For context, on sailboats, longer hulls are said to be faster because they create a longer wave on the water. Assuming they don’t travel faster than the wave they create, why would the longer wave be faster than a shorter one ?
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Its not that the waves are faster, its that the length of the waves are a major aspect of what prevents the boat from going faster.
As a boat goes faster, the length of the wave generated by the bow will get longer. If the length of the wave is long enough, then the wave will actually be longer than the boat, meaning the boat would be perpetually trying to climb up its own bow wave/wake.
Thus, the longer the waterline of the ship (i.e. the longer the ship is), the faster it can go before this phenomena occurs. This speed is called hull speed, and is directly calculated from the length of the ship.
The alternative for avoiding boat wake problems is to get the boat on plane (i.e. the forward motion of the boat across the water is actually generating an upward force analogous to lift under an aircraft’s wing), but planing isn’t always feasible for a lot of hull designs.
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Also there are two different waves. The bow wave you see angling away from the boat is one, it’s called a transverse wave. But the wave involved in the hull speed is a longitudinal wave. It’s inline with the boat, font to back. On a speed boat you can see it looking astern. The water goes down and then up, sometimes higher than the transom.
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