As noted in earlier entries, hull forms of yachts are interesting to view. Winter, when yachts are hauled, makes for a great time to wander yards and take a look at the part we seldom see during the sailing season. Planning to go for a voyage as opposed to a coastal cruise, knowing what's under the water is an early part of yacht selection.
Rick and Jasna of Calypso have some good comments about the importance of protected rudders. Read about it at their blog, SailingCalypso: http://www.sailingcalypso.com/
What are the pros and cons of protected rudders? Maneuverability and speed vs security is the essence of it.
A good site for reviewing sailboat designs: http://sailboatdata.com/firstpage.asp
Pictured above is a Morgan 36 One Tonner of 1973 design. The rudder is supported at both the top and bottom of the skeg. Back in her era, most racing boats had skeg-hung rudders. The keel is an innovation, fast shape but of very questionable strength. We don't any longer see new boats built with that shape.
The Aphrodite 101 I own. A race boat designed in 1977. The skeg is gone as a structural element and the keel is much less swept back. The rudder is a balanced shape which reduces tiller loading but not shaft load. The rudder shaft is supported by the tube at the top and bottom, no attachment to the small "fillet." The folding prop and shaft provide a small amount of protection to the rudder by deflecting flotsam.
Mc Curdy designed 35 footer that shows a good combination of keel shape and rudder with skeg. The skeg is full length and supports the rudder top and bottom. The keel has a long root. A folding propellor, in my opinion, would greatly reduce drag and catch less annoying flotsam such as weed and drifting lines, nets, and plastic.
A very old design, an Albin 27 with a full length keel, rudder supported top and bottom. These craft are sort of cult boats among the small-voyager crowd. Good sea boats.
The rudder from our Aphrodite 101, Averisera. The Stainless Steel shaft is strong... but... there are two issues that bear watching. SS is capable of corroding in the absence of oxygen, deep the rudder. The single point of load is at the rudder shaft interface which may be weakened by corrosion. The rudder was removed for inspection and there is no weeping, no rust, and no sign of distortion of the fiberglass so back in she goes.
Another thing we like about tiller steering is that the rudder comes out easily. Wheel steered boats require a bit more effort to drop the rudder. Drop the rudder once in a while.