Archtop Progress, With Photos!

Well, some people have been asking for some pictures of what I've been doing in school lately, and the only thing that would probably be of interest to them is the archtop construction. Here's a brief rundown of the process and what I've done so far:

The first thing we did in the class for a week or two was make templates to assist us in arching and prepare the molds. We are the first year class where we didn't have to make our own molds, which is kind of nice, but I also kind of wish that I would have so that I would have the mold to use in the future. The interesting thing about the molds that we are using is the fact that they are inside molds that break away from the body when the time comes. The pieces near the blocks come out and then the 2 main body mold pieces slide in and out. Here is a picture with some arrows to show how this works:



So once the molds and templates were ready, we started working on the blocks. The blocks are squared, planed to height, then glued into the mold using spacer sticks planed to a thickness of 13 milimeters accurate to within 1/10 of a milimeter. When gluing the blocks to the mold, a small spot of hot hide glue was used, as it is brittle and will break away from the mold easily when needed. Once in the mold, the blocks were carved, filed, and sanded to match the curves of the body outline and are flush with the mold.

The next step was to thickness the ribs(sides) and cut them to a couple milimeters over the final height. Then, I bent the ribs(sides) usinga handy dandy setup consisting of a basswood mold, some clamps, some cauls, some wooden sticks, some tinfoil, paper towels, a little water, some sheets of spring steel, and a silicone heating blanket. It was a pretty easy process with that setup, and I highly recommend it to anyone wanting to build a guitar. You can, however always bend the sides the old fashioned way by hand with a bending iron, but the heating blanket is sooo much easier. Before gluing the ribs, they were dry clamped into the mold overnight to settle and then trimmed up to form the butt joint and so they can be attached to the blocks. After gluing the ribs to the blocks, reversed kerfed lining was attached and then the whole thing was sanded flat and to final height using a big sheet of sandpaper on a granite flat plate. I now had the completed rib structure as seen below:


Well, I'm getting long-winded, but that's ok, you don't have to read this if you don't want to.

After the rib structure was completed, we started working on the plates. The plates are pieces of wood around 30 milimeters thick that are joined together to become the top and the back of the guitar. Considering the disastrous climate conditions in our labs for the first couple months of class, a lot of work was needed to flatten the plates for joining. Most of the flattening is done by putting the plates on a flat plate with chalk and planing off the areas where chalk is left on the wood. This can get kind of tedious, so at the pre-joining phase there is a certain level of flat enough. Then the edges to be joined were sent through the jointer a couple of times and then hand planed to perfect the joint, with gaps no more than a thousandth of an inch or so. The first time around, this took a while, but I got better at it after joining both my top and back. Once the seams were perfect, the plates were joined with some really big clamps and hot hide glue. Woohoo! My plates now have a perfect joint and the only way you can really tell there is a seam is from the varying grain direction in the wood.

After joining, the plates were then flattened with a big jointer plane and fine tuned to fit perfectly with the rib structure using the block plane. Once they were flat, I traced the outline of the body from the mold on the back of each with a scribe. They were then sent through the thickness sander and sanded down to a final arch height of 25 milimeters and cut to shape on the bandsaw. Here is the top at this point:





I was pretty excited at this point because I finally got to start the rough arching of the plates. Woohoo! Now it was time to remove a crapload of wood. Most plates for archtops come in wedges, so as to not have to remove so much wood. Mine were slabs, so I had a lot to take off. You can see in the picture above at the bottom of the picture my new favorite tool, the scrub plane. This thing has a blade that is rounded like a gouge to hog out wood like no other. It still took me two class periods to get my rough arching done, but it would have taken much longer if I were just using a gouge. There is another method to rough arching which involves an angle grinder with a round chainsaw blade. This method is not the safest one, but if one is careful it can really speed up the process. I think I may try it for my next archtop guitar. The gouge also came in handy for some of the areas I couldn't quite get right in with the scrub plane, and can be seen at the top right of the photo below. Here are a couple pictures of the back rough arching:

(Note: the outside has been taken down to just over 6 mm and the egg shape in the middle is still 25 mm thick.)



And here is a picture of the top in the process of rough arching (the mess in the picture is only about a third of the woodchips and shavings created throughout the rough arching):


And tomorrow night, it's on to refining the arching and getting the plates closer to their final shape. This is exciting stuff!