Author Topic: Is tillering really a constant for a given bow?  (Read 1110 times)

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Offline diliviu

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Is tillering really a constant for a given bow?
« on: September 10, 2021, 09:38:25 am »
Hello
I mean: say I had a very flexibile sinew backed cedar bow. Enough flexibile to allow pronounced bend and stacking. Up to 24" it wouldn't stack. Without string it would be straight as the light. At 24 I would have a perfect arch. Is it possible that at 28", because of crazy bending angle (levers working a little differently?), I get a little more bend in handle and inner limbs than in the outers (just assuming that belly wooden cells would not start to fail at all)?
Thanks.
« Last Edit: September 10, 2021, 09:51:41 am by diliviu »

Offline simson

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Re: Is tillering really a constant for a given bow?
« Reply #1 on: September 10, 2021, 10:33:23 am »
You are talking about a very short bow (perfect circle at 24).
Maybe I misunderstand what your question is. You want it to be ellipsoide at 28"??
Maybe  a sketch would be helpful ...
Simon
Bavaria, Germany

Offline diliviu

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Re: Is tillering really a constant for a given bow?
« Reply #2 on: September 10, 2021, 11:53:43 am »
I have attached a sketch, I hope it is visible. Not to take it exactly like it is (for exemple, maybe for a bow without levers the outers couldn't come more than parallel to the arrow?)
My main question is if in case of extreme stacking the tillering would slightly change like exemplified in the sketch, or not (assuming materials can easily take the stresses).
Thank you.
« Last Edit: September 10, 2021, 11:59:31 am by diliviu »

Offline Tuomo

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Re: Is tillering really a constant for a given bow?
« Reply #3 on: September 10, 2021, 12:23:40 pm »
Answer to the question of title is no. Optimal tiller shape varies according to bow length/draw length ratio, with the front profile of the bow.

Is it possible that at 28", because of crazy bending angle (levers working a little differently?), I get a little more bend in handle and inner limbs than in the outers (just assuming that belly wooden cells would not start to fail at all)?

Yes. The tiller shape of a bow varies according to draw length, because string angle varies also and thus force vector exerting to the bow.
« Last Edit: September 10, 2021, 02:49:49 pm by Tuomo »

Offline diliviu

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Re: Is tillering really a constant for a given bow?
« Reply #4 on: September 10, 2021, 12:35:25 pm »
Right, Tuomo. The title is confusing, indeed.
So the tiller shape will vary (slightly) with the draw length.
Thank you.