Primitive Archer
Main Discussion Area => Bows => Topic started by: Stick Bender on December 18, 2017, 05:16:08 pm
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Hi fellas I have a couple laminate bows in the works now ,I want to make a hickory/osage pyramid bow only using 2 lams but I want to make it like a tri lam running the osage belly lam up the fades of the riser I want to make the handle / riser about 10 1/2 in. With 3 in. fades and the belly lam will be 0.130 , for you guys that make laminate bows is there any issue with doing it that way ? I plan on feathering out the fade limb junction paper thin ! I know it's done with tri lams but haven't seen it with a 2 lam glue up ?
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You won't have much room for tillering so you will need to get it very close on the first shot.
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Thanks Steve I'm tapering the belly lam 0.001 just a minor taper I'm figuring about 7/16 butt thickness and glueing in about 2 in. reflex 66 in. bow so I'm thinking 45-53 lb I could side tiller to adjust the draw weight some but not much room for belly tapper ! might adjust the over all thickness yet !
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That sound pretty good, might take a couple of bows to nail it down, I like the idea of a thin belly lam for a lot of reasons.
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Steve I don't know if my thinking is right but I like the idea of the thin belly lam of osage keeping the core lighter with a shear resistant white wood but the more I think about the design ,the more I'm thinking tri lam and dropping the back lam by 0.130 and adding a bamboo parallel 0.130 ? The thing I'm exspermenting with on this one is minimizing the stresses of the so called neutral plan which isn't so neutral in terms of shear ? I'm really not that scientific of person just taking the concept & building it but interested in your reason for the thin belly lam ? In the pic is the 0.130 osage belly lam tappers 0.001
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0.001
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Hickory core thickness undecided !
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Steve I don't know if my thinking is right but I like the idea of the thin belly lam of osage keeping the core lighter with a shear resistant white wood but the more I think about the design ,the more I'm thinking tri lam and dropping the back lam by 0.130 and adding a bamboo parallel 0.130 ? The thing I'm exspermenting with on this one is minimizing the stresses of the so called neutral plan which isn't so neutral in terms of shear ? I'm really not that scientific of person just taking the concept & building it but interested in your reason for the thin belly lam ? In the pic is the 0.130 osage belly lam tappers 0.001
The idea of using thin belly lams to manage expensive wood species is sound but I've never seen any concrete evidence to suggest that a multi-lam bow performs better than a simple backed bow
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I agree Mark, one of the reasons I like the thin bottom lamb is just that it is easier to wrap the fade on the riser section. I have had handles develop just slight openings in the fades years after they were finished. I think wrapping the bottom lamb over the fade would eliminate this.
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Ok thanks let me ask you this if I where to add a lighter mass wood like say maple in the stack under the osage , you dont think it would add performance with a little lighter core ? I relies what was said and appreciate it , Im just trying to maxamise performance on this one ?
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I do think lighter cores help out, I use them a lot on Elbs with deep oval cross sections. Cherry is one of my main go to woods for this. I have made quite a few bows with a 1/4" thick backing strip for this reason when I am working with ipe. It makes it easier to reflex the bow during glue up as well as lightning up the limbs a little bit.
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I agree Mark, one of the reasons I like the thin bottom lamb is just that it is easier to wrap the fade on the riser section. I have had handles develop just slight openings in the fades years after they were finished. I think wrapping the bottom lamb over the fade would eliminate this.
Do you mean when you glue a handle block on? What glue if so?
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Pat, I don't want to go into the glues because it is movement in the area that is the root cause. I know some glues are better than others but I would prefer a solution that doesn't challenge the glue. 90% of the glued on handle blocks have no issues but it is very aggravating when you have a top notch bow that just happens to be the one that has the issue. I use all kinds of glues, and bow making epoxies. Wrapping the lam over the block seems to eliminate the issue, on really important bows I would rather address it that way.
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It seems to me, with thin belly lams, you have a chance of scraping through the belly lam while tillering unless you know exactly how much wood to use to achieve the desired weight. I'd rather start thicker just to be sure it's enough.
I've made a few tri-lam bows and was not happy with the final results. I'd rather build a backed bow with a 3/4" thick belly to start with. Actually I'd rather build a selfbow. ;)
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It seems to me, with thin belly lams, you have a chance of scraping through the belly lam while tillering unless you know exactly how much wood to use to achieve the desired weight. I'd rather start thicker just to be sure it's enough.
I've made a few tri-lam bows and was not happy with the final results. I'd rather build a backed bow with a 3/4" thick belly to start with. Actually I'd rather build a selfbow. ;)
I have had this problem more than once and it is aggravating. You pretty well have to nail it down in advance of building it. Once the belly lam gets so thin it stands a good chance of just buckling and ruining the bow. .130 is about 1/2 way to that point.
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Ok thanks Im going to try to keep all measurments with in a couple 1/1000 Im just going to build it and see where Im at like Steve & others have said, hopefully not much scraping will be needed belly wise and I will have to accept the draw weight with in a tight range so here are the specs so far
Tri lam Design
Stack 0.4375 (7/16 in)
Hickory. Parallel 0.1775
Osage Parallel. 0.130
Osage Taper 0.130. @0.001 TPI
TTT 66 in
NTN 64.5
WL 26.25
Front view 2 in. To 3/8 in. Pyramid
12 in. Riser 3 in. Fades
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Ok thanks let me ask you this if I where to add a lighter mass wood like say maple in the stack under the osage , you dont think it would add performance with a little lighter core ? I relies what was said and appreciate it , Im just trying to maxamise performance on this one ?
Still haven't seen any evidence to say yes or no. The ones I have made did not seem to perform any better than a simple backed bow
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I split the difference on all 3 opinions and added another lam of osage replacing the bamboo lam with the same dimension that way if I have to scrape ,I'm osage on osage a little more of a margin for error I adjusted it in the recipe posted so it's basically giving me a 0.260 core of osage with a 0.001 TPI belly taper Osage/Hickory !
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Most anytime I try something new I always consider the first one a prototype. Don't feel bad if the first one doesn't come out exactly right.
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Thanks Steve I defently considering this a prototype but I'm only have time this winter to make 2 bows so just trying to stack the odds in my favor I appreciate the help !
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What do you think about putting the tapered laminat in the middle of the stack?
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I thought about that but I'm going to guess if there is scraping to do it's probably is going to be mostly in the lowers and I thought I could control a even tapper better with the tapered lam on the belly but if the tiller is close from the start there is room in the design for side tillering will see ,like Steve said it's a prototype !