Wednesday, 27 January 2016

Yew AFB Long vs Short String

 I've stuck on some temporary Yew nocks and checked out the thickness taper by eye and fingers.
It's up on the tiller for a first flex. Lower (left) limb is a tad stiff, but it basically looks ok and almost ready for bracing. I can see the limbs flexing near the fades and the outers are stiff, which is pretty much how I start the tillering process on all my bows.
I may well add a little deflex near the fades and a V gentle recurve to the outers once it's all.

I've now planed the sides and narrowed the tips a little also planed a little off the corners of the belly so the tips are pulling back far enough to brace's back far enough to brace.
See top pic the tips are back about 7" at 45#
Now I brace it to a low brace and look (lower pic), the tips are back an average of 9" at 45# .
That shows how the short string applies much more stress than the long string. It's due to the geometry, the detailed maths of it doesn't really matter as long as you understand the effect and get braced as soon as you sensibly can.

Note I've tried to position the bow centrally on the tiller and pull from the centre to show it better. Normally I pull from where the string will be pulled in real use (above centre, that's right of centre as I always have upper limb to the right)

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