Sailboat racing technology has accelerated at a nearly exponential rate in the last few decades. The advancement of the winged keel-- which helped Australia capture the America's Cup-- is quaint by comparison.
Today's racing sailboats are incredible machines capable of remarkable speeds under a wide variety of conditions.
My cruising sailboat has a maximum hull speed of 6.14 knots. Here's the calculation.
HS = 1.34 X Square Root of the LWL
HS = Hull Speed while LWL = Length of the Water Line. Most boats have an overhang at the bow and the stern so the calculation of boat speed uses the length of the vessel where the surface of the water meets the hull. My boat has an LWL of 21-feet so it's maximum speed displacing water is 6.14 knots. A knot is one nautical mile per hour, (nautical miles are slightly longer than the statute miles that we use day to day and are based on geographical measurements).
My little boat, therefore, maxes out at a whopping 7.1 mph! Thankfully, were never in a hurry.
To my point of view, traveling 40 mph over the water in a light-weight boat is too scary!