Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on November 06, 2017, 04:14:21 pm
-
I generally layout my bows in a pyramid. Even taper from the fades to the tip. Aesthetics aside, is there a performance reason for doing it any other way?
-
If you mean side taper and little or no thickness taper, then yes, that's what is called a "pyramid" design. And I know of no physical reason to make a wood bow any other way.
All these "flipped" tips and such are just for the eye or to keep string angle within practical limits or twho overcome some defect in materials or workmanship.
I would rather shoot bows than make them, so I almost always make a "pyramid" bow, though I hate that term. They look NOTHING like a pyramid, even in front or back view. Now if there were some good reason to use an architectural term, then "obelisk" is a whole lot closer to the look. I suspect the person who plastered the pyramid moniker on the design had never even heard of an obelisk. The language grows from the bottom.
-
How many flight and speed records are held by pyramid bows? That might be the answer.
Pyramid bows are ugly though so I wouldn't make one even if they were better. ;)
Flipped tips and recurves are often put in to take advantage of superior material, not overcome defects in inferior material. Not that people don't try the latter.
-
How many flight and speed records are held by pyramid bows? That might be the answer.
Where's Badger??
Because I'm usually using small diameter staves(high crown) and the "pyramid" doesn't come to a point I always have some thickness taper. It's the even side taper that I'm asking about.
-
I know. I just wouldn't do that. The stave probably wants width retained farther out the limb so why not do that?
-
As far as I know a pyramid will keep up with an equally reflexed parallel limb bow. I prefer the parallel limbs because I feel it works better when heating in gentle curves and reflexing. I find the biggest difference has to do with how much reflex and not so much design. Even the elbs seem to be about the same speed. I always start mine off as parallel with the last 14" tapered, by the time I am done it is more closely resembling a pyramid most of the time anyway. I think the parallel gives me more options during the build if I need a little more bending limb, if I don't need it I end up shaving it off most of the time.
-
The most that can be asked of any material and any design is that as much material as possible should contribute to the draw force and that as little mass as possible be moved during the shot. Your version of that concept will determine the relative efficiency of the design.
-
I know, that's why light tipped recurves are better. ;)
-
...but...the mass at the tips of a recurve is much more than the mass at the tips of a "pyramid...."
-
Not to the degree that it isn't offset by more optimally straining the rest of the limb, which is designed to take advantage of that by carrying width farther out the limb.
-
The stave probably wants width retained farther out the limb
I hate to do this but,"Why would it want this?"
-
I feel it works better when heating in gentle curves and reflexing.
As in easier to do or better performance wise? Maybe recurves don't tend to twist on a wider limb? I think I've heard that.
-
I very rarely cut the front profile,, I just shape it as I go depending on the bend,,, sometimes it turns out a bit pyramid, and sometimes a bit more parallel... especially white woods might need to be a bit wider,,, especially heavier bows too,,,,
there is a reason most Native bows are not all pyramid,, right,, (-P
-
there is a reason most Native bows are not all pyramid,, right,, (-P
When you are using a sharp rock it's easier to taper 1' than 3'???? Did I get it, huh, huh.
-
Look what you got started, DC! I love the levity of experienced bowyers!
It’s actually a very good question about limb design and performance. Esthetics aside, I won’t say pyramids are ugly or pretty…they’re “cute”. And, I agree with Jim – if you want a quick-build, pyramid is the way to go and they have good shooting characteristics. My first consideration when deciding on a specific design is the quality of the stave, and then the available width. Some staves will only work with an ELB or a pyramid design. When using narrow staves, (you already know this) you will have more flexibility with the draw weight by using parallel sides – more wood, more power. The next variable is adjusting the length of the parallel sides…again, stave quality is the first priority, and then the intended use (hunting, target, kid’s bow, etc.) is factored-in to achieve the intended draw weight.
H
-
I'm with Steve about there being more wood for making adjustments with parallel limbs. I used to try to get a bow roughed out as close as possible to the finished dimensions, but I've learned the hard way too many times that "you can never put wood back on." Well, at least not most of the time :D
-
The stave probably wants width retained farther out the limb
I hate to do this but,"Why would it want this?"
To have more width to take strain when your stave is not perfect.
-
The stave probably wants width retained farther out the limb
I hate to do this but,"Why would it want this?"
