (for example) will.
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 02:46:47 pm
Isn't that reflex?
Title: Re: Bow design and development
Post by: Halfbow on November 09, 2018, 02:48:58 pm
DC you may have missed my previous post. ^
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 03:12:37 pm
I see what you're after now, I think. Don't think there is a name for it :D here's your opportunity to be famous.
Title: Re: Bow design and development
Post by: PatM on November 09, 2018, 04:37:07 pm
Reflex isn't the word. We agree that bow C is reflexed right? But it has no concavity of the back at brace. Reflex can become convex at brace.

Edit: For a reflexed longbow to flip, the limbs (while constrained by the string) have to bend sideways to the same degree you want them to bend toward the belly. This isn't out of the question on something like an out of alignment elb where the string doesn't track over the handle. Because it's a bow that's not far off from being as thick as it is wide (so it can bend to the side about as easily as it can bend toward the belly), and it has small string angles. This is pretty far from how I picture bow C being. I think we agree here, but I don't want the effect of a limb that's considerably wider than it is thick to be minimized. On a longbow, I think the effect would be profound without the width being extreme.

Concavity of the back at brace opens up another mechanism by which a flip can happen. Twist. Twisting a long bow won't change it's effective profile much, but twisting a recurve (for example) will.

  It's still reflex, it's just not flattened and bent past straight until the draw progresses.   The bow is a deflex /reflex. No need to re-name the parts and profile depending on what the bow is currently doing.

 Let's not have it become silly like a string follow versus set semantics discussion.
Title: Re: Bow design and development
Post by: Badger on November 09, 2018, 05:07:51 pm
What happens when you have very low string angles is that instead of a braced bow being pulled more toward the shooter the bow is being pulled straight in on itself just as if you were trying to push the top of it into the ground like a spear. Thats what makes them unstable.
Title: Re: Bow design and development
Post by: DC on November 09, 2018, 05:41:01 pm
How did you know that was going to be my next question? ??? I'm still unsure of the whole string angle thing although I do understand how using a long string for too long can affect tillerig. I think that's close to what's going on here.
Title: Re: Bow design and development
Post by: Halfbow on November 09, 2018, 05:51:20 pm
DC, oh man. The pressure. Lol

Pat, to be clear I'm not discounting the word reflex. Reflex is a very useful word that does a good job of describing what it describes. Very necessary. It's also definitely related to the word I'm looking for. And I agree, sections of limb that remain concave on the back when braced are merely the sections of reflex which weren't pulled past straight. Absolutely.

However, because you can make different areas of a limb bend different amounts, the profile at brace can take on a quite different character from the unbraced profile. I could draw out another thought experiment showing how the same unbraced profile could bend to become very different bows at brace. Kind of the reverse of the A B C experiment I already drew. Unbraced, these bows would be exactly as reflexed as each other, and have that reflex in the exact same places. But bending from there, strong reflex can disappear. Or remain. Strong convexity can form where there was none before. Or not.

We don't need an extreme example like bow C to show that. Common bows show that. And because the geometry of the bow in use (between brace and full draw) is what matters most for its stability in use, and the profile's effect on f/d curves, and other such concerns, it seems useful to me to have a piece of vocabulary to make clear that you're talking about the shape of the bow while in use.

As it is now, the word "reflexed" doesn't work at all to describe the braced shape of certain reflexed bows, bow C being a good example. Or any reflexed longbow really. If I handed one to you as a mystery bow, strung, you'd never call it reflexed either. You wouldn't be able to tell it was reflexed. Even though it very much is. Without some fairly detailed science, you'd have to unstring it to know much about its reflex. This is true of all bows really. Braced geometry seems like a sufficiently distinct concept from "reflex" as people usually mean it. But to talk about it, I'm stuck with the super awkward "concavity/convexity of the back of the bow at brace". Can you think of a better way to convey the same info?

It seems to me that we could all talk about things in a clearer way if the terms reflex and deflex referred to the unbraced profile (as they usually do already) and we had different words that described a braced profile. Suddenly communication becomes easier.

As an anology, I think about our language for animals and food. We have the words cow, pig, and chicken, and then the words beef, pork, and poultry. Your view seems similar to someone arguing the we shouldn't have the words beef, pork, or poultry. Who needs em? But the specific words only serve to clarify, and take away nothing. When I say I got some pork at the store, you don't have to wonder if I have a new pet.

(Are you describing bow C as a deflex/reflex bow? I wouldn't agree with that.)

