Are twin rudders as vulnerable as they look?

Arcady said:
Flaming - that is exactly the sort of empirical evidence I was seeking, thank you, and of itself is encouraging. The relative lack of problems in a fleet of fairly lightweight cruiser/racer bodes well for a more conservative cruising twin rudder design.

GHA - I loved this: how very true! "... John Vigor has talked about the same thing but adding some metaphors > http://johnvigor.blogspot.com/2014/0...ox-theory.html "
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I would say this - I think there is a big difference between a transAtlantic race and long-term cruising. For the first I would not hesitate to choose a twin- spade-rudder boat. For the second I would be more conservative.

That's me, personally.
 
bbg said:
I would say this - I think there is a big difference between a transAtlantic race and long-term cruising. For the first I would not hesitate to choose a twin- spade-rudder boat. For the second I would be more conservative.

That's me, personally.
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Actually twin transom mounted rudders, which can kick up for obstructions, could be the ideal blue water cruising design. Best stability upwind and downwind, impact resistant and easily accessible to check and maintain.
Very well proven in the toughest of southern Atlantic conditions
 
It is Ok suggesting that if a rudder was damaged a helmsman could use the other rudder, but if the damaged rudder was fixed in an angled position then I cannot imagine the working one having much effect.
The damaged one could be bent at 20-30 degrees to the vertical & 25 degrees to the horizontal with the top edge pinned to the hull. It would be a massive drag & cause too much side force for the other to steer against.
It would mean that the crew would have to drop it out of the boat. But, if it went so far &, say, the last 6 inches of shaft stuck. The leverage against the hull could be devastating; if a wave forced the rudder sideways, like a long arm lever. Most foam filled spade rudders float, so it might not want to just drop free, but want to float up as the crew pushed the shaft downwards.

If it part split,( very possible in an impact) it could open up like a drogue, causing a one sided brake.

It is a bit like the " carry a spare rudder" argument. A damaged rudder could render any attempt to steer with a reserve rudder useless, if the damaged blade cannot be ejected.
 
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Daydream believer said:
It is Ok suggesting that if a rudder was damaged a helmsman could use the other rudder, but if the damaged rudder was fixed in an angled position then I cannot imagine the working one having much effect.
The damaged one could be bent at 20-30 degrees to the vertical & 25 degrees to the horizontal with the top edge pinned to the hull. It would be a massive drag & cause too much side force for the other to steer against.
It would mean that the crew would have to drop it out of the boat. But, if it went so far &, say, the last 6 inches of shaft stuck. The leverage against the hull could be devastating; if a wave forced the rudder sideways, like a long arm lever. Most foam filled spade rudders float, so it might not want to just drop free, but want to float up as the crew pushed the shaft downwards.

If it part split,( very possible in an impact) it could open up like a drogue, causing a one sided brake.

It is a bit like the " carry a spare rudder" argument. A damaged rudder could render any attempt to steer with a reserve rudder useless, if the damaged blade cannot be ejected.
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Surely the same argument applies to a single rudder.and any attempt to steer with a jury rigged rudder would fail.
I've never heard of a lost rudder on a twin rudder boat although I'm sure that it has happened somewhere in the world. I've heard of and seen several lost or damaged rudders on single rudder boats who have been unable to rig an effective jury rudder even though the old rudder had been completely lost.
I've sailed a twin for more than 10 years and never had a problem with damage or picking up lines, nets etc. I accept that my sailing is coastal Atlantic Portugal and Spain and not long distance cruising but there are more lobster pots where I sail than out there in the ocean I'm sure. And yes I do sail at night.
Now I'm not saying that a twin rudder set up is better than single because it clearly is more at risk than a single from collision but they do bring other advantages and for me, those advantages outweigh the slightly increased risk of damage from collision.
 
Ladybirdgaffcutter said:
GHA I really like your phrase 'a constant source of background anxiety' and will try and mention it as a particular standalone thing to bring up,eg: to make a happy crew, try and get them to state any background anxiety and then demonstrate in plain sight that they don't need it on this boat, on this trip.
Obviously that won't work if it happens to be about being abducted by alien killer whales or whatever.. but recognising worries as just worries, must be likely to make for a less anxious atmosphere. Good one.

edited to add a photo of the only possible type of rudder which would NOT be a source of constant background anxiety to me:
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Never thought of it before that but that picture made realise a trick all the bluewater cruisers are missing. You could just fit another rudder, engine and prop at the bow and have total redundancy for your steering and propulsion systems - in fact put a schooner rig on her with same height masts and the job's a good'un.

