GMT Composites (Bristol, R.I.) recently shipped an innovative composite rudder to Vitters Shipyard (Zwartsluis, The Netherlands) for installation on the 44.7m/147-ft sloop Lady B, designed by Dubois Naval Architects and scheduled for 2009 delivery. GMT had previously worked successfully with both the designer and the builder on large-scale rudders.

The aluminum-hulled yacht’s 240-metric-tonne displacement demanded a carbon composites solution for the rudder: “The Lady B will cruise at over 20 knots, subjecting this rudder to extreme loads,” David Schwartz, president of GMT Composites, points out. “Precise engineering followed by zero-defect manufacturing ensure this rudder will perform, even when conditions are most demanding.”

Although most boats of this size have a bearing at the bottom of the rudder that connects the rudder to the keel and stabilizes it, the high strength of the rudder’s lightweight carbon/epoxy post reportedly eliminated the need for the bearing in the Lady B, allowing a cantilevered design. This translates to a shorter keel, less wetted surface and higher boat speed, says the company.

The GMT rudder is 6.1m/20 ft in height, has a chord depth of 1.4m/4.5 ft and yet, including the carbon stock, weighs only 421 kg/926 lb. By comparison, a rudder built with a steel stock to the same dimensions and equivalent strength would weigh five times as much, an unacceptable situation when aft weight reduction is so important for enhancing sailing performance, Schwartz notes.

GMT Composites is a well-known source for structural carbon composite engineering and custom manufacturing of components, including rudders, masts (with and without internal furling), booms, poles, sprits, stairs and boarding systems. The company also produces parts for robotic and other machine parts, medical devices, and aerospace and undersea applications as well as special items used in national defense.