advice building a achumawi bow

[DaveMac]

Hello I hope someone can help me. I'm a novice bowyer with only limited experience building board bows. I had a 4ft long off cut from an ash board that I decided to use to practice ring chasing. Anyway once I had chased the growth ring I was presented by a twisted piece of wood (approx 35 - 40 degree), but I hate to see wood go to waste so I thought I would see if I could make something from it. The achumawi bow from TBB vol1 (p176) seemed possible if I could straighten the wood.

So I roughed out the shape (40" ttt) and started to heat treat the wood using a heat gun and olive oil. Removing the twist seems to have been successful




however there is still some deflex bend in the stave, although it has improved it is certainly not straight.



So now I am unsure how to proceed.

Should I try to heat treat the bend out now into reflex, or try to long string tiller the bow and then add reflex when I sinew back it?

Also the depiction in the bowyers bible seems to show a rounded belly, at what point should I do this before or after tiller?

[Badger]

  Dave, on an ash bow I would not make the belly too rounded, maybe just round 1/2" or so on the sides, do this durring the tillering process or your tiller will change. Keep your bow in a semi finished state throughtout tillering.

[mikekeswick]

Make a form to clamp the stave to whilst heating and bending.
You round the belly during tillering.

[DaveMac]

I clamped it to a straight board while heating but it springed back to what you see in the pictures. When I got the twist out I found that I needed to twist past straight to compensate for the spring back. I'm concerned that if I build a form that a similar thing will happen.

How many times can I heat treat the wood before it gets damaged?

Thanks for the replies I appreciate the advice!

[Del the cat]

You are probably making the beginners mistake of not heating it long enough. You should be bored to the point of despair when doing any heat bending or heat treatment. If haven't lost the will to live, you haven't heated it long enough.
Also it needs to be clamped with a bit more bend than it needs as there will be some spring back. Adding slats or foil etc to help hold the heat in will help, remember the heat has to penetrate right into the wood and that wood is a pretty good insulator.
We've all done it, even the most experienced.
Del

[DaveMac]

Sounds about right I didn't heat it for that long.  If I make a form to put a slight recurve into it would I be right in thinking that it would spring back uneven because it is currently uneven?