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» Trad Gang.com » Main Forums » The Bowyer's Bench » Scratching my head over this one.

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Author Topic: Scratching my head over this one.
JamesV
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I was building a knock-off or copy of a recurve bow. Built the form using the original bow for the pattern. The original stack is .200 using .040 glass .003 taper, 18" riser and maple core. Limb width is just a tad under 1 3/4" draw weight 50# at 28. I wanted the new bow to be 45# @28,so I used 1 1/2" .040 glass, thinking the narrower limb would put me in the ball park. Everything else was exact except I used bamboo for the core but the new bow still came out at 57#.

Go figure, got me stumped

James

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Posts: 2046 | From: Rolling Fork, Mississippi | Registered: May 2010  |  IP: Logged | Report this post to a Moderator
kennym
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Just for curiosity, check the stack after glueup if you can. I think glue can add to stack on the new one when you are measuring off a completed bow.

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Stay sharp, Kenny.

https://www.kennysarchery.com/

Posts: 12070 | From: Linneus , Mo. | Registered: Jan 2004  |  IP: Logged | Report this post to a Moderator
Shredd
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Did you measure limb thicknesses of both bows after glue up???
Posts: 288 | From: Florida | Registered: Sep 2016  |  IP: Logged | Report this post to a Moderator
JamesV
Contributor 2013
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Just went out to the shop and checked the stack. the stack is .202 the original is .200.

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Proud supporter of Catch a Dream Foundation
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When you are having a bad day always remember: Everyone suffers at their own level.

Posts: 2046 | From: Rolling Fork, Mississippi | Registered: May 2010  |  IP: Logged | Report this post to a Moderator
rmorris
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Takedown or one piece? A few degrees differences in the limb angle off the riser can make a big difference

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"Havin' such a good time Oo-de-lally, Oo-de-lally Golly, what a day"

Posts: 1257 | From: Midland, Texas | Registered: Aug 2009  |  IP: Logged | Report this post to a Moderator
Roy from Pa
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The bamboo core could have caused it too. I ordered lams from Kenny a few years ago and used action boo for the core lam to make a set of limbs for my bear take down. Those limbs out preform a set of carbon limbs at the same draw weight.
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mikkekeswick
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Thickness is the real determining factor.
1/8th thicker limb is double the draw weight whereas you would have to double the width to get the same increase. One is proportional and one is exponential [Smile]

Posts: 913 | From: England | Registered: Sep 2014  |  IP: Logged | Report this post to a Moderator
mikkekeswick
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roy - the core cannot make that much difference, the glass is way stiff and does virtually all the work. The only way a core can make a difference is if it is lighter/heavier. Adding carbon changes a few things [Wink] Apples and oranges.
Posts: 913 | From: England | Registered: Sep 2014  |  IP: Logged | Report this post to a Moderator
Robertfishes
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That's weird science James.. I'm guessing that glass you used is "better"or stiffer than the glass in the bow you copied. You don't need to say the name of the now but is it one from outside the USA where they might have used glass other than Gordons . My one piece recurve formula is 1# for each 001 thickness. The ILF limbs I build are about 2# for each 001 thickness. For reducing weight I have read that removing 008 of width reduces the same amount as 001 of thickness, I have reduced width on a couple of recurves and I was surprised how little weight difference I got from the ammount of side material I sanded away.
Posts: 3636 | From: Ocala , Florida | Registered: Mar 2005  |  IP: Logged | Report this post to a Moderator
JamesV
Contributor 2013
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Robert................

The bow I copied was a 70's Kodiak Mag. I seem to have more problems with the shorter recurves.

James

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Proud supporter of Catch a Dream Foundation
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When you are having a bad day always remember: Everyone suffers at their own level.

Posts: 2046 | From: Rolling Fork, Mississippi | Registered: May 2010  |  IP: Logged | Report this post to a Moderator
kennym
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James, have you copied Bears from that era before?

Robert may have a point in the glass being better....

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Stay sharp, Kenny.

https://www.kennysarchery.com/

Posts: 12070 | From: Linneus , Mo. | Registered: Jan 2004  |  IP: Logged | Report this post to a Moderator
JamesV
Contributor 2013
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Kenny.......

Almost all the short recurves from the era seem to come in heavy. On the good side, I need the experience and I always hit the weight dead on for the second bow. Maybe use .030 glass next time.

It could be that the glass you sell is stronger,
LOL

James

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Proud supporter of Catch a Dream Foundation
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When you are having a bad day always remember: Everyone suffers at their own level.

Posts: 2046 | From: Rolling Fork, Mississippi | Registered: May 2010  |  IP: Logged | Report this post to a Moderator
mikkekeswick
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Yes it is likely down to stiffer glass. I've been using some from another company that is slightly stiffer than Gordons stuff.
Posts: 913 | From: England | Registered: Sep 2014  |  IP: Logged | Report this post to a Moderator
   

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