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My Name is Joe and I can’t Bend Sapele
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=9254		 Page 1 of 2
Author:  Joe Beaver [ Fri Nov 10, 2006 2:39 pm ]
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I'm trying a new design, nothing special, just my idea of a SJ, so I thought I'd make the first one out of Sapele. Nice wood, good sounding and cheap! (like Me!)

I made a new form for my side bender, Made a sandwich of SS slat on bottom, heating blanket, wood spritzed with a little water, and another SS slat. I clamped it all together and heated to 300. I bent the waist slow and it seemed to go okay. Then I did the lower bout and it was stiff, but OK. By the time I did the upper bout the wood was cooked hard and broke like glass.

The next side I stacked the wood the same way but only clamped it together at the waist. That way the blanket fell away from the sides until I moved the clamps. After it was around 300 I worked the waist slowly into the mold. Then I moved the clamps to the lower bout heating it up. Bent it, then the same with the upper bout.

It sounded like a plan but it didn't work either, cracked at the waist and major spring back on the bouts. I know what you are thinking..... it was me not the wood. Went down and bought a nice quarter sawn piece from Austin after the LMI wood broke. Same result.

Any tips on bending the stuff?
Author:  peterm [ Fri Nov 10, 2006 2:44 pm ]
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Joe, I always get the wood to the desired temp turn off the blanket bend a bit and turn the blanket back on... 4 times...
waist 3/4 of the way
lower bout all the way
upper bout all the way
and finish off the waist

If you keep the blanket on the whole time there is a possibility it'll get to hot and scorch the wood!
Author:  Joe Beaver [ Fri Nov 10, 2006 2:45 pm ]
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Michael,

i used paper.... mayble tomorrow I'll cut a couple more sides from the Austin stock and try again. How hot did you get it?
Author:  Joe Beaver [ Fri Nov 10, 2006 2:47 pm ]
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Peter,

Do you use a thermometer? How hot do you get it?
Author:  peterm [ Fri Nov 10, 2006 2:50 pm ]
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Joe, digital food thermometers can be purchased at walmart for around $10.00
For mahoganies I start the bend at around 290. That means I turn off the blanket and it will still raise up to about 300 after its turned off. I do this every step as mentioned above...
Author:  Louis Freilicher [ Fri Nov 10, 2006 2:52 pm ]
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How thick were your sides?   I would take them down to .080". The rest of
your process sounds right on to me. I skip the slats and paper. I sprits my
wood and lay it right on the blanket on the form, and I've never had a
problem. Now, I'll go bite my tong and break my next set!

Good luck,

Louis
Author:  Joe Beaver [ Fri Nov 10, 2006 3:00 pm ]
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Louis...

The first time I thinned to about .89, the second .84.

I like your idea of no paper, no slats, just me, my blanket and some wood... mono e mono..... I'll try it tomorrow... (along with several other methods the way it's going)
Author:  Joe Beaver [ Fri Nov 10, 2006 3:05 pm ]
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Peter,

That sounds about right. I have a stew mack thermometer I've been using. Maybe I'll pick up a wal-mart one tomorrow. A comparison might be interesting.
Author:  peterm [ Fri Nov 10, 2006 3:08 pm ]
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Joe, when I have troubling wood I also do the following:
spritz the wood and wrap in WET kraft paper. Then wrap the wrapped side in wax paper to really seal in the moisture. ( I guess you can do the same with aluminum foil) then bend as regularly!

Good luck...
Author:  Michael Dale Payne [ Fri Nov 10, 2006 4:09 pm ]
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You did not say if this sapele was figured, ribbon or quilted. Quilted has a nasty habit of vertical grain pulling loose in tight bends. This appears as a crack but it is a stress induced separation of the fifers that run in the vertical direction. this is almost always to the outside radius of the bend. at the waist this is the inside surface of the rim but the outside of the bend. Clear as mud right . Anyway if this is the case when bending quilted wood add just a bit more moisture on the down side at the waist. Don't use flimsy slats. Supporting the bend well is important. I bend quilted Sapele at 310-320. once at temp, bend 3/4 of the waist, bend upper bout complete, bend lower bout complete then finish the waist. What this bending schedule does for you is two fold. One it pulls your slats good and tight to the wood before you make the most stressful part of the waist bend and second it gives the waist a bit more time to absorb steam and heat. Cook for 10 min allow to cool over night. If extreme quilted you may still get some pull away at the waist but don't panic. Take some of the film from double stick tape, the stuff you peel off. CA will not stick to this film. Carefully apply slightly thinned with acetone, medium CA to the pull away. Place the film I spoke of between the wood and a clamping caul and clamp the pull away back down. clamp well so that all of the pull away is seated and allow to cure for one hour. all is good as new. I use thinned medium CA here because it does not setup faster than you can get the caul and clamp in place.

Sapele actualy bend pretty easy. It is usally high figureing that causes issues, like the near 90 deg change in grain of quilted.MichaelP39032.0133333333
Author:  Serge Poirier [ Fri Nov 10, 2006 5:00 pm ]
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Aluminum foil is sound advice, i tried it tonight for the first time with my white ash sides and it went very well, keeping the moisture in better IMHO.

Serge
Author:  TonyKarol [ Sat Nov 11, 2006 1:04 am ]
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How slow is slow - if its taking you more than 6-7 minutes to do the whole bend (once the blanket gets hot for a couple minutes from startup) you are going too slow, and the moisture is getting lost (especially with craft paper) and then the wood is case hardening on you. I bent the crazy quilt sapele with a new shape with very tight waist and upper bout and it works fine .. foil, wrapped tight with a good spritz, the foil completely traps the moisture in for you and keeps the wood supple once up to temp.
Author:  Joe Beaver [ Sat Nov 11, 2006 5:41 am ]
Post subject: 
Some excelent advice here. Thank you all.

