Official Luthiers Forum!

Many people advocate doubling up radius dishes back to back, but is this still ok to do if you plan to use them in a Go Bar deck? Wont the pressure from the bars distort the dish due to the cavity underneath created by the unused radius?

Many thanks for any advice offered!

What is in the bottom of your go bar deck ??? the radius dish has to sit on something right ??? If its sitting on something solid, it doenst need to be doubled up, it already is !!!! ( you need to account for the extra height now in your deck if you were to double up as well). Mine sits on a plywood lattice riser, on top of a pretty solid rolling router table .. its solid enough.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Not a good idea. They will indeed distort over time due to the pressure on them and the fact that the dished shape in the middle is unsupported.

If you need spacers to raise the work so the gobars fit, use flat plywood/MDF or a custom built torsion box with parallel surfaces.

FWIW, just this weekend I spent the time to measure a couple of commercially purchased radius dishes that I have been using for some time, but have not been happy with.
The 20' radius dish turns out to actually be a 15' radius dish, and the 28' one is actually a 20' one!!
I plan on complaining.

Going forward it's not going to bother me, since I will be making my own (custom radius/mounting hardware) on a CNC from now on.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Thanks for the replies chaps. I guess my concern with the dishes is whether the single layer dish on its own would be thick enough to be stable over the long term once I machine the radius out of it using 3/4" mdf?

A single thickness of 3/4" MDF with a dish shape milled out of it will not be stable enough over time IMO.
You should double up the MDF or glue it to some good quality plywood (that would be my choice).

I have some 1" thick MDF radius dishes that have curled up at the four corners over time so they no longer sit flat (they're a bit like a lazy susan, pivoting on the rise in the middle of the back!).

HTH,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Lee,

I am in the same dilemma. I glued my 28’ and 16’ radius dishes back to back years ago. I never thought I would use a go-bar deck. Now that I am thinking about doing just that, I think I will just make up several spacers to block under the bottom dish and take up that air space. Otherwise I'm sure I will be in for all sorts of wierd radiuses with the distortion.

Not perfect but I think it will work.

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Joe Beaver
Maker of Sawdust