I try to copy the NACA foil, but I’m not really precise. I keep the thickness pretty even from bottom to tip. Thickness forward is important. For the fins I did to fit a thruster, I tried to copy the center fin the best I could.
Grinder with the multi flap sanding disk about 36 to 50 grit. I made a cone with a large piece of heavy paper and sand the fin so that the debris goes into the cone and then my vac is at the bottom of the cone. I also use a belt sander setup stationary (upside down) and use a vac to catch the debris. I like that setup better.
just my 2cents… in my opinion Use the McKee spreadsheet… it takes a bit to work out for each size board but after sevaral boards the McKee setups especially on the quads is brilliant… you will notice the quads are measured from the stringer out not the rail in… by the working out the width at the 12" from tail and then referencing the chart in the spreadsheet… once i saw that and worked it out on the width of the tail etc… the boards started to really fly in quad form… again just my opinion…
i use for my 5’10… 3 1/4 from tail for center… 11 inch to back of front fins 1 1/4" from rails… quads sit from memory at 5" from tail and then work out from McKee sheet the distance between the quads you need by the width of your tail at the 12" point from the tail… i use toe in 1/4 and 1/8…
also do yourself a favour… look into the 4 way fin system www.4wfs.com… it allows fin movement after install… backwards, forwards and changing the toe in… also allows you to take discs out and change your degress/splay from 2 degrees to 4 or 6… it is such a fantastic system… if you set your fins up and your board is too tight you can loosen it up… if its too loose you can tighten it up… its under the glass and is super easy to install… it really allows you to play with all sorts of toe in options, moving fins closer together and further apart … really you can change your board to suit the conditions … really the most advanced system around im my opinion but i am being biased as i have used it for years…
couple if images [img_assist|nid=1072841|title=5'10 UFO|desc=|link=none|align=left|width=640|height=480]of said finished board … sorry but i dont have a close up of the fin system … i should have taken a photo from teh tail end!!! Will try to get one and post soon…