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Tomorrow I'm bending mahogany for the first time. The sides are thicknessed to .095" Here's what I'm planning to do:

1) Wrap in craft paper
2) Lightly spritz the wrapped wood
3) Metal slat/mahogany/metal slat/heating blanket
4) Light bulbs below...blanket on top
5) Lower waist screw just to contain the sandwich
6) At 215* slowly lower waist until seated
7) Lower the lower bout caul
8) Lower the upper bout caul
9) Stop heating at 275*
10) Re-heat to 275* after cooling to room temp
11) Remove after it reaches room temp

If anybody sees any glaring errors, please chime in.

TIA...JJ

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JJ
Napa, CA
http://www.DonohueGuitars.com

Good luck with the bend!

.095" sounds thick to me. I like my mahogany sides .085" or thinner, depending on how aggressive the bends are going to be. Mahogany can be a little more brittle than rosewoods (although I haven't tried Cuban mahogany before), so I wouldn't try .095.

Also, the wood will retain its shape better if you run it through several cycles of heating and cooling before removing it from the bender.

Be careful using both bulbs and a blanket, as too much heat will scorch the wood.

I'm anxious to hear your results. Do you have a cutaway?

Two thoughts, firstly, as Kelby says, the sides sound a bit thick to me I usually bend at about 80-85 thou especially if you have tight bends to negotiate.

Secondly I start my bend with mahogany at about 250-270 and just bend the waist halfway, check the alignment of the sides in the bender. As the temperature rises towards 300 first the lower bout then the upper bout are bent and held in place. Then the waist is the fully tightened down, this will pull everything nicely into the form. Hold the temperature at around 300 for 5 mins. Cool down to around 140 or so (not critical) then bring back up to 300 and hold again for 5mins. Switch off walk away and leave to cool right down.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Ya got good advice there JJ. On my little mahog guitars I'm taking the sides to .070" but depending on the size of your guitar you could probably go to .080" if it's say a 000 or something. I start clamping down at around 225 degress and max at 300. I also cycle it after cooling but usually only up to 275 or so.

What ya makin?

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Tickle your guitar daily, and it'll tickle you back.

Thanks, guys...Colin, I was hoping you'd post since you are our resident "Mahog-O-Maven."

This is a Mahogany & Lutz OLF-SJ...no cutaway. I'm actually building 3 at the same time...the other 2 are a 000-12 fret with Zootman's Quilted Sapele & Adi and an OM with EIR & Sitka.

Yesterday I bent the Sapele @.100" and it went flawlessly using the protocol I posted... with one exception. The only thing different was that I lightly sprayed the sides with Super-Soft 2 (a grain softener) about 2 hours before bending. There was absolutely NO grain rising after the bend and is smoother than I ever expected...especially with fresh memories of bending that WF Bubinga last time. BTW, Hesh...it started "hissing" at around 220*. In order to protect from scorching, I kept the temp no higher than 275*.

I was thinking that Sapele might be closely related to Mahogany and that's why I wanted to get opinions before I do these bends.

Soooo, that begs my next question...has anyone ever used Super-Soft 2 on Mahogany? Now that I'm pondering this bend I may just use it on the Mahogany as well.

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JJ
Napa, CA
http://www.DonohueGuitars.com

My first 'real' guitar was of the same species, although the wood was from Santo Domingo. It was a nightmare to bend! I got some Cuban about 15 years ago, and only recently got up the nerve to make a guitar from it; the runnout was just too scary. It came out fine.

What I did was to pre-bend the sides by hand the day before putting them in the bender. They were at .080 or a little thinner, and I took them about as far as I thought I could safely. The final bend the next day, after they'd had a chance to get used to the idea and get soome moisture back in them went fine. This was a classical guitar, with a cutaway, BTW.

