Assemble an F5/F4 Rim (rib) in 15 Steps

Rib assembly is rather simple but should be done methodically. Here are 15 easy steps to help you do it with ease. (A printed version of these instructions is also provided with our body assembly fixtures.):

Rib assembly 1 1. With center spreader out of the fixture, position the headblock in the fixture, and place a pencil mark on the fixture where the long rib piece ends at the notch in the headblock.

 

Rib assembly 2 2. Place the lower point block in the fixture and make a pencil mark on the fixture where the long rib piece will come to an end just beyond the forward tip of the lower block.

 

Rib assembly 3 3. Insert the spreader (don’t tighten it) and use a long “C” clamp to pull the bass side of the long rib piece to the fixture (by clamping the spreader to the fixture).

 

 

Rib assembly 4 4. Continue to tighten the rib around the fixture by clamping the tailblock in place. Then, tighten the spreader (snug only).

 

 

Rib assembly 5 5. Transfer the marks made in steps #1 and #2 from the fixture to the rib. Remove the rib from the fixture and cut the rib at the marks. Ensure that the cuts are perpendicular to the length of the rib.

 

Rib assembly 66. Taper the end of the long rib piece at the arrow (it should feather off where it mates with the rib piece that goes between the two points. Repeat steps 1 through 4. Test the fit of the headblock to the long rib piece. Do not clamp headblock yet.

 

Rib assembly 7 7. Hold the “S” rib piece (that goes from the upper point to the headblock) over the fixture. Mark on the rib where the cuts have to be made. The white lines indicate the angle of the cuts. Make the cuts and place the rib piece back in the fixture. Test how it mates to the headblock.

 

Rib assembly 8 8. Align the “W” rib piece that goes between the two body points and mark on the rib where the cuts have to be made. The white lines indicate the angle of the mortise cuts. Make the cuts and place the “W” rib piece in the fixture. Check the mortise joint at the upper point (this joint does NOT have to be perfect as it will be replaced by the bone corner point).

Rib assembly 99. With the upper point block in place, tighten the spreader and check how all the rib pieces fit. Make any necessary adjustments.

 

 

 

Rib assembly 10 10. Position the lower point block in the fixture. Make any adjustments to its size or shape.

 

 

 

Rib assembly 11 11. For the short rib piece below the lower point, select a curved scrap piece from the other cut-offs and measure how it will fit below the lower point block. The white lines indicate the angle of the mortise cuts where the small piece fits to the big rib and to the end of the lower point.

Rib assembly 12 12. Check the square of the back of the headblock cap. This is especially important on necks with dovetail joints because it determines the alignment of the centerline of the neck through the centerline of the instrument. In each following step, ensure that the rib pieces are pushed down flush to the work surface under the fixture.

Rib assembly 13 13. Loosen the spreader and use a thin spatula to work glue into the tapered seam between the long rib piece and the treble-side “W” piece. Place glue on the two gluing surfaces of the upper point block and place it in the fixture.

 

Rib assembly 14 14. Place glue on the ends of the small rib piece and insert it in the fixture. Now, tighten the spreader. With the spreader tightened, loosen the “C” clamp that holds the tailblock in place, put glue on its gluing surface, and re-clamp the tailblock in place.

 

Rib assembly 15 15. Put glue on the three sides of the lower point and on the three surfaces of the ribs it will mate to and then tap it into its resting place. Fabricate some small wood wedges and gently tap them into the openings in the headblock scroll to give it added strength and to prevent cracking the headblock during clamping. Glue and clamp the headblock in place.

Rib at the neck opening: Note that the “S” rib piece in step #7 ends in the middle of the dovetail or “V” joint. This rib piece should extend into the neck opening until after the soundboard is glued in place and entire assembly is removed from the fixture. Then cut and file the excess rib piece flush to the neck slot opening. (Therefore, it doesn’t really matter where this piece ends in the neck opening since the excess rib will be removed.)

Assembly of A5 ribs: Assembly of A5 rims is similar to the process for F5/F4 ribs. For the A5 rib, follow steps #1 through #4. Then, in step #5 mark the butt-seam centerline on the rib and the centerline at the headblock, remove the rib from the fixture, and cut the rib through the marks. Ensure that the cuts are perpendicular to the length of the rib. Next, install the treble-side rib and repeat the process. Place both rib pieces in the fixture, ensure they are both flush to the work surface below, and glue the tailblock in place, tightening it with a “C” clamp. Then, glue and tighten the headblock in place with a “C” clamp. Pull it up snug.

Note: For added interest, other woods or bindings can be glued into the centerline butt seam of A5 ribs to accentuate, rather than hide this connection point…


Download a copy of the 15 step-by-step instructions to assemble the rib set (Adobe PDF format).

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