Primitive Archer
Main Discussion Area => Bows => Topic started by: Badger on August 24, 2016, 06:06:05 pm
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I think this is a good topic and I expect somewhat theoretical as I can't give prove of any of my own theories. That being said I feel the best tiller shape would be one that allowed the outer limbs to start moving first during the draw and allow the bend to progress inward during the drawing process until the last few inches where the near handle wood starts to bend. Most of us including myself are usually tillering for a desired shape so to some degree we ignore the progression of the bend. An Elliptical tiller will usually facilitate this pretty well. Circular tillers I feel are the biggest cause of handshock. Having only the outer limbs bending as the string returns to brace during the shot lowers the momentum of the limbs and gives the arrow a lot better control over the limb mass. The arrow needs to slow the tips down to extract the energy or else it will be lost to vibration.
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hmmm let me think a minute,, :) nice topic
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I'm still trying to get my head around the definition of the word tiller ???
DBar
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I don't think there is a "best tiller shape"... just like there isn't a best fly rod taper or action for all fly casting.
I don't tiller for a desired shape, per se. That's a mistake I see some, especially less experienced folks make. They try to tiller all of their bows to the 'desired shape' in their mind's eye, regardless of the vagaries of the stave or blank's profile. Some even try to bring pronounced d/r or reflexed bows to the same full drawn shape as a straight standing bow, and assume all those limbs are working the same because they look the same at full draw.... nope.
I like your thoughts on bend progression, and that's how I tiller most of mine, shape notwithstanding.
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I look at this in terms of cars.
You have torque and horsepower. Your outter limbs are your horse power and inner your torque. Proof? All tje strain of a bow is focused in the handle. It is the highest concentration of potential energy. As you move outwards you get more kenetic energy simply because you have more movement. Hp is a measure of that.
So, on take off, you want high torque, and at top end is where your want all your hp. A bit redundant but making my point.
So you release your arrow, first thing you want to move is your inner limbs, letting all its torque into the arrow, and as tje arrow speeds up you want that energy to be coming from close to the tips. As the arrow releases the string you should have nothing moving except the tips. If the entire limb is still moving, a consequence of the inner limbs still having energy, the hand shock will be bad.
As common sense would follow the first thing to move on the draw would be the last on the release. Tips should move first on draw.
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Great topic. and one I have spent some time ruminating over. I like the idea Sleek put forward. Good analogy. As to whether getting the bend to run from outboard - inward...is that the ideal? I ask the question because I am unsure. That is to some degree is how I tiller most of mine, without giving it much thought during the process. I have been threatening to build an Elmer Wilcox Duoflex for years now. I have toyed with it on several staves and cant get the balance anywhere near right. Stability issues yadda yadda, so I've yet to get close. If you look at the FD curves on them as reported, they are pretty amazing for a wood bow. They are built quite to the opposite. Thick inner limbs bend first before the working recurves open up at the end of the draw. I believe Marc built one if not more some years back.
I think it was actually Russ Willcox.
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Interesting topic. I like your explanation, Sleek.
Now ya'll got my wheels turnin' in all kind of directions. :o
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Working recurves to me are an example of what a turbo would do. Dont think of them as tips, but as a small high power bow at the tip of another.
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Interesting topic. I like your explanation, Sleek.
Now ya'll got my wheels turnin' in all kind of directions. :o
Dont over stear, keep your tach inside the red, and stay out of the wall.
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So regarding kinetic energy wouldn't static limb tips like the mollie be the "fastest" design?
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I will probably remain in the entire limb working verses the Molly for better cast. Dead wood is dead wood. That being said I am sure there are some who think differently. Also if you have shock you probably also loose cast. A bow with lots of reflex does sometimes have more shock but has good cast. But at some point there will be a trade off. Arvin
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I would think that energy is still being transferred through the static limb tips even if they are not working. As I understand it, the molle's tips work the same as a simple lever.
