So there's no wind here on Sunday so I'm sitting around wishing I could be on the water. Yesterday, the same, so I took apart my foil and re-assambled it with a fresh coat of TefGel and Teflon tape on the screws. My i99 had acquired a few scratches over time (as well as some surface delamination from UV exposure) so I sanded it smooth with progressively finer grit, ending up with 1000 grit sandpaper for a smoother surface, followed by a coat of marine wax.

All of which made me think, is there much (any?) benefit to polishing the foil in terms of performance and lift? Intuitively one would think yes, but I'm curious to hear from those who know more.

Foulweatherjack said..
...followed by a coat of marine wax.

Clean off the wax immediately. It'll keep water from sticking to the foil and make it much more likely to ventilate (suck in air and lose lift).Even fingerprints from Tefgel on a wing will cause this. Plus, it increases drag. What you want is a clean, oil free environment on the wing. Water should not bead up but stick to it. The adhered boundary layer lets the main flow slip easily past.

The optimal sanding grit for a foil is debated and as much depends on the speeds you'll usually travel. If you aren't racing for money or prestige, there is little demonstrable benefit to going above 600-800.

boardlady.com/fast.htm

Edit: The only thing I'd disagree with the Board Lady on is that most now sand in the direction of the water flow. There is some research that supports that as well (and that research suggests the optimum grit for low speeds being as low as 200). Also bears repeating for others, super important that in sanding the original shape of the wing is retained. Fill the ding, then sand. Don't just "sand the ding out" and alter the profile of the foil.

Edit, edit: not trying to make you feel bad about the wax but it will have a negative impact the first time you use it until you remove it.