ORIGINAL: Rull
My friend, FSR racer , told me that he have tested sanding of bottom plane. He got up to 2 km/h plus on his FSR-15 with sanded bottom plane by a 240 grade sandpaper .
So polishing may get worse result.
For experiment try to move two pieces of glass with a water between them.
i'm not sure about that; because racing yachts nearly always have gloss undersides, they rarely use matt anti-fowling paint; simply because it slows them down, this FSR racer might be going faster; because he sanded the underside bow to stern, thus adding additional ( microscopic) tram lines in the sponson; aiding the flow of water.
i asked my father 3 weeks ago which was faster, he said ``gloss hull is faster``, that's why racing boats always have their undersides scrubbed clean before races and are best kept out of the water etc.