The U.S. Naval Surface Warfare Center, Carderock Division, has developed and patented a rudder for ships that is capable of “twisting” in order to vary the angle of attack to match the actual water flow pattern. The result is a reduction in cavitation that provides several benefits, including less rudder erosion, decreased drag, increased turn capabilities, and reduced noise. The rudder has been thoroughly tested and is currently in service on U.S. naval destroyers.
The action of a propeller causes the angle of water flow to vary along the span and chord of a rudder. When water flows at a high speed and at a slight angle over a rudder surface, the result is cavitation that reduces performance, increases erosion of the rudder’s coatings, and produces undesirable noise. The U.S. Navy has created a rudder that can twist from top to bottom in order to more favorably match the actual flow of water from a propeller and thus reduce or greatly delay the onset of cavitation.
- Higher speeds before experiencing cavitation: Cavitation experienced by naval vessels at 23 knots with the previous rudder design was delayed until 30+ knots with the twisted rudder design
- Lower maintenance requirements: Less cavitation greatly reduces the amount of rudder erosion
- Efficient: Drag is reduced, resulting in greater fuel efficiency and improved turning performance
- Proven technology: The twisted rudder technology is in service on active duty US Navy destroyers
- The technology has applications for high speed and/or high power twin-screw marine vessels as well as single-screw commercial ships at low, moderate, and high speeds
- US patent 7,316,194