Primitive Archer
Main Discussion Area => Bows => Topic started by: Fox on February 21, 2021, 10:00:20 pm
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At what length bow for say a 27” draw does stacking and string angle start to be a problem on Flat bows?
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R/D and recurves can pull farther than a straight limb bow before stacking because the string angle.
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Right... I should refraze my question, so just talking about flat bows.. would a 56" flat bow drawing 27" be uncomfortable? or how about a 54" I would imagine that would stack pretty bad... would the limit be 58" for it to still be manageable? or 60"?? 64"
where would you say the point to where you would need to recurve or make a r/d?
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I think uncomfortable is kind of relative,, I have a 54 inch flat bow that will shoot nice at 27,, but for someone else maybe they dont like it,, I dont mind a little stack at the end of the draw,, i think its more what you used to,, make one and try it,, and see what you think, thats what I did,,, (-S
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I do suppose thats true brad.. I can't just get y'all to tell me whats going to be comfortable. darn guess I will have to make one ;D
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64" for me.
Longer bows have lots of advantages over one too short.
58 - 60" would stack.
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Brad is right, it is what you are used to. I have short and long bows that I like to shoot. My favorite flat bows to shoot all day are always 64-66” but I don’t shy away from the short bows. Longer bows are just smoother to draw and easier on the fingers for me over a long shooting session.
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I like 60-64 for my 26 inch draw, flipping the tips a bit will help with the stack feeling on shorter bows, most of my shorter bow I just design with a shorter draw length in mind. 27 inch draw for a 54 inch bow is pushing the limits IMO I know others don't think so but for me I double the draw and add the non bending area[handle and fads] for safety/longevity and durability. :)
Pappy
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So it's possibile to make a bow shorter then duble the drow lenght plus stiff handle area and get away without flipping the tips?
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Once the string angle with the limb tip hits 90 degrees the bow stacks. I prefer 60" to 64"-66" for my 26" draw but I built a 47" sinew backed bow with flipped tips that was comfortable for me to shoot at 26".
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The change in direction of pull around the 90 degree mark doesn't change very quickly.
E.G The component of the force that is trying to stretch the limb rather than pull it back increases once you get past 90... but it only increases slowly at first.
It's a bit like how the length of daylight change noticeably at this time of year (spring/autumn), but you don't notice it much at midsummer or midwinter solstice. (All to do with geometry of a circle)
What I'm really saying is that you have to be noticeably past 90 for it to show up. (Or do we... let's look at the maths)
If you want the arithmetic/geometry I recon it's a reasonable approximation to the cosine of the angle.
So at 90 there is zero force inline with the tip (cos 90 degrees=0)
At 95 (cos 90=0.87) there is 0.087 x the draw weight. so at 50# about 4.5# is pulling along the limb, so I s'pose we'd certainly feel that :)
At 100 it would be about 8.7# :o
Oooh that's quite a lot... maybe my first assertion is wrong :o ::) >:D
To me the question is how do we measure the angle?... the string is a nice straight line...but the limb? Do we measure to a line corresponding to the last 3" of limb? Or maybe a line from mid limb to tip? If we took a line from grip to tip, then a flipped tip wouldn't make any difference ::). Dunno if there is even a proper answer?
Del
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Del, I think you should measure the angle the string makes with the non-bending part of the tips. These act like levers pulling on a spring. This would explain why whip tillered bows stack sooner.
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I got a question.. I got a 54" 1 inch wide osage.. I know limits are being pushed now.. I cringe every time I brace it.. lol..tilled out to 25.. 51lbs.. feels like its stacking at 25... could I flip tips to help or am I already too short to do that.. I draw 26 but will more than likely short draw due to this.. its bending boys... LOL... I been considering but I am already out of working limb.. it has a 3 1/2 handle 1" fades..I would try to only flip last 3 inches or so.. I left them stiff anyway..granted.. I would not go hard flip just over the bow maybe 1 1/2 inch .. bow is starting to take a lil set since 23.5 inches.. only about 1/2 inch after un stringing and it seems to settle back overnight.. gut...
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Reread PatB's post because he gave the essence of what is true.
Yes, reflexing decreases the string angle.
Jawge
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Del, I think you should measure the angle the string makes with the non-bending part of the tips. These act like levers pulling on a spring. This would explain why whip tillered bows stack sooner.
Fair enough :)
Obviously it's sometimes hard to quantify "non bending, and it's hard to measure and angle to a very short line... but if we say a straight line from the tip to a point 5" in from that, it should pretty much cover it.
Del
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If we draw the line at string angle being 90 degrees for stacking then that is the key. Length plays a role but it depends on tiller shape. A slightly elliptical tiller shape will result in close to 90deg when the working limb length and draw length are equal which is why the 2x draw weight + handle and fades formula works well for determining length. Pyramid bows or other styles like holmegaard or mollegabet that bend more in the inner limb will be able to be drawn further before reaching 90 degrees. Whip tillered bows will reach it earlier. If you take an extreme example of a limb that bends like a hinge at the fade, the limb length could be very short before reaching 90deg.
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This is the discussion I was looking for ;)
how about a 60" r/d not recurved r/d just a big Long reflex starting from mid and swooping say 4" to tips? with like 1/2" ro 1" reflex out of fades?
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It matters mostly where the tips are in relation to the handle. Forward of the handle will draw farther than a straight limb bow at the same plain as the handle. I don't know that whether it is reflexed, recurved or where in the limb the reflex is but where the tip lies in relation to the handle.
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So, just to recap... In my case, on a 63" pyramid bow with a 8" stiff handle section and straight tips I should be able to get 28" of draw lenght with a hair of stacking, right? Sorry for my intervenction, this seemed the right place to ask without starting a new thread :-[
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also, if you were shooting pinch grip,, then the string angle would not be as uncomfortable,,on the fingers,,
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seems right zugul :) but i dunno :P
so pat your saying that it doesn't matter where the reflex on the limbs are??? so a sharp hook at the end of a bow, and and a slow sweep both with the same amount of reflex should reduce string angle and stacking the same amount?
really?? Id thought recurves were specifically more useful for stack then just a whole reflexed limb?
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Where the reflex is on the limb or whether reflex or recurve doesn't matter as far as stacking but it definitely matters with other things. The tip in relation to the handle will affect stacking or no stacking.
Zugul, little or no stacking at 28" draw on your 63" pyramid bow. The bow style with stiff handle or not doesn't affect stacking. Only the string angle at the tip, as far as I know.
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Thank you very much, every time I have a question about bows you experienced people help me! You're the best!
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I think the longer the bow the less the string angle. I'm betting the longer the working limb the less the string angle too. Jawge
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Stacking depends on the draw length/ntn bow length ratio, recurves, a little on the braceheight setup and tillering. First 3 give string angle - the one between string and line from handle to nock. Longer bow and more bend near handle tillering give late draw energy advantage with some efficiency costs. Recurves bring late draw energy gain with almost no efficiency loss (there will be a small one in case of static recurves because overall tillering is changing, but can be compensated because static recurves can be made narrower, so lighter).