from a french racer video on ; http://kitefoil.forumactif.org/t5189-le ... nie+freine
Sorry, not all info on the web is in english
On YT, KZDnIQFGt2M title, "ENGIE Kite Tour Douarnenez J2"
At 2 minutes in the video, the runner "Jean Guillaume Rivaud" talks about the ponsage and sharpening of the foils ( ponsage = light sanding)
no holes, no uneven surface, clean lines on the leading edge, if so, filler compound.
At 4.25 in the video, he's talking about sanding
. mast and fuselage;
.. form 900-1000 (wet sanding paper)from top to button, up to 4000 - 6000 (for him), with those super fine ,no need to stay with a linear sanding patern
. form his experience, the wings (main + stab) stop with 2000 sanding paper.
Basically, if you can get a shark skin surface on your foil, it's a very good start.
NB. take your precaution sanding carbon fiber , not good for the lungs.....
i'm not a pro but a curious man