Saw this product advertised and wondered how it would affect the bottom of speed boards and/or even fins? Looks to be a simple 2-part application process.

looks like a good mold relase

Tribology is a complicated science with hydrophobia and hydrophilia both making cases for reducing drag. I'm sure there are studies out there saying which works best for reducing drag but they are difficult to find.

However just keeping water out of the luff pocket would make it worthwhile for me.

I'm not sure hydrophobic board bottoms etc would be a good thing, board /fin grip, are a big part of being able to control our gear.

If someone's got an old board, might be worth a go, I wouldn't be inclined to try it out on a newish board though, it might be the end of it functioning properly.

Found a good reference to all the drag reduction oils. royalsocietypublishing.org/action/cookieAbsent

Doesn't seem there's any danger of a board not working after becoming hydrophobic but a moderate reduction in drag has apparently been measured! Try longitudinal sanding of that old board with with maybe 120 grit paper.
A sacrificial layer of fish mucus (a special blend released by fish in times of stress) appears to be the go. A 50% drag reduction! A 20 litre drum should last at least a season.

I can understand putting the hydrophobic coating on the bottom of the board, it does make sense to me.
But on the fin? it just sounds like a recipe for disaster because the fin would repel water and be more inclined to get a bubble around it and spin out. Im not that experienced however and if someone could correct me if im wrong i would love to learn about it.


Edit: Also making things 'grippier' can also decrease overall drag. It's the reason that golfballs have dimples, so they travel further because they have less air being dragged behind them.

I suspect that putting the above coating on your fin would result in a significant reduction in upwind capability as it would reduce the friction between the fin and the water, reducing the circulation around the fin and hence the lift it is able to produce.

Also a note on the golf ball concept:

Pressure Drag - Caused by the difference in pressure between the leading and trailing faces of the object, usually due to the flow separating from the trailing face

Skin Friction Drag - The friction between the surface and the fluid passing it

Dimpling the ball causes the laminar flow around it to become turbulent, allowing it to maintain contact further around the ball's profile before separation, reducing profile drag, this however significantly increases skin friction drag so is only really applicable to blunt objects like golf balls where flow separation is a factor.

For a planing windsurfer the effects of profile drag are minimal as its profile is not submerged in the fluid. Golf-ball like dimples would likely have a degenerative effect by eliminating the laminar flow and needlessly increasing skin friction drag