Badger, yes, exactly.
Title: Re: Bow design and development
Post by: willie on November 09, 2018, 05:57:44 pm
Willie, that fixture looks great. I know you were mostly focused on arrows, but did you get any impressions about different setups for bows?

not yet, the range is not ready yet. I hope to use a consistent bow setup to evaluate arrows, then play with the bow variables to see what works for best cast.
Title: Re: Bow design and development
Post by: PatM on November 09, 2018, 09:09:10 pm
I'm not having trouble with any of the accepted ;labels.   No need to complicate things with mystery bows and  not knowing unbraced shapes.

I did not mean that bow C was a D/R.  I meant the actual pictured bow.
Title: Re: Bow design and development
Post by: Stick Bender on November 10, 2018, 02:15:03 am
Thanks for posting the real world bows & thanks for illustrations Half bow , but this thread has covered a lot of different areas , but my question is how are we judging the designs ,FDC or arrow speed or other ? Ben , Ed made a good point about brace height on those more angular braced bows needing more brace height , that's been my exsperience also !
Title: Re: Bow design and development
Post by: Badger on November 10, 2018, 08:48:24 am
       I think if you are judging a bow you would have to look at speed, stability while shooting, at least some degree of longevity, obviously a flight bow doesn't need to shoot a thousand arrows but it does need to be able to shoot enough arrows to tune the bow to the arrows. Good speed won't happen if a bow takes too much set regardless of the finished profile. You can still get very decent speed but a rocket launcher is unlikely.

       I am in the camp that feels extreme designs don't work well with wood and are not worth the trouble. In my opinion Mark St Louis bows incorporate the design features that allow for about as extreme as you can safely go. He reflexes them right out of the handle and produces nice sweeping curves in the outer limbs that are not difficult to tiller out. He also gets them working right into the fades giving the bow more working limb to work with. If I were to try and find fault in Marks design I would suspect that some of them mainly a few years back might have started with too much reflex to maintain through tillering and shooting in.

Title: Re: Bow design and development
Post by: DC on November 10, 2018, 09:10:35 am
We haven't talked much about stability over the years. Is it just about accuracy or does it affect speed and longevity. I'm thinking lack of vibration affecting the last two. Maybe someone could give a short dissertation about stability, it's causes and effects.
Title: Re: Bow design and development
Post by: Badger on November 10, 2018, 09:35:17 am
  DC, when I talk about stability I usually am just referring to a bow that comes back to a normal brace after the shot. Too much limb behind the handle with too much working limb will be unstable. Hornbows have very little working limb and remain pretty stable. Extremely low string angles for a long part of the outer limb will be unstable especially if you have quite a bit of reflex.
Title: Re: Bow design and development
Post by: Stick Bender on November 10, 2018, 09:48:15 am
I agree with what you said Steve one of the fastest wood bows I have made & some may remember this bow 65 in. 45 lb @30 1/2 all I could find was construction pics but it was a long riser sweeping faded short limb heat treated hickory  bow with only about 1 1/4 reflex it was flirting with 190s and at times higher and consitant in the high 180s it was under built exsperment with 1 1/2 width limbs but it was very stable fast bow for the first 150 arrows if I had stoped there it would have been a great bow ,but quickly deteriated from there , I often wondered if I had shortened the bow & added sinew what would have happened , but you made my point durability in any design is important , I think 1 size does not fit all with bow design ,Im not a real technical guy but I know there are design differences with making a high dry fire speed bow as oposed to a bow designed to shoot heavy hunting arrows and being durable talking self bows !
Title: Re: Bow design and development
Post by: bradsmith2010 on November 10, 2018, 09:52:04 am
as stated before,,its relative to the application,, a stable fllight shooting bow is one thing, and a stable hunting bow is another,,
I am not willing to give up stablility or longegevity for my hunting bow, if I wanted to flight shoot I would be willing to change my approach as Badger suggested and have a bow that might last long enough to tune the arrows and shoot for an event,,,
so stability can cover a wide range ,,, depending on the application at hand,,my needs are pretty simple and want a bow that wont break down with years of hard use,, so its overbuilt to achieve that "stability",, )P(



Title: Re: Bow design and development
Post by: DC on November 10, 2018, 10:04:02 am
  DC, when I talk about stability I usually am just referring to a bow that comes back to a normal brace after the shot.
What else can it do? The string stops it. Oh, wait, you mean a stable bow is one that doesn't flip inside out?
Title: Re: Bow design and development
Post by: Halfbow on November 10, 2018, 12:00:48 pm
I'm not having trouble with any of the accepted ;labels.   No need to complicate things with mystery bows and  not knowing unbraced shapes.

