Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on July 02, 2018, 06:10:13 pm
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Hi folks,
I just unwrapped and cleaned up a bamboo backed bow that has yet to be tillered. I discovered that the bamboo is quite a bit thicker in some spots than others (I hope the pics illustrate this). When I ran the bamboo through the jointer prior to glue up I didn't realize how much the thickness varied.
The wood's thickness was methodically prepared and tapered prior to glue up, so as you might imagine, this poses a challenge.
My question is can bamboo be removed from the back to even it up as could be done with a wood backing? (please say yes)
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I really can't see much difference but is there some kind of deep meaning to taking the picture over the garbage disposal ;)
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Are the top and bottom pictures the same distance away, like should they be the same thickness? How thick is it? It actually all looks a little thick.
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What glue did you use?
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No. Bamboo can't have the power fibers violated like that. Especially with regard to the nodes.
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Yeah PatM, the more I thought of it, the more I realized that.
I used Smooth On Pat B.
It was the same distance DC. The pics don't really illustrate what's going on that well. And I'm gonna try not to read too much into the disposal thing. ;D
I think I'll be okay as long as I take it very slow. Bamboo does have a crown, and I think it was a little uneven on this piece.
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Do you think you could use that fancy new bandsaw and cut right down the glue line and start again?
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I considered that, but the thought of doing the glue up all over is too much to bare. The lines are really good on this one! Think the bamboo will over power the ERC? If most of the forces are close to the back (tension) and belly (compression), I can't see why I couldn't make it work.
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I was thinking that looked like cedar...man the bamboo will be hard on that belly wood. I have even had thin hickory overpower ERC before...
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If the boo is too thick you will end up tillering away most of the belly wood
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Bummer. Guess I'm not sure what to do. :-\
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You can grind the belly off
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Too much to bare? I have replace the bamboo on a bunch of bows, no big deal. You will end up with a wood belly bamboo bow with what you have now and it won't be much of a performer with more bambo than wood.
On your next backing use the jointer to level the bamboo, lay out your pattern, cut it out and use a belt sander to reduce your bamboo evenly so every edge is 1/16". This will naturally taper your bamboo just right and keep the thickness uniform.
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Too much to bare? I have replace the bamboo on a bunch of bows, no big deal. You will end up with a wood belly bamboo bow with what you have now and it won't be much of a performer with more bambo than wood.
On your next backing use the jointer to level the bamboo, lay out your pattern, cut it out and use a belt sander to reduce your bamboo evenly so every edge is 1/16". This will naturally taper your bamboo just right and keep the thickness uniform.
+1...This is what I do and it comes out surprisingly accurate just by eyeing it. But most of the bows I build have a pyramid-ish width taper. You wouldn't get thickness taper doing it this way with a parallel limb bow. Just something to account for.
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"You will end up with a wood belly bamboo bow with what you have now and it won't be much of a performer with more bambo than wood."
This is what I did and you are absolutely correct Eric. Next time I'll be much more careful with the bamboo thickness. Oh well, live and learn.
Guess I need to buy a belt sander now. :'(
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Guess I need to buy a belt sander now. :'(
Never have enough tools.
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I once removed a cracked bamboo backing from an ipe belly with a heat gun (glued with smooth on), if you get one tip started put the heat between the layers and it will come off pretty easy.
Bit off topic maybe but thinning a full thickness slat of bamboo to paper thin sides takes me about ten minutes with a sharp drawknife. Just try it, it might surprise you how easy it is.
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People don't like the thought of tillering the power fibers, but yes, you can. It is straight grained, and holds together with or without a violation so long as you don't have rot. I wouldn't do it on a high poundage bow, but don't worry about it unless you are going past 50#. Some bamboo bows have the power fibers on the belly and the back is literally the inside of the stalk and is tillered on the back, not the belly. Point is, it is straight grained and will hold together unless you overdo it. If you want to get rid of the nodes, go for it. There are many examples of this online, but yes, it is not as sound. If you want a perfect bow with maximum performance and high poundage, of course don't dig into the power fibers. The power fibers give the bow stiffness and seem to enhance the performance for the oftentimes unusable belly wood it is working for.
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The jointer belt sander method worked for me to ,but it could all be done on the belt sander I like 36-50 grit belts leaves a nice surface for glue , on mine I get the edges knife like thin but easy to cut your self on !
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Back in the old days before I had a belt sander and jointer I thinned the bellies of bamboo slats with a block of wood and a piece of course sandpaper. If I remember right it took all day to do one slat but I was young and full of vigor back then.
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My first was done with a block plane.
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Back in the old days before I had a belt sander and jointer I thinned the bellies of bamboo slats with a block of wood and a piece of course sandpaper. If I remember right it took all day to do one slat but I was young and full of vigor back then.
Now that's dedication! I get tired after 10 minutes of a block & sandpaper!
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Width tapering Bamboo and core before glue-up is a good idea here, not to finished dimensions but close, as it allows you to better see what you will have once glued up.
There is the other option of trapping the back but that may not help much
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I use a hand held power planer, I plane it flat full width, then cut the front profile. Then plane it down real close and finish it with a belt sander almost to a knife edge