Official Luthiers Forum!

I have some Sapele that I thought would make decent tonewood - nice ribbon stripe figure.

What I didn't take into account was the runout through the face.

Every time I try to bend it on my Fox style bender, I get cracks. If you look at the photos, you'll see that the cracks happen where there's a lot of runout. Is it possible to bend wood with this much runout? I've bent Padauk & Wenge but Sapele seems more difficult to bend in general. I have to get it a lot hotter before it starts to become pliable.

Thanks,
Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

How thick is the wood you are trying to bend?
Tom

_________________
A person who has never made a mistake has never made anything!!!

All Sapele has some runout due to the interlocking grain (that's what gives it the ribbon figure). That piece isn't ideal but it should bend. I've been using Supersoft on all Sapele lately because it's so hard to predict. Some bends easy. Some doesn't.

If you have obvious localized runout, you can try to place it at a flatter spot.

If bending by hand, you can use a spring steel backer.

But Supersoft usually does the trick.

_________________
http://www.chassonguitars.com

It's right around 0.090" thick.

Thanks,
Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

You could go a little thinner and it will bend easier. I had a similar problem with some sides that refused to bend in the bender without breaking like that, I finally ended up doing it on the pipe and had much better results. I think because I had more control over heat/pressure/moisture. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

What temperature are you bending at? Are you using a controller ?
I have bent two sets with no problem around .085 at 300 degrees.

_________________
MK5acoustics.com

Sapele will bend but you need to do some things a little different . Use some wet paper over and under the wood . I hope you are using a heat blanket and slats . Get the temp of the blanket to about 250 to 325 degrees. Wate should be steaming off well. Do the lower bout first , Then check the the upper bout is still wet and be steaming , then bend the upper . The bending process should take about 4 to 5 minutes from the time you plug in the blanket , this is if you are using a 5 wt/pr/in unit . Once the bouts are in then complete the waist bend.
Allow the heat to go to about 350 - 375 for 1 minute then set at 250 for 15 minute and allow to 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

Kevin : I think .090 is too thick. Try .080 plus the tips from others and I think you will bend your wood.
Tom

_________________
A person who has never made a mistake has never made anything!!!

Hi Kevin,

In addition to what's been said, keep in mind that too much water will do that on wood that has runouts. If you soak the sides, try just spritzing instead. I personnally run my sides through the shower real quick, and I never had this sort of issue with my side bender.

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Thanks for all the replies.

I am using slats & a blanket that puts out 5W/sq in.

I don't have a controller but I do have an accurate thermometer.

I started bending around 270°F and yanked the plug when things got up to around 320°F.

This last attempt was dry but I've tried Todd's wet craft paper technique with similar results but I think I cooked it too long with the wet paper because there wasn't any steam coming out when I started bending.

I think the problem is in my slats which are approx 0.023" stainless. They are starting to get some set & don't conform to the wood very well even with multiple spring clamps in place which means I'm not getting good, even heat transfer (blanket/slat/wood/slat/form). I think this is the problem because I'm not getting cracks at the waist where I have good even contact between the blanket slats & wood that are under the waist caul.

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Try thinner... I have some Sapele that was sold as African Mahogany.... Spectacular, hard stuff with a ringing tap... but it works like Mahogany... I was finally able to get the sides to bend at 0.060"... Turned 1 set into charcoal and busted the 2nd to bits like yours... Thinner makes all the difference..

thanks

Your slats aren't hot enough. Just because the thermometer says you're up to temp doesn't mean you're ready to bend. I have a controller and I get that puppy up to 450F according to the thermocouple, and when I start seeing steam, I set the waist, drop the temp to 310, and finish the bending. There's a difference between the temperature of the blanket as measured by a thermocouple and whether the side you're bending is actually hot. I bend sapele all the time and with my tight waist, and I don't have any of the problems you're showing. Just go slow. You'll get a smoother bend if you take your time setting the waist and bouts. Bending a cutaway probably takes me five minutes to get everything down, then another 25 or so to set the bend and drive the water out.

Harder woods like ebonies, some rosewoods, and the like, want higher initial temperatures to get them to bend. Sapele doesn't need too much, but you've got to give it time to get hot before you bend it. Again, the thermometer means you've gotten the blanket up to temp, not necessarily the sides.

Where do most of you place the thermocouple?

From top to bottom I have blanket, slat, wood, slat then bending form.

I've been putting the thermocouple between the top slat & the wood just rear of where the waist caul engages.

Do you think my thick 0.023" stainless slats take too long to heat up? I think most you use slats that are around 0.014" or thinner?

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Look for steam. Bend slow.