Saturday, October 17, 2020

Spencer's Board Repair

 My friend Spencer had a little problem with his board:

Thanks to Kalmus chop, it had developed a crack, as if ready to break into two pieces. Spencer has several newer boards, both larger and smaller, but he really likes this one. So I said I'd have a look. I thought there was hope because the crack did not go all the way to the other side:

But there was a soft spot on the end of the crack:
First thing to do was to have a look inside:

Sanding off the top revealed a layer of carbon-kevlar fabric - nice! That stuff it really expensive, and the kevlar is almost indestructible. It was covered by a thin layer of fiber glass. The kevlar is probably why the board did not break all the way. On the other hand, the construction meant that just a partial layer of carbon provide all the structural strength. Carbon is quite brittle, so it just broke. Below the carbon was standard sandwich construction: high density foam (in a somewhat unusual bright red color), a thin layer of glass, and then the EPS core.

I cut out some of the sandwich layer, and removed a bit of foam underneath that was damaged:
Overall, the EPS foam was still in good shape, so I did not have to remove much. I then used polyurethane pour foam to rebuild what I had cut out:
Next, I had two options on how to proceed: rebuild the sandwich, or just glass over the foam. In nose repairs, I usually just glass over. That's good enough for typical use, and it the mast hits in a bad catapult, even a sandwich will break. But in standing areas, I discovered the hard way that rebuilding the sandwich is a better choice. The affected area was a bit a grey zone: it's in front of the foot pads, so it won't be exposed to the full stress of planing though chop, but it will get some load when not planing. 

One issue here was that the kevlar does not sand well - it just gets all fuzzy. That would have made a smooth connection of the new sandwich harder. Other factors were the age of the board, and that the short days severely limit how much time I can spend doing repairs. Finally, it is possible that the internal damages is worse than it seems, and that the board will soon break completely, anyway. So I decided to just glass directly onto the foam. The cut out area got an extra layer of 6 oz carbon, and the entire crack got a layer of 6 oz carbon and a top layer of 4 oz S-glass. Here's what it looked like afterwards:
Now it just needs some sanding, a top coat, and some anti-skid. I'll skip the painting for now so that any damage that might indicated a pending break will be easier to spot. Spencer can always paint it later :-).

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