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The kinetic energy imparted to the hull by striking a wave is directly proportional to the square of your velocity relative to the wave. 90% touchdown speed gives you 82% of the energy. Half the speed gives you one-quarter the energy into the hull.A secondary effect is the reduced time spent at higher speeds. Less time travelling at higher speeds reduces the probability of encountering a high wave at high speed. Another way to look at this is lower touch down speeds give you the ability to touch down and decelerate in between large waves. Then you can ride out the large waves at a low speed.An interesting reversal of this is the effect of wave height on take off distance. Tests with the Walrus showed shorter take off runs as the wave height increased, up to the theoretical maximum wave height. The aircraft at some point was skipping from wave top to wave top even below rotation speed, and accelerating quicker during the brief periods the hull was out of the water. This only works if your hull doesn't break during all this, and if your flight crew can hold on to the controls during all this.Structural loads on the hull are only part of the issue. A boat hull, compared to floats, will continue to give you greater buoyant forces as the hull submerges deeper due to an encounter with a wave or unfriendly aerodynamic and inertial forces (like a botched landing). A float, at some point, is completely submerged and driving it deeper into the water no longer creates greater upward forces. If the combination of inertial forces and wave forces continue to drive the aircraft down then other stuff contacts the water, like wings or props. Then you may have real problems.
The kinetic energy imparted to the hull by striking a wave is directly proportional to the square of your velocity relative to the wave. 90% touchdown speed gives you 82% of the energy. Half the speed gives you one-quarter the energy into the hull.
A secondary effect is the reduced time spent at higher speeds. Less time travelling at higher speeds reduces the probability of encountering a high wave at high speed. Another way to look at this is lower touch down speeds give you the ability to touch down and decelerate in between large waves. Then you can ride out the large waves at a low speed.
An interesting reversal of this is the effect of wave height on take off distance. Tests with the Walrus showed shorter take off runs as the wave height increased, up to the theoretical maximum wave height. The aircraft at some point was skipping from wave top to wave top even below rotation speed, and accelerating quicker during the brief periods the hull was out of the water. This only works if your hull doesn't break during all this, and if your flight crew can hold on to the controls during all this.
Structural loads on the hull are only part of the issue. A boat hull, compared to floats, will continue to give you greater buoyant forces as the hull submerges deeper due to an encounter with a wave or unfriendly aerodynamic and inertial forces (like a botched landing). A float, at some point, is completely submerged and driving it deeper into the water no longer creates greater upward forces. If the combination of inertial forces and wave forces continue to drive the aircraft down then other stuff contacts the water, like wings or props. Then you may have real problems.
