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The sound board radius, and the back radius for that matter are somewhat mystifying topics at this point. What are the different ways of achieving these radii? I don't really feel like forking over $100 for some big wooden dish from stewmac, so I'm wondering if there are other ways to do it?
Thanks

go to the youtube and search radius dish guitar, Chris Paulicks video will appear. And there is another there of the dish being lathe shaped easily. If I knew how to post the link, I would.

It also can be done with 1/8" hardboard, sprung in the center. Pretty cheap.

you might try Kenneth Michael Guitars for radius dish's...

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MK5acoustics.com

Or, you can go dishless like in the Cumpiano book with a flat sanding board.

Lots of ways to go about it, all of which produce a slightly different result

Spherical radius dish is of course widely used.

For a cylindrical radius, take a piece of plywood and put two thin boards along under the edges of it so it's suspended at the height of arch you want to create. Then clamp down the middle of the two edges between the supports. Actually creates a parabolic curve.

Another method is to dish out a solera workboard using finger planes, gouges, sanding, whatever. You can do non-spherical curves this way, which is nice.

A somewhat more time consuming and less consistent method is to plane/sand an arch into your braces, and then glue them to the plate one at a time using cam clamps and a flexible (but stiffer than the top) backing slat to help distribute the pressure and spring the top onto the brace. This is the method used in Cumpiano and Natelson's book, and is what I do. It still allows some useful non-spherical curves, such as arching the upper transverse brace, but flattening the portion that lies directly beneath the fingerboard (especially important if you have a flat headblock extension butted to it).

An even less consistent (but fast) method, is to dry out the plate before bracing it with flat braces on a flat workboard, and let it create its own dome by swelling up when it returns to normal moisture.

That's all I can think of for now.

So far I've made most of my tools and jigs, the radius dish was fairly easy. I used Alan Dunwell's Making Hollow Forms tutorial

http://www.dunwellguitar.com

Hardboard and cauls create a spline curve, as in boat building.
The best way to make a radius dish is with a router jig, namely a carriage with curved rails that can pivot around the already cut dish. The rest is smoothing out with a scraper and orbital sander. You need to be careful about calculation to obtain the desired curve. It's a fair amount of work and a lot of dust, especially with MDF, so doing it outside is recommended. I did mine years ago (and no longer use them). I laminated three 3/4" MDF sheets for a 20' dish on one side, a 15' on the other. Very stable and extra heavy.
Now, I would probably order it from John, Shane or any of the guys who don't charge an arm and a leg for a piece of CNC'd ply.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

So, what do you use now?

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"Never give in. Never give in. Never, never, never, never--in nothing, great or small, large or petty--never give in, except to convictions of honor and good sense. Never yield to force. Never yield to the apparently overwhelming might of the enemy." - Winston Churchill