To have more width to take strain when your stave is not perfect.
Got it, thanks
-
I'm with Steve about there being more wood for making adjustments with parallel limbs. I used to try to get a bow roughed out as close as possible to the finished dimensions, but I've learned the hard way too many times that "you can never put wood back on." Well, at least not most of the time :D
I've always done the front profile more or less to final size first. You guys are making sense. I'm going to rethink this. So you get the thickness to what, floor tiller, 20 inches? Then work the front profile?
-
No way! You need a front profile established first.
For fancy curves keep the width parallel. This means the outers limbs are thinner and will accept and hold reflex better than a thicker piece of wood.For a straight limbed bow pyramids can't be beaten. Even thickness = even bend = Equal strain....aka the holy grail of bow making :)
Of course all this is based on a stave that will allow you to make what ever design you want.
-
Why would you do anything other than pyramid?
1. Wood doesn't grow wide and flat backed in easy to harvest sizes....
2. Easy to harvest sizes wouldn't be a consistent thickness along or across the limb if simple sawed out to a pyramid profile.
Next! ::)
Del
-
Very interesting!
I mean the wood gives the design, that's for sure. I've read that some wood wants a more flat but thin design and some wood a thicker, narrower. The characteristics of the wood would be the reason for it. So "some wood wants to be an ELB, some a flat bow". Is that somehow true or completely wrong?
Historically, we see that there are periods where ELB's where mainly common even in cultures where bows where not as massively produced as in england at the time of the famous english longbowman. The reason for an ELB design in england might be the simplicity of the design, and the fact that you can get more ELBs of a tree than flatbows. But the other cultures did not need that amount of bows (at least bot as high as in England). The bows of that cultures all have a very high draw weight and where made of hard wood.
That in conjunction with what I've read ("some wood wants to be an ELB") made me think that:
(most) hard wood --> ELB
So.. what is true?
-
I'm with Steve about there being more wood for making adjustments with parallel limbs. I used to try to get a bow roughed out as close as possible to the finished dimensions, but I've learned the hard way too many times that "you can never put wood back on." Well, at least not most of the time :D
I've always done the front profile more or less to final size first. You guys are making sense. I'm going to rethink this. So you get the thickness to what, floor tiller, 20 inches? Then work the front profile?
That's not what I meant actually. I just meant that if I start with parallel limbs and I run into something in the wood that needs accommodation or modification I've got more wood to work with. Fundamentally, I'm with Mike. It's important to establish a front profile based on the design of the bow.
-
...
(most) hard wood --> ELB
So.. what is true?
No!...
If you mean hard as it physically hard.... well Yew is soft. It's also a "softwood". >:D
Osage is both hard and a hardwood! That'll make an ELB.
Hazel is a hardwood but it's soft, It's not best suited to an ELB, but can make one if allowances are made.
Ash is a hardwood and it's hard, It's not best suited to an ELB, but can make one if allowances are made.
Hope that's cleared it up ;)
Del
-
Okay, so not every hardwood is actually hard and not every softwood soft. :o
So if we take osage and a stave that is as perfect for a pyramid as it is for an ELB.. will it perform better as an ELB or as a pyramid?
-
It will perform better as a static recurve. Haven't we already covered this? lol
-
I think how well a pyramid design performs depends on how you define performance. If you only look at fps, then among straight-stave bows with no recurves or reflex, a pyramid is a superior design (in my opinion). My fastest straight-stave bows have all been pyramids. But with any design there are trade-offs. If you want a straight-stave bow and you choose to maximize fps, some other factor is suffering. For pyramid bows, in my mind one of the factors that suffers is the longevity of the bow. You're stressing the mid-limb of the pyramid bow so that it's about as efficient as it's going to get, but that means it's under more strain and the wood fibers will break down sooner from that strain.
Although they haven't been quite as fast, I've gravitated more towards paddle bows as of late because the wider mid-limb seems to buffer the bow against excessive strain a bit better. I'm willing to sacrifice a little efficiency in favor of a bow that maintains its performance longer.
But that's just me, of course. Others are free to make their own trade offs.
-
so is a paddle bow widest at mid-limb, as opposed to parallel chord?
-
The only engineers that I know of who wrote about bows were Paul Klopsteg and Clarence Hickman. Some of you need to read their works, since none of us is an engineer (as far as I know). You'd get lost in some of the math, as I do, but they draw their conclusions in plain words.
