The answer on this kind of question simply comes down to the engineering employed on the specific boat in question. While it is possible to engineer a skeg hung rudder so that the skeg is completely structurfal and capable of supporting the rudder, the typical skeg that is found on older designs rarely was engineered to be any stronger than a properly designed post hung rudder and in many cases the any structural gain that results from the skeg, is offset by the smaller rudder posts often employed with a skeg hung rudder.
Similarly a skeg hung rudder should in theory track better than a post hung rudder, but again, it comes down to execution of the specific design. At least under sail, tracking is primarily dynamic, the balance between sails and underwater foils. A boat that is designed to be properly balanced and with it sails properly trimmed, will track forever regardless of its keel or rudder type.
As you increase the rotational polar moment of by adding a skeg, the boat typically will wander through smaller course changes in relatively flat water. In a seaway, any given hull form will cause trim steering, meaning that assymetry in the shape of the hull that is in the wave will cause the boat to veer off course, and a boat with a higher rotational moment of inertia boat will tend to lock in on the altered course and take longer to return to balance. Again this is a design specific issue but this can cause increasingly large swings as the boat stores energy on each swing, in other words meaning that a skeg hung rudder will not necessarily inherently track better in all conditions.
In terms of ease of steering, and wearing out crew or grinding down batteries, it is not obvious to me that there is a clear advantage to a skeg vs post hung rudder. While it may be argued that post-hung rudders need more frequent adjustments, because a post hung rudder is more efficient and counterbalanced, these adjustments are smaller and require much less force. In my own experience skeg hung rudders are generally more tiring than a well designed counter-balanced post hung.
Then there is the warp getting caught in the rudder argument. In my life the only boats that I have ever done that on were full-keeled with attached rudder where the warp slid up the keel and into the gap. That said, getting a warp caught in a post hung rudder seems like a real possibility. One way around that is a small skeg with closer flaps. You can see and example of a shallow skeg with protective flaps on my boat in this picture taken from astern. (Sorry, I wish I knew how to insert pictures successfully)
http://www.sailnet.com/photogallery/...php?photo=1394
More and more, post hung rudders do seem to be accepted within the blue water community. Probably one of the most prolific purveyors of blue water cruisers, Island Packet, (assuming that you agree that Island Packets are offshore cruisers) typically employs post hung rudders rather than a skeg hung rudder and in their case thier post hung rudder is typically very close in depth to the depth of the keel.
To me, like so many things in yacht design, this is just another case where the right answer comes down to the specifics of the boat in question.
Jeff
Linear Mode
