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I'm at the step on my first guitar where i need to sand and radius the braces, and also the top and bottom ribs of my Martin D-28 copy. I need to make a couple sanding dishes soon. Luthier Suppliershas the acrylic Contour Pattern Radius Gauges that I need.
Here's my question....what two sizes would you guys recommend I get? I have a video from Robert O'Brien who is making an OM. He says to make the top 30' and the back 15'. Also, my plans for this dreadnaught doesn't specifiy. Will these radiuses O'Brien suggests work for a dreadnaught?
Thanks for the help, I'll want to order these gauges today.

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

30' and 15' are what I use on all my guitars.
For what I do, I found that the neck alines better or with less
fuss with the 30' radii.

Im am not sure but I would guess that a true martin is 25' and 15'. Im sure someone that knows will chime im.

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Lance@LuthiersForum.com

I use 28' for the top and 22' the back. The second back brace down from the top on the back is a little tighter (probably 20' - I eyeball it) and I use little wedges on the dish so it fits in tight. Makes great sounding guitars...or at least I think so.

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Jamie M

25' and 15' here.

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Ann Arbor Guitars

Chuck,

I am trying to reply to your PM but it says that my reply is sitting in my outbox along with 150 other messages. If you send me an email perhaps I can send the message along that way.

From what I gathered from plans and guitars I own - Dread 28'/20', OM 25'/20', OOO (12fret) 30'/15', GA 25'/15', L 30'/15', J200 25'/20', J45 25'/15'.

I made 28', 25', 20' and 15' dishes. Passed on the 30 and use 28 instead.

Zach, why did you pass on the 30', it seems to be quite popular. Why is it popular? Also, does a flattop guitar have a bassier sound? I think Martin tops are flat on the D28. Does anyone know?

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

28' or 30' it makes no difference.
Or to be precise, on a 16" wide body, the difference in depth between a 28' rad. and a 30' rad, at the centre of the curve is 0.006". Can anyone work to that degree of accuracy?
The difference at the centre between 28' and 25' is only 0.011".
I'd choose 25' or 28' or 30' and use that for the fronts on everything.
15' seems to be the popular choice for backs.
(unless you're Dave White of course )

Thanks for all your help guys. I just bought a 20 and 30 from Tracy.

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins