Twin rudders manoeuvrability

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H4B

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Just how unwieldy are mono hulls with twin rudders?

Thinking about a change to a boat with twin rudders and concerned that backing out of home berth into a tide flowing at right angles might prove to be an angst ridden manoeuvre.

Any comments gratefully received.
 
H4B said:
Just how unwieldy are mono hulls with twin rudders?

Thinking about a change to a boat with twin rudders and concerned that backing out of home berth into a tide flowing at right angles might prove to be an angst ridden manoeuvre.

Any comments gratefully received.
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I would have thought that a single rudder with a prop ahead of it would be more manoeuverable going forward because there will be some prop wash deflection. Going astern this does not apply and it's all about speed of the rudder through the water. Twin rudders might be even better if the surface area is higher than a single rudder.

I've no experience with twin rudder monohulls though!

Richard
 
I have one of the last Southerlys with a single rudder, when I was researchin the boat before I got her there seemed to be strong consensus amongst Southerly owners that twin rudders were very challenging to manoeuvre backwards at low speed, and a bow thruster was strongly recommended
 
In my experience no worse than some saildrives that are set well forward of the rudder but nothing like a fin keeler with the prop just in front of the rudder. Not like many long keelers either, which tend to do their own thing. A twin-rudder boat normally does nothing except start going backwards under the influence of wind and current until the rudder bites - basically the rudder has absolutely no effect in reverse unless you have way on. Once you stop trying to associate the control you have over direction with the noise the engine is making and start associating with the speed the water is flowing over the rudders it becomes a lot more intuitive. At the end of the day though you simply cannot control the boat in reverse until you get some flow over the rudders so you need to find an alternative method - bow thruster, warps, fenders, whatever. It's the period until you learn that that is a bit stressful for you and those around sometimes. Un-learning the habit of giving a bit throttle to bring the bows round doesn't take that long but you need to have an alternative as well.
 
I have had a twin rudder boat for around 3 years now and am still learning how to cope with reversing. I use marina's very rarely. What I have learned is that if I try to reverse out of a berth to starboard it will just go back in a straight line for a very long way (up until now too far and I have had to stop and go forward and back in) though if I reverse out to port it turns a treat although I don't know what anyone me watching thinks reversing until I have room to turn around.
My old boat had a prop in front of a single rudder and was much more manoeuvrable.
 
Having had twin rudders for several years (on a Feeling 32) I have become quite good at reversing - but it took some time to get the hang of it. They are much harder to manoeuvre in reverse than single rudder fin keelers, no question, which is why I generally moor bows in at marinas... Not only that, as has been stated, with twin rudders the prop is set between them so you don't get helpful prop wash to assist forward turns. On the other hand, twin rudders allow for reduced draft, and however far you are heeled over one of them should be functioning. You pays your money and you takes your choice...
 
twin rudders

I have a 14m Southerly with twin rudders, she also heavy at more than 14 tons in cruising mode. 14m is a big boat in many marinas and I wouldn't venture into one without a working bow thruster.

Going astern I need at least 1 knot of way to have any effect and she is very slow to respond at low speed in either direction.

I use the bow thruster to set the direction and more or less forget about the rudders until I have sufficient way on.

Once I get to 2 knots plus going ahead, she'll turn in her own length.

There is a lot of prop wash effect at low speed, starboard ahead, port astern, which makes coming along side, side port side too, very easy, but starboard side too, much more difficult.

I often use more traditional techniques, using springs to maneuver the boat in tight spaces, a bit like maneuvering a heavy long keeler.
 
Reverse manoeuvring in any boat can be an interesting proposition. There are two factors (besides wind and tide) that I take into account and they are the speed of the rudder or rudders through the water and prop walk. Prop walk on many boats has an effect when the engine is in reverse even when the vessel is moving forwards and stationary. All the boats I have had have had some form of prop walk and I have found it one of the most valuable tools available when manoeuvring astern or in tight spots and in particular executing a 10 point turn at the end of a marina run.
 
have only sailed one once - a 30 footer I think, and I swore would never do so again. Any wind at all in a marina and you are blown like a paper cup until you have good way on. Truly awful!
 
