[gurps] Ultra-Ships according to Vehicles

[Onno Meyer]

Take a 375-ton catamaran, powered by 30 MW of hydrojets. The 
engines give 300 tons of motive thrust. 

With no hydrodynamics, the drag is 6,879 and the speed is 
26.6 * 2 (planing) * 1.1 (streamlining) = 58.5 mph.
With mediocre lines, the drag is 1376 and the speed is 
45.5 * 2 (planing) * 1.1 (streamlining) = 100 mph.
With average lines, the drag is 688 and the speed is 
57.3 * 2 (planing) * 1.1 (streamlining) = 126 mph.
With fine lines, the drag is 457 and the speed is 
67.7 * 1.1 (streamlining) = 72.3 mph.
With very fine lines, the drag is 344 and the speed is 
72.2 * 1.1 (streamlining) = 79.4 mph.

So in order of efficiency the lines are average, mediocre,
very fine, fine and none. While it makes sense that a 
planing hull might beat a displacement hull, it seems a 
bit odd. Comments?