Primitive Archer
Main Discussion Area => Bows => Topic started by: willie on September 23, 2016, 03:02:25 pm
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In another thread, a discussion has me asking why I would want my tiller shape to be more circular or elliptical. Or put another way, why would I choose to make a parallel limb bow with a thickness taper, over a pyramid limb bow with a constant thickness limb.
Does one limb design shoot some kinds of arrows better than others? I am wondering which would be better for heavy arrows, and which would be better for lighter arrows. and why it is so. Does the tiller shape itself (circular or elliptical) make the difference? Or is tiller shape secondary to why one kind of limb works better for some arrows?
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Pretty much a toss up for a straight limbed bow. Pyramid is a great design and simple. I prefer what I call a semi pyramid or semi parallel. I build the bow with parallel limbs but refine the side tapers as I near completion of tiller. I try to remove mass from the outer and mid limbs when I can spare it. The parallel limb take better to the r/d designs we see so much of now I feel although I have seen plenty of pyramids that were r/d as well.
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I build a hybrid of parallel and pyramid. The first 7 inches after the fades is parallel the goes to pyramid to the tips. Then I work on narrowing the last 7 inches of the tips down to something of a eiffel tower profile. Not all i build are like that but most are.
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Looking at the extreme end of the spectrum, there are examples of highly whip-tillered yew target bows made to shoot very light cedar target arrows, and then there are bend through the handle longbows of the tropics that are made to shoot heavy long arrows. I see it as the mass in the limb moving forward relating to the mass of the arrow being shot, though it might not be that simple.
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I think you got it 100%... for whatever my opinion is worth on that...
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Really I personally think the goal would be is to get the energy storage of the limbs to be on the inner two thirds of the bow tillering well to take as little set as possible[so parallel limbs go there] and the outer third[narrowed but thickened] to be lighter but stiffer.Not doing much work at that position of the limbs so it's not stressed and retaining any reflex put to it.A bow like that will shoot any kind of arrow fast I feel.The full draw look on a bow like that will look more elipse if not reflexed much.Working almost right into the fades.Refining it to be a more streamlined lever type bow with the transition to the levers.It's the way I've been building bows for quite some time now.If it was reflexed it could be called a reflexed lever bow.These type bows don't conform to any type of tradition or culture but shoot very well for me.They conform to Tim Bakers' way of thinking.Carsons' point I agree with as a whole too.
So your gonna have to find through making and testing what you like and what works for you.
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Looking at the extreme end of the spectrum, there are examples ......
I like Carsons idea of looking at the extreme ends of the spectrum, but perhaps there are examples of both styles that shoot light arrows well? Steve mentions a toss-up, and I presume that is an opinion formed from his observations of winning shots in light arrow flight shooting?
As for the opposite extreme, are there events that shoot heavy grain per pound arrows? What do the shooters prefer?
I find it hard to draw conclusions from the tropical bows that shoot long heavy arrows, their low strain design bows might just be the best they can do with their humidity problems. Same with supposing "what might have been" with the warbows of hundreds of years ago.
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The only event I know of is just hunting as far as shooting heavy arrows go.The mantra Tim continually speaks of pretty much holds true for efficient type bows and that's where it's at.Although there are plenty of master type bowyres on here that do it with different styles of bows.
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Willie, I compete with 500 grain broadhead arrows at the flight shoots which are hunting weight arrows. The only real difference with the light flight arrow bows is that they tend to be slightly shorter and we might pay more attention to taking mass out of the outer limbs. My longest light arrow shots have always been in practice and they were always with regular hunting bows as opposed to the lighter flight arrow bows.
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Really I personally think the goal would be is to get the energy storage of the limbs to be on the inner two thirds of the bow tillering well to take as little set as possible[so parallel limbs go there] and the outer third[narrowed but thickened] to be lighter but stiffer.Not doing much work at that position of the limbs so it's not stressed and retaining any reflex put to it.A bow like that will shoot any kind of arrow fast I feel.The full draw look on a bow like that will look more elipse if not reflexed much.Working almost right into the fades.Refining it to be a more streamlined lever type bow with the transition to the levers.It's the way I've been building bows for quite some time now.If it was reflexed it could be called a reflexed lever bow.These type bows don't conform to any type of tradition or culture but shoot very well for me.They conform to Tim Bakers' way of thinking.Carsons' point I agree with as a whole too.
