Schilling Rudders vs. NACA section

[Danger Mouse]

I have recently been asked by a friend about Schilling rudders and how to design one. His problem is the lack of manouevrability on an 18 foot Cheverton Champ when towing larger vessels in a marina. Cheverton have told him that they have found a Schilling rudder to greatly improve the situation on one of their own similar launches.

My question is, what difference would it really make, having the fishtails of the Schilling, over say a standard NACA profile (considering the launch tows at 1-2 knots and has a top speed of only 7-8 knots).

Any thoughts would be appreciated.

[Lee Martindale]

It may be a little late in response, but i have just seen your question.

The Schilling rudder is a high lift rudder, produducing higher lift at the optimum angles, abt 35 degrees. What the Schilling rudder will also do is operate at angles up to 70 degrees and still produce a significant amount of lift. Whereas the NACA rudder would normally stall at angles higher than 45 degrees. The fishtail effect will also direct the propeller flow to a higher angle. We have had in certain cases a vessel to run slightly astern when the rudder is at full angle, just from the forward propeller motion.

If you wish to discuss this further, i recommend you to look at the website www.becker-marine-systems.com who have full design and manufacturing rights of the original shcilling profile rudder. You will also find my contact details on this website if you wish to get in touch.

Lee Martindale