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Preparing the mould and the ribstock
  1. Screw the four screws in the mould again so that they rise the corner blocks about 1.5-2 mm above the surface of your workbench. Put the mould on your flat surface and put the rib stock right next to the corner blocks checking that it overlaps by 2 mm at the bottom and 2+ mm at the top.

    Don`t forget that the height of the ribs is decreasing along the length of the violin body, so with a 2 mm overhang at the bottom block, you will get 4 mm at the top block.
  2. Choose the ribstock pieces for the C ribs. Decide the orientation of the pieces with regard to the slant of the flames. They usually slope down towards the player on both sides (the flames on the neck later on should match that). Make sure their surface is perfect, especially on the outside, correct with a scraper.
  3. Prepare the clamping blocks used to hold the C ribs in place as in Fig. 2. These can be made of some harder wood to the dimensions of 110 x 35 x 15 mm. Two pieces are needed. For the exact angles, you can print out the Fig. 2.

Bending tips

The temperature of the bending iron should range between 200-250 Celsius. You can get a thermostatically controlled bending iron, or you can learn to estimate the temperature by moistening your finger in the water and touching the iron briefly. This takes experience.

Also, practice bending on scrap rib stock first. You need to learn how much pressure to apply, how fast to proceed, how the heat in the iron is distributed and what is the best temperature for the actual wood you are bending. Too little heat and too much pressure and you will break the rib. This applies especially for highly flamed maple. Too much heat, on the other hand, applied for too long will vaporize all the water and you will scorch the rib.

Bending
  1. Put a sufficiently long piece of rib stock in water and let soak for a few minutes.
  2. Heat up the bending iron and bend the C ribs so that they fit the mould as closely as possible. No excessive force should be needed. You should be left with C ribs that have no gaps along their inner side, like in Fig. 1.

    When driven home, looking from the side, they should be in contact with the workbench, extending beyond the elevated corner blocks by about *2 mm*, as mentioned above. Also, using a small square, check that they are at right angles to the workbench.

    Clean the bending iron after each bending with a damp cloth to reduce the staining of the wood.
  3. Shorten the ends of the ribs, if necessary. They should extend only 3-4 mm beyond the point of the corner block. Make sure they are still at right angles.
  4. For a test, put on the C clamping blocks and make sure they sit well, are perpendicular to the surface and that they end up a couple of millimeters proud of the tip of the corner. When pressure is applied they should be "opening" the C rib slightly, see Fig. 2.

    If needed, file down the ends of the ribs to ensure good contact with the clamping blocks, and the proper "opening" action.
  5. Also, the clamps you will be using in the gluing, should be put on for a try. Only mild force from the clamps should drive the C ribs fully home, closing all gaps. The red arrows in Fig. 2 show where the action of the clamps should be.
  6. If there is any moisture left on the ribs, let dry.
  7. If necessary, reapply soap on the mould, in the vicinity of the blocks, where it might have been removed by sanding.
  8. Glue in using medium thickness hide glue, putting it on the blocks only.

Category: Ribs
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