Has anyone ever slung an apple impaled on a stick? (Showin' age and upbringin' here! :-X) The stick may not flex but the mechanical advantage provided by the stick as a lever allows a more efficient transfer of energy into the thrown apple.
The movement/transfer of energy outward from the handle to the limb tips seems much like the movement of a wave. Wave dynamics may not apply here but it helps me visualize how a stick and string flings an arrow.
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I keep the last 10" or so stiff on most bows, it improves the stored energy. As for shock, the only bows I have ever gotten shock on were bows I used the gizmo on so I could rush and get done.Elliptical tillers will seldom ever be shocky.
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Steve
I have often thought that the best tiller shape might be as you describe. Are you thinking it might be best because hopefully the limb will unwind in a reverse manner upon loosing?
If so, consider a bow limb that is equally strained through out its length. this limb also has the same thickness throughout, so that every part of the limb that has equal width, does equal work. Does tapering the width, (making a pyramid bow) give the progression of bend you desire?
I think when you are tillering for shape with a pyramid bow you are tillering for progressive bend, but how it unbends with arrows of different weights is the bigger question.
willie
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Probably because a circle tiller , the entire limb moves at the same time and stops at the same time. An elliptical tiller allows the tips, the lightest part of the bow, to be the last thing moving. Really that reinforces your suspicuons and my point above. Tips bend first, inner limb last.
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I would expect it to all move at their own constant rate (ie with elliptical tiller, tips would start moving more than towards the handle, but handle also bends, just less, and all at the same rate until full draw) but apparently not - I saw a full draw picture of a heavy warbow draw partially, and it looked like all the bend was close to the handle... apparently because it wasn't at full draw? I would expect the bending at the handle to get worse with more draw or something. Maybe the leverage of the whole thing changes as the bow is drawn and gets bent? Should just look at videos of warbows with whippy-ish/elliptical tillers getting pulled...
Then there's all the weird frequency harmony stuff that I can't even. Bowstrings look ridiculous upon release on slow motion videos..
so inefficient energy transfer to the arrow makes handshock worse, but would it be possible to dry loose a bow with massive tips (somehow not breaking it) without feeling handshock if the limbs were perfectly timed?
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I suspect the limbs will come to rest in the same fashion they are bent during draw no matter what the design is . In my opinion one consistent form of diminishing mass will give the best performance. If the mass is not working its dead mass. You are depending on energy from another source such as in a catapult with a stiff limb . You have to counter weight a catapult if you don't want it to rock and bounce on release. This is the same as shock in a bow. But I don't know everything for sure. Lol Arvin
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I think this is a good topic and I expect somewhat theoretical as I can't give prove of any of my own theories. That being said I feel the best tiller shape would be one that allowed the outer limbs to start moving first during the draw and allow the bend to progress inward during the drawing process until the last few inches where the near handle wood starts to bend. Most of us including myself are usually tillering for a desired shape so to some degree we ignore the progression of the bend. An Elliptical tiller will usually facilitate this pretty well. Circular tillers I feel are the biggest cause of handshock. Having only the outer limbs bending as the string returns to brace during the shot lowers the momentum of the limbs and gives the arrow a lot better control over the limb mass. The arrow needs to slow the tips down to extract the energy or else it will be lost to vibration.
I don't think it's possible to get that kind of tiller Steve unless you re-design the limbs to have more working wood in the outer limbs than the inner limbs and that would defeat the whole purpose.
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Marc, I dont understand?
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The thought is good. But, If we think of different types of bows open up at different times. Horn bows, Magyars, Recurves, Static recurves and finally a straight limbed bow would all have the tips moving at different times. As well as all of these showing a difference in performance.
The turbo analogy actually works out well for working recurves. You get the initial lag in the draw, and have the up front power on release.
So, a working recurve opens last, and closes first. So think of it in terms of what flight bows shoot the best, straight limbs that have the tips moving last, or working recurves that have the tips moving first.
