Making custom fit internal bridge gluing cauls

[Mark]

Hi all, how do you guys approach making custom bridge gluing cauls  for bridge plates and cauls to go around braces?

How do you trace the pattern to cut?

Cheers.

[Andrew]

I have an assortment of little magnets that i use to find all the braces and such through the top to a piece of paper (be gentle with the pencil). By putting a set of magnets at either end of a given brace you can connect the dots with a ruler and apply the finished pattern to a piece of hardwood or whathaveyou. You could augment this approach with a thickness gauge of some sort for heights of braces etc, but I typically just eyeball the recess i need to create to bridge an obstruction unless I specifically want support on a given area.

Another approach would be to apply some styrofoam insulation to a backer block and clamp that in place, so that the brace pattern will be impressed upon the foam, which can the be cut away using a razor knife (my Olfa is one of my favourite tools). 

Im sure Ive used a few other methods but these two jumped to mind first..

[Mark]

Thanks Andrew.

The styrofoam sounds good to me.

[Mark Fogleman]

Bright light inside the body under the bridge, tape tracing paper around the bridge, trace out the shadow.

[Mark]

Wow tha must be a hell of a bright light! What wattage are we talking about?

[Mark Fogleman]

I do it in a dark room with a 100 watt equivalent CFL or LED bulb. A spruce guitar top with a clear finish is very translucent and the braces show up clearly as shadows. Just put the light directly under the area you're tracing. 

[Mark]

Great! Thank you Mark.

[Russell Vance]

Just a quick addition to methods to trace braces which may add to the mix:   I stick a small dot magnet to my finger tip and with a sheet of paper taped to the outside run my finger around the area inside and track it with a similar dot magnet on the outside - crayon the path of the track and you end up with a rough and ready map of where everything is - rudimentary and quick.

Rusty. 

[Andrew]

Nice.

I wonder how this would work with a bit of carbon transfer paper taped to the magnet to do it in one motion. 

[onewent]

These are all great tips .. I've used the magnet trick, and also have used aluminum foil and folded it over the brace/s to make a 'pattern' then remove carefully and trace to wood.  I prefer the magnets, though, for optimum accuracy.

Tom

[Mark]

Nice one too!