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Stress and performance
Aussie Yeoman:
Absolutely agree with you there. The taper profile needs to converge on a theoretical zero width tip, which in practicality has to have some width, as you mentioned.
This means that the limbs, of tillered perfectly symmetrically, probably won't be exactly the same thickness throughout, but need to taper ever so slightly in the last 1/4 of the limb or so.
I once made a bow with tips just under 1/4" wide. So narrow I cut a single nock in the back of each tip. That was for a Molly rather than a pyramid, but the theory holds.
In fact I think cutting a single nock on the back increases the stability because the point at which the string contacts the cross section of the limb is closer to the neutral plane.
That hypothesis could do with testing, if anyone could be bothered.
mmattockx:
--- Quote from: Aussie Yeoman on May 16, 2024, 06:42:39 pm ---Absolutely agree with you there. The taper profile needs to converge on a theoretical zero width tip, which in practicality has to have some width, as you mentioned.
This means that the limbs, of tillered perfectly symmetrically, probably won't be exactly the same thickness throughout, but need to taper ever so slightly in the last 1/4 of the limb or so.
--- End quote ---
You are correct on needing to taper the outer limb thickness some if you straight taper to the nock width. You can keep the limbs constant thickness with a narrow lever to the nock, as shown here:
It is a bit hard to tell in the picture, but the end of the limb is parallel width for about the last 3.5" or so. It is 5/16" wide for that whole length. This lets the limb width taper follow the theoretical ideal that goes to a point at the nock, then transitions into a slightly stiff tip lever where the limb width goes below the 5/16" width. I added a tip wedge during layup to stiffen the tip a bit more and guarantee it was strong enough. This was the first time I had tried this and I was worried that the spindly narrow tip would be too fragile.
Mark
Aussie Yeoman:
Good job on that one! That's quite the gnarly looking arrow pass design you have there. What was the draw weight/length on that one?
mmattockx:
--- Quote from: Aussie Yeoman on May 17, 2024, 12:50:46 am ---Good job on that one! That's quite the gnarly looking arrow pass design you have there. What was the draw weight/length on that one?
--- End quote ---
http://www.primitivearcher.com/smf/index.php/topic,70862.msg994666.html#msg994666
Mark
Selfbowman:
--- Quote from: willie on May 15, 2024, 08:28:08 pm ---
--- Quote from: Selfbowman on May 15, 2024, 06:46:33 pm ---That requires more width fades to mid limb. Short or long bow. Just an opinion.
--- End quote ---
adding width to limit set certiany seems like you can get a good handle on how much extra width it takes to make your design shoot better.
does your width out of the handle run straight for a ways before you begin to taper? if so, have you changed the distance out the limb before the taper starts? or just go a little wider to the same point as before?
--- End quote ---
Willie if we overbuild the first three inches coming out of the fades but run parallel the limbs need to tapered in thickness ? If we overbuild in more overall width thru out the hole limb length but stay the same thickness could this be close to the same spreading the load. Extra mass in the first nine inches out of the fade has little effect on performance in my opinion. Again the added reflex in the last 9” of the limb is throwing a curve in the calculation. I think. Thats why I have been chasing the set with mass from bow to bow. Obviously I build by feel with mathematical measurements from the design in mind as I go. Not smart enough to do it any other way. 🤠🤠
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