Primitive Archer
Main Discussion Area => Bows => Topic started by: barebo on December 29, 2014, 06:50:11 am
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Hi All,
Been a long time since I've posted - haven't made shavings in over a year but winter is here in Central NY state and I have materials so I'm into a Bamboo backed Osage - "short longbow"
58" NTN. Just past the grip it's 1-1/4" and tapers to 7/16" tips. The problem I'm having is that I think I left the Bamboo too thick. I induced 4" of deflex at glue up. I have it bending about 10" and it's still holding a ton of weight. I trapped the Bamboo some, but wonder how far I can go without compromising it??? The Osage belly is about 30% thicker than the Bamboo. Can I thin the belly more ?? The bend (tiller) now is nice and even - just holding a LOT of tension. I can try to get some pics later as I know they help. Thanks for any input!!!
Mark in NY
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Do you have it braced?
If you are pulling on a long string the draw weight will be deceptively hight.
Del
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You remove belly wood until the limbs are bending evenly and together an you have achieved the draw weight you desire at the draw length you are shooting for.
Like Del said get it to brace if you haven't already. If everything is even then you take long scrapes the full length of each limb until you get to the weight you want to be at.
How thick is the boo backing?
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The thickness of the bamboo, in and of itself, won't affect the stiffness. Almost all the work happening in the limb happens in the first 20% of the back and belly thickness (40% total). I used to thin bamboo to 1/8, but often leave it 1/4" or 3/16" at least. If you have nearly half the limb thickness on the belly lam, you are going to be fine. When the belly gets closer to 1/3 the total thickness I start to worry a bit.
Bamboo/ osage is a stiff combination to begin with. My guess is that it the fact it is SHORT and REFLEXED is doing it to you. Getting reflexed and R/D bows back to brace often feels incredibly hard.
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Thanks to all !!! Haven't braced it yet, as it's holding far too much poundage and I'm going to take it slow bringing it to the short string. My Bamboo is right there with Springbuck's @ 1/4".
It glued up fine as far as taking the Reflex. I made a 70"ntn Bamboo backed Ipe, and it was straight limbed and took just 1/2" of set and has been shot a lot. This is a different style and I guess
I'll figure it out as I go and hope for the best.
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If you do find osage belly getting too thin you can start reducing the width to loose weight.
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I have gotten my osage down below 1/8 thick on many occassions, at about 1/16 I start looking for other avenues.