-
I like a sort of pyramid real close to a Badger bow. The better you
Have even diminishing . The better the performance . That is just
the way it works. Boat paddle Bows create wind drag. Swing a boat paddle
edge ways and then with the boat paddle flat into the wind. Just
facts of life. This is why I build long narrow bows . The trick is to eliminate
set. We all strive for that. Arvin
-
So which strait limb design launches heavy war or hunting arrows faster ? Parallel limb or Pyramid ?
-
A well made pyramid will out perform in my opinion .
The mass is the mass if fifty pounds or a hundred pounds.
Will the hundred pounder be wider ? Of course .
It's a hundred pounder. Arvin
-
no it wont,,, most well made good design bows can shoot about the same,, or very close,, I am pretty sure I have heard Badger say this on many threads,, he is my voice of reason on this,, mainly because he has made more bows than most and tested the effeciency of many kinds of bows,, I am guessing a well made pyramid bow will shoot as good as any well made wood bow,, but I dont think it will out perform other designs, if it would it would be documented here on a daily basis, I dont see that,,
also when the discussions about performance come up,, it would be nice to have some stats for comparison,, if you think a certain bow shoots harder,,,, then give an example,, example would be my pyramid bow shoots 180 fps with 10 gpp,, etc etc etc,, and this is what I am basing my opinion on,,
-
I somehow doubt a pyramid would out do a mollegebet it a controlled test would be almost impossible.i could be wrong though?
-
It would be easier to bottle unicorn farts than get a real side by side test of two different bow designs. Even two staves, taken side by side from the same tree will have sufficient variation in density, grain, elasticity, etc that the test would be inaccurate. Secondly, there are so many variables virtually out of our control simply because any two sessions of tillering might produce two differing degrees of early strain causing micro-collapsing of wood cells on the belly and losing efficiency.
Every bow is a "study of one". Every design is a series of tradeoffs between opposing options. I have worked with eight different engineering students at the South Dakota School of Mines and Technology, and two of their professors trying to design a test that will prove or disprove that backing a piece of wood with thin rawhide will or will not prevent a bow limb from failing under tension and/or to what degree. The best we could do is to do 500+ limbs from side by side staves and start to look for patterns to emerge.
I used to hate the pyramid design because it was (to my mind) inextricably linked to board bows and my snobbery would not allow for any lick of respect for board bows. These days, I enjoy knocking out a board bow WITH pyramid limbs. Anymore, for me it is no longer about the "best" bow, it's just about the "next" bow. (Caveat: I don't build bows to shoot, hate shooting bows because it is boring and I suck at it. When I build a bow, it is because I enjoy working wood in this manner. Your reasons for making a particular bow will necessarily be based on your reasons, and my opinions should carry little or no weight with you. Just be sure to post pics for the people like me that can't read. We like pretty pictures.)
-
:) (-P
-
it would be nice to have some stats for comparison
I agree Brad, some of this discussion seems to be a bit on the theoretical side, or at least somewhat over-generalized.
Also, It would be nice to hear what some think about the possibility of different trade-offs that Eric mentioned. Light vs heavy GPP arrows? are there others?
-
Well stated brad and jw! I never make same bow twice because of the nature of the material.
-
Well stated brad and jw! I never make same bow twice because of the nature of the material.
Bows are like kids. You wanna turn out the best you can with each, but they will all have varying qualities out of your total control. Best to enjoy each for what it is.
-
I think we can establish that the pyramid design is for people who really don't like woodworking too much. ;) It's the design that always has some guy wondering why we don't just CNC a bunch out of boards and call it good.
-
I fully agree with JW. I was hoping that with the number of bowyers on here and all their experiences that some general consensus would have surfaced. I'm going to guess, because of the responses, that it don't really matter a lick. There seems to be a few things like that in this game.
-
Steve what bow design holds the current broad head record? And is it closer to a pyramid design with flipped tips and some reflex? Arvin )F(
-
Well a holmgaard is basically a pyramid design,not to discredit!
