Thursday, May 07, 2009

New centerboard (part 4)

Used a plane to smooth the curves around the centerboard, followed by some 80 grit orbital sanding.

One of the steps is to bevel the leading and trailing wet edges, to reduce friction and increase lift. I started to do that along the bottom edge (which is the leading edge when the board is down).

I then realized I needed to cut the hook in so I would know where to stop bevelling. I want to keep plenty of wood in place there, to keep it strong. I used a 5/8" drill bit to shape the main pivot point, and the circular saw to cut the rest of the slot. A 4-in-hand file/rasp to round the edges and smooth the transition between the hole and the straight cuts.

I also want to leave the lowest point a little thicker, since it gets beat up a lot when grounding, beaching, launching, or loading.

As you can see in the picture, the colors of the plys help to make the bevel even. I'm not trying to create a scarf joint, so perfection isn't required, but it's a good place to practice. Ideally the stripes are straight / parallel / equal width. There are 12 plies in this 3/4" sheet (although it's actually slightly less than 3/4"). The outer plies (the veneer) are thinner than the others. My plan is to bevel 4 plies worth, leaving the middle 4 plies intact (although maybe I will round the transition from the bevel to the middle section).

I've also been shopping for lead-pouring equipment. So far I have:
  • small cast-iron pan as crucible (thrift store)
  • long metal spoon to scoop impurities (thrift store)
  • weed burner / valve / hose / regulator to melt the lead (Marine Exchange)
  • lead (gonna pull it out of the old centerboard)
Still need:
  • asbestos tile
  • maybe a coffee can as an alternate crucible
  • heat-proof gloves
  • tongs
  • propane tank

Updated TODO list:

- Clean up the cuts that went off the line
- Draw and cut the curve at the top
- Plane down the leading and trailing edges (in progress)
- Cut a hole and pour in a lead sink weight (first time pouring lead)
- Cut a gap for the pivot
- Cut some 1/8" sheet metal to reinforce the pivot (will try to reuse the old one)
- Drill 5 holes (ooh, the easy part)
- Paint (no epoxy)
- Install centerboard
- Put boat back on trailer.

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