Alto

Foil specs.
Thickness 16%
Thick point from LE = 20%
LE diameter = 6%
TE = 0.0086956%
Twist = Not much – To be tested with equipment later.
LE sideways deflection = TBA
TE sideways deflection = TBA
Recoil time = TBA
Depth / span = 94.5

Profile Specs
Area = 86.014 cm2

This is my first attempt at 3D printing a surfboard fin. The thickest part of the foil being set at 20% from the leading edge will give the fin a wide angle of attack. Although it will cause turbulent flow at relatively slow speeds. That’s OK though as I am making it for the ‘Oh so many’ grovelling 2ft days we have around here where I just can’t get going. All the sub 80kg guys can surf, but the 100kg people like myself can’t move. I really have to shape a new wider board, but I thought I’d play with the fins first because I’m lazy.

I was trying to get the tip twist right in CAD, but was not sure about the stiffness of the print. It did not turn out and the tip is too stiff. I’ll start to fix this on following prints.
The intention here is just to get planing earlier. I’ll worry about control and adding power through the turns at a later date.

The foil is proportionately the same for the entire depth (span). Thus the lift to drag ratio should stay the same all the way down apart from the tip.

Another point. Your board may turn more easily with these fins just because the forward sweep moves the centre of lift forward. It will cause some boards to not function so well. Unfortunately FCS are not adjustable fore and aft.

There is also a little nub at the leading edge of the tip you’ll need to sand off. I might fix it in in CAD soon, but for now it’s there. If you don’t sand it off it will create a lot of turbulence.


The full specs for this fin are in the text file in the download.
Download the .zip file below for all the 3D print files.