HS is not unbreakable, I do it all the time, sometimes with just the genoa up. Keep using your knot meter for hull speed...GPS is not good for anything except ground speed. Here is a definition of HS: by Jim Antrim A boat displaces its own weight in water. When the boat is moving, it must push that much water out of the way as it goes forward. Since a heavy boat has to push more water out of the way, it makes bigger waves. (As a boat moves faster it has to push aside more water in less time, so that makes the waves bigger too.) Each boat creates a bow wave and a stern wave. When a boat reaches "hull speed" the bow and stern waves coincide to make one huge wave system. A heavy boat gets trapped in its own wave system. (For a 20 foot boat, hull speed is about 6 knots. For a 30 foot boat, hull speed is about 7.3 knots.) The best example of this is a tugboat. Tugboats are very heavy, since they have huge engines for shoving ships around; and when they are not shoving a ship, they are racing as fast as they can to the next job. That's why you see them with a huge bow wave, a huge stern wave, and a deep wave trough in between. In spite of their enormous horsepower, they can't break loose from the trap of their own wave system. They dig a big hole in the water, and can't climb out of it.
