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I'm preparing to glue a pyramid style bridge onto a parlour guitar with a radiused top. The bottom of the bridge has been radiused to the same curvature as the top.It's a new build, and I'll be using a Fox type bridge clamp which involves screwing through an interior caul and attaching wing nuts. My question is: What is the prefered way to deal with the caul that goes against the bridge plate? As I see it, I have two options; 1) Make a caul with the same radius as the top and screw into that, or, 2) Use a piece of 3/16" plexiglass with some flexibility to it and assume that it will conform appropriately. What are other people doing with this? Am I on the right track?

Thanks! Sure is good to know that all this experience and knowledge is available to me as I muddle through some of this stuff!

Look into using something like the two part molding puttys or "friendly plastic". Use this to make a caul that fits the inside of the top. It may be necessary to face it with some plastic food wrap to keep it from sticking to the top. [Just FYI, it is a lot easier to make the caul if you do this before gluing on the top.] Make a caul that includes a piece of scrap 1/4" plywood as the backer. This then distributes the load inside and protect the top and braces from any additional clamps that you might add. If you have regular models that you do over and over you might make more permanent versions with casting resin and faced with cork.

Alan D.

The face of the bridge plate should be flat, so a flat caul should be used.

When you fitted the bridge plate, I assume that you radiused the gluing surface of the plate in your dish to fit the internal radius of the top, (rather than force a flat plate into the radius). The other side, the one that the caul will bear against, should therefore still be flat, so the caul that fits against it should also be flat.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I can't see where this is stated, so I assumed that best practice, ie radiusing the bridge plate, had be followed. The bridge plate is a large brace, so should be radiused.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

The bridge plate was not radiused. It started out flat, but, as it was glued in on the go bar deck against a hollow form, it now has a radius.

Then do what Todd said....

I only radiused a bridgeplate once and never again. When installed after the X brace it more easily conforms to the top then the opposite way.The use of a radiused caul when gluing works for me. My bridges are flat on top at least until after installation and I use a Charles Fox clamp without an inner caul. As long as the bridge matches the radius of the top,check with .002" feeler gauge,I thinks things will be fine. I have never had a bridge glued with the Fox clamp come off but have when glued with cam clamps. Might be due to better preperation though.
Tom

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A person who has never made a mistake has never made anything!!!

I don't use a caul with my Fox style clamp. I don't radius the bridge plate either.


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