-
Pat I'm a builder not a cabinet man. Removing mass is a not a work of art. However tillering a bow to a fine shooting weapon is. Until you get to the last 10# of tiller you are just getting the mass out of the way. Arvin
-
I try not to fixate on one design over the other but I think the choice between the parallel limb vs Pyramid boils down to which design can hold the most reflex for the same over all mass , I try to build my bows using Tim Bakers mantra mass where it's needed and none where it's not , but I would bet the Molly type design would match or best the pyramid ,maybe Bubby will chim in he has made a lot of both designs !
-
I'm definitely a woodworker, and I like the look of pyramid bows over parallel limb bows and prefer to make them. Based on collective experience of everyone here, one won't outperform the other if both are made with a proper tiller and to know that is made to its optimum performance, it would take more than just an eyeball. It could be I'm not good enough that I can't get the last 2 fps out of a given design.
-
I'm with Pat here, just build a nice static and it will be better in all aspects 8) 8) 8) did I mention before that I like static recurves? ::)
Maybe I just suck at building pyramids but my statics, rd's and my mollys are all faster then my pyramids. (Backed up by chrono results)
On the other hand, it all comes down to how well the bow is tillered and how you match the design to the wood. An overstressed "whateverdesign" wil never outperform a well tillered pyramid which is as narrow as the wood will allow without taking set.
-
how fast are they,, )F(
-
Steve what bow design holds the current broad head record? And is it closer to a pyramid design with flipped tips and some reflex? Arvin )F(
Back in the day Chet Stevenson used a heavy static recurve to toss a broadhead shaft some ridiculous distance over 300 yards.
-
arent all well designed bows as narrow as the wood will allow without taking set,, ??
-
arent all well designed bows as narrow as the wood will allow without taking set,, ??
That was exactly my point ;D
-
I think how well a pyramid design performs depends on how you define performance. If you only look at fps, then among straight-stave bows with no recurves or reflex, a pyramid is a superior design (in my opinion).
Performance, as in FPS? If so, at what arrow mass?
you could also look at bow efficiency, how much of the energy that entered the draw is actually (and potentially) translated to arrow speed.
See for example Kooi & Bergman 1997, who compared efficiency of different bow designs.
https://www.researchgate.net/publication/285362259_An_approach_to_the_study_of_ancient_archery_using_mathematical_modelling
But for flight shooting, efficiency doesn't matter, rather arrow speed with very light arrows (dry fire speed).
this is where static recurves can shine. At 10 gpp, however, they don't perform better than the best straight self bows. Since pyramids inherently optimize mass versus strain in the lower limbs, just like ELBs actually, they can have higher dry fire speed than other straight bow designs. But at high arrow masses, this difference hardly matters.
Look for example at the broadhead flight records: they hardly differ between selfbow, sinew-backed recurves (I assume these are the most likely simple composite) and complex composite recurves (sinew-wood-horn recurves).
http://www.usflightarchery.com/pdf/2017-Flight-Records-Broadhead.pdf
The difference is marked, however, when comparing regular flight archery
http://www.usflightarchery.com/pdf/2017-Flight-Records-Regular.pdf
-
wow,, (-P
-
Well stated brad and jw! I never make same bow twice because of the nature of the material.
Bows are like kids. You wanna turn out the best you can with each, but they will all have varying qualities out of your total control. Best to enjoy each for what it is.
I like the bows are like kids . Well put! Arvin
-
Pat, Both the 50# broadhead records that I hold are with moderate r/d designs, maybe 1 1/2" reflex. The limb shapes are similar to pyramid but the first inside 8 or so inches is parallel. One of the unlimited broadhead records is held by an English long bow I built for a guy, about 90#, I think it went somewhere over 280 yards but easily has 300 or more in it. I predict 70# self bows will be hitting 300 yards in the broadhead. If not a self bow then at least a 70# simple composite.
In all honesty I am not very impressed with my own broadhead records. I haven't seen any real aggressive designs show up and push us to go a little more extreme to compete. I think the 50# will be creeping up into the 250 yard range.
I did recently have an extremely fast 35# bow with parallel limbs and gentle recurves. Hitting over 200 yards with a broadhead.
-
I somehow doubt a pyramid would out do a mollegebet it a controlled test would be almost impossible.i could be wrong though?
Bring one to the salt flats . From experience that separates the old men from the boys. ;D
Arvin
-
Wow....I'm enjoying the heck out of this thread. One of these days I'm going to shoot a couple of bows I've made through a chrony or for distance. this one sure has inspired me to give it a shot....
DBar
-
@ Badger and Selfbowman.....How important is arrow design when shooting distance? from my research you need to be a "good" bowyer and a "great" arrowsmith to do good at the salt flats (distance). appreciate any comments....
DBar
-
Danza Bar arrows are about 40 present as I found out. I went with a 500 gr. heavy foc . Bad mistake! It cost me probably 20 yds. My distances was 202 yds in 50# selfbow broadhead class. I was 40yrds short in the 50# selfbow flight class with some borrowed arrows. I will be fixing that arrow error! Can't load pics tonight for some reason. Probably me! My bows vary in width but all are not a pyramid or parallel limbs. They usually are about a1/4" narrower at mid limb verses the fade, then to about a1/4 " at tips. Arvin
-
Danza Bar arrows are about 40 present as I found out. I went with a 500 gr. heavy foc . Bad mistake! It cost me probably 20 yds. My distances was 202 yds in 50# selfbow broadhead class. I was 40yrds short in the 50# selfbow flight class with some borrowed arrows. I will be fixing that arrow error! Can't load pics tonight for some reason. Probably me! My bows vary in width but all are not a pyramid or parallel limbs. They usually are about a1/4" narrower at mid limb verses the fade, then to about a1/4 " at tips. Arvin
Why not experiment? I know you've shown pics of stacks of similar bows with very similar results. Why not shake it up?
-
Well Pat when I get this design right I will. I am still working on the no set thing. I plan on learning from that bow that I cut up. Testing with that at this point. I am determined to get 180fps out of this design. With a proper arrow I'll get Steve! All in good fun though. Wish some of you guys would join us at the flats next year. Arvin
-
I think we can establish that the pyramid design is for people who really don't like woodworking too much. ;) It's the design that always has some guy wondering why we don't just CNC a bunch out of boards and call it good.
That is a pretty negativw generalization Patm. I love working with wood in way more than this medium and i make pyramid, or variations of pyramid bows all the time
-
Those guys push it as the only way though. That's a lot more negative.
-
Pat come play and learn me something. I don't care what kind of bow anyone builds. I certainly don't claim to have this all figured out. But I am on a mission to try and beat a record. That is as fun for me as building the bows. I don't like building arrows near as much but yes that is part of the flight shooting. Then you get to the natural string material. That is what I really don't care for. I build a lot better bow than a compeditive string. The strings are breaking. Build them not to break and you end up with a rope. So much is frustrating yet the closer you get to one of those records , the more excited you get. At least for me anyway. Arvin
-
@ Badger and Selfbowman.....How important is arrow design when shooting distance? from my research you need to be a "good" bowyer and a "great" arrowsmith to do good at the salt flats (distance). appreciate any comments....
DBar
The broadhead division is pretty straight forward. The bow is the most important as long as the archer does his part. The arrows fly pretty true at 450 grains. In the flight division I would divide it up into three eqal parts of performance. The archer needs to find the sweet spot and get the proper release and the arrow has to come out clean and straighten up fast. My best shots have all been from decent but not what I would call exceptional bows, all of my bows that have tested fast through a chrono have not done so well in regular flight.
-
I somehow doubt a pyramid would out do a mollegebet it a controlled test would be almost impossible.i could be wrong though?
Bring one to the salt flats . From experience that separates the old men from the boys. ;D
Arvin
sounds like we are comparing apples to oranges.my thought was hunting weight arrows at 20 yards!sorry,to many variable to be objective on this one
-
I have been staying out of this one to see where it would go (W. All I can say is that they are all good (SH) ;D
-
My reason for always making pyramid bows is that apart from the fact that they shoot very well, they are exponentially easier to make. I might miss my weight now and then, but have not failed to make a shootable bow more than one time in 50, if that.
This is particularly true of bows that have dips and bumps in the side view. Just keep the thickness even through the bumps and taper the sides evenly.
Tillering by thickness is much more an art and a matter of scraping or sanding, since a change in thickness changes the strength at that spot by the cube of the change in thickness. (making the limb 90% as thick as it was reduces the strength to about 73% of what it was.) So a little too much off can make a hinge in a hurry.
I can make a pyramid bow that's ready to shoot in half an hour. So since I'd rather be shooting than shaving wood, that's what I do.
I'm good with hunting the hard way. But not so much with tillering the hard way.
