FAQ

1. Why is the Pareto 80/20 rule relevant to the windknfe hydrofoil.

In life, engineering and boat building the 80/20 rule is a great maxim. You can get 80% of what you need with 20% of the effort and cost. The Windknife foils are designed with this in mind. Sure you can make or buy a faster, lighter, more efficient hydrofoil than the Windknife hydrofoil, but you will probably have to put 80% more effort and cost in to get just 20% more benefit in most cases. So unless you are looking to break records or enter the America's cup then the Windknife hydrofoil may be just what you need.

2. Which has more lift, symmetric or asymmetric sections?

Some symmetric sections generate more lift than some symmetric sections and vice versa. so it is rather like asking how long is a piece of string. That said, in general, asymmetric hydrofoils are designed to produce more lift with less drag. However, if it is only the maximum lift you are looking for then the standard NACA00XX sections are pretty good. For instance, the symmetric NACA0012 section produces the same maximum lift as the equivalent and popular asymmetric NACA2412 section. Both have a maximum lift coefficient of 0.15 at 15 degrees angle of attack. The difference between the two is that the NACA2412 section has less drag for a given amount of lift.

So if your aim is only to produce lift then you can stick with a symmetrical section but if you are racing someone in a similar boat then the sailor with the asymmetric foil may be faster than you!

A great resource for looking at this is airfoiltools.com

3. What are the material properies for strength and deflection calculations?

For all parts the Modulus of Elasticity is 69GPa and Tensile Yield Strength is 145MPa

For the FF27 the second moment of area is 97,600mm^4

For the FF13 the second moment of area is 6,970mm^4