Acornhouseworkshop

One of the most intimidating task in making a mandola, mandolin, or really any instrument with a carved arched top, is taking a solid piece of wood, and carving the convex top and a concave back to match. I start with a bookmatched wedge of spruce, Adirondack in this case, and, after flattening the bottom, I mark out the rough contours and use a router to hog off a good part of the wood.

This gives me a good platform to start carving, and save me a lot of grunt work. Next, I break out my large(ish) instrument makers plane. These little hand planes, also called thumb planes, were first develop for violin makers, but when archtop guitars and mandolins started being mad, they found another, albeit very similar, group of users. With the thumb plane, I start to connect the terraces into a smooth arch.

Until, finally, I have an approximation of the final contour, still a little rough, though; creating a nice pile of hamster bedding in the process.

At this point, its time to refine the curves, and make sure I’m getting the arcs I want. So, I make some cross section templates at important points, like the bridge, and where the soundholes start and end, as well as down the middle. Since my last mando build, I’ve found that they are much easier to use if they are solid, so, instead of just using stiff poster board, I transferred them onto wood.. Plus they’ll be ready to go for any future mandola builds. They won’t go tight to my curves until the recurve is finished (which I won’t do until much later), but I can still see how much I match the ideal by looking for a consistent gap.

With the rough arches planed, now I turn to my two tiny block planes, to smooth out the curves, removing the mark of the curved bottom thumb plane.

Next, come the double curved planes to start working on the transition to the recurve.

Scrapers step in to help smooth out those planes’ marks.

Finally, an orbital sander gives a final smoothing of all tool marks, and blends the surface into one.

To get the inside to match the outer curves, I set up a jig at the drill press that will register of the newly created top surface, and drill down to within 1/4″ of the top. This gives me an indication of when to stop carving, at least for the rough out.

Then, a gouge hogs off the bulk of the wood, before the thumb plane again steps in to plane down until the drill bit holes disappear. The I know I’m 1/4″ from the outer surface, and I can begin more refined planing, as before, with the goal to have the thickest part where the bridge will rest, going thinner as it approaches the rim. The thinnest part will be at the recurve, which may be as thin as 3/32″. That allows the mandola’s top to react to the strings’ vibrations and transfer the maximum amount of sound; its what makes a “lively” instrument.

The process goes as before, although I can’t use the flat bottomed block planes this time on the concave surface. A finish sanding and we’re ready to cut the f-holes and brace the top, before gluing it to the sides.

I definitely need to get a padded glove for my planing hand before working on the maple back.

This entry was posted on May 31, 2016 at 3:11 pm and is filed under Acorn House. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.