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| How to deal with bent sides cupping http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=25243 |
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| Author: | WendyW [ Wed Dec 30, 2009 5:11 pm ] |
| Post subject: | How to deal with bent sides cupping |
I was really happy to find that the birdseye maple sides that I bent last weekend bent like rubber. I guess I used a little too much water and they were still damp when I took them out of the bender hours later. I clamped them in the mold to dry and they have no springback whatsoever, but the upper bouts have cupped. What is the best way to deal with the cupping? It is definitely too much to sand out. Would it help to dampen the side and heat it in the bender and then cool and leave it in the bender overnight? Thanks, Wendy |
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| Author: | meddlingfool [ Thu Dec 31, 2009 2:22 am ] |
| Post subject: | Re: How to deal with bent sides cupping |
Well since no one else is biting... This happened to me a lot before I bought a heat blanket set up (and before I knew that extra water was bad not good). I don't really know what you consider bad cupping, but I always put in 1/4x1/4" side braces and clamped them in with a flat backing caul. I can't see how redamping the sides and putting them back in the bender would hurt, as long as you don't dry it out and scorch it. Hope that helps even a bit. Cheers |
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| Author: | woody b [ Thu Dec 31, 2009 7:30 am ] |
| Post subject: | Re: How to deal with bent sides cupping |
You're right, or at least I agree that too much moisture caused the cupping. I've done it, (and still do every now and then) To fix the cupping I use a clothes iron to "iron" the cupped places back flat. |
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| Author: | bluescreek [ Thu Dec 31, 2009 8:10 am ] |
| Post subject: | Re: How to deal with bent sides cupping |
Maple and Mahogany in my experience will bend much better , hot with little water. I actually bend them dry and will take the temp to 275 to start bending and finish off at 375. I will just lightly spray the upper bout just before bending. Other than that the procedure is the same. |
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| Author: | HippetyHop [ Thu Dec 31, 2009 8:18 am ] |
| Post subject: | Re: How to deal with bent sides cupping |
Put it in the mould, and make a caul to fit at that position and clamp overnight. If that doesn't work, stick the end of your heat blanket in under the caul. I had some success - half fixed some koa sides this way. Good luck Cheers Hip. |
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| Author: | Alexandru Marian [ Thu Dec 31, 2009 11:01 am ] |
| Post subject: | Re: How to deal with bent sides cupping |
I bend by hand on an iron and currently use zero water. The less water I used, the less cupping I got. |
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| Author: | woody b [ Thu Dec 31, 2009 1:35 pm ] |
| Post subject: | Re: How to deal with bent sides cupping |
Alexandru Marian wrote: I bend by hand on an iron and currently use zero water. The less water I used, the less cupping I got. I'll be bending the sides for my 25th soon. I've used less water everytime. By my 100th I'll be doing something to dry the sides before bending 
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| Author: | WendyW [ Thu Dec 31, 2009 3:38 pm ] |
| Post subject: | Re: How to deal with bent sides cupping |
The cupping is in the exact same place on both sides. It's on the ramp between the waist and the upper bout. I did bend at a higher temp as per your instructions, John, but I know I used way too much water. I wrapped in kraft paper which was soaked and squeegeed, and I also misted the side before wrapping in the paper. When I took it out of the bender hours later it was still damp. I will know better for the future. I've thought about dampening just the section that is cupped and clamping it in the mold using one of my bending plates as a caul on the inside. I hadn't thought about using an iron. Woody, when you iron it do you use any moisture? I've given up on the idea of putting it back in the bender since there is no way to put pressure on that particular area. It is buried between the sides of my bender (a homemade fox style) so even an extra caul would be too far out on the bout. This is the area where the curve just comes out of the waist. I will also consider a side brace let into the linings, even though this is a classical. Thanks for all your answers so far. Wendy |
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| Author: | woody b [ Thu Dec 31, 2009 3:53 pm ] |
| Post subject: | Re: How to deal with bent sides cupping |
I had one Walnut side that was cupped really bad. I used a clothes iron, on the hottest setting with the automatic steam on low. This is that side. |
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| Author: | WendyW [ Thu Dec 31, 2009 5:28 pm ] |
| Post subject: | Re: How to deal with bent sides cupping |
Thanks Woody. I'm getting ready to iron it right now. It looks like it will be pretty easy to iron out. That sure is a nice looking guitar, and some beautiful side wood. Thanks for your help. Wendy |
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