Comment Sandpaper Smooth Fiberglass Sailboat Hulls (Score 5, Interesting) 112
small sailboat racers knew in 1970s that using 800 grit sandpaper to rough the smooth surface of fiberglass hulls reduced drag by noticeable amounts.
The Engineers and Physicists at the yacht club explained the roughness held a layer of water which is far smoother than the fiberglass or waxed fiberglass.