Twin Rudders

[Seajet]

Please show me where I asked about your past. Seriously think you are losing the plot. Why do you ignore, or worse dismiss what everybody else says, when what they say is usually based on experience or sound argument?

Talking about your "past" - as you seem obsessed with it, IIRC your boat experience is Osprey, Centaur, Carter 30 , Anderson 22. All very valid, but worlds away from the kind of boats you try express opinions on.

Tranona,

my boat experience covers a lot more than you describe, both owning and regularly crewing; but I don't think my sailing CV is what people want to see !

If you want it please PM but I'm sure you have better things to do like checking your keel is still there !

I'm genuinely sorry if people are upset, I can only express my opinions & thoughts towards a discussion, I never said " anyone with a twin rudder boat, get off and burn it then buy an Anderson " !!!

BTW for the poster who commented about A22's having swing blade dinghy style rudders, this design has a pintle the full depth of the transom, with a solid 1 piece iroko rudder going up and down it.

Some people will be pleased to hear this system isn't perfect, if the boat settles on something hard at the stern the pintle can be slightly bent, the first clue is the rudder being stiff to lower or raise.

It's having experienced this sort of thing that makes me very dubious still about twin rudders, coupled with seeing the problems splayed twin keels get.

The A22 set-up also means the rudder won't kick up if it hits flotsam etc ( though it's protected behind the keel, another point in favour of single rudders compared to twins ) but overall I'd much rather have a solid strong rudder than a dinghy / Seal 22 style pivoted blade which can have a lot of slack, and sticks out behind the boat on the mooring so is either vulnerable or threatening to boats close by.

I would emphasize that I only wanted a discussion, I haven't said to anyone 'you must do it my way', apologies if I have been a bit forthright !

 

[Tranona]

Tranona,

my boat experience covers a lot more than you describe, both owning and regularly crewing; but I don't think my sailing CV is what people want to see !

If you want it please PM but I'm sure you have better things to do like checking your keel is still there !

I'm genuinely sorry if people are upset, I can only express my opinions & thoughts towards a discussion, I never said " anyone with a twin rudder boat, get off and burn it then buy an Anderson " !!!

BTW for the poster who commented about A22's having swing blade dinghy style rudders, this design has a pintle the full depth of the transom, with a solid 1 piece iroko rudder going up and down it.

Some people will be pleased to hear this system isn't perfect, if the boat settles on something hard at the stern the pintle can be slightly bent, the first clue is the rudder being stiff to lower or raise.

It's having experienced this sort of thing that makes me very dubious still about twin rudders, coupled with seeing the problems splayed twin keels get.

The A22 set-up also means the rudder won't kick up if it hits flotsam etc ( though it's protected behind the keel, another point in favour of single rudders compared to twins ) but overall I'd much rather have a solid strong rudder than a dinghy / Seal 22 style pivoted blade which can have a lot of slack, and sticks out behind the boat on the mooring so is either vulnerable or threatening to boats close by.

I would emphasize that I only wanted a discussion, I haven't said to anyone 'you must do it my way', apologies if I have been a bit forthright !

Rambling once again! Think you are missing the message. Not particularly interested in your assessment of your experience - you have told it enough times in the past as some sort of justification for your opinions. If you want to engage in debate, listen to what other people say. Don't think anybody is "upset" by what you say, just have difficulty in taking it seriously as it is often at odds with other peoples' real experience.

Constantly saying this or that does not work or is no good in the face of clear evidence to the contrary is not the basis for a discussion. Just look at this thread. Several people with REAL experience say that twin rudder boats track well, don't break and dry out without problems (complete with photos) - and yet you still insist they don't! Just the same as the furling mainsail "discussion" Loads of people saying how well they work, would not change etc - all based on REAL experience - but still you insist (based on what?) that they are the invention of the devil!

So, hope you see why folks sometimes have little time for your opinions and your unwillingness to accept that others might have valid reasons for making different choices.

 

[TSB240]

Tranona,


The A22 set-up also means the rudder won't kick up if it hits flotsam etc ( though it's protected behind the keel, another point in favour of single rudders compared to twins )

Andy it would be great if you would have a discussion rather than just keep spouting your opinions without accepting facts from other posters.

Please show me a modern lifting keel design with twin rudders that has rudders set deeper than its retracted lift keel. You have already had more than one poster mention this and ignored this fact again in your mumblings about the A22...

