how far back from the leading edge of a fin should the thickest part of the foil be? i am not asking for a exact number but rather a proportion. i am sure there are differences in where it should be depending upon the fins desired preformance characteristics. if this is a factor then please give your ratios with the pro’s and cons of each. thanks for your time. K. Dexheimer
Find a fin you like , put a thick rubber band around the fin a few places, eyeball it and copy the foil. A thicker leading edge will be loser and sharper will be more directional.
Hey R.O.W.
Softer leading edge ~ facilitates smoother directional transition ~ not so grabby ~ however makes the fin want to go one direction or the other with little force, makes it touchy.
Foil thickness location: 45% to 20% off the leading
is the effective parenthetical range:
forward to 20 % ~ more drive
aft ~ less drive, less turbulence, more speed.
Good Waves, Rich
Are you looking for specific NACA numbers or just for a fin that works well?
I’m NO techno weenie.
Anything around the outline of an old single fin surfboard, foiled to a pintail with straighter trailing edge works fine.
Actually, TomBloke should post a pic of his teardrop outline board.
What Halcyon said.
perfect halycon that was the answer i was looking for.
Hi blakestah,
A few months ago I tried the fin system on your link at OB. It was an interesting ride. Kinda like having a lazy susan on the bottom of the board. The thing I noticed most was the ability of the board to change directions at any moment. The board would swivel through turns rather than carve. It worked great in the mushy sections, but it felt a little squishy in driving sections.
On the other end of the spectrum, I’ve tried some experimental setups by Futures using extreme versions their vector technology. Zero sideways slip… directional changes always include added forward thrust. By shaping the inside foils to complement the outside ones, they get the water to move at the same speed on both sides of the fins and direct the board forward. They’ve done tests using onboard gps and found they averaged 18% more speed using vector fins versus flat sided with similar templates.
These two fin systems are about as diverse as can be. Both have their place depending on what you want your board to do.
I think it would be cool to have swivel fins on a board for mushier junkier waves. The board I tried was great in mush. I could blast away at will in the slop or whitewash.
When it gets steep and hairy, I want something stiff and positive like the vectors. They turn like you’re on rails, No tail slip, all forward drive. Forget lip bashing in the mush and tails-out tricks.