We have done a lot of experimentation on the D 4 with fin style and fin and bulb position and now all boats have a set position of the keel .
We have found the champaign shape fin is good and works particularly well in B rig conditions where less sideways resistance down low on the fin stops the boat tipping the boat in the gusts
We also have found that the wider top of the fin stops the boat sliding sideways when lining up for the start. Another advantage is that when the boat goes through the tack it has a bigger turning circle that can result in a gain compared to the convention fin where the bow of the boat seems to swing down after the tack. The one drawback of this fin is that if the boat goes into irons it takes a little longer to get out
We make the fin out of solid carbon with the uni of the fiber carefully placed to stop any twisting of the fin. The fin is thinner and slightly heavier than the more standard fin that we see
The weight of the bulb ever slightly twists the fin that we think helps with the boats pointing ability
We finish all our foils with epoxy resin and graphite. This surface is sanded with 1500 wet dry sandpaper and is very easy to maintain and keep clean