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Made my own dish this morning and I didn't even need a dust mask or router. I used 1/4" and 3/4" MDF for a 1" dish with a 40' radius.

I calculated .14" for my spacer/chord height and glued that in the center of the 3/4" MDF and then screwed the 1/4" MDF on top of this.



Run it through the sander a few times.





Take it apart, remove the shim and glue them together.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Oh yeah I forgot to mention, the total cost, $10. Yay!!!

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Hutch

Get the heck off the couch and go build a guitar!!!!

Clever!

Sorry to say this, but that will not result in an accurate radius.

why not?

I understood that going in. It will be close enough for me. It's not like it has to fit into a mating part.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I built a similar set of radius dishes years ago, using a somewhat different method. I am still using them and they work fine. It's almost a catenary curve, but not quite. At the time I mentioned my approximated dome dishes in a forum and numerous people told me this was wrong wrong wrong. Since the dome produced by this method is bare thousandths of in inch different from a true spherical shape, I thought (and have observed since) that it strengthens the plate in a similar way. In any case, once the bridge of the top pulls up slightly, it's no longer a perfect section of a sphere.

One helpful thing someone mentioned was that, because of the way these domes are formed, one area of it may be very slightly different in arch than another. For that reason, when I do final sanding of each brace in the dish, I sand the brace back and forth over the area where it will go. Maybe that improves the fit a little.

If I were to build these again I would mostly use plywood. Those big sheets of particle board are awkward and heavy to move around. I have to be careful how I lift them. To minimize possible back injuries, I'm trying to lighten up the forms I use.

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Tim Allen
"Never hurry, never rest."

Actually, that is exactly what dishes are used for; mating parts. But as long as you know that the curve will be slightly off, you should be able to compensate for it.

This comes up from time to time and yes, this is not a spherical dish but the difference is negligible. It is not like the completed guitar tops will keep the exact shape of the dish once the RH changes. We happily sand the radius of the dish into our braces then offset that curve by the thickness of the top when we glue. The curve of the inside of the top (in relation to the curve of the dish) probably varies more but I don’t know how to do that math.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

When I said mating parts, I meant the finished guitar fitting into something. It doesn't do this. As long as there is some sort of dome, the wood has somewhere to go when it dries out and that, I believe is the purpose of the dome.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I sometime use a similar technique to thin out the edges of the top. That is placing tape around the perimeter then sanding.

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Jim Watts
http://jameswattsguitars.com

That's an interesting concept.

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Hutch

Get the heck off the couch and go build a guitar!!!!