-
Been a while since this site had a nice, heated discussion. Its a good thing.
I'm with Marc.
-
Been a while since this site had a nice, heated discussion. Its a good thing.
I'm with Marc.
Show me your ugly pyramid bows. ;)
-
Never considered building one.
-
Verrrry interesting! I don't know enough to comment, but I like JW's point! Bows are like kids, some are not as pretty as others. beauty is in the eye of the beholder, and performance has to be proven.
Enjoyed reading all the points of view!
My level of expertise is zero, I'm still trying to get my bow bench built - I think the "garage troll" farted on my lumber. May need some unicorn farts to counter act them! Do have the stave marked and roughed out, thanks to a friend with a bandsaw,though
Hawkdancer
-
I have found that a well made bow whose front profile matches its tillered profile will usually shoot right around 170 with a 10 grain arrow drawn 28" and using a clean release. This is with no string follow. Most all of my bows regardless of style end up right around this number. My ELBs used to come in about 5fps lower but when I changed my technique a bit they came right up with the rest of them.
-
I think that is pattern that keeps emerging as I study what guys are making,, on any given day a great bow of good design with a good shooter and arrow could be the best,,,
-
I have found that a well made bow whose front profile matches its tillered profile will usually shoot right around 170 with a 10 grain arrow drawn 28" and using a clean release. This is with no string follow. Most all of my bows regardless of style end up right around this number.
Agreed. :)
-
this should be a sticky note,, (SH)
-
I guess this question is in the every thing else category but which front profile launches heavy arrows say 700 grain fastest ? I know the lighter mass bows in the mid & outers have a quick limb return speed but wondering if that apply's as the arrow weight rises ?
-
I would put my money on a elb.
-
Heavier arrow weights will tend to favor bows with high energy storage, could be a long elb, or a recurve or a reflexed mid length longbow, they all have pretty high energy storage. Arrow weights mean nothing if you are not talking grains per pound of draw weight. A 700 grain arrow in a 100# bow is a light arrow. I would prefer to see us use grains per pound when talking bow design and efficiency.
-
I have found that a well made bow whose front profile matches its tillered profile will usually shoot right around 170 with a 10 grain arrow drawn 28" and using a clean release. This is with no string follow. Most all of my bows regardless of style end up right around this number. My ELBs used to come in about 5fps lower but when I changed my technique a bit they came right up with the rest of them.
I would also agree. Most of mine come in the 160-165 range but four or five times when the gods were with me I got into the 170's. More good luck than good management but I'll take it anyway ;D ;D
-
According to some the Manchu style bow substantially beats an ELB in casting heavy arrows per draw weight.
http://www.manchuarchery.org/bows
-
Should have stated 50 lb. 28 draw for comparison .
-
A well made composite I'm sure would out perform most self bow designs all though it is in the every thing else catagory :laugh:
-
I have heard lots of theories on this,, heavier ggp shooting better from certain types of bows,, some say the wierd bow with 4 limbs,, Penobscot,, shoots heavier arrows better than normal self bows, but again,, I never see any real documentation,, I think since most of us have no need to shoot heavy arrow not much research or testing is done,,, I am the same way,, I feel like if the bow is shootig great with 10ggp,, I usually dont test it with heavy arrow,, I may hunt with a heavy arrow but just assume since the bow shoots the lighter arrow well,, it will shoot the heavy arrow well too,, and rarely chorongraph the heavy arrow,, I do hunt with a 700 grain arrow quite often,, from my 50 to 60# self bows,,they fly nice, ,just dont know how fast they are going,, I would guess that with most bows, the bow shooting the best at 10ggp,, will shoot the heavier arrow the best, ,but in archery things can be counter intuitive so I am staying open minded,, (SH)
-
Heavier arrow weights will tend to favor bows with high energy storage, could be a long elb, or a recurve or a reflexed mid length longbow, they all have pretty high energy storage. Arrow weights mean nothing if you are not talking grains per pound of draw weight. A 700 grain arrow in a 100# bow is a light arrow. I would prefer to see us use grains per pound when talking bow design and efficiency.
I think you probably mean bows with high energy storage and high efficiency.
