I posted this on “that other forum site” and didn’t get much in the way of responses, so I am trying here:
Fairly soon I will be building a US1M whose design decisions are all slanted to a low wind venue (scientific drifting to 3 mph and puffy).
The hull will have a low prismatic coefficient and minimum wetted surface, but I am uncertain if any changes should be made to the standard 6% max chord depth for the fin and about 8%-9% for the rudder, with the rudder area being about 27% - 30% of the area of the fin. These “norms” seem fine for a boat that sees 5 - 8 mph wind and the resulting boat speeds, but this boat is going to be going much slower.
My thinking is that the boat will make more leeway at the lower speeds and the fin will need to be thicker to prevent separation at the larger angle. At lower speeds reducing form drag is less important than reducing the surface drag what input I got was that I should use the same 6% depth of chord, but use a shorter chord to reduce wetted surface.
Has anyone thought this through or done any research on this?
Any help would be appreciated.