Heat treating and then gluing lams

[DC]

I've often toyed with the idea of building a tube oven. I was thinking of a six inch diameter metal duct with a long heating element. I just wasn't sure if the radiant heat from the element that close to the stave/billet would be a good idea. Maybe an 8 or 12" tube would be better but being bigger it would be harder to heat I imagine.

[lonbow]

Wohooo! This might really take laminated bows to a new level!

1. The heat treatment reaches the inner parts of the wood. So the effect is much stronger than with selfbows.
2. The inner frictioof the wood will be reduced to a minimum due to the heat treatening.
3. The mass of the bow will be also really small.
4. Heat treatment can be combined with perry reflex.

I am certain your bow will rock, Dell!

lonbow

[PatM]

I have cut up the limbs of a heat treated bow and if done properly the  heat easily penetrates to the full depth of the limb which takes the compression.

 The cross section ends up looking remarkably like either an ideal yew limb sap/heart ratio or a typical backed bow with a  bit less of a distinct margin obviously.

 The belly is browned to within about 1/4 inch of the back through the depth of the limb.

 The Finno Ugrian bowyers already did the heat treat the belly first separately and then laminate in Perry reflex.

[DC]

Have you treated wood in an oven? If so, what temp and how long? I just did a triangular piece at 350°f for an hour. The outside has gone a nice brown, not as brown as the 400°, but nice. When I cut across it and sanded the ends it doesn't look like it penetrated much. Not sure what to make of this. It's back in the oven a 350 for another hour.

[DC]

I think I'm heating them too long. I did a roughly 2x2" piece at 350 for an hour and I can't see a line. I'll try 15 min next.

[PatM]

http://www .westwoodcorporation.com/what.html

[willie]

Not sure what to make of this.

the typical thermostat on a kitchen range, in addition to being not regulated well for accuracy, also suffers from a high differential. so when a call for heat is made, a surface exposed to the radiant heat from the element may get quite a bit hotter than the air near the oven temp probe. the large differential between off and on leads to long cycles.

I use a digital unit like this...and set my oven dial so that the cycle tops out at the desired heat. I shade the wood from the element with tinfoil also.

as pat points out, the commercial guys use an oxygen deprived chamber. heat treating is used in place of chemical treating more in europe and is well documented

[Limbit]

Why don't you just heat the belly lam and remove the wood as you tiller? So long as you evenly apply heat, this shouldn't be a problem. I saw a carbonized composite boo bow made this way years ago. Heated the belly boo till it turned black, glued it up, then tillered normally. Plenty of heat still got through the lam. Lams are thin so you aren't really having a transition of heated material as in a self bow. It is more conistent due to how thin it is. Really, you are creating a heat treated lam, not a heat treated bow. No need to over think it. The yumi smoking thing is just to preserve the bamboo by the way. I read some info on it years ago and that is what they mentioned, although there may be more benefits to smoking. Boo grows mold easily.

[DC]

I was thinking more about hard backed bows where the belly piece(lam? I wasn't sure what to call it) is maybe too thick to get a good heat treat with a heat gun.

[PatM]

 A heat gun will cook right through an inch of wood.

[DC]

In order to go that deep how far would you hold the gun from the wood and how dark wood you let the wood get? Ballpark is close enough. I usually do 3 1/2-4" until it noticeably darkens and I could still hold my hand on the back of a half inch thick limb

[Del the cat]

The use of a pizza type oven is well known as a heat treating method.

 What actually happens with heat treating is as well documented as we need it to be and it's certainly much more than just super drying wood.

Ah.. it may be well documented , but the interweb isn't always good at finding stuff!
There's a place in the UK called "Sale" ... try searching for that 
I found it eventually!
Del