Primitive Archer
Main Discussion Area => Bows => Topic started by: arachnid on February 08, 2015, 02:21:31 am
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Hi Guys.
I`m working on a tri-lam: ipe belly, walnut core and boo back.
The boo is 1/8", the walnut is also 1/8" thick, all are 1 1/4" wide at the fades, with a pyramide taper. The bow is glued up with perry reflex and I`m floor tillering
now. I got the limbs moving and the ipe is about 7mm thick. My main concern is the ipe getting too thin and getting overpowered.
So, how thin can the ipe be?
I have a white oak backed ipe, 40#@26" with the ipe 7mm thick and the white oak backing 3/16" thick. That my target weight with this bow as well.
Thanks,
Dor
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You can get away with a couple of mm (0.078) but best if you can stick around 5mm (0.200).
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If you used epoxy you can get away with scary thin, with tighbond 2 or 3 should be ok.
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I used Elmer`s yellow carpenters glue. Any difference?
What`s the absolute minimum I can get from the ipe before starting to tiller from the sides (it`s not that wide anyway so
I don`t want to get there...)
Dor
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If you used epoxy you can get away with scary thin, with tighbond 2 or 3 should be ok.
Could you please explain to me why there is a difference in minimum belly thickness depending on the glue? What happend to the belly in combination with the glue, that makes a failure?
In my experience, three millimeters is about the minimum for an ipé belly. But then the grain must be perfect. Any pin knot or imperfection will chrysal rapidly.
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I don't know what the difference is. I just know that I usually use tightbond and have had my ipe buckle before when I got too thin. On the ones I use smooth on it didn't seem to be an issue. I wouldn't go below anout 3 before I started trapping the boo a little if I had to.
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The shear strength starts to matter more when the thickness is minimal. PVA glues are not hard glues.
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I would go just under 1/4" with the belly. I wouldent trust Elmers. If you use wood glue, go with tb3. I personally use epoxy on my glue ups, I probably will never go back to wood glue.
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For tri-lams, try making your core wood layer 1/8". That way, you'll have more belly wood, and you won't have to worry about running too thin. I use TB3 exclusively for all my glue-ups, and have never had a problem with it.
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I always used Elmer's and never had a problem. Plus, it's the only thing I can get for a resonable price.
My core is 1/8" thick so I guess I'm good.... Hope everthing runs smoothly. I the first time I'm using boo and it took forever to thin it down with hand tools.
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Is your bamboo tapered? Is the walnut core tapered?
When I make such a bow, prior to glue up, I taper both of these lams in thickness (while leaving the belly lam parallel) so I don't have to worry about the belly piece getting too thin during tillering.
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On the boo if you thin to a knife edge then cut to profile shape and thin again it will be tapered if you are going to taper the core might as well taper the belly and save some tillering right ;) just takes a little pre planning
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It's all parallel- boo and core. I thought of thinning the boo to a knife egde but, again, it's the first time I'm using boo and didn't want to get too thin with it. As for the core, I just don't have the machinary needed.
Dor
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The shear strength starts to matter more when the thickness is minimal. PVA glues are not hard glues.
This is likely it, Pat. They are very tough, but do seem to retain that tiny bit of flexibility and plasticity.