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Trying to make a radiused sanding caul for the top and back of my guitar (pictured). Here is my first attempt at a 15' radius. As you can see it did not come out very straight. I had cut a 2x2 to 18", used 2 tape measures to draw the radius, and then used my father-in-law's ban saw to cut the curve. Tried sanding it, but couldn't get it even all the way around.

Suggestions? Do they make a gauge for this stuff?

Tom

I think a double layers of mdf would be a little more stable and hold the radius better. I have a couple of radius gauges and use them with a flush cut bit to make the radii I need.

Tom
When we get together, I can show you easy ways to do this.
Ed

Thank you. Just finished gluing the kerfed lining, so I am at a stand-still until I can figure out this radius thing. Next step is to glue the braces on, but I am going to try to do it without buying the gobar deck or the sanding discs.

Tom

I'm on my first guitar too and used the template with flush trim bit as mentioned by someone else. The idea is that it's much easier to create a smooth curve in 1/8" thick wood than in thick stock used for the caul:

1. Make a template from 1/8 plywood or hardboard
Trace the curve from the brace to the hardboard
Cut the curve using a jig saw. Go slow and try to split the line
Tape or glue 80 grit sandpaper to something flexible such as plastics laminate
Sand the curve smooth. The flexible backing will make it easier to sand the high spots without sanding in any deep spots.

2. Make the caul
Trace the curve from the template to the caul stock
Rough cut the cufromitunes the caul stock. Stay 1/16" clear of the curve
Double stick tape the template to the caul.
Use a flush trim bit and adjust the router depth so the bearing rides on the template.

Btw, as per the stew Mac instructions, I did not use a caul for the top, only the back. Another option I read in an old book by Cumpiano is to use a flexible caul and let the brace itself define the curve. I should repeat that I'm as green as a guitar builder can be. Although I've been woodworking for years and am quite familiar with the template technique I described.

Mitch

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