Gorgeous boat by the way...
 
greeny said:
Surely the same argument applies to a single rudder.and any attempt to steer with a jury rigged rudder would fail.
I've never heard of a lost rudder on a twin rudder boat although I'm sure that it has happened somewhere in the world. I've heard of and seen several lost or damaged rudders on single rudder boats who have been unable to rig an effective jury rudder even though the old rudder had been completely lost.
I've sailed a twin for more than 10 years and never had a problem with damage or picking up lines, nets etc. I accept that my sailing is coastal Atlantic Portugal and Spain and not long distance cruising but there are more lobster pots where I sail than out there in the ocean I'm sure. And yes I do sail at night.
Now I'm not saying that a twin rudder set up is better than single because it clearly is more at risk than a single from collision but they do bring other advantages and for me, those advantages outweigh the slightly increased risk of damage from collision.
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I am not arguing against twin rudders. If i was younger & looking for a new larger boat I would not baulk at twin rudders or twin wheels. ( In fact the ability to get further outboard would be good in my view , but another subject)
What I was responding to, was the suggestion that twin rudders meant that one always had a spare in event of rudder damage. I do not think that one can rely on that & that was my point.

I note that you have not had any damage & that is good. I lost my single rudder in zero wind due to de-lamination after quite light grounding. In the particular circumstances twins would have got me out of trouble. So one might suggest that "the exception proves the rule"

On the other hand, last year, whilst surfing down a wave at 9 kts, I hit something, very hard, that broke my Aeries ( which was canted out to one side) & damaged one side of my, single, rudder.
What might have happened if that had been twin rudders?
One never knows.
 
Daydream believer said:
I am not arguing against twin rudders. If i was younger & looking for a new larger boat I would not baulk at twin rudders or twin wheels. ( In fact the ability to get further outboard would be good in my view , but another subject)
What I was responding to, was the suggestion that twin rudders meant that one always had a spare in event of rudder damage. I do not think that one can rely on that & that was my point.
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I think on most boats you should be able to rely on it, both the twin rudder boats that I have had have had tillers and on any tiller based setup I think you should be able to disconnect the linkage between the rudders - in the worst case scenario by cutting it, you may be left only being able to steer with one of the two tillers though. I have also had a quick google and again with the wheel steer systems that are generally in use there is a mechanical linkage between the rudders that you would be able to sever if you had to so that you could continue to use the other rudder.
 
greeny said:
Surely the same argument applies to a single rudder.and any attempt to steer with a jury rigged rudder would fail.
I've never heard of a lost rudder on a twin rudder boat although I'm sure that it has happened somewhere in the world. I've heard of and seen several lost or damaged rudders on single rudder boats who have been unable to rig an effective jury rudder even though the old rudder had been completely lost.
I've sailed a twin for more than 10 years and never had a problem with damage or picking up lines, nets etc. I accept that my sailing is coastal Atlantic Portugal and Spain and not long distance cruising but there are more lobster pots where I sail than out there in the ocean I'm sure. And yes I do sail at night.
Now I'm not saying that a twin rudder set up is better than single because it clearly is more at risk than a single from collision but they do bring other advantages and for me, those advantages outweigh the slightly increased risk of damage from collision.
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Correct me if I am wrong but lets start a list with most vulnerable at the top and less vulnerable at the bottom

Twin spade rudders
Single spade rudder
Single partial skeg hung rudder
Single full skeg hung rudder
Keel hung rudder

You have the most vulnerable rudder arrangement. Its the only arrangement not protected by a keel. To say you only have a slightly increased risk of damage doesnt ring true. I suspect if you were to sail down a river full of logs your rudder configuaration would be considerably more at risk than any other in the list.
 
geem said:
Correct me if I am wrong but lets start a list with most vulnerable at the top and less vulnerable at the bottom

Twin spade rudders
Single spade rudder
Single partial skeg hung rudder
Single full skeg hung rudder
Keel hung rudder

You have the most vulnerable rudder arrangement. Its the only arrangement not protected by a keel. To say you only have a slightly increased risk of damage doesnt ring true. I suspect if you were to sail down a river full of logs your rudder configuaration would be considerably more at risk than any other in the list.
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I don't sail in rivers "full" of logs although I do sail in rivers.
It's "horses for courses" as far as I'm concerned. For the environment I sail in, I consider the risk to be SLIGHTLY increased with twin rudder set up. That's what I said in my earlier post and I'm sticking to it.
According to my risk analysis, your list is correct as a generalization for sailing boats.
Let me ask another question now. What happens to a single keel/rudder boat if it runs aground? It falls over.
Mine doesn't.
For the type of sailing I do and the area I sail in, I have taken many things into consideration, not just rudder damage, and as with many things to do with sailing, choice is often a compromise. Twin rudders are my choice You are entitled to your choice, dependent on your risk analysis of the type of sailing you do.
 
