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I have broken two sides now in two different sets of sides. One set broke at the upper bout radius and the other on the lower bout radius. Very plain straight grain. Really took my time on the second set and I still broke one.

Fox bender, OM body, used one blanket below wood, sandwhiched between two SS slats, lightly spritzed with water, preheated for 7 minutes until upper SS slat would sizzle water. No issues with the waist bend.

I don't have any experienece with this wood. It seems very brittle. Any help from Colin or other experienced Cuban Mahoagni users would be appreciated. TIA

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tim...
http://www.mcknightguitars.com

I've used Cuban a few times, and have never had a problem with it. I do,
however, use two blankets and although some doubt it the extra one
really does make quite a difference although it is not necessary.

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John Mayes
http://www.mayesluthier.com

Tim,

I've made 7 guitars with Cuban so far and have only had problems with one set so far when I tried to bend too tight a cutaway with the side too thick.

I've bent it a number of ways - by hand, in my home made Fox Bender with lightbulbs, and as I do it now in the Fox Bender with the bulbs and a heating blanket. I normally bend the waist first by hand. Then my set up is slat, side lightly sprayed with water, wiped down with kitchen towel to remove droplets and wrapped in baking parchment, slat, heating blanket, slat. I don't have a temperature gauge or timer (slapped wrist) but just put light pressure on the lower bout area until I feel the wood become "plastic", then bend the lower bout, followed by the upper taking it nice and slow.

The wood I use comes from small plantation grown trees in Micronesia so may differ in it's bending properties from really old growth stuff. Colin may have more experience here.

Good luck, as I think this is a fantastic wood for acoustic guitars.Dave White38755.1234953704

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

I've used old growth Cuban 5 times, and never had a problem bending it. Basically the same bending system as Dave, but I do use a thermometer and bend at about 290-310F. Don't over wet and take slow. I bend waist first, leaving a 1/2" gap then lower bout, upper bout and finish the waist. I run the heat cycle twice then leave to cool overnight. Next day run up to temperature again take out while hot and set into mould and tighten clamping cauls.

Did both sets come from the same plank? could have been an inherant fault in the timber.

Certainly one of the easier bending woods.

Colin

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

Tim

What thickness are you bending at?

Josh

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Josh House

Canadian Luthier Supply
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House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

After cracking for sides in the last week, I discovered that my (new) setup was too hot. I had changed from a variac to a light dimmer to control the blanket - I checked the voltage and found the setting on my variac only set the blanket at about 105-110 volts, while the dimmer on full was 120. That translates to about 50-60 watts on the blanket. I have been setting it back to about 3/4 on the dial since, and everything has bent fine. The extra heat makes the wood drier and brittle fast, thus causing the cracks on tighter bends. As well, if you do the waist first, it worked fine, but the upper bout would be tough since it was heated longer, and thats where I was cracking. An OM shape should cause no problems with pretty much anything at about .090 side thickness.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

I don't use a thermometer (I know, shame on me)but I guess I will at least to get an idea of the heat. I use a light dimmer set at 75% and never have any scorching problems. I don't use parchment or use excessive water. Sides are .080".

Tony, I do bend the waist first then do the upper bout next so your theory of overheating (drying and brittlesness)does make sense. This is old growth with tight straight grain.

Yes, these sides were from the same plank. There was a small knot about two inches long running across the grain in the waist area and I thought that would fracture but it bent fine in that area.

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tim...
http://www.mcknightguitars.com

Tim,
I have sold over 80 (old growth)sets and as far as I know people have had no trouble bending it.
I have had many repeat customers for this wood.
I have sold to small builders and small "factories" so they are using all different types of benders.
Brad

Tim, I had a run of bad luck a month or 2 ago and found that my slats were getting quite rippled from repeated use. After I replaced them Things went much smoother. Course I replaced my whole bender too .

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

I don't mean to hijack the thread, but does anyone know where to get cuban mahogany. I've been dying to try it.

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Randy Muth
RS Muth Guitars Website
RS Muth Guitars Blog
Facebook Fan Page

I have it.
email or call me.
Brad