Fingerboard Crack and Divot Repair - Final Sanding Crawls Backward (When Alarmed)

I let the ebony sawdust/CA fill dry overnight. You'd think that superglue would dry quickly, but my experience with that much volume of the stuff is that it takes a few hours to really harden.

Next step is to get the mounds of filler down closer to the level of the fingerboard. I just used some small files for this.

I'm really wary of changing the radius of the fingerboard, so I don't file the fills flat.

Once they're down to a manageable height, I can sand the whole fingerboard.

Stew-Mac will sell you sanding blocks that are cut to various radii (radiuses?). I actually have a 7 1/4 inch one to use on Fender boards. But I didn't want to spend the money on another one, and I figured I might be able to cook one up myself.

At first I thought I'd try to somehow just cut one out of a hunk of wood.

But then I had a brainstorm.

I have some of this InstaMorph moldable plastic. I actually bought it to use as a caul on another part of the project, which is upcoming, but I wondered if I might make a fingerboard sanding caul out of it.

This stuff is pretty amazing. It's little pellets of plastic.

Put them in some 140 degree F water. I find that 160 actually works better. Just toss the pellets in there.

They glob together, and turn from white to clear. That's when they're ready for action!

Take the plastic blob (careful, it's hot), and mold it to whatever shape you want.

I stuck a piece of waxed paper on the fingerboard, and then molded the InstaMorph around it.

It took me a couple tries to get it right - the blob was too big and too tight on the sides of the board. Whattya do? Just toss it back into the water and mold it again! Crazy!

Here's my 20 inch radius fingerboard sanding caul.

It fits the board very closely, and the radius is perfect. Stick a piece of sandpaper on it, and go to town.

Need a 12 inch radius for a Gibby? Mold one up!