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View Full Version : Fitting a bridge on a domed soundboard



mwaller
06-25-2010, 08:55 AM
If you build the soundboard on a 25' radius dish, do you need to sand a 25' radius into the underside of the bridge before gluing? If so, what's the best way to sand the bridge?
Thanks,
Mika

Dusepo
06-25-2010, 09:22 AM
In my experience, domed soundboards usually have floating bridges instead of fixed.

Timbuck
06-25-2010, 10:30 AM
25' is not domed, its a slight radius...just take small piece of MDF about 4" square mark a pencil cross on it from corner to corner...then rub it on the concave radius dish until the cross is gone..you now have a 25' convex block, just glue on some 150 grit sandpaper (on the convex side)..then rub the bridge base on the block until it fits the Uke top.

Moore Bettah Ukuleles
06-25-2010, 10:55 AM
Like Ken I sand my bridges on a convex block. An exact fit, with no light shining through is critical. Glue and clamp securely and wait 24 hours before stringing it to tension.

mwaller
06-25-2010, 11:31 AM
Thanks for the responses! That makes perfect sense.
Mika


Like Ken I sand my bridges on a convex block. An exact fit, with no light shining through is critical. Glue and clamp securely and wait 24 hours before stringing it to tension.

Allen
06-26-2010, 10:45 AM
I use a cabinet scraper to put a slight concave curve on the bottom of my bridges, and just trial fit it in place on the uke top. When close I draw witness lines on the bottom of the bridge, and then place a piece of 120 - 150 grit sandpaper on the top and slide the bridge bland back and forth over the area that it will sit. Useing the top as the sanding block so to speak. Very easy to get an exact fit,

Reason I use the top itself is that with thin soundboards it's real easy for them to take on more or less dome depending on the relative humidity when the instrument was assembled, the way it was clamped up or even the RH on the day you are glueing on the bridge. Perhaps small differences, but they will most likely be evident more often than not.

Dave Higham
06-26-2010, 11:37 AM
In my experience, domed soundboards usually have floating bridges instead of fixed.

You're thinking of archtops. Instruments often referred to as 'flat-tops' usually (but not always) have a slight dome induced into the top and back by making part of the bracing curved and/or gluing the bracing to the back and front in a radius dish. As explained elsewhere, this serves several purposes, including pre-tensioning the soundboard for acoustic reasons and allowing for changes in humidity without the front or back going concave or cracking.

Vic D
06-27-2010, 09:38 AM
I use a cabinet scraper to put a slight concave curve on the bottom of my bridges, and just trial fit it in place on the uke top. When close I draw witness lines on the bottom of the bridge, and then place a piece of 120 - 150 grit sandpaper on the top and slide the bridge bland back and forth over the area that it will sit. Useing the top as the sanding block so to speak. Very easy to get an exact fit,

Reason I use the top itself is that with thin soundboards it's real easy for them to take on more or less dome depending on the relative humidity when the instrument was assembled, the way it was clamped up or even the RH on the day you are glueing on the bridge. Perhaps small differences, but they will most likely be evident more often than not.

That was my thinking and that's why I do it this way too. No gaps at all.