FINS

I recently got asked to answer some questions on fin design. Hope it helps.

Apart from the obvious objective of ‘speed’, what tributes make a good speed fin?

Grip, you will never achieve fast speeds unless you have confindence that your fin won't spin out. Even more important then a fast fin.

Asymmetric or symmetrical - which is best?

Depends how many directions you want to sail.

You have two ranges of speed fins within Black Project, why is this?  

Ultimate speed on one tack. Ultimate speed on both tacks in all sea conditions

Do different weights of riders need different styles of fin, or just a different sizes?

Style of sailor would depict what fin size he would use. I am 115kg and have used smaller fins that someone 95kg on the same day. Board choice / width would make a difference but again I have used bigger board smaller fin than lighter guys.

Do different styles of fin work better with different boards and rigs, or is a good fin, simply a good fin?

Most definitely board to fin, not so much sail size. A good design is a good design in a number of sizes.

We were using 22cm fins quite comfortably with 6.4m sails for speed course use, what would be the ideal fin size for 5.5m record breaking conditions?

Board size will make the difference. In Luderitz I will use the same size fin for my 5.4, 5.8 and 6.4 if using the same board. The board is still going over the same water conditions. (6" chop in Luderitz. It's not flat water like everyone thinks)

Is fin flex important?  And if so, should we be looking for soft or stiff?

Stiff stiff stiff, in fast conditions a flexible fin is seriously dangerous.

What are the fundamental differences between a speed fin and a slalom fin?

A slalom fin will always be better at getting you upwind and onto the plane quicker. Speed is for downwind

Carbon vs G10, which is best?

A good G10 fin is as good as Carbon 

The base of the speed fins are quite short compared to the length of the box, which gives you range for positioning (forward and back within the box when shaping)….how do you decide upon this or do you just mould the fin into the middle of the box and let the board designer worry about that?

The board designer will be placing the box for the centre of effort of the fin to be in the middle of the box