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I have had a little spare time of late since I am away from the shop so I have been fooling around in sketchup. I have been wanting to come up with a way to better control the contouring of my sides for the purpose of more effortless neck to box transitions and figured that just laying the guitar in a dish and grinding away is not the best way. I think this may be a more repeatable way to do it since I will be able to lock the sides down (in the mold) the same way each time. Of course the radii will be different for the top and back and the front portion of the top is flat but one jig will be used for any size guitar. I have seen something like this several times on the net but now that I'm looking, of course I can't find it. Has anyone seen a jig like this and where?
Thanks

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John, take a look at Jim Olson's site on this page, about 1/4 way down. You'll see this picture



And with it is some details of the mold which has the 15' radius built into it, and Jim just routes the ledge to the radius.

I've come up with a bit of a different design myself (I'll take some pictures tonight) in which I have the dish on a lazy susan bearing, then I take some 1/2" threaded rod, and mount it to my bench outside of the dish. The threaded rod has some 1/2" lock nuts which I set to height. I have added a plate to my mold which also has holes on the same spread as the threaded rod. The mold than slides over the rods and the rims (in the mold) down on the sanding dish. This way I get an even sand all the way around.

Pictures will really help with my details

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Thanks Rod, I have seen this one but I would like something just a bit more universal. I have the threaded rods on my motorized sanding dish as well but I think this will be much easier and faster once it is set up. We'll see.

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Charles Hoffman's website shows something like what you have there. Its shown on his "step by step" pages under the heading "assembling the body".

Warren.

Yes that is similar but I want to incorporate the same jig to do the entire top so the arched and the flat for the upper bout will be in the same guide however the guide attached to the router will have to be flat instead of radiused like the lower bout section shown in my drawing. My goal is to just put the guitar sides in mold onto this this thing and route.

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To show a little better what I want to do.

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That looks like a great idea (if you have the room for it, which you do). So both rails have the desired radius built in. You set locators for the mold and Bob's your uncle.

Slick.

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If you make it just like your sketchup, you'll have a 25' dome in the lower bout and a 25' cylinder in the UB. This would be most noticed on the plane where the neck attaches to the guit.

To get a truly 'flat' UB I think you'd need to switch router sleds to a flat one too.

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Right, and that is my intention for doing the top side

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John, I am glad you brought this up...I have been wanting a better way to set the upper bout for the neck angle and transition. This looks like a really good idea. The only problem I see is where you would change from the radius sled to the flat sled, there would be a step in the kerfed lining. I guess you could transition by hand with a plane...

Chuck

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Chuck, that step would be so small that it would almost be impossible to detect. The drop (for most gutiars) from the front of the soundhole to the front of the body is only about 1/16" so the step would be very slight. Just hit the top of it with some 220 and you'd be good to go.

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Looks like it should work fine John. I like it. Be sure to let us know when it's operational and you've worked out the gremlins. I've been doing something kind of similar for the upper bout angle with a sanding jig.

http://kennedyguitars.com/_Kennedy_Guit ... t_Jig.html

The transition point does not really seem to require much if any smoothing. I do notice that once the top is on the upper bout may not be at exactly the angle you put into the rimset or be perfectly flat and usually needs a minor touch-up with the Fox paddle or similar device. Do this before you measure your angle to rout the tenon if you use the Fox-Woolson type jig.
Terry

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Terry...Thanks for posting your UB leveling jig. I have been using the Woolson/Fox tenon routing jig and have also experienced a remarkable simplification in the fitting. Your sanding jig seems like a valuable addition to the process.

John...I like the concept that you are noodling...keep us posted and thanks for sharing.

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john,
check this link out: http://bevelsnob.com/RyanShrine/ryanshop2.html
there are several clips over there and one of them shows a similar idea to yours.

Udi.

Here is my approach to making the sides to exact shape, every time.

It is an over engineered inside mold built to exact internal dimension of the guitar corpus. I use strap bands and blocks to clamp the sides in and hold them while I use a block plane to shape the sides first, then remove the top sandwich of the mold, then put in the linings and again just using a block plane I get them exact. Next I do the back and then collapse the mold.

Crazy but it works... but it is not universal so it won't be of much help to you John.

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Ken

Thanks Udi, that is exactly what I'm trying to do and have been looking for online.

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Here is a pretty good shot of Kevins rig from the site Udi showed us.
Boy that is a deep guitar box and quite a severe radius on the back. I'm guessing 12' or so.
Notice the use om magnets to hold the guitar against the form uprights.
I can't wait to get home and get started.

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IIRC .. I read somewhere Kevin's back radius is like 8or 10 feet.. binding that is tough.

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