When gluing the bridge on cedar?

[viento]

I´m not sure when to glue the bridge on a red cedar top.

Should I glue it on before spraying the top with nitro or after?

I could take an adhesive paper , put the bridge on and mark the outlines with an exacto knife. Then lift up all of the surrounding paper. Then spray the top. There will stay an untreated area under the paper where to glue the bridge on.

But I´m a bit unsure that the exacto knife could scratch the cedar top...

Or would it be better to first glue the bridge, mask it off entirely and then spray the top?

[Glen H]

Typical process is to nitro then glue bridge. Some mask off the bridge footprint , spray, remove mask and then glue. Some, including myself, spray without masking and remove finish under the bridge, then glue. Your concern about the xacto knife is valid. The trick is to cut through finish with cutting the top. Use a light touch and a sharp blade.

[keith.rogers]

I put masking tape on before spraying. Mark with a pencil, cut slightly inside the bridge outline. When you are ready to glue the bridge, remove the tape, recheck the fit, and if you want, lightly score and remove the small bit of lacquer that will be under the edges of the bridge.

I'm sure things have gotten more high tech since I did it that way 40 years ago...

[viento]

Thanks for your advices!
I guess, I will do as Keith wrote.
Mark the bridge outline on a tape and remove the rest of tape.
Then spray and after that glue the bridge on the top.
I will use fishglue and wipe off the squeezed out glue
at the edges of the bridge with a wet rag or Q-tips.

[Alan Carruth]

What Kieth said is pretty normal.

Cedar has low peeling resistance, so you do have to be more careful. Make sure you don't score into the top wood when you're scribing around the bridge, particularly along the back edge, where the torque and shear loads add up. We had the bridge come off a Lowden guitar in the shop because of that once. My partner and I were in the back room when we heard it let go. The glue line was fine; the whole bottom of the bridge had top wood on it, but the wood had sheared off the top cleanly all the way around.

It helps to use a somewhat wider bridge footprint; 1-1/2" along the line of string pull rather than the usual ~1-3/8" or so. That helps to lower the peeling stress a lot.

[viento]

Originally Posted by Alan Carruth

What Kieth said is pretty normal.

Cedar has low peeling resistance, so you do have to be more careful.
Make sure you don't score into the top wood when you're scribing around the bridge,
particularly along the back edge, where the torque and shear loads add up. ...

It helps to use a somewhat wider bridge footprint; 1-1/2" along the line of string pull
rather than the usual ~1-3/8" or so. That helps to lower the peeling stress a lot.

Yes, you´re right, I will scribe around the bridge on my table - not on the cedar top.
Then cut it out and stick the adhesive paper carefully and precisely on the cedar.
And I am going to design and make the bridge with a larger footprint.
I have an Ovation pinless bridge made of walnut lying on my working bench
but I plan to use a piece of White Ebony- the same wood I used for the fingerboard.
I do hope it doesn´t lift when I tune the strings for the first time ...