Inner tubes making staves twist/warp when gluing up...

[toomanyknots]

Well I learned yesterday that inner tubes, when using them to glue up staves, can make the stave twist from the actual pull of the rubber I guess. This is with staves where all the laminates had been width tapered, and the belly had been thickness tapered as well. So it was close to final dimensions, just needed to have the belly rounded. I started thickness tapering my glue ups so I could hang something heavy from the middle and get an even reflex, and then I started width tapering using a template due to my bamboo being pretty warped and pretty impossible to get a straight piece of. So I just started using a template on the bamboo and cutting out a pre-width tapered piece. Anyway, I noticed after gluing up a couple bows yesterday that the staves had actually twisted at the ends, in the direction that the inner tubes were wrapped around the stave. So I guess I will either use clamps with my bamboo bows, or leave the entire stave thick and cut the profile out later. ( I do like thickness tapering though and getting a nice even reflex, ) Maybe I can use like a wide un-tapered template for bamboo, and just cut the profile out later during glue up? I used spring clamps the other day to glue up a bow, only spring clamps, the glue was tb3. And the glue line did not turn out very good at all. It was holey and patchy. I find c - clamps work best with tb3, as it really needs a good amount of pressure, or really tight inner tubes. Just thought I would pass this on.

[PatM]

Double wrap in an x fashion coming back down the limb and the opposing wrap should cancel out the twisting effect.

[toomanyknots]

Double wrap in an x fashion coming back down the limb and the opposing wrap should cancel out the twisting effect.

Didn't even think of that, thanks.

[bubby]

I haven't had any problems like you describe, but with tubes you don't have to wrap super tight, as long as the glue runs out in front of the wrap it is tight enough, maybe wrap it and then clamp the ends down to a straight board

[Gordon]

Did you use a form? I often use inner tubes and a form for my glue-ups and have never had the limbs twist or any problem with glue lines.

[toomanyknots]

Did you use a form? I often use inner tubes and a form for my glue-ups and have never had the limbs twist or any problem with glue lines.

No, I didn't use a form. I am making me a straight form though right now. I am gonna take a 2 x 4 and drill some holes in it, and gorilla glue down a strip of aluminum.

[Cameroo]

For flatbows I just use a 2x4 on it's side as a backer board, stack the lams on top, and wrap inner tubes around the whole works.  I imagine you could cut a graceful curve into a 2x6 and use it the same same way to induce a nice even reflex without running into the twisting problems you are having.

[KrisDelger]

Personally I've been playing with cutting forms out of 2x12 on my bandsaw or with my jigsaw to make two halves of a form and then lining those with a pressure strip to keep from gluing the bow onto the form. Though about doing two 2x12's side by side but with the single it's been working out pretty well for the glue up. Now if only I could get the tiller right haha!

[hedgeapple]

Double wrap in an x fashion coming back down the limb and the opposing wrap should cancel out the twisting effect.

+1 on that.  I've done a couple hickory backed bow and found that the inner tube would pull the backing to one side.  Doing a second wrap the other way straighten it back out. 

I've also used a form with small dowel rods suck through the form about one inch on each side about 1" below the top of the form.  Then I cut 2" bike inner tube into 1/4" wide rubberbands. Then stretched them across the bow and form, hooking them on the dowel rods.  When doing glue ups on forms, I tape wax paper to the top of the form to prevent gluing the bow to the form.  I'm messy that way. 

[Cameroo]

Another thing that just occurred to me that might be causing this is if you are not stretching the tube enough as you bring it over top of the lams.  If you are pulling the tube over the top and then stretching it as you are pulling down, it would pull to the side like you described.