Michael, It was just straight grained, nicley quartered ribon sapele. It should be easy. I might have a thermometer problem, trying to bend to cold?


Tony... Maybe to slow?
My blanket takes about ten or fifteen minutes to get the wood to temperature per my thermometer, then I take maybe a minute or two to bend into the waist. Then move the clamps to heat up the lower bout, about another ten minutes. Then I do the same with the upper bout. The whole thing from turning the blanket on to full in the mold takes about thirty to forty minutes.

Serge,
Maybe the foil is the way to go?Joe Beaver39032.571400463
Author:  Joe Beaver [ Sat Nov 11, 2006 5:47 am ]
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[QUOTE=MichaelP] Quilted has a nasty habit of vertical grain pulling loose in tight bends. This appears as a crack but it is a stress induced separation of the fifers that run in the vertical direction. [/QUOTE]

Michael,

Do you use paper or foil? It sounds like you are leaving the wood bare but do spray water on the outside of the bend?
Author:  peterm [ Sat Nov 11, 2006 5:48 am ]
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10 to 15 minutes to get it to the right temp?
you may have a bad thermometer or a bad blanket!!!

Thats your problem right there.... cooking the wood for WAY too long! It takes me 2-3 minutes (or less) to get to the desired temperature....

get another thermometer to make sure
Author:  Joe Beaver [ Sat Nov 11, 2006 5:55 am ]
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Peter

That makes since. Do you use a rheostate on your blanket or just plug it in and let it get hot?

I've been using a rheostat to kind of sneak up on 300 degrees
Author:  peterm [ Sat Nov 11, 2006 6:34 am ]
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I just plug it straight in!!
Author:  TonyKarol [ Sat Nov 11, 2006 7:35 am ]
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I use a light dimmer on my blanket (the 6x36 2.5 watter), set about 3/4 to heat up and bend the waist, then I drop it to about 2/3s and bend the bouts (there will be plenty of heat in the wood by then). Its hot enough in about a minute to start lowering the waist, 1/2 to full turn every 20 seconds - when you get close to having the caul fully down, the wood has been up to temp for a couple minutes. I find the 2.5 watt is too hot to run full blast, unless you are only doing it for the first 30 seconds or so to get up to temp, then turn it down.
Author:  Joe Beaver [ Sat Nov 11, 2006 9:02 am ]
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I think I may be over thinking the whole thing and as a result heating to long and bending to cold.

When I started making classical guitars eight years ago I bought the blanket but had no thermometer. I just heated it up until a splash of water sizzled and bent away. Never had a problem but it was always rosewood.

I stopped building for six years and don't remember exactly how I did it. I bought a thermometer, layed it on the blanket and heated to 300 degrees. I marked a spot on my dimmer switch and when I tried to bend wood I set it at the 300 degree mark.

Looking back on it I think it never got hot enough to bend wood because of the thermal drain caused by the backs, slats, forms, etc, but it did get hot enough to case harden the wood as Tony said.... Fracture City

Joe Beaver39032.7112384259
Author:  peterm [ Sat Nov 11, 2006 9:12 am ]
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Joe, keep in mind oily woods such as rosewoods are a lot more forgiving and the oils in the wood alow it to be bent even if no moisture is present. mahoganies and others are a different story!
If you need help you can give me a call.... I'd be glad to help!
Author:  Joe Beaver [ Sat Nov 11, 2006 9:18 am ]
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Thank you Peter. I just cut four more sides from the piece I bought at Austins.

I'm taking it down to .08 this time then I'll give it another try, a little smarter now after all the help I got here. If I still can't bend it I'll be in touch!!!

Thanks again.
Author:  Michael Dale Payne [ Sun Nov 12, 2006 1:39 am ]
Post subject: 
I use a bottom slat wood raped in foil, top slat blanket, light gauge outer slat. I don't know what i said that made you think I left the wood bare.
Author:  JJ Donohue [ Sun Nov 12, 2006 2:07 am ]
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I've been using Super Soft 2 (joewoodworker.com) by lightly spraying both sides and let sit for about 2 hours. This is a grain relaxer that has been effective for me on highly figured wood like Waterfall Bubings and Quilted Sapele so far. I then wrap in craft paper and lightly spritz with distilled H2O until the paper is damp.

My sandwich consists of slat-- wrapped wood--slat--heating blanket. My bender also has light bulbs on the bottom. I lay the clamped sandwich flat on the bender and heat for a few minutes before starting the bend. I use a SM surface thermometer on the lower bout and slowly begin the bend at 220*...waist first until it gets 1" from being fully seated. Seat the lower, then upper bouts and finish the waist once it reaches about 300*. Cook for 5 minutes at 300-320 and cool. After reaching room temp, heat again at 300* for a few minutes and cool overnight.

With the Sapele, I had perfect bends with no cracking anywhere. I feel that the Super Soft 2 is really relaxing that grain and helping the process.

Author:  Joe Beaver [ Sun Nov 12, 2006 3:02 am ]
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Two Sides bent as smooth as can be

I listened to the advice here, did some experimenting, and it went so smooth I was wondering what all the fuss was about???

Thank You All

JJ
So the wood softener leaves no bad efects on the sides once it all said and done?Joe Beaver39033.4612615741
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