You may have mistook my point about the mystery bow there a bit. Was just pointing out that you can't know much about a bow's reflex from its braced profile. I think that's interesting. I guess you don't and that's fine. You can say I'm over complicating things, but I say that bows are going to be exactly as complicated as they are regardless of how we talk about them. And given that the braced profile of a bow is largely what matters for stability, and you can't know much about reflex from the braced profile, there's more to this situation than you seem to be thinking about. I'm sure that hasn't stopped you from making great bows, but I, for one, like to understand as much as I can.

I vote we call concavity of the back at brace "persistent reflex".

Thanks for posting the real world bows & thanks for illustrations Half bow , but this thread has covered a lot of different areas , but my question is how are we judging the designs ,FDC or arrow speed or other ?

Sure! So many areas! I agree with everything being said by everyone on how to judge a bow. I think what Badger said about wood bows is right on. And of course different designs will be better for different tasks. For a lot of this convo I've been kind of drilling down on one concept at a time. Maybe focusing on energy storage in one post, stability in another, etc. That was never to suggest that energy storage is all that matters, or stability is all that matters. (By stability I'm mostly talking about lateral stability. String tracking over the handle, not being overly sensitive to release, no twist in bows with persistent reflex, accurate, low vibration, and certainly no flipping) I like to understand concepts one at a time instead of as a convoluted mash. But of course the bow that stores the most energy imaginable will never be stable, and the bow that's the most stable imaginable will never store much energy. You find these inverse relationships everywhere in bow making. So when you go to actually make a bow, the task is a balancing act of blending all your understandings of different concepts to best suit the purpose you want the bow for and the material you're using.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 10, 2018, 12:11:19 pm
then we can talk about what is the best bow,, (-P
Title: Re: Bow design and development
Post by: Selfbowman on November 11, 2018, 12:19:17 pm
Brad .Presently I think it's a pyramid design.  Just saying. Also a flight bow after a couple hundred shots might not be what it once was. Will still be a great hunting bow that last for years. Us old men are not what we once was.  ;D Arvin
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 05:37:08 am
DC....That's what is cool about making bows.A person can work and work and refine a certain design to be the best it can be.Most times it takes many bows and a person can get all the bugs worked out and down to the nitty gritty.Then move on to refine a different design.No reason to get bored.Most every design has it's accalades.Even with the same type wood there will be characteristics about it that make a bow more to your satisfaction.Your tillering skills get refined doing this too.The bows I shot at the flight shoot at Mo Jam verified my suspicions just from testing at home.Those bows had thousands of shots through them individually before the event and still held their own.I like levered type bows myself.
Title: Re: Bow design and development
Post by: DC on November 12, 2018, 08:45:58 am
I like levered type bows myself.
What do you mean by "lever type"? I've not heard that before.
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 09:22:38 am
Sure you do DC.It's been talked about on here many many times.Straight bows that have a little more extended lighter narrow tips.It's the old function difference of a ball being thrown by hand or thrown by a lacrosse stick.
Title: Re: Bow design and development
Post by: DC on November 12, 2018, 09:27:31 am
Like a Molle. Gotcha, it's early here. I'm only halfway through my coffee ;D
Title: Re: Bow design and development
Post by: Bayou Ben on November 12, 2018, 09:28:39 am
Sure you do DC.It's been talked about on here many many times.Straight bows that have a little more extended lighter narrow tips.It's the old function difference of a ball being thrown by hand or thrown by a lacrosse stick.