Straight self bows with ideal tillering have theoretical efficiencies (see table below from Kooi & Bergman 1997, middle column, greek letter èta) that are only marginally bested by working recurves, and higher efficiencies than static recurves. Static recurves have less efficiency because until lift-off of the recurves, the recurves are just dead mass, also during the limb return.
Energy storage, however (provided by the static quality coefficient in the figure below, q), of straight self bows is rather low, and higher in recurves.
The excessive working recurve designed by Clarence Hickman in 1937 (https://www.flickr.com/photos/farflinger/5177069236/), has very high energy storage, but very low efficiency. As a result, it's only marginally faster than the working recurve. And probably shoots like a dog, because it has massive hand shock.
So all considered, the fastest bow design for heavy arrows (10 gpp) will be working recurves.
I remember some pics from Marc St Louis of bows like this. deflexed out of the fades, gently reflexed in the outer limbs (attached).
A lot like this bow from Alan Case https://www.flickr.com/photos/farflinger/5311429764/in/photostream/
If you scroll up and down in his flickr album, you see the same bow from different angles.
A Manchu bow might beat an ELB, but that's because it has a draw length of 36-38", not 32". Hence it has higher energy storage. Still it will have lower efficiency.
-
I do pretty much the same as you Brad I find my self lately liking heavier & heaver arrows for hunting I'm just curious on designs optimized for heavy arrows or if there is a difference in a pyramid bow shooting them as opposed to other designs !
-
The Manchu bow in the linked test was drawn 32"
-
Again I'm miffed,thought whe were talking about straight stave bows?kinda all over the map.
-
Can I get a clarification about these attributes?
Energy storage = clear what it is. But more means sending a heavy arrow faster?
Energy efficiency = what? Pulling for example 100# but getting 120# in the arrow? Or is it a smoother draw?
So adding a working recurve to a bow grants more efficiency and energy storage, but the tips need to be wider?
Adding a static recurve to a bow adds a lot of energy storage but reduces energy efficiency, the tipa need to be wider and may cause handshock easyer if not done right?
Wider tips means less energy for the arrow, that's why the benefits of the recurves are that small?
I know it's all theoretical.
Sry if I am annoying anybody with these questions. It's just not easy for a not english speaker that is still green behind his ears to get it right away.
The people at my archery club have no experience with stuff like that so you are my teachers here. )P(
-
dont worry its not clear to alot of us,, :)
-
Energy storage and efficiency are too different but important characteristics. Many of the things that increase energy storage will also reduce efficiency.
One area that Kooi and many others from that period got wrong was efficiency losses due to hysteresis. It doesn't have to be nearly as high as they indicated, almost all of it is induced by the bowyer during construction of the bow, proper techniques can greatly reduce it.
-
Badger, not trying to over simplify, but when you speak of high energy storage, is that pretty much indicated by the "fat FD curve"?
-
Willie, yep that's what it is. Just a fat FDC.
-
BTW, I have read you mention a few times about changing the way you tiller ELB's now, but I must have missed where you describe what those changes were, (or perhaps you haven't said). Have you been tillering them more elliptical?
-
Somewhat more elliptical but I also have the outer limbs pretty stiff, just showing very slight flex.
-
Thanks Steve, apparently those improvements could be considered to improve energy efficiency rather than energy storage? Not sure what you meant earlier how....
Many of the things that increase energy storage will also reduce efficiency.
Does, for instance, increasing reflex in a given design reduce efficiency or add hysteresis?
-
Thanks Steve, apparently those improvements could be considered to improve energy efficiency rather than energy storage? Not sure what you meant earlier how....
Many of the things that increase energy storage will also reduce efficiency.
Does, for instance, increasing reflex in a given design reduce efficiency or add hysteresis?
Willie, adding reflex will always increase the risk of adding set which increases hysteresis. Depending on the design it could increase efficiency. Lower string angles at brace will normally tend to boos efficiency. Reflexed bow will often also have lower string angles but not necessarily.
-
Again I'm miffed,thought whe were talking about straight stave bows?kinda all over the map.
Absolutely. Without parameters, defining better or best is impossible. I mean, would I pick a record holding flight bow to go on a river of no return Alaskan bush hunt? Would I pick an Agincourt replica longbow to sit in a tiny groundblind? Or funnier yet, carry Marc's fiberglass and plastic horse manure fantasy Penobscot abomination to an Agincourt reenactment!!!
