Multiple heat treatment?

[MattZA]

Hi all, just a quick question about bamboo backing and heat treatment.

I understand that one can heat treat the belly of a bamboo bow to plasticise the cells and improve compression strength (or something. Cast improves either way).

My question is: has anybody ever tried to heat a bamboo backed bamboo self bow? My thinking is before laminating the back and the belly, one could heat treat not only the belly, but also the belly of the backing? Therefore you'll have a heat treated 'inner belly' as well as a heat treated external belly.

Will it make any difference? Even in theory? Is it something everyone already does and I'm just not aware (likely option)?

Cheers!

[Del the cat]

A backing should IMO be thin enough so that it doesn't have a back and belly insofar as any heat treating done correctly would penetrate its entire thickness, backs aren't generally heat treated.
Del

[MattZA]

Ah okay, that makes sense. I just considered it from effectively a flattened bamboo self bow. In that case you tend to use a thicker back, which might lend itself to further treatment.

But I get your point about the depth of treatment. Thanks mate!

[PatM]

It wouldn't be a self bow and the compressive forces wouldn't be in that area anyway.

[MattZA]

Pat does it not count as a self bow if you're taking one piece of bamboo, shaving it flat and then gluing it back together? Not challenging you, genuinely asking.

I figured it might help, because even though the extra heat treatment isn't occuring on the actual belly, the internal belly (of the backing strip) is still undergoing a similar movement. But as Del says, if the heat treatment reaches through the entire bow it shouldn't have any effect.

It's a pity. It'd be great to somehow get bamboo up to equal compression strength as it has tension strength.

[leonwood]

If you cut a stave or bamboo and glue it back together it will always be a backed bow.

Heat treating a backing does not make much sense since it will make any wood or bamboo more brittle and less strong in tension.
Even if you have a thick backing, the then heated belly will be the core and neutral plane of the bow where it does not really need the extra compression strength.

Now if you are talking bamboo only bows, just heat treat the belly lamination, this will bring the compression strength closer to the tension strength of the back. Use the outside of the bamboo for both the back and the belly so you can make maximum use of the bamboo power fibers. Tiller each lam from the inside before glue up because you can only tiller a minimal amount from the sides after glueing

[Pat B]

What Leonwood said.  Anytime you glue 2 pieces of wood or boo together, with the exception of a handle splice, you create a backed or laminated bow.

[MattZA]

That all makes total sense, thanks fellas! Ironically I'm toying with the idea of building an all bamboo laminated bow. A 13 year old student of mine is keen to start horseback archery. Obviously I don't have the experience to even venture into the world of horn bows, so was considering a short plains bow shape (setback handle, deflexed inner limbs) and then simply gluing and wrapping some smallish siyahs onto the ends. The end product only needs to be 35# at maximum, and with a short 24" draw.

I'm busy building a mini model to see if the idea is viable. 30" in total, 26" without the little siyahs. Flattened bamboo back and belly. Heat treated belly. The weight was too high, so I've been forced to start tillering the back very slightly as well as the sides (obviously). Aiming for 16" draw. Let's see...

[MattZA]

Here's the little model version so far. 30" from tip to tip. 1/2" wide at the handle with a gentle taper down to 3/8" tips. The bulletwood statics are tiiiny at 1/8" width.

It feels too heavy to survive, though.