Join Date: Sep 2006
Thanked 11 Times in 11 Posts
Rep Power: 10
Yes, surface finish below waterline is vital. I once calibrated my 36 ft ship with fine weed on the hull, and it pulled 5.5 kt at 1750 rpm, in flat calm.
Next day, with the weed scraped off, at the same revs it pulled 6.6 kt !!