I know there is some discussion on this issue, but I’m still a little unsure of how to correctly foil my 9mm plywood down to the correct thickness and right amount of foil in the right places! Any help will be much appreciated!!
Bascically, I’ve cut out yhe template and now beginning to foil with a sander, but I’m not sure how much to foil off the leading and trailing edge, and ultimately how thick the thickest part of the fin should be when finished? If any one has a cross profile image that could indicate the overall foil that would be great. Otherwise, just a general indication of how much I need to foil off and to what extent. I know the angle of the leading edge is greater than the trailing edge, but that’s about it! This is my first attempt!! Also, the fins are single foiled.
Hey Neil just stick them in a vice together and foil them back to back as if they are a single fin. Keep the chord ( thickest part of the fin) about a quater way back from the leading edge and really taper off to the trailing edge to just about zero…but remember its a curve across the foil and not two facets…take a look at some professionally foiled fins as a guide. Think aircraft wings…maybe look at the profile of those too…make sure you foil the tips out too so you don’t end up too thick there also…you’ll get the feel for it pretty quickly…just keep running your hand over them…cheers rich
Back when twin fins first came out we layed up our own fin panels. We cut them out and glassed them on. All the foiling was done when sanding the board.
Just put the board in the pocket of the stand on it’s side. Secure it and do the foiling. It only took a few minutes.Plus the fin was secured to the board…no need for clamps or vices etc etc
I used a 60 grit hard back disc. (The type with a hole in the middle and a hard rubber back)
Sometimes we tend to complicated things when the easy way is right in front of you.
Tons of great reading about fin foils here. Search “Naca” it is some super scientific way of figuring out how air moves over an airplane wing and surfers have accepted it to work in water.
FYI… “chord” = base length of fin and most of your calculations regarding where to put the thickest part of your fin is in relation to this number. Also, how thick your fin should be is calculated off of chord.
To make things more complex you can single foil your twins or double foil or 80/20 split and so on…
Hey Neil. I use a 5 inch orbital sander with 60 grit or whatever I have laying around. I clamp the wood onto a flat surface and sand the leading edge at around 30 or 40 degrees so the wide point is around 25 or 30 percent of the length from the leading edge. Flip it around and sand the rear 70 percent or so up to the wide point. Do the same to the other side of the fin for double foils. Put on a thick work glove and hold the fin in my hand and sand it until it looks like a fin with the sander and both sides are as close to the same as possible. I sit on a stool and hold the fin on my knee too. Cold beer at arms length works good. 9mm is good and no need to thin. Check out the Gepharts on True Ames website for inspiration. I like having the fin in my hand for the details and control, but don’t forget the thick glove. The sander will take skin off in the blink of an eye. Believe me. Mike
