Shoal rudder with endplate - how to do it?

[James Brook]

I was interested to read the side bar "A Rudder with Wings" in the article on the Arey's Pond Daysailor (WB 186, page 60). The article discusses minimising the loss of lift with a short, low aspect ratio rudder by building it with swept back foil shaped wings at the end, not just a simple endplate.

I have a 23ft shoal draft displacement boat with a transom mounted rudder. Only about 10 inches of the rudder extends below the water line and that part is only about 16 inches from leading to trailing edge. I am interested to know if anyone has any experience or opinions on how such a rudder might be modified to have an endplate or wings. I could try a small and simple endplate, but I am also intrigued by the idea of the swallow shaped wings in the article.

I imagine that the forces acting on the joint between the rudder and the endplate woukd be considerable. What would be the best means of attachment? The existing rudder is shaped from solid wood.

I would appreciate any thoughts.

--
James

[Thorne]

Don't know what other's advice might be, but as far as I know that design is still new enough to be more of an art than science. I'd say order another set of pintles, pull the tiller off your existing rudder but leave it alone otherwise, and make up a test rudder from cheap ply. Fool around with various wing shapes to see what works best, then make up a final, second rudder from proper materials of your choice.

[JimConlin]

Phil Bolger has also designed a number of shallow draft end-plate rudders. They were somewhat less fancy than the Tony Dias design mentioned. Anybody got any links in that direction?