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| Thinning for cutaway http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19260 |
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| Author: | Ricardo [ Mon Oct 20, 2008 12:12 pm ] |
| Post subject: | Thinning for cutaway |
I would appreciate some tips on how to thin the cutaway area of the side. I've seen a lot of postings saying that the cutaway area from just before the horn should be thinned to .065-.070, but my question is how is this done? I am concerned that thinning introduces runout at the very place that the most stress is placed on the side during bending. Is there a gradual taper? Do you thin the inside of the side or both sides? 
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| Author: | Michael Dale Payne [ Mon Oct 20, 2008 12:29 pm ] |
| Post subject: | Re: Thinning for cutaway |
Unless dealing with figured or difficult wood or bending a cutaway with a horn radius less tha 1.50" I don't thin any less than normal. If I do need to thin extra I run it though my 10-20 drum sander sideways on a carrier bord so that only the area I want is sanded thinner. this leaves a small ridge that blend out with a ROS. |
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| Author: | Dave Stewart [ Mon Oct 20, 2008 2:09 pm ] |
| Post subject: | Re: Thinning for cutaway |
I've only done curly maple and that's the range I use. My tightest radius is the cutaway of my 16", which is just under 1" radius. I just get the side uniform, mark bands across the interior surface denoting waist, horn & cutaway, and scrape away. (Then go ahead & bend on my bulbs only Fox!) |
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| Author: | Kevin Gallagher [ Mon Oct 20, 2008 4:43 pm ] |
| Post subject: | Re: Thinning for cutaway |
I never thin any woods in the cut area, but I still do all of my bending by hand on an electric bending iron. I have two nice Fox style benders, but they occupy a spot on a shelf in my machinery room and have bent a grand total of one pair of sides. I just like being in contact with the wood and enjoying that part of the process. I love the bending machines that everybody uses, but just chose to keep to my old way. Regards, Kevin Gallagher/Omega Guitars |
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| Author: | Laurent Brondel [ Tue Oct 21, 2008 5:55 am ] |
| Post subject: | Re: Thinning for cutaway |
Ricardo wrote: Is there a gradual taper? Do you thin the inside of the side or both sides? Leave the outside alone and start on the inside at the very end, gradually going through the cutaway and stopping at the beginning of the curve. A sharp block plane, scraper and flat sanding block are all you need. A lot of builders thin the cutaway section, especially with curly maple and the tight cutaway bend of archtops. Depending of the wood you're using and the tightness of the bend you can go as thin as .040" and reinforce the cutaway with a piece of veneer on the inside when bent. For most cutaways there's no need though, and perhaps no need to thin at all. What wood are you using, how thick is it and what's your tightest curve? |
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| Author: | Ricardo [ Tue Oct 21, 2008 9:22 am ] |
| Post subject: | Re: Thinning for cutaway |
Laurent, I'm using EIR and the radius of my cutaway is 2". I'm down to around .085" on thickness. |
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| Author: | Michael Dale Payne [ Tue Oct 21, 2008 9:40 am ] |
| Post subject: | Re: Thinning for cutaway |
The radius of the horn is 2"? That is one honking horn  . 2" is common for the return radius but most horns wil be 1"-1.25". There is nothing wrong with a 2" radius horn if you have the room but that means that from the outside of the horn to the inside of the horn is nearly 4". I am guessing you mean the horn is 2" diameter rather than 2" radius.
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| Author: | Ricardo [ Tue Oct 21, 2008 10:25 am ] |
| Post subject: | Re: Thinning for cutaway |
Michael, you are right it is a 1.25" radius. 
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| Author: | Laurent Brondel [ Tue Oct 21, 2008 10:57 am ] |
| Post subject: | Re: Thinning for cutaway |
Rick, I generally thin rosewood to .075" for sides and it should bend fine for your cutaway without thinning. Even at .085" it should be fine, EIR is one of the easiest woods to bend. In doubt thin your cutaway location from the inside at .075", should take you all of 3 minutes with a scraper. |
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