grumpy_o_g said:
In my experience no worse than some saildrives that are set well forward of the rudder but nothing like a fin keeler with the prop just in front of the rudder. Not like many long keelers either, which tend to do their own thing. A twin-rudder boat normally does nothing except start going backwards under the influence of wind and current until the rudder bites - basically the rudder has absolutely no effect in reverse unless you have way on. Once you stop trying to associate the control you have over direction with the noise the engine is making and start associating with the speed the water is flowing over the rudders it becomes a lot more intuitive. At the end of the day though you simply cannot control the boat in reverse until you get some flow over the rudders so you need to find an alternative method - bow thruster, warps, fenders, whatever. It's the period until you learn that that is a bit stressful for you and those around sometimes. Un-learning the habit of giving a bit throttle to bring the bows round doesn't take that long but you need to have an alternative as well.
Click to expand...

All very true, but I do believe it's become something of an over stated myth about saildrives and props along way from rudders...my last boat was a saildrive, and my current has the prop immediately abaft the keel about 6 feet from the prop (both small single rudder boats, 27 and 28.5 feet). I've never noticed that gap as a concern. My current boat has a two bladed self pitching Autoprop; a quick burst of revs to flick the blades out, then the drive astern is remarkable because the blades reverse. However, as you say, one should think only in terms of flow over the rudder foil for them to have any efficacy.......
 
I ask these questions because I am contemplating a move from the totally vice free Westerly Fulmar to something more flighty with twin rudders. My home berth is a drying fore and aft mud berth in a narrow channel , that requires a reverse out into the tide flowing at right angles the the berth. Let alone the prospect of sitting twin splayed rudders into the very soft mud at each ebb. Negatives seem to outweigh the positive in totally practical terms. Not really the answers I am looking for.
 
I have experience of a Bavaria 40(?) Cruiser which had twin rudders. She could not be steered in reverse very well at all and her turning circle in reverse compared to a fin and spade rudder was terrible. With no wind she could be steered but any cross wind and the bows were off downwind. She had a bow thruster and it made reversing a piece of cake. My experience is based on one week’s charter only. Perhaps more practice reversing without a bow thruster, or a different shaped hull, would make it easier and manageable.
 
BlowingOldBoots said:
I have experience of a Bavaria 40(?) Cruiser which had twin rudders. She could not be steered in reverse very well at all and her turning circle in reverse compared to a fin and spade rudder was terrible. With no wind she could be steered but any cross wind and the bows were off downwind. She had a bow thruster and it made reversing a piece of cake. My experience is based on one week’s charter only. Perhaps more practice reversing without a bow thruster, or a different shaped hull, would make it easier and manageable.
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Don't think it was a Bavaria - Perhaps someone will correct me If there are Bavaria's with twin rudders??
 
I'm failing to understand why twin rudders per se, will make any difference astern compared to a single with the prop forward of the rudders?
Keels, windage, hull shape, yes......but not twin rudders, because any rudder as had been said before, will only work with water passing over it. Propwash will not affect any rudder astern if so positioned. (Prop forward of rudder(s)....before anyone mentions Vegas!!)

And no, I don't know of a twin rudder Bavaria either?
 
Pretty terrifying - at least with conventional boats you get some steerage at low speed in forward - but with twin rudders you have to get up speed in forward to have any steerage and reverse is even worse.
One twin-rudder sailor I knew used an OB on a pad for steering rather than rely on the rudders.
I've only tried helming two!!
 
Laurie said:
.... And no, I don't know of a twin rudder Bavaria either?
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Now you do, if you read my post preceding this one. Perhaps the reason is that both rudders are quite small area, relative to a large single spade, addition to the geometry of the blades are very optimised for normal flow direction, hence the combination is just very inefficient when the water is flowing over the blades backwards. Perhaps they stall easily with reverse flow at low speeds. Just guesses really.
 
BlowingOldBoots said:
Now you do, if you read my post preceding this one. Perhaps the reason is that both rudders are quite small area, relative to a large single spade, addition to the geometry of the blades are very optimised for normal flow direction, hence the combination is just very inefficient when the water is flowing over the blades backwards. Perhaps they stall easily with reverse flow at low speeds. Just guesses really.
Click to expand...

Quite right, thank you:encouragement:
And thank you for at least postulating some reason as to why such a configuration may not work as well astern.
 
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