one rudder or two?

What do you guy think. On a tubby, heavy cruising cat such as a Gemini, Catalac, etc that are never going to lift a hull out of the water is there any good reason to have two rudders vs one? The Gemini uses a teleflex push/pull cable steering system without Ackerman geometry built in as far as i can tell so when it is turning one rudder is going to be fighting the other.It appears to me that one larger rudder in the center may work at least as well if not better,while freeing up the transoms for other things. I have noticed cruising cats from Kelsal, Grainger and others with a single rudder that i presume work ok. I realize that spade rudders are theoretically the most efficient hydrodynamically are less efficient when it comes to beaching so im only interested in transom hung for comparison. I know that a number of cats use only one daggerboard and by all accounts this works well. I suspect it is more a case of mans desire for symmetry than anything else, obviously cats that fly a hull have different needs.

Steve.

 

easier to engineer the pintles when they are mounted on a transom as opposed to 400mm or so above the water. You've only got one rudder so it had better be strong!

 

You might want to check with Mike Waller and Ray Kendrick web sites, Both use a singe ruder and center board on their smaller catermarans

 

Im not concerned with the engineering,most of these coastal cruising cats have plenty of structure to mount to, monohulls have been running single rudders for centuries and get by. Theres a rather nice 36ft Grainger cruising cat for sale on yachtworld with a single rudder, i would really like to hear from someone who has sailed with such a configuration.

Steve.

 

You missed my point

 

Im not sure of your point then,please elaborate. I agree that it is more difficult to engineer the bottom pintle but by no means difficult. On a Gemini for example they use a single outboard up to 40hp which turns with the rudders,this is mounted on a fiberglass hinged bucket which could easily be removed and modified into a nice nacelle to get the bottom pintle much lower down, really very easy to do. The structural side of this is a non issue to me, im more interested in the operation of a single rudder on this specific type of cat, ie,narrow beam,heavy, never going to lift a hull.

Steve

 

Steve , what you want to know is how it works out with a single rudder in terms of handling?

 

Correct, impressions from anyone who may have sailed such a settup. My gut feeling is that one slightly larger (but smaller than two) center mounted rudder would work at least as well as two rudders without (ackerman geometry)where one is fighting the other any time other than straight ahead, it would be lighter and less drag.I cant help but feel that cats have two rudders because thats what is expected of them. When i sail my beachcat with one rudder retracted it makes no difference unless of course you lift a hull.

Steve.