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| Cupping In Maple Sides http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=41450 |
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| Author: | sgonwa [ Thu Sep 19, 2013 8:46 pm ] |
| Post subject: | Cupping In Maple Sides |
I successfully bent a pair of curly maple sides in a fox-style bender using a heating blanket. After being in the form for a period of several weeks and thoroughly dried, I noticed that the sides have cupped slightly across their width, mostly in the lower bout. Is there a recommended way to re-flatten the sides in these areas ? I do have a bending iron but am not sure of the proper method to correct the cupping issue. I have also seen it suggested to use a bending blanket in the form, one side at a time, to reheat the wood and use metal slats to help re-flatten the side. If this is an option, suggestions on a correct procedure would be helpful. I would say the greatest amount of cupping is about 1/16 inch across the width, maybe 3/32. Thanks for any advice. |
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| Author: | Michael.N. [ Fri Sep 20, 2013 4:44 am ] |
| Post subject: | Re: Cupping In Maple Sides |
1/16 th is fairly substantial cupping across a width of just 4 "? I'd probably sand/scrape some of it out, perhaps half of it if you have enough side thickness. You would be down to around 1/32 nd. That's fine from my point of view. I'm not very fond of ruler flat Sides anyway. Something very static and rigid about that aesthetic, plastic wood looking. You might think it looks a bit wacky if it's not dead flat though. |
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| Author: | Joe Beaver [ Fri Sep 20, 2013 2:02 pm ] |
| Post subject: | Re: Cupping In Maple Sides |
I would make an inner and outer caul. Put the sides in it with a heating blanket. Warm to 250-275, clamp tight and turn the blanket off. Leave in the cauls for a few days. Should be flat when you take out. I would immediately put a fairly substantial side brace in the area. (a little taller than normal). You might be able to correct it without the cauls and heat, if you put a little curve in your side brace before you install it. Then clamp to the side and see if it causes it to straighten. |
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| Author: | Michael Keller [ Sat Sep 21, 2013 4:11 pm ] |
| Post subject: | Re: Cupping In Maple Sides |
Here is my solution to your problem. a .032 sheet of stainless with good tension from a pair of destaco pull lever clamps. I had this problem on many different types of guitar woods till I saw this set up in jim olsons guitar shop, and it solved the problem. The plywood mold is covered in .020 aluminum , the heater blanket goes on next, and then the wood, that gets a little water on it a few minutes before it goes into the bender. 
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| Author: | Joe Beaver [ Sat Sep 21, 2013 4:32 pm ] |
| Post subject: | Re: Cupping In Maple Sides |
Michael, That is an excellent setup. Putting the top piece under tension reminds me of what Taylor shows on his videos. Excellent!!! |
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| Author: | sgonwa [ Sat Sep 21, 2013 8:58 pm ] |
| Post subject: | Re: Cupping In Maple Sides |
Thanks for the great input and suggestions. I think the sides came out acceptably flat from my fox style bender into the mold, but I didn't follow through with further assembly for a few weeks afterwards. Perhaps had I continued on with construction they might not have had the opportunity to cup as much. But the suggestions provided here should take care of the issue. Thanks again. |
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