So your gonna have to find through making and testing what you like and what works for you.
I don't like set anywhere on a bow. I like to think of a bow being 3 seperate parts, handle, springs and levers. The least amount of spring you can get away with the better because it causes problems in every other aspect of the bow besides supplying the raw power. If the levers are designed right they give the leverage back to the arrow so the arrow can slow down the arms as it is coming back to brace. The limbs are not supposed to slam home as is often said.
If you are to compare bows built right here on PA to the bows shot at the first mojam, these bows today would far exceed the speed they measured then. Your best references are looking at the present day bows. The bow that one that contest would be ok by todays standards but nothing special.
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Thanks Steve. Flight shooting sounds like fun, and there must be a lot more involved than design.
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From a scientific point of view a given piece of wood can bend so far without taking set. Make it thinner - it can bend further. Make it thicker - it can't bend as far.
No set inner limb, a fraction midlimb and the rest out to the tips.
you can work it all out from that ;)
A pyramid (theoretically!) should have automatic even strain as the wood will be the same thickness, therefore should all be bending the same amount, same bend same strain. Parallel width limbs need some thickness taper and therefore require a little more skill to distribute the stress evenly.
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Then once you have all that sorted you can start to make bows that will shoot light arrows best (light,fast moving limbs) and bows that will shoot heavy arrows best (elb's long,slower moving limbs).
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Then once you have all that sorted you can start to make bows that will shoot light arrows best (light,fast moving limbs) and bows that will shoot heavy arrows best (elb's long,slower moving limbs).
Mike one thing funny about shooting the light arrows is that none of the very fast flight bows I have built so far have really gotten any great distance because of arrow flight and release problems. Overall little 62" pyramid style bows with a little reflex and real light thin out limbs seem to score better even though they don't have quite the speed. Most of the records set are set using simple designs.
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Most of the records set are set using simple designs.
Thanks again Steve. Something to contemplate
and bows that will shoot heavy arrows best (elb's long,slower moving limbs)
Mike, if this is your experience, please take a moment and say why you think it's so. Is it because of the tiller profile, or other reasons ?
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Tiller profile is dictated by the width profile of the limbs. What I said above about set is really all there is to making nicely strained bows.
The wood will always tell you if you have done a good job of tillering a bow. You just have to watch set as it starts to show up. I like to trace the profile of a bow before bending it at all so that I have a definite reference of where exactly along the limbs the set is. Also when I say set I'm talking about the first hints of set not 2 inches! Only tiny amounts but they tell you with no second guessing where the strain is highest.
Elb's and heavy arrows go hand in hand not because of tiller profile per se but because the limbs are long and therefore heavier and slower moving than a shorter bows limbs and need a long heavy arrow for decent efficiency.
Badger I know what you mean. Although my fastest bow yet seems to be doing well with the light arrows (split cane). 75# ish and 200 - 240 grain arrows are going around 350 - 400yds. It is doing 250fps with 5gpp.
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A few weeks ago I built an elb for Josef to flight shoot. He got one world record in the simple comp broadhead class but missed the ELB flight record. He told me that he was hitting over 440 yards regularly durring his practice session but only scored 380 something yards in the official shoot. This bow is 90# @26" and is 66" long.
Mike your bow is doing very well and would be a cood candidate fo a world record. Especially in the new 70 class.
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Yes I've noticed too the standards have definitely been raised from the first Mojam.Monitoring set makes the difference.Many very good bow makers on here.
To me now though a 500 grain arrow is not that heavy really.I'm sure it's because I don't flight shoot at all and am not familiar with the rules etc. account for that.What weight arrow did the 90# bow shoot?
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willie, bows with parallel limbs or pyramid limbs will shoot just as well provided they are tillered well.
What does tillered well mean?
I and others have outlined that in the previous thread so that ship, seemingly, has sailed? But read on.
After 35 years of teaching and answering questions I sense that there is another underlying question that's bothering you.