Like Ritchie's bow above I'm assuming
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 09:34:03 am
I just call them bows with levers.Their more work to make but can be made very durable.
Title: Re: Bow design and development
Post by: Stick Bender on November 12, 2018, 09:52:37 am
Here is a example of a osage lever bow made like Eds recipe , I made a while back before I cleaned up the leavers still holding original reflex after I would guess 1600 arrows or better in fact ,shooting better after it took more reflex after last winter !
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 09:56:31 am
Thanks Ritch but it's all been done before though.Not really my recipe per sa.I was wondering if you heat treated the hickory bows' working limbs any in your first picture?
Title: Re: Bow design and development
Post by: Stick Bender on November 12, 2018, 10:02:28 am
Yep I limbered up the fades a littile more and heat treated it but at 65 in with only 1 1/2 width pulling it to 30 1/2 it was to much ,I would still like to try a sinew version of it , was a sweet shooting high horse power bow for a while....lol
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 10:06:36 am
I see.2 and 1/2" beyond 28" is pushing it for sure.A little more width and thinner would have helped I bet,but sinew would do the trick I'm sure but just on the working limbs.
Title: Re: Bow design and development
Post by: BowEd on November 12, 2018, 10:11:19 am
That's what I was saying earlier.More refinement of a design to get it better.
Title: Re: Bow design and development
Post by: Stick Bender on November 12, 2018, 12:57:47 pm
I guess you made my point for me I have a whole corner of the bow room that need refinement....lol but a lot can be said about working with one design and taking it as far as you can go refining it but there is no way you can find a design or a book that's going to tell you that , like a friend of mine says you need to make the bow to find out , but for me in all wood bows the ones that seem to hold up with good speed & good hunting durability  are the slightly reflexed long leaver bows , I like the shorter sexier looking ones but they never hold up for my long draw with out sinew , I think the slightly reflexed self long bow is over looked a lot and if built right is with in 10 fps of there counter parts for me !
Title: Re: Bow design and development
Post by: avcase on November 12, 2018, 03:46:43 pm
I was waiting for my turn at the range the other night and was looking at the bows. Not counting the compounds every bow there(except mine) was a FG recurve.( I can be a little slow sometimes ;D ;D) Ignoring the FG part all the designs were deflexed recurves. Not one FG longbow and I know they made them when I was a kid. This got me thinking that somewhere in the past bow making companies must have done a lot of testing of various designs and all decided to make basically the same design. There must be a lot of data squirrelled away on the effect of various tests. Does anyone have access to any of this stuff? I realise that FG data won't be directly transferable to wood but a good design is a good design.

I go back and forth between natural material bows and glass bows. I don’t know if there is much data squirreled away for glass bows.  Most glass bow builders tend to copy prior designs as a starting point and this gets them something that works well and reliably most of the time. I feel the primitive bow builders have a much better understanding of materials and design because they have to. The wood bow builder has to design their bows much closer to the limits of the materials in order to achieve similar levels of performance.

So why do most glass bows look very similar to one another?  It is because they are very economical to build this way. All you need is a fixed thickness of glass on the back and belly, a decent core with a constant taper, and a tried and true recurve profile, and you end up with a decent performing bow that should last almost forever.  Performance with 10ggp arrows and 28” draw length doesn’t vary much from the best to worst. The deflexed limbs help make the bows easier to string. There are also various standards in place (for example AMO) which standardizes some features of the bow limbs. For example, it standardizes the string length relative to the limb length, and this limits the design possibilities for those manufacturers who conform to these standards.  There are other formal and informal standards for takedown bows that help insure interchangeability of various manufacturers limbs and risers.

Some bow builders try to get a bit of an edge over others by experimenting with materials and taper rates in their bow limbs. Carbon fiber doesn’t guarantee a boost in performance.  Most designs that report an increase in performance are pushing carbon much closer to its durability limits than their original glass designs.  For example, there was a trend for awhile to make high performance compound bow limbs using carbon, but the limbs were a disaster when it came to durability. Now, the pendulum has swung the other way and short glass limbs are used to store the energy. This combined with big cams takes full advantage of the capability of glass to store tremendous energy in bending. The idea is similar to using the material of horn and sinew to store energy and a large stiff and light wooden ear or throwing arm to perform a similar role as a cam.

Glass is able to store much more energy in bending for its weight than unidirectional carbon. But unidirectional carbon is a much more efficient structural material (better stiffness to weight) than glass. A bow requires the materials to store energy in bending and provide structure to hold the limb shape and control bending, so the two materials have their pluses and minuses. A carbon limb requires more limb length to store energy in bending. This allows room for more energy robbing vibration modes which counteract some of the advantages carbon has.

There are a new breed of modern bows showing up called “Super Recurves” that use huge recurves to give force-draw curves that rival a compound. Some even show some letoff at the end of the draw. The designs are not really new. Hickman proposed a similar design for a wood bow in the 1930’s. The difference is that lighter carbon fiber designs are using interesting combinations of weaves and fiber orientation to allow the material to behave a little more like unidirectional glass (much lower stiffness, but better energy storage capability in bending). The lighter materials reduce the limb mass to the point that these can outperform most conventional designs with heavy arrows. They also do not rely on reflex to improve the force-draw curve so the limb is under very low stress when the bow is braced, which favors keeping the bending stresses under control for a carbon composite limb.  Unfortunately, the efficiency drops off so bad with lighter arrows that a conventional glass bow will run blow the Super Recurve away in a flight shoot with very light arrows. The old saying “the fastest bow with heavy arrows will be the fastest with lighter arrows” does not apply to a modern Super Recurve.

