steaming osage

[J. Holden]

My latest bow also has propeller twist in the limbs.  One limb tip going one way and the other tip twisting opposite.

I'm steaming the one limb but it is fairly thick (3/4" +) still.  I was going to steam for half an hour.

Can you over steam osage?  I've wrecked good osage with dry heat before.  Just not sure about steam.

-Jeremy

[Pat B]

I'd suggest getting your bow to floor tiller stage or even low brace first. This will give you less wood to have to work with. I don't think you can steam it too much.A half hour to 45 minutes is typical. Depending on where the twist is you should do it in a couple of sessions. Getting the stave clamped before it cools off can be difficult. I use a heat gun for this and oil the wood with cooking oil.
Clamp the handle area, back down and heat at the fades first and work out the limb, clamping and adding wedges as you go. Once that limb is done go over the entire limb again heating it until it is hot then let it rest over night. Get the other limb done the same way. With the handle area clamped you will have both limbs lined up with each other.

[J. Holden]

Thank you Pat.

[Pat B]

A little twist will not adversely affect the shooting of a selfbow.
 By waiting until after your first low brace you can add reflex while removing the twist also.

[Bowjunkie]

I make them about 1 3/4" wide for their whole length, 3/4 thick at the dips tapering to 5/8 at the tips... steam the entire stave for 1 hour... 1 1/4 hours tops, then correct the whole stave at once on a reflexed caul with pipe clamps.

The caul has 1/8" rubber on its surface, and plywood pads are put between the clamps and the stave's belly.

I clamp the handle area down first, it'll usually sit square. Then work out each limb with clamps, over correcting slightly by putting the clamp on the side that needs to go down farther. It'll roll over some on a crowned back and 1/8" rubber, and that's usually enough to slightly over correct for springback. If it's not, I made shims to help it twist farther under the clamp. These things are judged prior to steaming, a loose plan formulated, and everything layed on the bench in arm's reach so it can be done before the stave cools off. Two minutes of scrambling and the whole thing is done. Bang-Bang... Pow-Pow :^)

[BMorv]

Bowjunkie, what kind of contraption do you use to hold the entire stave for steaming?

[EwokArcher]

I used a method like junkie  using drier duct work with foil caps using a T in the middle that allowed the steam up.

[Bowjunkie]

At its center, there's a galvanized 4" stove pipe T set down into a ceramic coated camp coffee pot. Fits perfect. Coffee pot sitting on an electric hot plate, 3/4 full of water... cranked as hot as it will go.

A few pieces of 4" galvanized stove pipe shoved into each end of the T to make it long enough to hold a full length stave. And pipe caps on each end with several 1/2" holes drilled in them to let the steam escape and move down the length of the stave. I keep a couple of chunks of 2x4 cut to length to support the ends of the pipe so it doesn't try to tip one way or the other.

Some insulation, a blanket, or sleeping bag thrown over the pipe will insulate it and make it heat up quicker and be more efficient.

It's pretty simple, but I can post a picture if my description is inadequate.

[Pat B]

I had the same set up.

[BMorv]

No need to post a picture, I can imagine exactly what you are describing.  It seems like a good way to knock out all of the shaping and bending at once. I figured the OP would want an explanation too if he didn't know how it was setup.  
Thanks.