speed-length ratio

While it is possible to drive a displacement hull faster than a speed-length ratio of 1.34, it is prohibitively expensive to do so.

The concept of hull speed is not used in modern naval architecture, where considerations of speed-length ratio or Froude number are considered more helpful.

When the Froude Number grows to 0.40 (speed-length ratio about 1.35), the wave-making resistance increases further due to the divergent wave train.

Most large vessels operate at speed-length ratios well below that level, at speed-length ratios of under 1.0.

The ratio of speed to is often called the "speed-length ratio", even though it's a ratio of speed to the square root of length.

This very sharp rise in resistance at around a speed-length ratio of 1.3 to 1.5 probably seemed insurmountable in early sailing ships and so became an apparent barrier.

As the vessel exceeds a speed-length ratio of 1.34, the hull speed, the wavelength is now longer than the hull, and the stern is no longer supported by the wake, causing the stern to squat, and the bow rise.

This effect increases dramatically in full-formed hulls at a Froude number of about 0.35, which corresponds to a speed-length ratio (see below for definition) of slightly less than 1.20 (this is due to a rapid increase of resistance due to the transverse wave train).

When the vessel exceeds a "speed-length ratio" (speed in knots divided by square root of length in feet) of 0.94, it starts to outrun most of its bow wave, the hull actually settles slightly in the water as it is now only supported by two wave peaks.