The question, as it stands now, is only marginally more defined than just the question "what is best?" Someone out there loves chocolate pudding more than bows, so obviously chocolate pudding is best and bows just plain suck.
That being said, there is a post doctoral graduate study level of education going on in this thread, that is the only reason I follow this thread when it seems to show up annually! And it shows up annually, almost like clockwork.
Carry on.
-
John, actually the bows I have done best with in flight were exactly the kind you would take on an Alaskan bear hunt. They are low stressed and very reliable. 5 or 6 years ago this might not have been true. I could make my tips a bit thinner but I prefer to keep them beefy enough to use for other things besides flight.
-
Can I get a clarification about these attributes?
Energy storage = clear what it is. But more means sending a heavy arrow faster?
Energy efficiency = what? Pulling for example 100# but getting 120# in the arrow? Or is it a smoother draw?
Energy storage: the area below the force-draw curve. Actually, the area below the curve is the expended energy by the archer. A fat draw curve is convex. A bow that stacks has (near the end of the draw) a concave curve. Hence it stores less energy than expected for the draw weight.
Efficiency is how much of this energy is actually transferred upon the arrow. The arrow is not the only thing that needs to be moved, the limbs also need to return to their original position, which also requires energy. And there are energy losses within the bow, friction between wood fibers so to say. This is hysteresis. Dick Baugh explains it well here: http://www.primitiveways.com/Bow_and_Arrow_Efficiency.pdf and here http://www.primitiveways.com/Bow%20and%20Arrow%20Efficiency-2-16-11.pdf
To cut a long story short: with a 50# 28" draw and a straight force-draw curve, a 500 grain arrow could theoretically fly a touch over 200 fps, at 100% efficiency. In reality, most bows aren't 70% efficient, and shooting 170 fps is already very good.
Some designs store more energy, some are less efficient.
-
Actually, the area below the curve is the expended energy by the archer.
I'd never thought of it that way. That's a good one. :)
-
Can I get a clarification about these attributes?
Energy storage = clear what it is. But more means sending a heavy arrow faster?
Energy efficiency = what? Pulling for example 100# but getting 120# in the arrow? Or is it a smoother draw?
Energy storage: the area below the force-draw curve. Actually, the area below the curve is the expended energy by the archer. A fat draw curve is convex. A bow that stacks has (near the end of the draw) a concave curve. Hence it stores less energy than expected for the draw weight.
Good post and a good piece written by Dick Baugh. Energy storage is very straight forward, all about geometry while efficiency relies heavily on the bowyer. I did some work on the hysteresis issue a few years ago hoping to be able to pin it down and find out much more closely how much we actually dealing with. The test I came up with was based on a real simple concept but a pain to do on a regular basis. It simply establishes the virtual mass of the bow and then tracks how the virtual mass seems to change with lighter and heavier arrows. In reality the virtual mass should stay about the same as it does in synthetic material bows. This clearly illustrates that hysteresis is the culprit that causes the VM to change with the speed of the bow limbs. Hysteresis is time sensitive so it is easy to see how it is affected. Over straining the wood is the main cause of this and is very provable.
Efficiency is how much of this energy is actually transferred upon the arrow. The arrow is not the only thing that needs to be moved, the limbs also need to return to their original position, which also requires energy. And there are energy losses within the bow, friction between wood fibers so to say. This is hysteresis. Dick Baugh explains it well here: http://www.primitiveways.com/Bow_and_Arrow_Efficiency.pdf and here http://www.primitiveways.com/Bow%20and%20Arrow%20Efficiency-2-16-11.pdf
To cut a long story short: with a 50# 28" draw and a straight force-draw curve, a 500 grain arrow could theoretically fly a touch over 200 fps, at 100% efficiency. In reality, most bows aren't 70% efficient, and shooting 170 fps is already very good.
Some designs store more energy, some are less efficient.
-
Holy cow you guys really get technical! There’s no way I can wrap my head around a lot of the stuff discussed. I have a hard enough time making two limbs bend right. I do want to try a pyramid from a stave one day when I have a straight stave to work with.
-
Well I have been busy and so have you guys. :) it's been interesting for sure. Work has been in my way! These warm discussions bring us to try harder at perfecting our work. Proving someone else wrong! I don't know about everyone else it makes me work harder and I learn from it if my hardhead allows me to. Arvin