Bike tube wrapping questions

[DC]

Does anyone have any idea what kind of pressure(in psi) that you get wrapping a glue up with bike tube strips? I can imagine cobbling up something to measure it but why bother if someone has done it already

When you are wrapping with bike tube strips do you ever use a strip of wood down the center of the bow to increase/equalise the pressure across the bow? If so how do you decide when, how thick, how wide? That sort of stuff.

[Pat B]

DC, I've had my best luck with glue up using bicycle tubes. I cut the valve section off and split the tube in half lengthwise. I wrap from the handle to the tip on each limb, one half of the tube for each limb. Even after you've wrapped the bow you can still put it on a form and it will conform. I wrap as tight as I can with the tubes, I don't think you can wrap it too tight.
 I always use a pressure strip when laminating. It give more even pressure.

[willie]

no actual pressure numbers, but if the tubing does not get you enough pressure, you can do the same with stretchy twine and get more pressure still.

[DC]

I do the same Pat but with my "elderly" hands I have to cut it into four strips. I pull it until it "stops". It seems to have a natural point where it starts to stack real bad so I think the pressure is pretty consistent. I just thought there might be some  rules about pressure strips. Like a narrow bow with a high crowned backing(boo) wouldn't need one and a wide bow with a flat backing would need a fairly tall one.

I thought I might adapt a pressure gauge to fit a PET Coke bottle and then wrap it with the rubber and see what kind of pressure I get. it would take a little fiddling so I thought maybe someone has already done it.

[Badger]

   I have always wanted to test this, using a plastic coke bottle with a valve stem at the top might work pretty good. I would wildly guess somewhere around 5# psi. I know it is tight enough for flawless seems with no visible gap.

[simk]

DC: Applied firmly, a whole lot. I have had horn splitting with it because of all the pressure on the edges. since then started to put a small wooden ridge in the middle to equal pressure. I go for the wide heavy duty mountainbike downhill downhill tubes and split in 4 

[willie]

with "elderly hands", you might like the traditional method  stevet shared on one of his builds. I recently posted a link to a PP thread,  in the bubbles in glue thread.
 if you cut the tubes into fourths, then you just need four times as many strips to give the same pressure.

[mmattockx]

I thought I might adapt a pressure gauge to fit a PET Coke bottle and then wrap it with the rubber and see what kind of pressure I get. it would take a little fiddling so I thought maybe someone has already done it.

That's not going to be very accurate. You would get a better number if you put an intact bike tube into the stack with the valve stem sticking out. Put a bit of air in to give it something to squish, then wrap the stack and see what the gauge pressure is.


Mark

[DC]

I thought I might adapt a pressure gauge to fit a PET Coke bottle and then wrap it with the rubber and see what kind of pressure I get. it would take a little fiddling so I thought maybe someone has already done it.

That's not going to be very accurate. You would get a better number if you put an intact bike tube into the stack with the valve stem sticking out. Put a bit of air in to give it something to squish, then wrap the stack and see what the gauge pressure is.


Mark

I thought of that but I thought that you would be chasing a big bubble of bike tube as you wrapped it.

   I have always wanted to test this, using a plastic coke bottle with a valve stem at the top might work pretty good. I would wildly guess somewhere around 5# psi. I know it is tight enough for flawless seems with no visible gap.

I'm thinking more than that. I'd take a WAG at about 50# but I don't know. Gues I'll start looking for a guage.

with "elderly hands", you might like the traditional method  stevet shared on one of his builds. I recently posted a link to a PP thread,  in the bubbles in glue thread.
 if you cut the tubes into fourths, then you just need four times as many strips to give the same pressure.

I completely cover the bow with a single layer of tube. I think using narrower strips is just like putting it on in low gear

[DC]

DC: Applied firmly, a whole lot. I have had horn splitting with it because of all the pressure on the edges. since then started to put a small wooden ridge in the middle to equal pressure. I go for the wide heavy duty mountainbike downhill downhill tubes and split in 4 

How thick is your ridge stick? Is it tapered? I just did a glue up and used an arrow shaft as a pressure strip. It's a pyramid shape about 1 3/4" wide. To me it looked like there would still be pressure on the edges where the limb was widest but toward the tip it didn't look like there would be that much. The rubber seemed to go almost straight from the top of the arrow shaft to the edge of the limb.

[simk]

DC: I just grab some random piece of wood around, offcuts from thicker backing strips are fine, 5-6mm (2/8") thick and max half the wide of limbs. works for me. sure could be done more sophisticated... undr 30mm you dont need that. that other elb I didnt used it. Also: With most epoxies you actually anyway dont need too extreme pressure I think.

[HH~]

I have aluminum 1/16x 1.5” shaped and glued 3/16 wood to it. Use it for my pressure belly plate when wrapping if i use inner tubes.

Have one Boo, Hickory, Hedge need to help out with this week in fact. Think i will drag that form and pressure plates out.

How much pressure? With a belly plate you can grab a bunch! Better than any clamp method I would say.

HH~

[DC]

A belly plate? The only reason I can think of for that is a thin belly lam. Is that what you're doing? When I'm backing a bow the belly is usually/always thick enough to not move. Am I missing something here?

[mmattockx]

I thought of that but I thought that you would be chasing a big bubble of bike tube as you wrapped it.

I could see that happening. I was thinking you wouldn't do it during an actual glue up and just do a mock up to see what kind of pressure you are getting.

FWIW, the fibreglass bowyers use air pressure in a hose to clamp their glue ups and they often use 40-50psi, sometimes more. I would expect you to be somewhat less than that with the inner tube.


Mark

[PatM]

Wrap your hand or arm with a  maxed out inner tube and see how  it feels.  To some degree it all amounts to about the same.  You're not able to crush the wood so as soon as the surfaces contact it all becomes a bit superfluous.