For a displacement boat, the maximum efficient speed that a particular hull can attain is called hull speed. It can be calculated by the formula:

      Hull Speed = 1.34 * sqrt(LWL)
Hull Speed is measured in knots, and
LWL is the length at the waterline of the hull in feet.

For example, a boat with a waterline length of 500 feet would have a hull speed of:
	  1.34 * sqrt(500)
	= 30 knots
To achieve this speed, a boat needs power of approximately 2-3 horsepower per ton. To exceed hull speed, a boat needs 50-100 horsepower per ton.

If the 500 foot boat above weighed 10000 tons, it would need about 30000 horsepower to travel at 30 knots. To go faster than 30 knots, the boat would need more than 500000 horsepower.

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