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PostPosted: Fri Feb 22, 2013 1:20 pm 
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Cocobolo
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I have some very old Mahogany that was given to me (same stash as the old Maple I posted earlier - 40+ years), that I'd like to use. I've never built with Mahogany and want to know a good thickness for backs. The wood is very nice, but doesn't have a lot of cross grain stiffness. In it's rough state, it's between .12 and .11. I usually take my EIR backs down to ~.85-.95, so I don't have a lot of wiggle room with this wood to bring it down.

Thoughts?
Steve


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PostPosted: Fri Feb 22, 2013 3:29 pm 
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Steve, Depending on what you're looking for, you have a lot of wiggle room.

I like a responsive back, so mine are typically between .085-.09". Some people like a more reflective, stiff back. Those tend to be around .1" and usually get braced more heavily.

I like to bend sides around .085".


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PostPosted: Sat Feb 23, 2013 3:53 am 
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To complicate things, smaller bodies require thinner boards... same with sides, because smaller bodies require sharper bends. I like my sides to be around .080", in some cases thinner (down to .065") if cutaways or ukeleles are built. I try to make the backs slightly thicker than the side, like about .01" thicker than the side.

I am still kinda experimenting though, I mean to most people my guitar sounds good but to musicians with very picky ears its different altogether.

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PostPosted: Sun Feb 24, 2013 10:35 pm 
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Quote:
The wood is very nice, but doesn't have a lot of cross grain stiffness.

Is it sliced rather than sawn? I got some 1/8" thick sliced mahogany from Constantine's in the early 1970's, but I found that the cross-grain flexibility made it unusable for guitars.
The slicing process can produce micro cracks on the side of the veneer that was next to the blade.

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PostPosted: Mon Feb 25, 2013 11:09 am 
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Cocobolo
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Has the re-saw marks, so I assume it's sawn. I'll use it for a small guitar and see what happens. Wish the back had as much figure as the sides, but I suppose people look at the sides more than the back anyway as they play <grin>.


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PostPosted: Mon Feb 25, 2013 2:57 pm 
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The more thinner the sides are the more easy they will bend! Mahogany is not the easiest wood to bend anyway and the cross-grain tends to split if you dont take it easy! I bend it by hand tho..


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PostPosted: Tue Feb 26, 2013 11:04 am 
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I agree with James.
The sides should be no more then .080.
You must bend Hog wood with high but not scorching heat.
If you try to bend to fast or if the wood is too thick you'll
get compression breaks.

Try some samples first.
Mike

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PostPosted: Tue Feb 26, 2013 11:12 am 
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Mahogany can vary widely in how it bends but less water and more heat BUT NOT DURATION of heat.
I use wet paper . I bend typically at .090 on Mahogany , this will allow some sanding room for flattening the sides. Mahogany can be a pain for cupping if not careful.
Typical bending process is
Lower bout first at 245 to 250 degrees F
upper bout at 275 F
then waist.
When the thermometer is located can also make a difference. If you over dry it , you can expect this to crack so don't be slow. You should be finished bending in about 4 to 5 min , but once on the pattern allow heat to rise to 350 to 375.
I want to know the temp of the blanket not the wood. As long as there is moisture you may get a false read lower than the wood may be . You can feel the heat through the stack buy checking the bottom , and you want to feel the heat is penetrating the bundle. If you wait too long the wood will start to set , this is where you can get cracking . Again it is about matching the heat and moisture levels.
The higher the quality the better your chances of success.

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PostPosted: Tue Feb 26, 2013 11:22 am 
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Brazilian Rosewood
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Joined: Mon Jan 28, 2008 5:21 am
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Location: Central PA
First name: john
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City: Hegins
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Country: usa
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Mahogany can vary widely in how it bends but less water and more heat BUT NOT DURATION of heat.
I use wet paper . I bend typically at .090 on Mahogany , this will allow some sanding room for flattening the sides. Mahogany can be a pain for cupping if not careful.
Typical bending process is
Lower bout first at 245 to 250 degrees F
upper bout at 275 F
then waist.
When the thermometer is located can also make a difference. If you over dry it , you can expect this to crack so don't be slow. You should be finished bending in about 4 to 5 min , but once on the pattern allow heat to rise to 350 to 375.
I want to know the temp of the blanket not the wood. As long as there is moisture you may get a false read lower than the wood may be . You can feel the heat through the stack buy checking the bottom , and you want to feel the heat is penetrating the bundle. If you wait too long the wood will start to set , this is where you can get cracking . Again it is about matching the heat and moisture levels.
The higher the quality the better your chances of success.

_________________
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


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