Production line

Warning: I have almost no pictures to supplement this installment.

I laid out a diagram in CAD of all the gussets that had to be cut and how to best fit them on my two 4'x4' sheets of 1/16" plywood. From here it was just a simple matter of ripping the sheet down into strips, then cross-cutting those strips on my crosscut sled. There are a few triangle shaped gussets for the trailing edge that were made by cutting a rectangular gusset on the diagonal with my band saw. The leading edge of the rib has a custom gusset that covers the nose block made last time and butts against the forward spar opening. These were made much the same as the nose blocks, but were able to be cut 4 at a time. There are 50 nose gussets (part# 1), 50 Trailing edge gussets (part# 22), 50 long gussets (part#19), and 602 standard gussets (part# 18). All these gussets are 1/16" birch plywood. Birch plywood needs to be sanded to roughen the surface before gluing. I forgot this fact until after I had cut out all of the nose gussets and trailing edge gussets, but remembered before cross-cutting the 20 strips of plywood that would become the remaining 652 gussets. A palm sander made quick work of this task, but it would have been easier if I'd sanded the whole sheet of plywood before cutting anything in the first place.

 The intercostal capstrips (uprights and diagonals) were cut in much the same way. I took the piece I fitted to the jig last time and set it in the crosscut sled. A stop block was clamped in place and used to cut a test piece. This piece was compared with the original and trial fit in the rib jig. If it fit I cut the remaining 24 pieces needed for the 26 ribs. If not, the stop block was adjusted and the process repeated. Each gusset and intercostal got it's own numbered cup for organization. Not pictured below are the #1 nose gussets or the #18 standard gussets.

The last thing to do before I can production line these ribs is to bend the upper and lower capstrips. I was able to force the upper and lower capstrips into place for fitting the intercostals and finishing up the rib jig, but there is a risk of snapping them. To help alleviate this risk we pre-bend the capstrips. The key to all of this is a 2x4. A slightly deepened airfoil curve is cut into the 2x4; in this case my band saw did the dirty work, but a jigsaw or scroll saw could serve as well. Try to keep both halves of the 2x4 a nice smooth curve. Now we take our capstrips and drop one end in a pot of boiling water. Keep them boiling for 15-20 minutes, then pull them out, stick them between the 2x4 pieces, and clamp them tightly. Let this sit for 12 hours or so. I was able to load up 5-6 capstrips at a time in this makeshift press. The upper capstrips sit flush with the end of the 2x4. The lower capstrips, since their curve is slightly less and located more forward than that of the uppers, are placed a few inches back in the press. Shown below is the 2x4 press block with an upper and a lower capstrip in the press and how they look after being bent.

 

I said the last thing to do was bend the capstrips, but I lied. The nose blocks have a cutout in the leading edge for a 3x4" square spruce leading edge to fit into. The router left these slots with round corners and intentionally undersized. I need to square up these corners before the nose blocks are attached to the rib. I built a jig for the tablesaw and set up stop blocks on my crosscut sled to define the edges of the slot. 16 of the 28 nose blocks cut fine, but about half way through my stop blocks got bumped and the remaining 12 nose blocks received a slot that was 1/8" too wide. I was tempted to ignore this error and just glue in a shim to make up the difference when assembling the wing. I realized, however, that was the wrong attitude to take in this endeavor, and remade 10 nose blocks. Now, again, I had the 26 pieces I would need to start assembling ribs.

Total time invested so far: 30.75 hours.