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Attempting to bend my first Honduran Mahogany sides and having some trouble. Any advice? Using a Bluescreek bender & steel slats, with the heat blanket and controller. Placing the thermometer right under the blanket and bending at 300/310 degrees. .077 thick.
My stack was steel slat, blanket, wood, steel slat?

you are waiting too long
start bending at 225 and you should be done bending in 4 minutes also are you using wet paper on the wood? Call me I will be happy to help.
http://www.youtube.com/watch?v=JFNy93PM0Kc

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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

It looks as if you are using the blanket on the wood. Are you supporting the curves with the steel slats? That's very important.
A steel slat on the outside will give some support to the fibers that want to bend outward and snap.

I got my bender from BluesCreek as well, I use the slat, side,slat, blanket setup with good results and no cracking (so far!) without even using SuperSoft veneer softener, which will soon be suggested by people who use it.

We'll see how my Gaboon Ebony sides do on this next project.

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Old growth, shmold growth!

I did use the blanket right on this side the other I had wrapped in aluminum foil and the sides were dampened. The stack was, steel, blanket, wood, steel.

Yeah, I'm definitely seeing scorch marks on the wood from the blanket. You're missing a few layers. You need a pair of bending slats. I got my whole setup from John as well. Following the included directions, I spritz the wood with distilled water, wrap it in parchment paper (I think John calls for Kraft paper), then sandwich it between the slats, with the blanket on top of the upper slat. I heat to 220, start bending the lower bout, do the upper bout around 280, then the waist around 310. Works like a charm. It's very important with mahogany to go slow -- take your time while working the cauls around the form, and don't go too hot. From my experience, mahogany tends to crimp and fold at too high a temp, which I'd guess to be around 320 max. Btw, I wrote the temps on my bender for quick reference.

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Mountain Song Guitars www.mountainsongguitars.com

I always start bending around 275-300, with the blanket on the outside, so perhaps the wood is cooler as John suggested. Also, perhaps the silicone didn't offer the support that steel would have.

By the time I'm done bending the temp is about 350, and I turn it down and let it bake for a half hour.

Maybe you need SuperSoft.

Also, I wouldn't discount the possibility the side had a microscopic crack in it already.

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Old growth, shmold growth!

It never hurts to use super soft. Ony drawback is the 12 hour wait time. I don't know why folks keep saying use slats.. Seems from your own description, u are using them.

Get the super soft.
Mike

Btw, are u bending Uke sides?

Martin D size.

I was just thinking that the silicone layer before the outside steel slat lessened the support the side would have received from direct contact.

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Old growth, shmold growth!

What about gaboon ebony?

Bent any?

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Old growth, shmold growth!

I agree, SSII not needed for Mahogany, but that break looks just like the breaks I dealt with using Koa (low figure, no flame). Those were uke sides, very tight radii

How are u getting scorch marks from the elements on the wood? I wrap my wood in Kraft paper (brown stuff I buy at hobby lobby or Lowes). Spray wet, then another layer. SS slat, blanket, wrapped wood, SS slat. Then I secure the stack with blue tape. Maybe your spring blocks were not tight enough in the curved part?

Where can I get some anger? That sounds like a cool wood!

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Old growth, shmold growth!

when I use the SSll I bent after 2 hrs and had no problems. Like anything , there is a learning curve. Some woods hate water Maple , Mahogany and some want a lot of heat Padauck is one I think
The key is the heat and duration , Once you take the cell heat to a point the wood becomes plastic , but it can set and then you are untying a pretzel. From the time I turn on the machine till I am done the bending part 4 mins tops. I will allow the heat to 350 when it is on the patterns and bent
then set to L and 220 to 250 to cook off the water . Let cool

_________________
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

There doesn't appear to be any scroch marks on the break area and would suggest to me that you're bending too early in the process.

I would check the thermometer for accuracy.

I generally just spray a little water on Mahogany before I put it in the bender.

Try taking the temperature up slowly and look for steam. Once you have steam start the process and continue slowly. You shouldn't need to increase the temperature at this point. At least not enough to scorch IMHO.

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Michael Lloyd

“I was born to ignorance, yes, and lesser poverties ...
I was born to privilege that I did not see ... I didn’t know it, but my way was paved” – John Gorka

the scorch marks are on the out side The inside won't show the marks unless you ebonize the set. I have seen this happen and often it is because you waited too long the the wood set before it was bent.
Every once in a while you may find some Brackish mahogany that cracks no matter what you do. Using wet paper helps to lengthen the work time but too much water is not a good thing either.
Remember 4 minutes ,
lower bout 220 degree
upper 250 to 270
then waist
allow to heat to 350
then set to 220 to 250 to dry off and set bend.

_________________
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

This wood is being scorched at 310. The wood in IMHO is thin .077 inch. Approximately 2mm. Just right by the way.

Even without water and at that temperature 310 it should have bent like butter. With no scorching.

Scorching tells me too much heat. The breaks tell me bending too soon in the process.

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Michael Lloyd

“I was born to ignorance, yes, and lesser poverties ...
I was born to privilege that I did not see ... I didn’t know it, but my way was paved” – John Gorka

Success! One more set of sides bit the dust (all failures were out of the same board) Re-sawed another board and these sides bent perfectly. Moistened wood wrapped in damp craft paper, from the top Steel slat, heat blanket, wrapped wood, steel slat. I used a shop rag held on the steel slat and when the temp hit 240 I slowly bent the rear bout with hand pressure and then used the spring caul to hold in place, same with the front bout and then the waist. Pretty much what John Hall laid out. No scorching got the sides clamped in the mold. Ready to trim the ends and glue the neck and tail block.
Thanks for all the advice.

I think that most people, myself included put the wood between metal slats, then the heating pad on top.
I think you'll get a more even heat this way. But it sounds like you've got it down now.

Also, I worry about letting that blanket touch the wood, it is silicone blanket. We know about silicone and problems finishing.

John Hall's videos are very helpful.

So did that first board have a hidden flaw in it that just busted on every one? Bummer.

I called John Hall yesterday and followed his instructions, I might give that a try sometime, the sides I have bent, White Oak and Sycamore bend like macaroni.

I wrapped these in craft paper.

I don't know......nothing I could see, they were perfectly quarter sawn so that was a bummer. I have a good stash of mahogany so chalk it up to a lesson learned.

This is a different type of silicone in the rubber and it does not leach out and cause finishing problems.

Thanks Barry, that's good to know.
I was worried about that, the blanket feels all greasy, probably because it's brand new.

Cheers!

Follow up: I bent another set of Mahogany sides for a size O I'm going to be starting later in the year. Much tighter radius on upper and lower bouts. When the temp was around 160 I started applying hand pressure and completed the bend, then used the spring cauls to hold in position. You can feel the wood relaxing as the temperature goes up. Seems Mahogany starts to relax much quicker than the White Oak I've worked with.