I only know of one main stream manufacturer who offers a mono wing stub keel designed and marketed to be grounded on its keel and supported by its twin rudders.

Do you reckon MARC LOMBARD or Jeanneau would get it so wrong.....

http://www.sea-ventures.co.uk/sitefiles/file/Marketing Books 2012/GB-BK-SO30i-270612.pdf

 

[Seajet]

Tranona,

that was hardly a discussion from you was it ?!

I don't ramble or repeat, that's your opinion as we have argued about things before; I'd thought we came to a gentlemans' agreement but obviously not.

As for peoples' experience with twin rudders, I'd like to hear from someone who has owned such a boat for say the best part of 10 years on a drying mooring, re stress on the blades and wear on the posts / pintles keeping the blades tracking relative to each other and the boat...

 

[Sailfree]

, re stress on the blades and wear on the posts / pintles ...

FWIW I have replaced the rudder shaft bearings on my spade rudder twice in 7yrs!!

It was how you manage to steer them in berthing situations that I was interested in.

I can't remember which boat but either a Southerly or a French Allures (both twin rudders)had a side thruster at both bows and stern!

 

[Boomshanka]

FWIW I have replaced the rudder shaft bearings on my spade rudder twice in 7yrs!!

It was how you manage to steer them in berthing situations that I was interested in.

I can't remember which boat but either a Southerly or a French Allures (both twin rudders)had a side thruster at both bows and stern!

... or Beneteau's 'Dock n Go'... parking by joystick...

 

[Tranona]

Tranona,

that was hardly a discussion from you was it ?!

I don't ramble or repeat, that's your opinion as we have argued about things before; I'd thought we came to a gentlemans' agreement but obviously not.

As for peoples' experience with twin rudders, I'd like to hear from someone who has owned such a boat for say the best part of 10 years on a drying mooring, re stress on the blades and wear on the posts / pintles keeping the blades tracking relative to each other and the boat...

Lets get this straight. I did not "discuss" anything with you - pointless exercise, which is why I did not continue with the furling sails thread where you you just went on saying the same (incorrect) things despite various people suggesting exactly the opposite of what you were saying. As to rambling - just look at what you wrote above - how does that contribute anything - to anything other than add more about Anderson 22s?, when the topic is twin rudder boats.

As to twin rudders and drying out. Doubt that many buy them to keep on drying moorings. There are other perfectly valid reasons for buying such a boat apart than having a drying mooring. As to 10 years - they have not been around that long, but so far, nobody (except you) and least of all the people who design, build, sell and own such boats see it as an issue. The main issue raised by all those who know about these boats is the difficulty of control at low speeds under power, and in boats where there is a potential problem because of their size a bow thruster is often fitted.

 

[Sailfree]

... or Beneteau's 'Dock n Go'... parking by joystick...

QUOTE]

Did you enquire as to extra cost of the Yanmar rotating pod? It was expensive!

 

[Boomshanka]

... or Beneteau's 'Dock n Go'... parking by joystick...

QUOTE]

Did you enquire as to extra cost of the Yanmar rotating pod? It was expensive!

I'm sure it is expensive, and lots to go wrong too!

Whilst on the twin rudder story (in amongst the arguing), here's a small twin rudder/bulb lifting keel that takes the ground by design, made from plywood no less... no stories that I know of to indicate any problems with it... the Souriceau

 

[TSB240]

I'm sure it is expensive, and lots to go wrong too!

Whilst on the twin rudder story (in amongst the arguing), here's a small twin rudder/bulb lifting keel that takes the ground by design, made from plywood no less... no stories that I know of to indicate any problems with it... the Souriceau

Thanks for posting that link. French are brilliant at minimalistic designs. With those hull lines it could almost have evolved from an international 14!!!!

 

[boguing]

Seajet. Just stop. Now. Before you make more of a fool of yourself.

You pitch into a conversation, knowledge of which you have none, and use words that you have heard whilst taking pictures of things designed by Engineers. Snag is that you are not using them correctly.

Can you tell me why a (your term only) 'splaying load' on an angle of one degree can be safely ignored?

The fact that you couldn't be arsed to ask Google how to solve the trivial question that I asked, I will assume that you are not an Engineer.

And I wish you well with your boat, fair winds.

My hunch is that some of us might one day regard just two foils as hilarious, and using hundreds, thousands or millions of tiny devices to modify flow, resulting in raised speed and directional control that we have not dreamed of.

