Carving and smoothing the inside of the tops

Last post, I showed how I surfaced the inside of the backs to an even 3/16". Surfacing the inside of the tops is a little harder - because of the string tension, the tops need to be a little thicker than the backs under the bridge, yet because the tops are the primary sounding board of the instrument, they need to be thinner than the backs near the edges. Thickness at different spots on the tops ranges from 1/8" to 3/16, and needs to be graduated carefully for the best resonance of the sound board. Here's how I'm doing it:

I dug out about half the wood quickly, guessing at about 3/8 thick overall, because it would mean less jarring gouging work later. Then I mapped out 3 different depths to work to: 1/8" around the rim to about 3/16" under the bridge in the center. Then on to the drill press once again.

Using the same setup as for the backs, I drilled about a million holes with my hand-ground, no-spur 3/4" Forstner bit, angling the work a little as I went to make the bottoms of the holes vaguely parallel to the other sides.

Guess the number of holes and win a prize! Note how the center parts of the plates are a little "raised" - that's because the holes were 1/32 less deep than those nearby,

Next step was very pleasant - planing down to the bottoms of the holes with my hand-made double convex plane. This tool works really well, and is indispensable here. This is the job I made it for.

Planing getting done - about 1/2 hour a plate.

After planing, I used a hand-held curved scraper to reduce the thickness overall, checking repeatedly with the thickness caliper. Learning to sharpen and use this tool was another of my goals for this project. I must say, it works much more aggressively than I had thought. With a good cutting burr, it gets too hot to hold after about 5 minutes of use. WHich is OK, because my thumbs start to ache from holding it at the proper angle.  I'll use this tool again for scraping the recurve of the tops and backs once the body is assembled and the bindings are on.

After scarping the plate to the thicknesses I wanted, I gave the inside a quick smoothing with medium-grit sandpaper. I hold it up to angled sunlight like this to see where there might be irregularities - such as the waves in the upper rim and a slight bulge to the right of my thumb. These will be scraped and checked until each back has a fair curve to it, and then the plates will formed at last.