[QUOTE=JJ Donohue]
...
Yesterday I bent the Sapele @.100" and it went flawlessly
...
[/QUOTE]

Any springback? I've yet to bend sapele without at least one inch of spring back at each end, compared to rosewood it's like bending rubber.

Marc...Sapele was a breeze. Some springback but I clamped it in the mold form overnight. Gluing to the blocks this morning was uneventful.

Back to the Mahogany. You guys have my begeebers working overtime so I have a test in progress. I took the long cutoffs from the side profiling and bent one using just water sprayed on the craft paper. It's cooling down now but I didn't hear any cracking. The big question...how predictive will this be for when I bend the actual sides?

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JJ
Napa, CA
http://www.DonohueGuitars.com

No experience with Cuban Mahog specifically, but anything at .95 for me runs to high a risk of snap,crackle,pop problems. I take the hard to bend sides (most high figure) down to .75 and (easier strait grained) others to .80 and have not had any problems with cracks or blemishes since. When I was working from .85-.90 I had to many problems.

Mike

"3) Metal slat/mahogany/metal slat/heating blanket"


Be sure your slats are spring steel or stainless steel, otherwise there is a possibility of galvinistic staining.
MichaelP39008.6556018519

It's spring steel, Michael. John Hall taught me well

BTW...the strip trial was successful...no snap, crackle nor pop I'm off to go live with the sides. Since I've had good luck with Super Soft 2 I already have one conditioned for an hour...stay tuned.

Incidentally, this wood has no figure to speak of...very plain in grain and appearance.

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JJ
Napa, CA
http://www.DonohueGuitars.com

[QUOTE=JJ Donohue]
Incidentally, this wood has no figure to speak of...very plain in grain and appearance.[/QUOTE]

Straight grained Cuban mahogany JJ, probably the finest tonewood in the world! (discusss)

Good luck with the bend, I can't see any reason for it not to go just fine.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

UPDATE...The first side bent without any problems whatsoever. I'm off to do the second side.

Thanks all for the help!!! I love this place

BTW, Colin...I'm really looking forward to test the performance of this wood. I already have a completed OLF-SJ (Carpathian & Bubinga) and am anxious to hear Miss Mahogany's voice and experience her personality in comparison. I'm actually relieved in a way to work on something plain and understated for a change...of course it will be zooted up a bit with the bindings I'm planning to use.

I'll post some pics once I complete the boat.

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JJ
Napa, CA
http://www.DonohueGuitars.com

[QUOTE=Kelby]   Mahogany can be a little more brittle than rosewoods (although I haven't tried Cuban mahogany before), so I wouldn't try .095.

[QUOTE]

Glad to see this thread but now you are scaring me.

I have Cuban Mahogany for my first acoustic (back and sides) so this will be handy later.

I'm sooo far behind on my other pre guitar projects to finish it may be next summer before I can attempt any bending.

Fear not, Scooter...they both bent beautifully. It's always good to be cautious, however and go slowly and deliberately.

I don't know how much of an effect the Super Soft pre-treatment had on the bends, but all I know is that since I started usng the stuff I've had zero problems. It also has had no deleterious effect with bonding and finishing.

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JJ
Napa, CA
http://www.DonohueGuitars.com

JJ
Where are you getting Super soft treatment from. I bent my
Cuban mahogany sides .090 and they gave me a bit of spring back and now I have to cook again. Unfortunately the first got a little hot and scorched a little. Whoops. Live and learn. They weren't brittle, and no breakage. Just way to much spring back. I will try some of the ideas mentioned in this thread. Thanks for asking the question. Hope your build goes excellent for you.

Ron...Check it out at
http://www.joewoodworker.com/catalog/product_info.php?produc ts_id=616

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JJ
Napa, CA
http://www.DonohueGuitars.com

Super Soft sure sounds like a good insurance policy for the tone wood.

I did get some "practice sets" from Stew Mac for bending so that should come in handy as well.

Glad to hear it all went well bro, cuban mahog is now on my list for future try!