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My neighbour and I are attempting to build our first guitars. East Indian Rosewood B&S, Sitka top,..
We are testing an OM cutaway bending jig, using a silicon heating blanket, 2 peices of steel, into an inside mold

For test wood, we started with 4 practice sides of poorly sawn Honduras Mahogany that we hand planed to a questionable thickness, and 2 sides of machine sanded QS Bubinga(0.080" or 2mm). we got it pretty good and were feeling ready to try the East Indian Rosewood, but wanted to try a few more bends to refine the process.

A friend gave us 4 sides of QS South African Mahogany at 2mm thick, to which we promptly put through the identical process, and broke in 3 places before we were halfway home.

What is with this wood? It never stood a chance!
we bent it at the same temperature as the Bubinga, but it seemed super dry. Perhaps it is too hot?

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Dee Tee

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"If something is worth doing, it's worth doing right."

did you wet the wood at all and how much? check out this video from john hall from blues creek. http://www.youtube.com/user/glasalle#p/u/42/tkuiiNZNpGA

We tried both spritzing and soaking 30 minutes hot water.
The Bubinga that worked so well was soaked.

We bought our blanket from him. We don't have a thermomoter but set it to H

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Dee Tee

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"If something is worth doing, it's worth doing right."

try the paper trick that he does in the video and get a therm. from what I understand you want to start bending over 245 and let it bake for a little bit. I have a timer so I let it run for 15 mins then let it cool to room temp. I have bent 4 zebrawood side and haven't cracked one and I''m doing cutaway's and I did the paper trick on all of them.

get on ebay and get a PID, solid state relay and a thermocouple to control the heat blanket also use a timer its easy to wire up...check forum archives for info, good stuff from Mr. Teller on how to use it.

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MK5acoustics.com

These are all good tips. Thanks.

What still confuses me is why the wood was so ridiculous. I assumed the mahogany would be an easier go, but where the previous mahogany, and the bubinga started to sag naturally as the heat was applied, the mahogany was almost completely rigid the whole way.

Is South African Mahogany just a terrible wood to bend?

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Dee Tee

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"If something is worth doing, it's worth doing right."

No it's not a terrible wood to bend, but it is more sensitive, in my experience to being dried with the proper kiln schedule. It's quite possible the side you are bending is the outside cut and as such might be case hardened.

I've seen it bend like butter and I've seen it refuse to bend. Tackle a few more bends with some more sides before you give up on it. It can be beautiful wood.

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There is no difference between the man that thinks he can....and the man that thinks he cannot.