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Hull speed can be calculated by the following formula: where is the length of the waterline in feet, and is the hull speed of the vessel in knots. If the length of waterline is given in metres and desired hull speed in knots, the coefficient is 2.43 kn·m −½.
Mariners have used the log for a long time. The first known description of the device in print is in A Regiment for the Sea by William Bourne, in 1574. Bourne devised a half-minute sandglass for timing. [7] At the time, a mile was reckoned as 5,000 feet, so in 30 seconds at one mile per hour, a ship would travel about 42 feet:
In particular, any "displacement" or non-planing boat requires much greater power to accelerate beyond its hull speed, which is determined by the length of the waterline, and can be calculated using the formula: Vmax (in knots) = square root of LWL (in feet) x 1.34. The hull speed is the speed at which the wavelength of the bow wave stretches ...
A Dead Reckoning, DR, is calculated by using a previously determined position on a chart, and advancing that position based on known or estimated speed over a set amount of time. This can be calculated by using the formula Speed = Distance ÷ Time. [3] Once an advance position has been plotted, then set and drift can be factored in.
Knots tied at a distance of 47 feet 3 inches (14.4018 m) from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass (28-second sand-glass is the currently accepted timing) to time the operation. [9] The knot count would be reported and used in the sailing master's dead reckoning and navigation.
Boat prices vary depending on the model, make, size, features and condition. For instance, an 18- to 25-foot used pontoon can cost between $8,000 and $12,000 .
Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and ...
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