Problems bending Indian rosewood sides

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Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

Problems bending Indian rosewood sides

Just curious if anyone has encountered anything like this before..
I'm bending sides with a silicone heating blanket on a form. The last couple of sets have come out with a very noticeable ripple especially in the lower bout, like almost 1 mm between the highest and lowest spots. Here's the best picture I have of it, somewhat mitigated by sanding but I had to live with some ripple so I wouldn't weaken the side too much.
You can see it in the upper right of the picture on the lower bout of the guitar.
So is it just this batch of rosewood perhaps? (from LMI) Anyone else get anything like this ever?

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Andy Culpepper, luthier
http://www.andyculpepper.com

REPORT THIS POST AS INAPPROPRIATE | Date Jul. 17 2010 23:23:01

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: Problems bending Indian rosewood... (in reply to Andy Culpepper)

quote:

ORIGINAL: deteresa1

So is it just this batch of rosewood perhaps? (from LMI) Anyone else get anything like this ever?

I've had sides ripple when they were not cured long enough. It may also have something to do with excess moisture when bending. The moisture supposition is due to the fact that I haven't had a ripple since switching to dry bending (I use an iron).

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John Shelton - www.sheltonfarrettaguitars.com

REPORT THIS POST AS INAPPROPRIATE | Date Jul. 18 2010 14:17:18

estebanana

Posts: 9358
Joined: Oct. 16 2009

RE: Problems bending Indian rosewood... (in reply to Andy Culpepper)

D,

It's your bending technique not the wood. You are not letting the rib totally dry on the bending form and it is warping after you remove the rib.

Two things to try. One is to do a second heating with the blanket after the first heating has cooled. You need to cook off all the moisture in the rib before you remove it from the form. The second is to a drill a group of 5/8th holes in the top stainless steel sheet so the moisture can escape. If you do this then put the blanket under the rib instead of on top. The rib will dry in the bender.

If you remove the rib and there is any moisture it will stand a chance to wobble.

Bend once, cook twice.

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REPORT THIS POST AS INAPPROPRIATE | Date Jul. 18 2010 18:12:30

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: Problems bending Indian rosewood... (in reply to Andy Culpepper)

Interesting.
John, thanks. The wood came in in '07 and was already kiln dried from LMI. Seems like it should have been cured?
I do spray the sides down with a little water, not dripping or even quite wet everywhere.

Stephen, the way I usually bend is, I heat it on the form for about 20-30 mins., then let it cool completely and cook it again for another 10-20. I always have the blanket under the wood. After the first one came out rippled, I tried soaking both sides in "Supersoft", this stuff we had lying around that's supposed to make things bend easier. Then I put them both back on the bender and did my usual routine on both. The one that was still unbent when I put on the Supersoft came out quite a bit better than the first but it still had some ripple (it was the players side luckily). I also recooked the already bent one but it came out unchanged.
I guess in the future I will just give it longer to sit on there....

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Andy Culpepper, luthier
http://www.andyculpepper.com

REPORT THIS POST AS INAPPROPRIATE | Date Jul. 18 2010 19:24:56

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: Problems bending Indian rosewood... (in reply to Andy Culpepper)

quote:

ORIGINAL: deteresa1

Interesting.
John, thanks. The wood came in in '07 and was already kiln dried from LMI. Seems like it should have been cured?
I do spray the sides down with a little water, not dripping or even quite wet everywhere.

I would consider 07 to be borderline too young to use. I usually try to wait at least 5 years for hardwoods and 3 for soft. Kiln drying is not curing. I know there is some controversy about the effect of kiln drying on wood but if possible I would avoid it. A long slow air dry cure in a humidity controlled environment is best. At least that's the old axiom.

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John Shelton - www.sheltonfarrettaguitars.com

REPORT THIS POST AS INAPPROPRIATE | Date Jul. 18 2010 19:53:45