Before I could prepare the back plate of this five-string fiddle, I had to complete the rest of the corpus (body of the violin:) First, the inside willow blocks and willow linings had to be tapered and shaped so they are completely smooth. Then, the back of the entire corpus (including the heel of the neck) has to be leveled, so that it will lie flat on the back plate. So, here is the main part of the 5-string violin, with the interior clean and smooth, and the back leveled and flat:
Beginning the Back Plate
I clamped the corpus flat on the back plate billet, then traced around the ribs, using a small washer to establish the correct rib overhang. Then I corrected the corners, using a straightedge and a series of circle patterns. Finally, I cut out the plate “footprint”, and began the arching process. Oregon Big Leaf Maple is a relatively soft maple, but it is still a good deal harder and tougher than Sitka spruce, so the back plate is a lot more work to carve. Here is the beginning:
In the above photo, the back plate is sitting in a work cradle, so that it will stay in place while I carve it. The Ibex plane in the photo has been slightly modified, to add the palm-fitting handle. This reduces the stress on my fingers and transfers the force to the palm of my hand as opposed to my thumb and forefinger. (To Ibex plane-owners: you will observe that I have removed the adjusting screw and reinstalled it upside down to allow insertion of the maple handle.)
I have been on vacation for two weeks, which has allowed me to accomplish more work than usual, in a shorter period of time. I go back to my regular job, on Monday, though, so things are about to slow to a crawl. (Sorry…that’s life. :-))
(Further progress on building a custom-made 5-string bluegrass fiddle.)
The neck was ready to set into the neck-block, last night, but I had reached my limit. So, today, I prepared both the neck and the garland, by ascertaining that all angles and dimensions were correct, and then laying out the shape of the neck mortise on the neck block of the garland. This is a critical step, and always raises my blood pressure a little, as I know that, if I make a mistake, it will require serious rework to get back to a usable status.
However, this time, the job went pretty smoothly, and I was able to set the neck in a fairly short time. One thing I do a little differently than I was originally taught, is that I set the neck before installing the maple back plate. This allows me to achieve a good fit with the rib garland and neck block, and not have to worry about the fit against the back plate button. Then I saw off the stub of the neck heel, and plane and file it flush with the rib garland. After I remove the mold and add the back linings, I will level the back of the garland, and be ready to trace the back plate shape.
Here is the completed corpus (Sitka Spruce top plate and Big Leaf maple ribs still on the mold) with the wild-grain Big-leaf maple back plate billet.
So, the next step was to remove the plywood mold. This is another stressful step because it involves literally using a hammer and chisel, to break the glue-bond between the blocks and the mold, so as to release the garland from the mold. I used to have a difficult time doing this, because occasionally a drop of hide glue had seeped between the rib and the mold, and anchored the fragile rib material to the very solid mold. The likelihood of breaking a rib at that point became nearly 100%. Eventually, however, I learned to liberally coat all the non-gluing surfaces of the mold with candle-wax (paraffin,) by vigorously rubbing a candle over all the areas I felt were likely to get a drop of glue on them.
The result today was that, when I removed the mold, it went smoothly, and I could see a place where glue had definitely intruded but it had dried with zero adhesion to the waxy mold. (What a relief!)
Installing the Back Linings
The linings are important for two reasons: they strengthen the fragile rib-edges, and they triple the gluing surfaces between the rib-garland and the front and back plates.
So, I cut the mortices in both sides of each of the six blocks to receive the lining strips, and then inserted the linings dry, to get a perfect fit.
Afterward, I removed each lining, one by one, coated them liberally with hot hide-glue, and re-inserted them, clamping immediately with small spring-clamps.
Shaping Blocks and Linings
If you look closely you can also see, in the above photos, that I had trimmed the blocks on the front side, before removing the mold. After the glue is dry on the back linings, I will also trim the back side of the blocks, to achieve a smooth, curved surface on the interior of all the blocks. At that same time, I will taper the linings so that they are very thin on the edge toward the middle of each rib, but still 2 mm thick at the edge where they will contact the back and front plates.
After that, it will be time to level the back surface of the entire corpus (garland and neck-heel) so as to fit tightly against the back plate billet. Then I can trace the final shape of the back plate, cut it to shape, and get going on completing the back plate.
For now, I am satisfied to allow the glue to dry, and take the rest of the evening off.