Heat treating and then gluing lams

[DC]

When you heat treating and then glue a surface is there any special care with the joint?

[PatM]

Freshen up the gluing surface.

[Marc St Louis]

May depend on the wood species.  HHB benefits quite a bit from heat-treating on hard backed bows.  I only prep the surface of the HHB for gluing after heat-treating

[maitus]

The question is if the belly needs tillering after heat treating and gluing lams... wont You tiller the treated part off?

[Del the cat]

Similar, related question, aimed at Marc really  :-
I'm making a flight bow, heat treated Yew belly, 'Boo back.
I've done a good slow heat treat on what will be the back face of the Yew which is about 1/2" thick mid limb. I felt the other side as I was doing it and it was too hot to keep my finger on.
How far into the wood does the heat treating go? Is it worth heat treating the other side too (the side which will have the Boo back glued onto it).
Sorry if this is an unanswerable Q and I don't mean to hijack the thread... I just don't want to glue it all up and then wish I'd heat treated more thoroughly 
Del

[DC]

Not a hijack Del, just stating my question a little clearer than me. That's exactly what I am doing

[DC]

The question is if the belly needs tillering after heat treating and gluing lams... wont You tiller the treated part off?

In my experience, yes. That's why you delay the heat treat as long as you can or do it twice.

[willie]

with a laminated bow, couldnt a glueline be considered a workable moisture barrier? my thought is to give a nice thorough (maybe longer at a slightly lower temp?) heat treat to the belly lam. The back could be glued to it  a bit green even.

If the belly treat is thorough, one might not have to worry about removing some of  it during tillering

[Marc St Louis]

Del. I've found that with a slow heat-treat the effects travel perhaps 1/8". 

I've never tried treating both side of the core and I don't think there would be much advantage since the back side of the core wouldn't be doing any work but on the other hand it wouldn't hurt

[maitus]

The question is if the belly needs tillering after heat treating and gluing lams... wont You tiller the treated part off?

In my experience, yes. That's why you delay the heat treat as long as you can or do it twice.

I have seen video about making yumi bow. They smoke (i would say heat-treat)their lams for a long time in the special smoking houses. There must be some point ...Maybe to use some metal pipe over the fire to get even and long treating thru the material?

[simk]

another approach:

why in that case not use epoxy that resists heat? eg

https://www.shop.swiss-composite.ch/shop/resources/downloads/t-LY5210_HY5210_HY5211_HY5212_e.pdf

or natural fish glue that resists temps of 160C celsius?

Cheers

[Del the cat]

Thanks Marc:-
This thread really sums up the problem with trying to heat treat a bow that is laminated or backed.
Got to get it almost spot on right before glue up .

Regarding lower temperature and longer.... it needs about 200C (390F) degrees to heat treat, and that's more than any glues I'm found can cope with. It would need extreme care to keep the heat off the glue line.

Must admit I was surprised how hot the underside of the piece I was heat treating had got. I think heat treat a 2nd time for good measure, as it's been cleaned up a tad on the belt sander.
I think this has been the prob with mk1 bow, I've gone through the heat treating on the top limb 
Del

I think

[lonbow]

Thatīs a very difficult question. There is one possible solution I can think of (Iīve never tried it):

At first, you take the belly lam alone and reduce it close to the measurements youīre looking for. You can compare the measurements with other laminated bows. You tiller the belly lam alone without the backing on it. Of cause you should not pull it too far, as the belly lam might crack. Maybe you can pull until the belly lam reaches brace hight? Of cause, the wood should have a streight grain then. When youīre happy with the tiller, you can heat treat the belly. After that you glue on the bamboo backing. Hopefully the bow wonīt be out of tiller too much after that, so you can correct the tiller without removing too much wood on the belly.
An other possibility might be using hickory instead of bambo. You could correct the tiller in the end by removing wood from the hickory backing.

lonbow

[lonbow]

There might be a second solution:

You glue on the backing with hide glue, and tiller the bow to a draw length of about 20". When youīre happy with the tiller, you put the bow in the water for some hours until you can remove the backing from the belly. Then you wait for one or two weeks until the wood is dry again. Now you can heat treat the belly and glue the backing on the bow again. Then you can tiller it to your draw length. I donīt know if this works! Itīs just an idea that might be worth trying!

lonbow

[Del the cat]

There might be a second solution:

You glue on the backing with hide glue, and tiller the bow to a draw length of about 20". When youīre happy with the tiller, you put the bow in the water for some hours until you can remove the backing from the belly. Then you wait for one or two weeks until the wood is dry again. Now you can heat treat the belly and glue the backing on the bow again. Then you can tiller it to your draw length. I donīt know if this works! Itīs just an idea that might be worth trying!

lonbow

Good idea but a bit labour intensive.
I'm hoping to get mine close first time, but I have extra length to play with and can do some tillering on the width.
Del