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The Sabre Rudder (Patent Pending)

The Challenge

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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 drag at higher angles.

Advanced Design

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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 and fits existing rudder cheek hardware for quick retrofits. The board's hydrofoils and planform have been custom-designed for sailing craft at typical speeds.

New vs Old

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CL/CD (ratio of lift to drag) versus angle of attack for the new AeroSouth Sabre rudder (red) and the standard Sunfish rudder design (blue). The Sabre rudder has  has a 60% higher maximum CL/CD, meaning significantly lower drag for the same side force. Lower sweep and a modern hydrofoil shape result in better performance when maneuvering.


The Prototype

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The first prototype is now in test (December 2019). Tests will be concluded by the end of 2019.

Production Rudders

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Production rudders are made from a laminate of Sapele wood, a widely-available species of mahogany. Surfaces are accurately shaped using modern CNC milling equipment and then sealed with epoxy coatings for near-impervious protection from water and UV radiation.

Available in early 2020!

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Watch here for progress reports!

Does it Matter?

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 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."