E27 rudder re-shape

[Mark F]

There have been some posts in the past about 1970's vintage re-designed rudders. I'm curious how they turned out. I acquired a second e27 rudder recently and plan to make some modifications to it. The most common updated designs seem to be from Foss and use "Cal 40" shape. Any e27's or e29's with new rudder shapes sailing out there?

Thanks

 

[PDX]

To clarify, those Foss "Cal 40" rudders are actually Carl Schumacher redesigns of the original Cal 40 rudder to give it an elliptical shape. The original Cal 40 rudder looks reasonably similar to the E27 stock rudder shape, to my eye. The Schumacher designs, as applied to E-32 and E-35, are vertical, rather than swept back, and deeper. One thing I noticed from the NA drawing of the E-27 is the prop is not only close to the rudder but the swept back angle of the rudder allows it to miss the prop. I wonder if there would be room for a more vertical rudder?

http://sailboatdata.com/viewrecord.asp?class_id=680

On my boat (not an E-27, and not a Foss rudder but rather a home brew copy of Schumacher) my impression is better sailing control at speed--especially at heel. Probably giving up some low speed motoring control because the new rudder has shorter cord length.

 

[Mark F]

Hi PDX,

I think there is enough room behind the prop to add to the leading edge of the rudder. The rudder slopes aft at a pretty steep angle. Do you have any photos of your re-design?

Thanks.

 

[Mark F]

Hi PDX,
This is the Schumacher design I'm thinking about. Is yours similar?

 

[PDX]

Yes. I wish I had a better picture. Don't know if you can make it out from the picture but the rudder has a large upper skeg. Makes the rudder look even deeper than it is.

 

[Mark F]

Thanks PDX. The drawing from Foss shows a change in the leading edge angle, did you change the LE angle?

BTW beautiful job on your E30-1!

 

[PDX]

Yes. I started with an internet photo of a Foss E-32-2 rudder and changed the sizing slightly to fit my boat. The problem I ran into was the overhead skeg on my boat was too narrow, front to back, to use the Schumacher design's straight leading edge. You won't have the same problem. Anyway, I tapered the leading edge in at the top slightly to fit. I compensated for the resulting curved in the leading edge by lessening the curve of the trailing edge. I had some help from an engineer. To get an idea of the differences contrast the wing of a Spitfire with that of a P-47. Both are elliptical wings. The P-47 has a straight leading edge, the Spitfire has moderate curves on both trailing and leading edges.

I'm not suggesting I know more about this than Schumacher. I was forced to make due with the hand I was dealt. If you can get a shrunken down Schumacher E-29 design to fit my guess is you will be quite happy with it. My advice, based on complaints I have heard from people who formerly owned King IOR designs, is try to fit the largest size possible.