Heat bending advice

[DaveMac]

Hi guys I have a short ash stave which I'm trying to straighten. I'm not having much luck bending it straight.  
 

it has improved but still springs back. I think that I'm heating for long enough around 15 mins per 6 inch section and then clamping to a straight board.

My question is should I make a form to add a small amount of reflex or will it just spring back uneven because the stave is currently uneven? Or should I try to bend a small section at a time over bending so it springs back straight?

[Draffish]

Hi dave if using a heat gun isn't working could heat steaming it and then clamping in position until dry work , never tried it on a bow but gave done other projects using this technique

[Bowjunkie]

You need to over-correct slightly. It will usually spring back some. It shouldnt be too thick, say less than 3/4"... floor tiller thickness is even better. With a good heat gun, you should be able to heat and correct half a limb or more at a time. How long heat needs applied depends on wood thickness, how fast you move the gun and how far away you hold it from the piece.

What is the moisture content of the wood?

[DaveMac]

Ok so a form won't work. It's 15 mms thick about 5/8 inch. As for moisture content I don't know but as it's a board that I've ring chased I expect it's kiln dried so low moisture content.

[Bowjunkie]

So it's dry. Heat gun is the ticket. You can use a form, or caul, just a simple piece of lumber cut to the desired shape, over correction factored in... then heat and clamp til it cools.

[Randy]

I have heat treated all my staves on a caul. I heat up a section and then add the clamps. Do the same with the next section and so on. After I get the entire stave clamped in the shape/form I want, then I heat the entire stave again doing short sections a t a time. Like stated earlier, the trick is to over-correct the stave so that if/when it moves back it should be straight.
Good Luck and post some pictures.
Randy

[DaveMac]

I think it's the over correction that I'm concerned about doing correctly. Can I ask how long do you heat each section for? Also how long are these sections?

[Roy from Pa]

Heat a 12" section till it's too hot to hold your hand on.