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The FS rudder blade is made from a laminate of naturally rot-resistant sapele wood and carbon fiber. Blades are epoxy coated and pre-drilled to fit existing rudder cheek assembly, making the upgrade from the legacy blade simple. The smaller surface area, thinner hydrofoils and use of wood plus carbon fiber result in a strong but light blade that results in noticeably improved sailing performance.
NOW AVAILABLE FOR ONLY $250 EACH, SEE PURCHASE INFORMATION BELOW.
Combining the most advanced flow prediction methods with 40 years of experience in wing design, AeroSouth has developed a new rudder that significantly reduces drag. The board's hydrofoils and planform have been custom-designed for sailing craft at typical speeds. A unique aspect is the small, thin chord where the fin pierces the water's "free surface", lowering free-surface drag and moving the center of side force away from the water surface to reduce losses. The elimination of sweep and distribution of area fore and aft of the rudder's axis of rotation reduces weather helm to a minimum.
CL/CD (ratio of lift to drag) versus angle of attack for the new AeroSouth FS rudder (red) and the legacy Sunfish rudder design (blue). The FS rudder has a 100% higher maximum CL/CD, meaning half the drag at the same side force. Low sweep and a modern, laminar hydrofoil shape result in low weather helm and better performance when maneuvering.
AeroSouth's FS rudder has been inspired by the important work of famed Dutch scientist Joop Sloof, whose hydrodynamics research played a critical role in the inverse taper / winged keel of the 1983 America's Cup winner, Australia II. (Sloop and the owner of AeroSouth, Kent Misegades, attended the same graduate school, the Von Karman Institute of Fluid Dynamics in Brussels, Belgium.)
The standard Sunfish rudder is a simple design with high sweep and a relatively flat cross-section. It creates more drag than the standard daggerboard despite having 40% less area. With the daggerboard retracted, it produces most of the underwater parasite drag. Its high sweep reduces maximum side force while increasing weather helm and drag.
Production rudders are made from a laminate of Sapele wood, a widely-available species of mahogany. Strength is maintained through the strategic use of CFRP (Carbon Fiber Reinforced Plastic) elements. Surfaces are accurately shaped using modern CNC milling equipment and then sealed with epoxy coatings for near-impervious protection from water and UV radiation. We partner with Prestige Millwork of Star, North Carolina, an outstanding company specializing in precision woodwork for a number of markets.
Smooth contours optimized for low drag combined with a smooth finished surface are the key to improved performance of the FS rudder blade. The unique, narrow chord (width) of the FS rudder blade at its upper end lowers the normal performance losses where a rudder blade penetrates the water surface.
The narrow chord leads naturally to a very thin blade at the point of the highest bending force. AeroSouth has developed a proprietary method to laminate long carbon fiber strands (rovings) into the wood to achieve remarkable strength but keep the blade light. AeroSouth can use the same design and fabrication methods for a variety of rudder blades, dagger boards and center boards.
AeroSouth founder and president Kent Misegades (160 lbs/73kg) demonstrates the remarkable strength of the FS rudder blade. Don't sail a Sunfish? Let us design a rudder blade, dagger board or center board for your sailboat using our advanced "FS" methods. Contact us here.
Figure 168 in the classic reference for sailboat design, 'Sailing Theory and Practice' by C.A.Marchaj, shows what a difference of only one degree lower drift angle makes - 106 feet when sailing close-hauled over a course of only one mile length. Drift angle is directly related to the ratio of lift to drag for the daggerboard and rudder. Marchaj further states: "Over a typical triangular regatta course 10 miles long, some half of it the windward leg, the gap between the two yachts will be over 500 feet."
Details coming - allows the sweep of blade to be adjusted during sailing to improve sculling forces as needed. Hardware for this simple, 10-minute modification will be included at no extra cost with all rudder blades purchased.
FS Rudder Blade for Sunfish, made of a laminate of Sapele wood and carbon fiber. Pre-drilled for standard rudder cheek assembly. Epoxy-coated for protection from water and UV. Color: Natural grain of Sapele wood. Price shown does not include shipping, handling and taxes. AeroSouth regrets that sales are currently limited within the United States. Contact us for volume discounts.
PROUDLY MADE IN THE USA