I just can't get a handle on what it is.
If you start out with parallel limbs tiller elliptically. If you start out with pyramid limbs go for a circular tiller. Its personal preference. This is so set is kept to a minimum.
I prefer parallel limbs; with pyramids I have a hard time getting the circular tiller that is needed.
Like Steve I often tiller both from the belly and the sides even on parallel limbed bows..
For example, if I start out too wide for the strength of the wood the stave stops responding to belly wood removal. So to keep the stave from getting to thin I begin to narrow it. My parallel limbed bow ends up slightly pyramid.
We are creating an artificial dichotomy for teaching purposes.
Just make bows and let the wood dictate how it wants to be.
Jawge
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Beadman, all broadhead bows shoot 500 grains regardless of weight. I shoot in the 50# class so for me I am shooting 10 grains per pound. A 100# bow is only shooting 5 grains per pound. In regular flight you can shoot any weight arrow you want.
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This has been a good post and I have enjoyed reading all the opinions. I think most everybody has touched on an important idea or 2. For me, set tells the story. Keeping that to a minimum starts with the proper design for the bow you want. Part of that is wrapped up in front profile. I personally like the bow Ed mentioned. Semi parallel to mid limb, so elliptical tiller (low set inner limbs), then a nice taper to the lever like reflexed tips. Monitor set as Mike mentioned all through out the build and keep it to a minimum while keeping the mid (pyramid) to outer limbs (lever) as light as possible. Finesse the tiller from start to finish and get it as close to ideal as possible from step one, all the way to the finish line.
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about the first Mojam standards,, well,, most the bows were shooting b 50,, and thick hunting strings,,
the bows werent really set up for speed,,
I think the bows would have shot quite a bit faster with just a bit of fine tuning
I know the bow I shot had a 16 strand string and silencers,, well anyway,,
I think if with Badgers release and some fast flight or more linen,( I think Tim shot the only linen string) the results would have been closer to what we see today,, just my thoughts,, :)
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Brad, I think you are probably right. Tim gave me a list of all the results and I was really surprised at how low most of them were. B 50 and linen are actuall pretty close in speed even though linen is non stretch, string weight seems to be the biggest factor. I found with fast flight for every 1 strands I remove I pick up about 3/4 of a ft per second in speed. One big factor in performance was the older bows tended to be wide and flatter and bend all through the limb. Thse loose quite a bit to vibration. If you go back about 70 years the bows being made then would be on a par with the bows being made now. Those guys were making some really nice osage and yew bows ithe 1940's and 50's. Thin outer stiff limbs, a little reflex. Great shooters.
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wow thats cool, that the older bows shot that well,, nice to know,,I guess when the figerglass came out ,,some of the wood making got a little lost,,
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I sense that there is another underlying question
yes George, there is something that I am trying to understand better. I will try to explain.
with all due respect to Mike, whom I quote below, I think that some of the "dictations" need qualification.
Tiller profile is dictated by the width profile of the limbs.
This is certainly true if a constant thickness taper is assumed. It is the physics or beam theory that he mentioned earlier.
Let's for the sake of a thought experiment, consider a pyramid bow that is almost tillered out. It has the desired circular profile that is considered correct for the width shape, and the assumed constant thickness. If I then thin the thickness of the mid to outer limbs, they will come around more into an elliptical shape considered "proper" for the straight limbed bow. Have I created set anywhere by doing this?
Or consider the opposite width profile, a straight limbed bow with the preferred stiffer inner limb. Will thinning that inner limb to make the overall appearance more circular create set? Only if I go too far and create a hinge. For the sake of examining tiller profiles, Lets assume that we can tiller either limb to any profile we want
The purpose of this "experiment" is to try to separate the out the reasons or (at least, suspicions), of whether one kind of tiller profile might outperform the other. There are two things that come to mind. The first being the mass distribution of the limb.
not because of tiller profile per se but because the limbs are long and therefore heavier and slower moving
Mike states the case for heavy arrows well, and others have mentioned similar logic. Heavy arrows are a joy to shoot, taming the vibrations of the limbs, and extracting efficiency from the bow. They can also be uninteresting.
