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Hey Folks,

I just re-sawed some beautiful Khaya mohagany guitar backs (3/16) from a quarter sawn 2" thick billet cut from a 10' plank, straight as can be.. The wood could easily pass for Hondouras in appearance with the usual subtile ribbon striping .....however.... every slice immediately warped noticeably, the same way (not horribly though) and I had to keep truing up the billet as I progressed as well... has any one else noticed this trouble with this stuff? I did hear of one shop that wont use it.

I've re-sawn lots of wood and have never seen anything quite like this... usually warping is associated with grain that is crooked and has internal pressure or case hardening, where the first slice or two will warp.

Its a shame ...such lovely looking wood. Nice tap tone.

I find Khaya to be more sensitive to the use of the proper kiln schedule. Often, once a kiln is set up, the same schedule is used to dry many different species of woods, some more sensitive to how it's dried, and others less sensitive. I've had it come off a billet straight as an arrow...and I've had it come off a billet and immediately take the fetal position. Try stacking it for a while and see it it settles down. Given your statement that you had to keep truing the billet I'd say you've got your hands on some improperly dried Khaya. That's not to say that some Khaya just won't behave no matter what, but usually these examples are easily identified by the presence of compression wood, crazy runout, etc.

Chris

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Much Thanks Chris,

I was thinking something like that myself.

I might try what I call "conditioning", which is what I do with the kiln dried french maple I use for my viola da gambas ...I'd seen the necks move around and twist as I removed wood to shape them, so I made an insulated box with two 150 watt bulbs and a rheostat and slowly, over several days, bring roughed out blanks up to 145 degrees, keep them there for a 5 or so days, then slowly lower them to normal temp over several days and then let the box slowly come back to normal humidity through a little vent for a couple weeks, as it gets very dry inside.

This seems to totally de-stress the wood (you can see the movement on the various pieces after the process ) and when I trued up pieces and put them the process again, just to check, there is zero movement, even if the grain is a little squirrely. As far as I know there is no chemical change to wood until 155 or 160 degrees, from what I've read.

I have cut a lot of this and found that if you press it with stickers you can get this to flatten out. Flat and rift are the worse for cupping but it stabilizes in a few weeks

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I've used a ton of 16/4, re-sawing it for 3 piece necks. All of it was quartered and came off the saw perfectly flat and remained stable. But I've used some 4/4 for cabinets that was pretty squirrely. That could fit with the kiln drying theory as the 16/4 was probably dried on it's own schedule. Or it could be that the 16/4 was taken from bigger trees.

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http://www.chassonguitars.com

Thanks guys,

It's very helpful to hear of your own experience's with it ...It must be a wood that needs to be dried more carefully or else, like so many other products these days, there's more corner cutting in the process.