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I keep the last 10" or so stiff on most bows, it improves the stored energy. As for shock, the only bows I have ever gotten shock on were bows I used the gizmo on so I could rush and get done.Elliptical tillers will seldom ever be shocky.
Steve could you post a f/d pic of a bow that you describe here?
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Most of my straight bows also have 10" of stiff tip. I always plan on 7-8", but it fades into the working limb and ends up closer to 10". I like it, cant speak for everybody.
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The thought is good. But, If we think of different types of bows open up at different times. Horn bows, Magyars, Recurves, Static recurves and finally a straight limbed bow would all have the tips moving at different times. As well as all of these showing a difference in performance.
The turbo analogy actually works out well for working recurves. You get the initial lag in the draw, and have the up front power on release.
So, a working recurve opens last, and closes first. So think of it in terms of what flight bows shoot the best, straight limbs that have the tips moving last, or working recurves that have the tips moving first.
Jojo, flight bows are like rice butners. All horsepower and no torque.
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Jojo, flight bows are like rice butners. All horsepower and no torque.
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Kinda funny, Ken Blocks Ford Focus is 600 HP and 650 Ft\LB of torque. 0-60 in 2 seconds flat.
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I think this is a good topic and I expect somewhat theoretical as I can't give prove of any of my own theories. That being said I feel the best tiller shape would be one that allowed the outer limbs to start moving first during the draw and allow the bend to progress inward during the drawing process until the last few inches where the near handle wood starts to bend. Most of us including myself are usually tillering for a desired shape so to some degree we ignore the progression of the bend. An Elliptical tiller will usually facilitate this pretty well. Circular tillers I feel are the biggest cause of handshock. Having only the outer limbs bending as the string returns to brace during the shot lowers the momentum of the limbs and gives the arrow a lot better control over the limb mass. The arrow needs to slow the tips down to extract the energy or else it will be lost to vibration.
I don't think it's possible to get that kind of tiller Steve unless you re-design the limbs to have more working wood in the outer limbs than the inner limbs and that would defeat the whole purpose.
When I say outer limbs I am actually meaning outer mid limb, I keep the outer limbs almost stiff on most bows. I like to use the least amount of working limb I can get away with, but 90% of the time we still need most of the limb to avoid taking set. I asked a freind one time to build a glass bow using stiff outer limbs but fairly extreme tapers in the working area. This was on an r/d longbow. We used a reverse wedge in the tips and a power wedge near the fades with .008 tapers and the bow was extremely quick with 10 grain per pound arrows but only lasted for a few hundred shots. About 4" of reflex behind the back. It seemed to open up as I described, not a pretty tiller shape to look at.
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Jojo, flight bows are like rice butners. All horsepower and no torque.
Kinda funny, Ken Blocks Ford Focus is 600 HP and 650 Ft\LB of torque. 0-60 in 2 seconds flat.
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Ok fine, my point is still the same.
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Been making bows with 8 to 10 inches of stiff tips for some time now.Call em lever bows.Narrowed down and light as possible.Small handles[down to 6"] used with hardly any hand shock tell me it works.Reflexed or not.
There's the matter of mass weight distribution on these limbs.To get an extreme working recurve to hold up properly you need enough wood to handle it.Negating a bit of the extra energy from it as far as speed given to the arrow the way I see it.Not saying it's a bad design but just saying they are more touchy to tiller to get right.
Mild R/D profiles are the cats meow for bows though.Balancing the reflex given to not need so much wood to handle the strain.
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Badger...I have a friend who makes his own FG bows[he's made self bows too] and has adopted the stiffer tips design I shoot.Don't exactly understand all of the reverse wedges etc. used to get the job done but he likes the bow better and it is faster.Not so much reflex though as you described on his.Maybe a couple inches at the very most.
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I'm a little slow. I can't wrap my head around an elliptical tiller with 10" stiff tips.
