Finishing the rib structure
  1. When the linings have dried, sand the whole rib structure down on both sides to the final heights, ie. 32 mm at the bottom and 30 mm at the top /Messiah/.
  2. Glue size the ends of all blocks with thin hide glue.
  3. Finish the corners up to the tips using a fine file and sandpaper on a stick.

The rib structure is almost finished. For now, you should leave it on the mould to prevent warping. The remaining steps in this chapter are carried out after the top and back plates have been finished. If you are ready to start on the front plate, refer to the next chapter called Front.

Removing the ribs from the mould
  1. Mark distinctly the top of the rib structure, so that later you are able to tell the top-bottom orientation.
  2. To snap the blocks free of the mould, put your fingers where the red ellipses are in Fig. 1. to serve as a kind of safety bed and tap lightly with a small hammer on the opposite side, on the block, see red arrows in Fig. 1.
  3. Repeat with other blocks, until the whole rib structure is unglued.
  4. To slide the ribs off the mould, hold the ribs in the waist and spread them so that the upper and lower corner blocks are completely outside their mortices, resting on the edges, see the red arrows pointing to those places in Fig. 2. Of course, you need to be careful not to break the rather fragile structure, the top and bottom spruce blocks are sometimes also prone to splitting.
  5. Now you should be able to remove the ribs from the mould starting with the bottom block, working your way up.
  6. Inspect and carefully remove any excess of glue. Check the ribs for any missing parts/splinters that may have broken off/gotten stuck to the mould. Reglue if necessary.

Trimming the blocks
  1. Put the ribs on a flat surface and take a look at the shapes of the top and bottom blocks in Fig. 3.. If you want, you can mark the round outlines to guide your cutting.
  2. Using a sharp chisel trim the top and bottom blocks. Work gradually, the first cut being always small to read the splitting angle, to allow for corrections in case the wood splits unevenly a make sure the newly created walls are perfectly perpendicular.

    The final thickness of the top block "a" is 18 mm, and of the bottom block "b" is 16 mm.
  3. Use a shallow gouge for the cornerblocks.

    See Fig. 3. for how the finalized blocks should look like.
  4. Inspect the blocks again making sure there are no splinters or loose parts that might cause buzzes later on. Finish with sanding paper, if you wish.

Shaping the linings
  1. Take a pencil and draw a guiding line in the middle of each lining along their length.
  2. With a suitable sharp knife start cutting the lower half of each lining leaving the bottom about 0.5 mm thick. See the "1" profile in Fig 3. for reference.
  3. Smooth the resulting "hump" with a scraper to create a good beveled surface as in "2". Finish with sanding paper, if you wish.

You should inspect the whole structure again to see there are no loose pieces of wood or splinters which might later cause buzzes in the finished instrument. Also check that everything is glued together and that there are no gaps.

If you need to store the ribs elsewhere, put it somewhere with constant humidity, preferably about 50 percent, and room temperature.

The weight of the finished ribs should be about 50 grams.

Category: Ribs
Comment by
2017-04-28 03:13:01
The ribs are planed so they're level with the blocks, right?
[Comment deleted]
Comment by Vojtech Blahout
2017-07-23 23:57:34
Initially yes, but for the final stages, sanding is better.
[Comment deleted]
Comment by Vojtech Blahout
2017-07-25 16:36:28
Glue-sizing - applying thin hide glue to porous areas, ie. the ends of blocks, to effectively seal them and make them ready for future gluing.