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Working on an old Aria from the seventies. Had to rebuild the neck block as it originally had a knot defect on one side and gave way. Came at it from the back, and as I was reinstalling it, realized I was not adequately prepared to realign the sides perfectly with the back. Used boucoup clamps and got it pretty good, but I really should make something that is a universal aid before I try this again. Ideally it would be adjustable from a dread size to a classical. Only idea I have is to build a carrier with many adjustable side brackets. How many? Dunno. They would have to be up to 4 inches tall, so I'd have to use the go bar deck to apply the clamping force. Thought I'd ask if others had better ideas, or could share what method works best for you. Thanks, Roy

I use or make a mold then use tape . cut the tape at the joint that gives a reference point. figure about 6 per side

The late Ken Cierpiloski used to offer tools and kits for guitars and had a adjustable mold he called a MegaMold that would do what you are asking about, Roy. They're no longer available, but here's a link to a reprint of his old webpage with pics that would help with a DIY version you could make, http://harvestmoonguitars.com/kennethmi ... rfixt.html.

Here's another page that shows the fixture in more detail, http://harvestmoonguitars.com/kennethmi ... emold.html
Another way would be to make a mold for the shape you want from 2" rigid foam insulation. Make it before you take the back off and shape it around the neck heel. Either leave it on during interior repairs or reinstall before putting the back on. Might work, just speculating....

Thanks for the reply(s). I did make a foam mold but it was not strong enough (or accurate enough) to keep the sides from moving. I used a buncha wooden wedges to move one corner back in. Hope I moved it enough.

Although the second link didn't work for me, the first did, and his arrangement would absolutely work. Probably take me months to build. But I'll think on it. Actually looks like you could make a different shape guitar from that (with a template) and not have to make a mold if you're only doing one. Wonder if I could buy the wooden rollers; I don't wanna cut them.

Thanks again.

Roy

I'm curious about what OP is using to determine 'rightness' and whether 'almost perfect' would suit the task. I built a kit guitar which arrived with the body assembled but for the top and breakaway internal spreaders were used instead of a mold. Worked out fine.

Think closet poles cut up to 3", lag bolts w/wing nuts. should work OK.
Here's another idea from Frank Fords webpage, http://frets.com/FretsPages/Luthier/Tec ... ptest.html.
Check that other link again. I edited it and it worked for me.
Yes it can be used for a mold, but I've just made my own based on the first one I bought from John years ago (Martin Jumbo). They work a lot better with the go-bar deck and radius tops.

Thanks, now I can see the detailed pix in the second link. For some reason the Fret one didn't want to work for me; I just changed to Win 10 recently and don't know all I probably should.

As far as how accurate I'm trying to be in locating the back; I'd like to think I'm accurate enough to get a binding back on with no gaps, and on this guitar, I'm pretty sure I'll also have to use some purfling to try to hide a gap, and even that may not be enough. I mostly want to be able to do this on the next guitar and it not be obvious that the back was removed and reinstalled.

Roy

I'm assuming without photos, that your sides have relaxed, so the back isn't fitting right? Boy, I've been there and had that problem with 3 rebuilds.

Have you tried internal spreaders? You can make your own out of wood and turnbuckles. I'd make a waist and lower bout spreaders. I think as you adjust them, you'll find that it changes the shape of the sides enough to get the back on so that it's centered nicely. You'll most likely have to reroute the existing binding channel and replace the binding, but when done, it'll match up.

Just make sure that your spreaders are small enough to remove through the soundhole. You may get away with just the waist, but you'll probably need both.

to be honest I never had luck with the variable molds. I always like to be able to lock things down. Sometimes just using tape will get you back in the ball game