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Old 13-09-2017, 14:56   #1
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one rudder catamaran

ANY ONE , WITH A CENTRAL RUDDER ONLY ON A 40 FT PLUS CATAMARAN???????????
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Old 13-09-2017, 15:18   #2
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Re: one rudder catamaran

Doubt it. Why would you do that?
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Old 13-09-2017, 15:24   #3
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Re: one rudder catamaran

Malcolm Tennant did that back in the 80ies on some of his smaller boats.
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Old 13-09-2017, 15:34   #4
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Re: one rudder catamaran

There is a 45 foot cat in mozambique (wooden built) with a pod in the middle housing a single yanmar Diesel engine and centre single rudder and dual centreboards
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Old 13-09-2017, 15:42   #5
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Re: one rudder catamaran

thanks for the info,,, modern cat???
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Old 13-09-2017, 15:45   #6
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Re: one rudder catamaran

No it's been here for 17 years now. Originally it had two outboards mounted in the rear of the hulls that could be raised up manually from the inside when not in use. I heard it was a woods design but not sure. The rudder is also adjustable up and down so you can beach the boat
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Old 14-09-2017, 06:27   #7
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Re: one rudder catamaran

Dereck Kelsall designed quite a few cats with central rudder.
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Old 14-09-2017, 07:06   #8
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Re: one rudder catamaran

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Originally Posted by smj View Post
Dereck Kelsall designed quite a few cats with central rudder.
Attachment 156051
Aye. There was one for sale in Mexico a few years back. It was quite well traveled as I recall.
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Old 14-09-2017, 07:11   #9
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Re: one rudder catamaran

The central rudder has the same disadvantage as a central outboard, it tends to catch weeds which greatly decreases boat speed. Maybe having the rudder hung of a pod which extends below the waterline will deflect the weeds?
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Old 14-09-2017, 07:45   #10
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Re: one rudder catamaran

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The central rudder has the same disadvantage as a central outboard, it tends to catch weeds which greatly decreases boat speed. Maybe having the rudder hung of a pod which extends below the waterline will deflect the weeds?
There's a few more disadvantages. Specifically, there's naught in front of it to protect it from striking objects, like hulls & mini keels, or daggerboards. So it's much more vulnerable even to things like heavy kelp, or crab pot floats. Let alone substantial floating debris like logs, etc.

Also surface piercing rudders (those not underneath of hulls) are only about half as effective, as there's no end plate effect to enhance their efficacy. Although some transom hung rudders, such as on Class 40 monohulls, & other high speed solo boats, have end plate built onto the rudders themselves, so as to somewhat mitigate this loss in efficacy. And a much shorter distance in between it's bearings/pintles & gudgeons.

And with a central rudder on a catamaran, the rudder has a much longer cantilever distance. So that the hardware connecting it to the boat is under a lot more load than that found on transom hung, or rudders underneath of hulls. Cantilever distance meaning lever arm. Since the rudder has to span a couple of feet of air, along with the portion of the blade which is in the water. Thus making it much longer than say one which is transom hung, with attendent increased loads.
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Old 14-09-2017, 10:04   #11
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Re: one rudder catamaran

What are the advantages? Just a more direct tiller to rudder linkage?
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Old 14-09-2017, 12:23   #12
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Re: one rudder catamaran

I have a 11m cat with a single central lifting rudder which, when fully lowered, is about 1.3m deep. The rudder is also prebalanced. From a sailing perspective I cannot detect any negatives when comparing it to a two rudder set up. I have now sailed 9,000+ miles and never caught anything on the rudder - had a pod of delphins though in the Bay of Biscay playing their "touch the rudder game" with their snout!
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Old 14-09-2017, 12:34   #13
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Re: one rudder catamaran

It would need to be a fairly large central rudder to be effective.

I know of one catamaran that lost a rudder in the Gulf of Mexico, and then during their circumnavigation they lost a rudder when approaching South Africa. Both times that they lost one of their rudders, they immediately knew that something was wrong because their sailboat overpowered the remaining rudder.

I personally like having two rudders, but I have no illusions that if I lose one of them, our catamaran will be less responsive and harder to control in certain wind conditions and sea state.
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Old 14-09-2017, 13:20   #14
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Re: one rudder catamaran

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Malcolm Tennant did that back in the 80ies on some of his smaller boats.
THANKS FOR THE REPLY,,,, YOUR OPINION????
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Old 14-09-2017, 13:21   #15
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Re: one rudder catamaran

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Dereck Kelsall designed quite a few cats with central rudder.
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THANKS FOR THE PHOTO,,,,
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