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This trend of increase in wave-making resistance continues up to a Froude number of ~0.45 (speed/length ratio ~1.50), and peaks at a Froude number of ~0.50 (speed/length ratio ~1.70). This very sharp rise in resistance at speed/length ratio around 1.3 to 1.5 probably seemed insurmountable in early sailing ships and so became an apparent barrier.
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 polar diagram, or polar plot, is a graph that shows a sailboat's potential speed over a range of wind speeds and relative wind angles. [1] It normally consists of the right side of a line chart with the radius representing the yacht speed and the angle representing the wind direction blowing from top to bottom. Several lines are normally ...
Forward resistance comprises the types of drag that impede a sailboat's speed through water (or an ice boat's speed over the surface) include components of parasitic drag, consisting primarily of form drag, which arises because of the shape of the hull, and skin friction, which arises from the friction of the water (for boats) or air (for ice ...
The capsize screening formula (CSF) is a controversial method of establishing the ability of boats to resist capsizing. It is defined for sailboats as: Beam / ((Displacement/64.2) 1/3), with Displacement measured in pounds, and Beam in feet. A lower figure supposedly indicates greater stability, however the calculation does not consider factors ...
A velocity prediction program (VPP) is a computer program which solves for the performance of a sailing yacht in various wind conditions by balancing hull and sail forces. VPPs are used by yacht designers, boat builders, model testers, sailors, sailmakers, also America's Cup teams, to predict the performance of a sailboat before it has been built or prior to major modifications.
An example would be a light displacement, planing hull versus a heavy displacement non-planing hull. To mitigate this, as with other rating systems, PHRF suggests that race organizers assign boats with similar design in their fleet divisions. This reduces the planing boat vs heavy displacement variable.
[1] [4] [6] The boat is normally fitted with a small outboard motor for docking and maneuvering. [1] [4] The design has a PHRF racing average handicap of 189 with the swing keel or the fin keel and 195 with the wing keel. [7] The boat has a hull speed of 6.03 kn (11.17 km/h). [2] [4]