Mahogany Bending Failure

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Eric Knapp
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Mahogany Bending Failure

Post by Eric Knapp »

Hi, all. I have this beautiful mahogany board and I wanted to make a guitar with it. You can see why I wanted to in this short video.

https://youtu.be/aUarRrP5yU8

I bought the LMI Bending Machine as I could not get samples to bend with my hot pipe. We cut 4 side pieces from board and bent them all in the LMI bender. We followed the directions exactly and they all cracked badly. One even broke apart. This wood is perfectly quarter-sawn which makes it hard to detect runout. It must have bad runout or have some other features that prevent it from bending. We need a plan B.

My daughter and I have limited time this summer before she heads back to college. We are going to use the mahogany for the backs and a different wood for the sides. Time is of the essence so we’re using sets of East Indian rosewood sides I have that don’t have backs. The guitars will be interesting and it’s more important that we make progress than have them match. These are learning instruments.

From comments in my previous post about this wood I am guessing this is just not appropriate wood for guitars.

-Eric

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Barry Daniels
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Re: Mahogany Bending Failure

Post by Barry Daniels »

It's pretty wood. A few questions:

1) How thick did you bend it?
2) At what temperature did you start bending at?
3) What was your process for adding water?
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Eric Knapp
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Re: Mahogany Bending Failure

Post by Eric Knapp »

Barry Daniels wrote:
Wed Aug 10, 2022 5:36 pm
It's pretty wood. A few questions:

1) How thick did you bend it?
A couple were 2mm and the other two were about 1.8mm.
Barry Daniels wrote:
Wed Aug 10, 2022 5:36 pm
2) At what temperature did you start bending at?
We did one at 320 and the others at 300. The instructions for the LMI bender says different temps in different places. The video by Robert O’Brien says to use 350 but then there’s an overlay that says LMI now recommends 300.
Barry Daniels wrote:
Wed Aug 10, 2022 5:36 pm
3) What was your process for adding water?
We spritzed the sides with distilled water just before wrapping them in foil.

We are bending the EIR now which is 2.2mm thick and we’re hoping for success. That wood is supposed to be much easier to bend.

-Eric

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Eric Knapp
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Re: Mahogany Bending Failure

Post by Eric Knapp »

Here’s a follow up on the bender. We just used the LMI bender with a piece of 2.2mm East Indian Rosewood and it worked perfectly.

E6B0EFED-CE47-44BA-91E6-177AB0BF8A7D.jpeg

-Eric

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Barry Daniels
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Re: Mahogany Bending Failure

Post by Barry Daniels »

That looks good! Keep it clamped in the form for a few days till it dries out.
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Eric Knapp
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Re: Mahogany Bending Failure

Post by Eric Knapp »

Barry Daniels wrote:
Wed Aug 10, 2022 8:32 pm
That looks good! Keep it clamped in the form for a few days till it dries out.
Thanks, Barry. I was trying to not get discouraged and this helps.

-Eric

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Barry Daniels
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Re: Mahogany Bending Failure

Post by Barry Daniels »

Actually, it doesn't look good, it looks great. Zero springback is a worthy goal that is not readily achieved.

What you did here indicates that the trouble with the mahogany may be more the fault of the wood.
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Dave Meyrick
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Re: Mahogany Bending Failure

Post by Dave Meyrick »

Some wood simply doesn't want to bend. When I was starting out I thicknessed some Sycamore which I had dried myself. It wasn't pretty timber and I just thought I would have a practice at bending before using some decent stuff. The results were not good!
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Eric Knapp
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Re: Mahogany Bending Failure

Post by Eric Knapp »

Dave Meyrick wrote:
Sun Aug 14, 2022 12:21 pm
Some wood simply doesn't want to bend. When I was starting out I thicknessed some Sycamore which I had dried myself. It wasn't pretty timber and I just thought I would have a practice at bending before using some decent stuff. The results were not good!
This is good to know, thanks. I have a lot of wood I was hoping to use for guitars. I hope some of it will work. The spruce and redwood for tops I have is probably OK. The backs and sides are more of a challenge.

-Eric

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