Considering the case for light G.P.P arrows seems a bit trickier. Ignoring the weight distribution "dictated" by the back shape. (I know, that's a co-premise to what Mike actually said), Is there anything inherent in tiller shape it'self, or the way the limb "unwinds" and returns it's energy to the arrow, that can be ascertained? Performance of light arrows is not just raw speed, as Steve frequently points out, and creating a "sweet shooting" bow while shooting light arrows is of interest. Steves observations about simpler limb designs often out shooting more complex designs are keenly noted.
I do not actually expect that anyone can answer these questions definitively with facts and numbers, but we all have our intuitive ideas formed from experience, and I appreciate all the comments, ideas and even speculations of all.
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Willie. I see a small problem with your question in the first question you posed, the pyramid that was retillered to give it an elliptical shape. It might not take set because you have lowered the draw weight. If however the first bow was 50 lbs at 28 inches, circular, and you built the identical bow elliptical in shape also 50 lbs at 28 inches, then yes, I believe it would take more set mid limb. If you instead kept the mid limbs wider, they would not take set. Getting them wider would be a function of lessening the width taper to some degree, perhaps as much as parallel.
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As to the second theoretical bow, parallel retillered to a circular shape. Your mid limbs are heavier than ideal as they are wider than needed.
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Slim
yes, of course both hypothetical bows have excess mass that could be eliminated with the "proper" tiller, but as I hoped to point out in my last paragraph, raw speed, does not always indicate down range performance. The arrow has to leave the bow as best as it can. A sweet shooting bow, to to me, anyways, is one that seems to plunk the arrows in the same spot consistently, and I have found that arrow tuning and string/nockpoint tuning can only go so far.
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" Let's for the sake of a thought experiment, consider a pyramid bow that is almost tillered out. It has the desired circular profile that is considered correct for the width shape, and the assumed constant thickness. If I then thin the thickness of the mid to outer limbs, they will come around more into an elliptical shape considered "proper" for the straight limbed bow. Have I created set anywhere by doing this?"
Yes, you more than likely will get too much bending mid limb on where the limb is at its narrowest.
Jawge
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George you are exactly right, you have not created more set. Most everyone I know slightly tapers pyramid bows.
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Ahhhh yes I can vouch for that with bows I made the first couple of years.Taking too much set mostly mid a little outer till I had to refine the wood removal there to hold up better or putting more reflex there to hold up better.Choosing to narrow and thicken there to reduce mass.
I wanted to say now something about limb tip profile[the last 8 to 10"] affecting brace and full draw look.Maybe this is a given here or moot.Narrower and thicker there will bend less to affect that.Flat,wide and thinner it bends more.When someone posts a bow that is streamilned as I've heard Badger say,you can see it's a more than probably a good sweet performer from the top profile seems like especially if it's shown at rest from full draw.
For the archer that wants performance speed is all that's important.For the hunter I would say arrow placement is all that's important.Why not do both heh???
As for consistency of arrow placement in the target your right that is a group effort type thing.The handle/string nocking point/arrow spine.The way a person holds the bow.Sweet shooting to me is no stack/no handshock.Even along the whole way of draw so my bow arm does not deviate from position I want it at.
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Wiilie - you haven't 'created' set because humans cannot create things....;)
Joking aside on the first bow with a circular tiller which is then made elliptical - no extra set because you have thinned the limb therefore it can take the extra bend. However your inner limbs aren't now doing their share of the work and the now overly worked outer limbs are thinner.....a thinner limb doesn't have the same return speed as a thicker limb. So by doing this to a pyramid bow you have lowered energy storage and made it less efficient. Not my idea of ideal!
Again you may not induce anymore set by making a parallel limbed bow have too much bend in the inner limbs but again the same principle above applies and this time you will also have handshock added into the mix. again not exactly ideal.
You may assume that you can make any front profile have any tiller and indeed you can if you really want but that is not correct for the materials we are working with.
It is not me that is making all this up you know and I don't for one minute suggest that these are my 'original' ideas it is backed by plain old facts and common sense! The theory for all this stuff has been worked out many years ago - read the book 'Archery the Technical Side'. It explains all this in detail and gives the equations to work it all out mathematically. If you want me to repeat what is already out there I could 'back up' what I have already said with numbers but.....I guess most people wouldn't be too interested in the proofs.
