On The Level Page 2
On The Level
Part 2: Fast yachts will require smaller fins and drive mechanisms than would slower yachts of similar size.
By George L. Petrie — July 2004
With systems installed on several high-end yachts in the 150-foot-and-up range, including Gallant Lady, Princess Marla, and Aurora B, Quantum Controls arguably has the most prestigious client list in the “stabilization-at-anchor” market. It can also take credit for one of the more challenging installations, in the Sparkman & Stephens-designed and Palmer Johnson-built Anson Bell, a 156-footer, with two pairs of stabilizers that allow reduction of pitch as well as roll.
Stabilization at speed. The advent of solid-state sensors and digital controllers paved the way for stabilization systems on yachts operating at speeds of 20 to 30 knots or more. Older analog systems simply cannot respond quickly enough and pose the potential risk that control-system lags might actually cause the fins to increase roll motion.
Ironically, because fins produce more lift with higher speed, fast yachts will require smaller fins and drive mechanisms than would slower yachts of similar size. Thus, if the stabilizers on an 80-foot yacht designed for 15 knots cost $60,000, the stabilizers on the same-size yacht designed for 25 knots might cost only $40,000.
How good are today’s stabilization systems compared to the flopper-stoppers of ten or 15 years ago? According to Milo Halliberg of American Bow Thruster, for yachts in the 40- to 80-foot range, “roll-damping” systems using analog technology typically achieve about 40 percent roll reduction, whereas yachts with digital control systems can expect a 90- to 98-percent roll reduction in beam seas of three to four feet.
Ride control systems. Going beyond roll stabilization, for yachts operating at semiplaning and planing speeds, there are a variety of systems available that provide pitch control in addition to roll reduction. KoopNautic Holland (an affiliate of VT Naiad Marine) makes a system combining specially designed trim tabs and electronic controls that automatically adjusts the tabs to counter the pitch-and-roll forces that are produced by each wave.
Next page > Part 3: Mitsubishi Heavy Industries has developed a system that involves no components outside the hull. > Page 1, 2, 3, 4
This article originally appeared in the June 2004 issue of Power & Motoryacht magazine.