David's Guitar Building: Exploding dinosaurs and doing the twist......

So before I started my to-do list for today, I went up to the shop and got some work done on the SJ. First up was to cut the tenon on the neck. I used my tenoning jig to make most of the cuts on the table saw, and then I used the miter gauge to do the rest of the cuts. One thing I did was mis-measure the depth of the tenon versus the mortise I made. The tenon was about 1/8" too long and because the brass inserts were already installed, cutting the tenon wasn't an option. After a bit of head scratching, I finally figured out how to deepen the mortise without damaging the shape of it. I used a 1/2" mortising router bit that I slid a bearing and collet under the cutter. The bearing would ride inside the existing mortise and the bit would cut the bottom out. It worked fine. The only thing I wasn't thrilled with is that the shortest bit I had still made the slot a little deeper than I wanted. No big deal though, it just means there will be a 3/16" space between the back of the mortise and the end of the tenon. There should be a gap anyways, I just like to keep it a little smaller than that. After the tenon was finished, I took a couple of minutes and rough cut the radius of the heel with my band saw.

Once that was done, it was time to sand the top and back edges of the sides to the 15' and 30' radius' that I wanted. First I sanded the top edge to 30' using a radius dish. Once that was done I then could measure the depth of the sides, transfer a line around it and cut it to the correct size.

The method I use to do this is something I picked up from the kit guitar builders website. Essentially you make a cardboard grid with lines spaced 2" apart to set the sides on. Then you mark the plans in 2" increments, and then measure those locations for body depth. Those measurements are then transferred to the body using the cardboard grid, a square and a ruler. Tape is run around the perimeter of the body to 'connect the dots' so to speak. This gives you a line all around the body that matches the plans. This method works great but has one significant flaw if you are trying to build a radiused dome in the back and top. The side drawings of the guitar never actually represent the correct dimensions at the waist. This is because the waist, as it goes in towards the center of the body will need to be wider because the dome is deeper at that point. My first try at using this method is where I found this flaw. I rough cut the sides to the line but when I put it in the sanding dish, I realized that the waist was cut too deeply. I was able to compensate by sanding the neck and tail blocks down until the waist touched but this made the guitar a bit thinner than it should have been. When I built my OOO, I used the same method, however I left the waist a bit thicker to compensate for this. It worked great so I did the same thing here. This might not make sense to read, but I am posting pictures that should help you visualize what I am talking about.

Anyways, I taped the line around the body and rough cut it using my microplane and cordless drill. I then changed sanding dishes and then started dancing "The Twist" ! It must look funny watching me swivel the sides back and forth sanding them down. It's good exercise I must say!

So I now have a neck blank ready for carving, and sides ready for kerfing. Next up will be kerfing and then I will start working on the soundboard and rosette. The OOO is also ready for final sanding so I might get started on that this week if time permits.

This is the tenoning jig I use for this kind of cut. It holds the neck securely and square. It make it a very safe operation.

The mitre gauge helps with these side cuts.

The neck with the tenon cut out. Okay, you caught me. I have a bit of a sweet tooth!

I cut the rough heel arch with my band saw.

First I sanded the top radius to 30'.

Here is the radius dish after the top sanding. Here you can see just how purple the wood really is.

To transfer the body depth, I marked the dimensions in 2" intervals on the plan.

Then I used a grid board to transfer these measurements on the body. Then I wrapped tape around the body to connect the dots. The top edge of the tape is the cutting depth.

Here is the body after I rough cut close to the line using a microplane. You will notice I kept the cut quite high of the line at the waist going down into the lower bout. I told you the place was going to look like Barney exploded during this build!

This picture really shows what I was trying to explain above. This has been sanded to the 15' radius and you will notice that the sides don't even come close to the tape line. That is because the dome is deeper the closer to the center you get. If I had rough cut down to the tape line, I would have to remove a lot of material at the neck and tail to get the waist to the correct radius again.