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Badger...I have a friend who makes his own FG bows[he's made self bows too] and has adopted the stiffer tips design I shoot.Don't exactly understand all of the reverse wedges etc. used to get the job done but he likes the bow better and it is faster.Not so much reflex though as you described on his.Maybe a couple inches at the very most.
The r/d bows get squirely once you get past about 2" reflex. The limbs will rock back and forth at brace. The soulution for that is less working limb. Actually less working limb solves a whole plethora of problems but it brings a few of its own, mostly just too much strain.
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I'm a little slow. I can't wrap my head around an elliptical tiller with 10" stiff tips.
A bow has to have an amount of stiff tips to form an ellipse at draw and not be a round shape. The length of the stiff portion only changes the shape of the ellipse, but its still elliptical. Hope that makes sense.
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So the ellipse is only reflected in the working portion and not the whole limb? Am I getting it?
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Nope, the whole limb. The working portion is nearly round on most bows for around 16" or so, but as it stiffens at the tips it straightens and that stops it from being round and makes it ellipse in shape. Ellipse is basically half an oval.
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Not to be argumentative but how can an ellipse have a straight section?
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That's what makes it an ellipse, if it was all round it would be round, not ellipse. Think of it this way Jon, split a tear drop shape in half the long way and you have an ellipse shaped bow limb.
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I am sure now I'm dizzy. Still looking though. :-[ ;D Arvin
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Badger...I have a friend who makes his own FG bows[he's made self bows too] and has adopted the stiffer tips design I shoot.Don't exactly understand all of the reverse wedges etc. used to get the job done but he likes the bow better and it is faster.Not so much reflex though as you described on his.Maybe a couple inches at the very most.
The r/d bows get squirely once you get past about 2" reflex. The limbs will rock back and forth at brace. The soulution for that is less working limb. Actually less working limb solves a whole plethora of problems but it brings a few of its own, mostly just too much strain.
Yes his bows like that we noticed had less working limb.On a 64" R/D bow.Sort of like horn bows in a way.Not as short of bow but with FG limbs weighing less mass wise it is working for him.Glue ups on that had to be perfect for it to hold up.
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Great topic. and one I have spent some time ruminating over. I like the idea Sleek put forward. Good analogy. As to whether getting the bend to run from outboard - inward...is that the ideal? I ask the question because I am unsure. That is to some degree is how I tiller most of mine, without giving it much thought during the process. I have been threatening to build an Elmer Wilcox Duoflex for years now. I have toyed with it on several staves and cant get the balance anywhere near right. Stability issues yadda yadda, so I've yet to get close. If you look at the FD curves on them as reported, they are pretty amazing for a wood bow. They are built quite to the opposite. Thick inner limbs bend first before the working recurves open up at the end of the draw. I believe Marc built one if not more some years back.
I think it was actually Russ Willcox.
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SLIMBOB.....I think your right with Elmers's bows there.They have to be shorter limbs though to negate the mass weight of the working recurves.
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JonW....Anytime I make a what I'm calling a stiff levered bow eliptically tillered my working limbs are for the most part parallel width.The taper is in thickness along it.
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Ed I guess that is what I'm saying. The "working" section is elliptically tillered not the whole limb. Maybe "stiff" tips and "non working" are where I'm getting hung up. :-[
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Yes could be.The tips are just along for the ride so I try to get them as light as I dare.Reducing string angle in the process too.The more I make bows the farther I want to push the wood.So I've gotten out of characterish type bows looking for cleaner wood lately,but and a big BUT if I could find an osage stave around here that has the nice snake to it[like Pappys' bow] I would cherish that paticular bow making it in a within reason type build.
Tillering affecting performance.....Personally I think it can make a difference on how heavy of arrows a person wants to shoot too.Lighter arrows where the outside parts of limb work more and heavier arrows where the inside parts of the limb work more.
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Marc, I dont understand?
If you don't have more working wood in the outer limbs then the bow will take a lot of set from being tillered like that and the extra mass won't help either especially shooting flight arrows
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All I know is when I tillers tha bows good they shoots good thanks bye