thickness to bend ratio?

[stuckinthemud]

Did a quick search but can't find it. Anyone know the maximum thickness to bend ratio for yew? thanks guys

[Del the cat]

Not sure the question is answerable?
If you take an ELB with a circular tiller then it has the same bend radius along it's length yet the thickness varies along the length.
Not sure how you'd expect the answer to be framed? Say in the example above the radius of the bend was 36" and the thickness mid limb 1" that would be 1:36   is that what you's want?
Maybe you can frame the question in a different way? 
Del
(Or is the question about heat bending radius? .... I am a confused kitty now... I shall go and have a nap)

[stuckinthemud]

I thought that once, long ago, I read a post that stated a stave should not exceed a maximum thickness relative to the amount it has to bend or it will suffer compression failure. Dunno why but 5% is stuck in my head??

[willie]

should not exceed a maximum thickness relative to the amount it has to bend or it will suffer compression failure. Dunno why but 5% is stuck in my head??

Cant say about the 5% or yew, but what you heard and Dels explanation are both correct. A beam or limb tends to vary its bend  depending on how far away the loads are from each other unless you taper.  But if you were to take a slat of consistent crossection and bend it around a circular form, there would be a minimum diameter

[Badger]

       Yew is one of the more elastic ones and less than 2%. The figure is so small that it is near impossible to measure with any real accuracy.

[sleek]

Thickness controlls your draw length, width and length control your draw weight. So any calculation  you make is a function of all 3. I have been planning on writting a book on the art of short bows and this is a topic heavily involved. Maybe ratger than a book, I can talk yo PA and ask about writting a few articles. Most ots already written out in note form.

Id of course have to talk to some of the minds greater than mine to male certain im not crazy... now where did that Badger go? Oh Marc...

[Bayou Ben]

Is this maybe what you are referring to :  http://www.primitivearcher.com/smf/index.php/topic,62670.msg878716.html#msg878716

[Badger]

  Ben when I actually started working with a gage I quickly found out the increments are so small it is beyond manual accuracy of any kind, best off doing it as we do now.

[Woodbear]

There is an old book called "archery he technical side" that has a bend radius to thickness value for Yew.

The answer is bend-radius/full-thickness = 50/1.
This ratio can also be expressed as a percent strain which = (thickness/2)/bend-radius. For Yew this comes out to 1/100 = 1% strain.

This kind of value is somewhat a "rule of thumb", and since wood varies from tree to tree, some judgement is needed as some wood may not quite be up to that much strain.

Dave