dunedin said:
Actually twin transom mounted rudders, which can kick up for obstructions, could be the ideal blue water cruising design. Best stability upwind and downwind, impact resistant and easily accessible to check and maintain.
Very well proven in the toughest of southern Atlantic conditions
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I agree completely with that. Unfortunately I am not aware of any production cruising boats with that design.
 
greeny said:
I don't sail in rivers "full" of logs although I do sail in rivers.
It's "horses for courses" as far as I'm concerned. For the environment I sail in, I consider the risk to be SLIGHTLY increased with twin rudder set up. That's what I said in my earlier post and I'm sticking to it.
According to my risk analysis, your list is correct as a generalization for sailing boats.
Let me ask another question now. What happens to a single keel/rudder boat if it runs aground? It falls over.
Mine doesn't.
For the type of sailing I do and the area I sail in, I have taken many things into consideration, not just rudder damage, and as with many things to do with sailing, choice is often a compromise. Twin rudders are my choice You are entitled to your choice, dependent on your risk analysis of the type of sailing you do.
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Well this post was about the risk with twin rudders. We all make compromises and choices when we choose a boat.
A few years a go, in our previous boat, we hit a huge submerged log in the Rio Guadiana. The log was about 2feet diameter and 20 feet long. It lifted our boat up in the air as we went over it. Thankfully we had no damage other than the loss of some bottom paint. It could had been quite different.
If you want to add in what happens to a single rudder boat when it runs aground then for my particular boat, not a lot. We dont sail in tidal waters at the moment. Falling over isnt an issue. We have hit an unmarked wreck off Cuba, touched the bottom a couple of times in the Bahamas but never touched the rudder as its 18” higher than the bottom of the keel.
I have seen what happens to a Southerly 42 when is messed with the rocks off Criceth, Northh Wales. It lost the bottom half of one of its rudders. The local boat yard made a new rudder and also a spare at the same time!
I think when you have shallow draft then you get closer obstacles than you tend to do in deep draft boat. We have no need to try and get close to the shore. We have a large dinghy and big engine so its no issue where we anchor
 
Ladybirdgaffcutter said:
edited to add a photo of the only possible type of rudder which would NOT be a source of constant background anxiety to me:
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I had more than background anxiety when I spent twenty minutes moored by the stern by a pot rope jammed in the slot in front of a rudder just like that. I now have a stainless bridging plate across the gap at the bottom.
 
flaming said:
I've only just started sailing a twin rudder boat, but so far the impression of grip etc is just phenomenal. From a pure performance point of view I think I'd take quite some convincing to go back to a single rudder in anything but the narrowest boats now.
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Genuine question. Have you figured-out berthing/close quarters/low speed manoeuvring? My own fin & spade is quite responsive in astern at slow speed but I also helm another design fin & spade boat that has no control astern without a scary amount of way. Getting that much water flow over the rudders going forwards and backwards in a marina fairway isn't something I fancy. How is it done with twin rudder configuration?
 
See that a lot of the new Oysters and Amels have gone twin rudder.. Does that mean they can't be classed as blue water cruisers any more?

Also remember that a twin rudder will typically have less draft than a single one. Comes in handy when backing in med style where it gets shallow close the dock and also reduces the chance of colliding with something under way.
 
davidjackson said:
Genuine question. Have you figured-out berthing/close quarters/low speed manoeuvring? My own fin & spade is quite responsive in astern at slow speed but I also helm another design fin & spade boat that has no control astern without a scary amount of way. Getting that much water flow over the rudders going forwards and backwards in a marina fairway isn't something I fancy. How is it done with twin rudder configuration?
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Not yet... I started this thread for some tips though.
http://www.ybw.com/forums/showthread.php?507927-Parking-with-twin-rudders
 
davidjackson said:
Thanks for pointing me to the thread. So it’s pretty much how I feared :) Being caught by a gust blowing the bow off in a marina fairway before you have flow over the rudder isn’t a nice thought.
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But on a cruising boat over 35ft with twin rudders you would specify a bow thruster for this very reason.
 
Keep the speed on. Keep the boat moving. Think it through before you enter the blind alley of a marina fairway, work out the plan and a get out plan. Things usually go ok then. Not had a problem since I worked out that speed is your friend in astern. Prop walk is still effective though and can help you turn as on a single rudder boat. If it's really windy and awkward then do as in any boat. Moor somewhere easier and move later when the wind drops a bit.
Once you get to know the boat it's not as difficult as you may fear. I don't have a bow thruster on my 31ft'r and don't feel the need for one but have no doubt it would make things a bit easier in tight corners and windy conditions.
 
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