Gluing the rib corners

Here is a photo I promised a while back. It shows the method I use to clamp the ribs while gluing them on the blocks. I have holes drilled in the mold that hold a dowel. They are situated so that when some cord, or twine like I have here, is wrapped around the dowel, over the clamping block, and around the dowel on the other side, the clamping pressure pushes the rib in place. That sentence is too long. That's why they say a picture is worth a thousand words! The picture tells it much more eloquently. I use small drills to twist each side of the cord until it is tight. Then sit it aside until the next day. It is a very simple clamp. It is not hard to imagine Stradivarius doing it the same way.
I tried the other day to bend the c bout ribs for the last violin that needs a ribcage. Those were the ones I made inline with the medulary rays. The red maple stock is much more flamed than other ribs I've bent. The other red maple ones for the violin in the photo that I just glued up didn't give me too much trouble. These ones were nasty. I had a hard time keeping the back side from splitting. Thought I had the iron hot. Thought I had it pulled tight with the band. Thought I had the back side wet enough so it would steam and relax. I thought wrong. I never had so much trouble. Luckily I have more stock if I run out of strips I've already cut and thinned to 1.2mm. Maybe I need to double check the thickness. Maybe there are some thick spots. Maybe 1.0mm would be better.
Some of you may notice I glued the corners before the bottom joint. This was on purpose. I thought I'd try it that way this time. Once I had one ribs slightly on an angle and had to move it to get it to fit on the corner block. Another time I thought I had it good and the bottom joint on one side must have moved while gluing the corner block. I figure this way neither one of those things will happen. The last couple I had long enough ribs stock I used a one piece rib on the bottom. The way to go for sure. I let you know how this new method works.

Back up a little

Most violin makers begin with the mold and ribcage. I showed my mold before, but didn't explain how it works. Here is my PG mold and the plates I've already made to fit it. The plywood outline of the mold is made so that when the ribs are bent around them they will be 2.5mm - 3mm inside the desired outline. The blocks are the gluing points for the ribs, and the neck, and the support for the end pin. The aluminum template is the outline showing the corner and end block shape. There are two reamed holes in the mold that line up with the reamed holes in the template. That is how the mold is made, so it is somewhat symmetrical. It also allows the maker to mark out the corner and end blocks. Without a template the corners would be hard to make anywheres near the way the design called for. I go around the template, re-positioning it 4 times to get the blocks marked out. Then I use a gouge, chisel and file to get the blocks shaped to both sides of the line. That way the ribs have a decent chance of being square. Now I'm ready to glue the c-bouts on. First I'll have to bend them.
The belly wood on this one has a lot of bear claw on it, but the photo doesn't bring it out. Hopefully my varnish will make it stand out. The back still needs the purfling put in and the edge finished. I tap the plates to get a rough idea of the stiffness. Since I've never flexed a "real" violin back or belly I have no idea what it should be. Not being taught by anyone I don't even have the luxury of the teacher telling me, "still too stiff". There is a formula to come up with a "stiffness number". It is frequency squared time the weight in grams. The frequency is the ring mode, or mode 5 of the plate. I measure that by placing the plate on a piece of foam and tapping in the middle. The belly on this one is 330hertz with the f holes cut and the bass bar in. With a weight of 61g the number is 6.6. The back is 120g, but will probably lose some. With a frequency of 311hertz the number is 11.6. According to the plate stiffness figures on the platetuning.org website the back is about right, but the belly is too wimpy, should be closer to 8. It doesn't seem whimpy, will have to see about that when it is glued together. Any thoughts out there on these numbers, or on this method? Any help or information would be appreciated.

Back in the groove

Well I'm back to work. At work and in the basement. I thought I would have more time to work on violins going back to my old job, but we're working weekends there too. Either you're laid off, or working overtime. I did get the purfling grooves cut, except for the corners, on the birch violin. And I cut out another set of ribs for the slab Sugar Maple one that I never made ribs for. The mold for that one is the same as the Birch one, I based it on the Viotti poster I have, the PG mold. The newest one is based on the Titan, the P mold. Not to say that my molds are the same as Mr. Tony's, but just that they are different, and "supposed" to be like the P and PG molds.
I bought a replacement blade for my Japanese Ryoba saw. Made a big difference. I cut a 2mm thick piece that was wide enough for 3 ribs in about half an hour. And it was fairly flat. After cutting them to the width it took about another half an hour to get them planed and scraped to 1.2mm or so thick. An hour to get a set of ribs ready to bend. I don't think that is too bad. These ones I made sure I cut them inline with the medular rays. Some people on line say that it may make the ribs stiffer. I'd like something that makes them as easy to bend as a wet noodle, but I haven't seen anything about that.
I have thought about getting one of those electric heaters for the bending iron. The heat gun just doesn't get as hot as I would like. I drilled two holes in the base of my bending iron and bolted it to the table. That helps it a lot. I don't have to worry about flying backwards if the clamps let loose! So I need to bend and glue some ribs up, and finish up the purfling on all the plates so I can start doing some tuning. That should be fun. On the photo you can see that I put some thinned glue all around the edge before cutting the groove. Never did that before. It helps prevent chunks from coming out of the groove when you clean it out. Seems to work.