I recently had a repair done on a foil and it left parts of the foil with more resin and a rougher finish. I’m pretty sure that sanding the excess down will help, but does polishing it make a difference? I would assume it could reduce drag, but don’t really know if it’s something worth exploring.
Any of you have tried it?
Waste of time
You might get minor difference speed , but most of it will be in you head
You polish when it’s time to sell at a swapmeet. People like the shiny straight from the factory look when buying. Sanded to a hydrophilic finish is better for daily performance.
There are different theories as to what grit is better (800 through 3000), but the general consensus is that a shiny polished surface is bad. I’ve been happy with about 2000 grit.
How do you acheive a hydrophobic finish? I might try to use the mentioned 2000 grit and call it a day
Hydrophobic finish is bad.
Sanded finish is good.
If water drops bead on foil then degrease (alcohol is good,do not use cleaners with silicons etc..) .
If it still beads then sand.
I use 1000 wet,but lots of different opinions on this.
PS : I once cleaned the foil with KH7 , a general cleaner-degreaser.I was generous with it 
It must have some silicon,wax or whatnot because the foil was almost unrideable afterwards, draggy,high stall speed,unpredictably twitchy.
Had to come in and clean it with acohol.
Hydrophobic is factory finish or polish finish. You don’t want your foil scared of water though.
Hydrophilic is very easy to get and you can tell when your foil gets wet and stays wet instead of beading up and kicking the water off. I pretty much only sand using 2000 grit and rarely go higher or lower.
Here’s an under 60 second repair with a hydrophilic finish:
Before:
One ultra thin clearcoat to fill in the scratches (takes5 seconds) and then a quick sand at 2000 for 30 seconds.
What clear coat do you use?
do you coat the entire wing or just a spot?
As recommended by a local shaper:
Entire wing is best for as much damage as that foil had. Sometimes you can get away with a small spot but it’s easier to spray the whole thing evenly and then sand the entire thing evenly.
I didn’t have time to properly sand a foil once after repairing it. Think I ended up sanding it with 300. It was a dock start foil and it was almost impossible to start with. Felt extremely draggy and difficult to control. Once I sanded it down to 600 it felt pretty much like it did before. Haven’t tested how much of a difference going to 1000 or 2000 does compared to 600 but nowadays I always sand down to at least 1000 to be sure.
This is insanely helpful. I wing in an area where hitting debris below the surface is common. Do you have any tricks for restoring the trailing edge of foils? Super small less than 1mm deviations along the trailing edge.
@TooMuchEpoxy I’ve been meaning to respond but here we are with a related thread.
I try to avoid rebuilding the trailing edges because whatever I use to fill them in usually isn’t the same hardness as the carbon. As such, sanding gets wacky and imperfect which causes problems.
With the clear coat you for minor scratches you are just spraying it on and then sanding it back off so I have minimal concern about changing the shape of the foil.
Sanding trailing edge is tricky to get it right.
But if I had to do it, I would make 1/8" cut out in the broken area, stick a clear plastic tape on the underside of the wing, fill the cutouts with wetted-out carbon strand, use my finger to mash them fuzzy and finaly put a clear tape on top of it all. You can then sand it back to the original shape.
Hope it help!
There is a grit where it won’t matter above it. The idea of the “boundary layer” being further off the foil than the peaks and valleys of the grit you are using.
One thing is 100% and that is you can’t do any wrong polishing to a mirror. Worst case is it’s a waste of time above grit X, and people can argue what grit that is. (Also you can totally mess up a foil sanding it and changing the profile but that’s not what I mean here).
My process is sand to 1,000 or a bit higher then use cutting compound designed for 1,000 grit+ and finally finishing compound. Most of the time is dealing with little chips and things and having enough epoxy or whatever to actually sand. I saw recently the f4 foils have a lot of epoxy on the exterior to sand for example. A mikeslab you will be into the carbon in no time.
After seeing banged up foils working OK was sceptical about surface finish being perfect until last year something (algae?) left a thin film on out foils, especially bumpy on the leading edge. We all experienced reduced speed, instability and drop outs until cleaned off
Somewhere (near here) someone explained that the top side first 1/3 of leading edge is all that really matters, and because it doesn’t get scratched it’s mostly fine
Stab facing down means it probably does meaningfully benefit from a cleanup
how do you get the scratches to disappear like this. If I apply clear (same clear you’re using) the scratches are still visible. I was going to use super glue with graphite per a friends rec.
Are your scratches pretty deep? If so, a bit more work is necessary. A black paint pen is nice for filling in larger scratches. Tape off the area precisely, fill with the paint pen, scrape off any excess right away, let it dry, then do a quick final sand to make sure water isn’t beading on it.
Super glue is hard. If you overfill the scratch (highly likely) then you need good sanding skills to level it out without creating a divot all around it. I don’t like superglue for scratch repair.