Alan
Title: Re: Bow design and development
Post by: DC on November 12, 2018, 03:57:45 pm
Thanks Alan, interesting post.
Title: Re: Bow design and development
Post by: Halfbow on November 12, 2018, 06:55:00 pm
Good to hear it from someone who knows a lot about the industry. :OK Interesting stuff. Thanks avcase.
Title: Re: Bow design and development
Post by: BowEd on November 16, 2018, 07:21:57 am
I'm of the opinion the wooden and composite bow makers are the ones the FG makers are following in design and developement.
Title: Re: Bow design and development
Post by: Stick Bender on November 16, 2018, 03:22:27 pm
I think your right Ed sense most designs are based on a historical design regardless of material used ,I think there are innovative and talented bowyers on both sides of the fence but there designs are all loosely based on something out of history !
Title: Re: Bow design and development
Post by: Badger on November 16, 2018, 05:39:03 pm
  the design is one thing and then you get into the bending properties of the material you are using and start addressing things like vibration and optimized reflex based on what you are working with. But I do agree that wood bowyers were a big part of the designers in modern bows.
Title: Re: Bow design and development
Post by: willie on November 16, 2018, 06:11:08 pm

The old saying “the fastest bow with heavy arrows will be the fastest with lighter arrows” does not apply to a modern Super Recurve.

Alan

Interesting post Alan. Thanks.

 In reference to your closing thought, I should ask if you have seen any trends in FG bow limb development aimed towards improving designs for use with lighter arrows? 
Title: Re: Bow design and development
Post by: willie on November 16, 2018, 06:12:37 pm
I'm of the opinion the wooden and composite bow makers are the ones the FG makers are following in design and developement.
:OK
Title: Re: Bow design and development
Post by: Stick Bender on November 17, 2018, 04:46:03 am
When I was a kid I use to read my dad's hunting magazines & names like Ben Pearson , Dan Quinlin, Fred Bear, Howard Hill, Jack Howard , Paul Shafer, Glen St Charels eventual inspired me to make wood bows all those guys got there roots in natural material bows ,I think there big African game hunting stories inspired me too...lol  to me a bow is a bow and if I close my mind on any design or material I would have missed the boat on a lot of design keys , I think you learn a lot about bow making by studying both ,it certainly makes you understand in a hands on way what works and what doesn't !
Title: Re: Bow design and development
Post by: BowEd on November 17, 2018, 09:51:59 am
The thing about making self and composite bows is that it developes a persons' tillering skills very well IMO.
Title: Re: Bow design and development
Post by: Badger on November 17, 2018, 10:03:22 am
  Ed, something I have been seeing a lot of the last few years is glass bowyers using horn composite designs basically making reproductions from modern materials.  This has been going on for a long time but they are starting to incorporate features of horn composite bows more into the traditional glass bow designs which does make a lot of sense.
Title: Re: Bow design and development
Post by: bradsmith2010 on November 17, 2018, 11:20:28 am
I have made fiberglass bows that shot well,, I just done enjoy grinding the fiberglass,,but feel I learned some things universal to bow making that help me with my self bows, (-_)
Title: Re: Bow design and development
Post by: willie on November 17, 2018, 03:04:42 pm
Steve,
I guess it is safe to say that most of the fg guys utilize the precast lams that come in a couple of uniform thicknesses from a just a few primary suppliers.

Are you aware of designs that use fg of varying thickness? custom fg or otherwise?
Title: Re: Bow design and development
Post by: Stick Bender on November 17, 2018, 03:35:25 pm
I think most dedicated FG bowyers or for that matter wood lam bowyers grind there own lams in any combination they want ,I have grinding sleds to grind from .001 to .010 taper rates or any combanation including parallels or supper lams with power lam & wedge tips ground into the same lam I can grind a typical 4 lam limb profile for about $12 as opposed to buying them  with sleds like these !  There are a lot of guys that use various thickness of FG in a design for example .040 on the back & .030 on the belly !
Title: Re: Bow design and development
Post by: Badger on November 17, 2018, 05:40:08 pm
  I made my sleds out of 1/4" plate glass, I used different gauges of wire as spacers to set my tapers and used silicone to glue them together, very accurate but a little on the heavy side which is fine.
Title: Re: Bow design and development
Post by: Stick Bender on November 17, 2018, 05:53:20 pm
 These are vertical grain bamboo ,I'm making matching sleds for the band saw so I can cut the ruff tapers right on the bandsaw saving lam material plus less grinding time , I'm setting my shop up to where I can make them in a short period of time, I like to use fresh ground lams vs leaving the set and get oxides on the surface , re sanding them can get varied tolerances.