When you start talking about light flight arrows the same principles apply but most people don't shoot flight arrows and are therefore generally making bows to shoot 'normal' weight arrows. Clean arrow flight has little to do with tiller profile. Clean arrow flight has many variables not linked to the shape of the bows limbs.....
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Mike-
You may assume that you can make any front profile have any tiller and indeed you can if you really want but that is not correct
I agree entirely, if of course by "correct" you mean to say, getting the most efficiency or speed out of the arrow.
I started this thread with hopes to look into some of the less tangible qualities of arrow launching, a bow may have. Qualities that one may wish to have, even if giving up a few FPS. I cannot help to think of a few bows in the past that were just a joy to shoot, even if they were not the fastest. Of course my "thought experiment" bows were not meant to be efficient, but were examples of what might be done, if one so desired
Thanks for your input, your assertion that "Clean arrow flight has little to do with tiller profile." is well received. Perhaps a thread on "what makes for clean arrow flight" would be a good thread for another day.
Just a question if I may ask,
.....a thinner limb doesn't have the same return speed as a thicker limb.
those of us who find performance defined as "FPS", don't have to be reminded that the fiberglass guys have us beat with their high modulus materials. Do thinner limbs have anything to do with that performance gain? Or am I taking your statement out of context?
willie
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I don't think thickness should receive any consideration. We have energy storage and efficiency. You make the bow as thin as it takes to accomplish whatever your design calls for without damaging the wood. A thicker limb will usually have more working limb which does not always contribute to high efficiency.
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Regarding your question Willie, I am pretty certain I am referencing Badger here when I say that the problem with thin limbs is they tend to deform on release. Its not just a pretty lottle arch back as when you slowly let down. The limb actually starts to set up a wave pattern, though i could be describing wrong. Point is, thin limbs tend to distort, or do distort, on release making a negative impact on efficiency. But I believe that can be countered with shorter limbs, which allows then to resist distortion better. There may be a width to thickness to length formula to be made.
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Sleek
you describe the sort of limb motions that I wonder about sometimes. I appreciate your bring it to the discussion. Today as I was driving home from work, I thought about another observation made by Badger earlier. About "Most of the records set are set using simple designs."
Seems like some of the more radical designs focus on high early draw weight as a goal. High early draw weight certainty makes for a fat F/D curve, and theoretically would seem to offer the potential for better arrow performance.
I have to wonder if high early weight makes it harder for the limbs to return to brace at the same time because of that distortion. Of course that assumes a well timed limb is supposed to return at the same time as the other, and nothing else causes the string to impart any unwanted forces to the arrow. Too much pent up energy at brace height might make for a bow that is harder to tune or keep in tune from shot to shot.
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The old flight records dispute your radical design being less optimum theory Seems there would be less distortion in a radical design because more limb is eliminated from joining the wave.
Don't get Steve started on timing and limb return. ;D
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PatM, I was only referring to arrow flight when I made that statement. I have bows that will shoot up to 300 fps but I can't seem to get the distance from them that I get from much slower bows.If tuned properly and properly matched to an arrow of course a faster bow will shoot further. Just using shorter arrows makes a huge distance difference but they are illegal in the primitive classes.
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seems like the arrow is a fault with the 300 fps bow,,not the bow,, am I oversimplifying,,??
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seems like the arrow is a fault with the 300 fps bow,,not the bow,, am I oversimplifying,,??
Brad, really difficult to get good arrow flight from a 23" arrow below about 180 grains. Once in a while you get lucky but the slightest sideways motion or tailwagging coming out of the bow kills the arrow. It might straighten right out within 20 yard or less but all the power is already gone. If you can see you arrow you can almost be sure you didn't get a good shot off. Nocking point and release have to be right on.
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Wow, 300 fps is pretty quick. What design are you getting that from steve?
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Wow, 300 fps is pretty quick. What design are you getting that from steve?
Just a short recurve about 52" long but that is shooting very light arrows about 130 grains, not fast at all with a 500 grain arrow.