What are the little winglets on the propeller tips? Do they really do something or are they just a gimmick?
The winglets are there to reduce noise. On most sailboats there is not sufficient clearance between the tips of the propeller blades and the hull. Naval Architects typically want to see a clearance equal to 15-20% of the propeller diameter. As the RPM of a propeller increased, vortices are shed from the tips of the blades due to difference in pressure on the forward and aft faces of the propeller. If there is insufficient clearances, these vortices slam against the hull (it sounds like a chain rattling on the hull). The winglets divert the vortices aft, in effect increasing the blade to hull clearance and reducing or eliminating the noise. Additionally, the winglets produce a little more thrust.