Oh and. Since you say that you know what a Harrier looks like, what is the devastatingly simple device that it features?

 

[Seajet]

Seajet. Just stop. Now. Before you make more of a fool of yourself.

You pitch into a conversation, knowledge of which you have none, and use words that you have heard whilst taking pictures of things designed by Engineers. Snag is that you are not using them correctly.

Can you tell me why a (your term only) 'splaying load' on an angle of one degree can be safely ignored?

The fact that you couldn't be arsed to ask Google how to solve the trivial question that I asked, I will assume that you are not an Engineer.

And I wish you well with your boat, fair winds.

My hunch is that some of us might one day regard just two foils as hilarious, and using hundreds, thousands or millions of tiny devices to modify flow, resulting in raised speed and directional control that we have not dreamed of.

Oh and. Since you say that you know what a Harrier looks like, what is the devastatingly simple device that it features?

Well,

not twin rudders / tailfins that's for sure, though there are a few reasons such things work on aircraft but not on cruising yachts !

Are you suggesting vectored thrust for sailing boats ?!

'Oh and' I'm a qualified engineer and sailor.

Let's end this stupid debate now.

 

[wotayottie]

I like the Southerly but have heard various storeys over ineffective rudders until boat gets to a speed (no prop wash over rudder). Bad in marinas

Now I appreciate that Ex and current owners of twin rudder boats will be biased but are there any sailors out there who have switched between single and twin rudder set ups that would like to comment on marina manouvrebility

Yes I switched from single to double and back again. In my case the double was a Prout cat but the same principle applies.

Rudders can only ever work with water flow over them so they wont work if the boat is stationary and the prop does not direct water onto them. To put it another way, the prop pushes water backwards to get the boat to go forwards and in so doing puts water over the rudder far faster than would be the case from boat speed alone. Take away this prop wash and you have a slower flow of water and less steering effect from the rudders.

You learn to live with it. Southerly recommend a bow thruster because of this effect.

Before they went to twin rudders Southerly had a shallow single rudder amidships. Problem was that as the boat heeled the rudder became less and less effective. So essentially the choice is between a single shoal draft rudder that doesnt work well at sea or double rudders that dont work as well in harbour. You can get round the latter.

 

[wotayottie]

As for peoples' experience with twin rudders, I'd like to hear from someone who has owned such a boat for say the best part of 10 years on a drying mooring, re stress on the blades and wear on the posts / pintles keeping the blades tracking relative to each other and the boat...

Me for one. No problem. The tracking was adjustable just like car steering though I never needed to do it. And the boat took to the ground twice a day for 8 years.

Clearly in a bigger heavy boat there are problems with all the alternatives. For example the Ovni system can put a huge sideways bending load on the rudder blade as it flips up into a T shape. A lifting rudder means a complicated mechanical arrangement and a transom mount. Both these types become less effective as the boat heels whereas the twin set up becomes more effective. The overwhelming predominance of twin rudders on modern shoal draft boats might just be a fashion issue but I suspect its down to engineering and cost - easier and cheaper to engineer well.

 

[Fourbees]

Yes I switched from single to double and back again. In my case the double was a Prout cat but the same principle applies.

Rudders can only ever work with water flow over them so they wont work if the boat is stationary and the prop does not direct water onto them. To put it another way, the prop pushes water backwards to get the boat to go forwards and in so doing puts water over the rudder far faster than would be the case from boat speed alone. Take away this prop wash and you have a slower flow of water and less steering effect from the rudders.

You learn to live with it. Southerly recommend a bow thruster because of this effect.

Before they went to twin rudders Southerly had a shallow single rudder amidships. Problem was that as the boat heeled the rudder became less and less effective. So essentially the choice is between a single shoal draft rudder that doesnt work well at sea or double rudders that dont work as well in harbour. You can get round the latter.

Another solution is what Ovni do - they have a single deep rudder which can be folded hydraulically when about to take the ground. There would be a lot of resistance when steering it with the rudder folded in two, but it would only be necessary at slow speeds. The grounding is on a ballast plate, like Southerlies and Feelings, with the rudder off the ground. The advantage with the Ovni method is that you would get prop wash to help with turning; the disadvantage is added complexity of a folding rudder compared with a pair of fixed ones.

 

[boguing]

Nope. VT is more than a bit complex. I was asking you to tell be about the elegantly simple feature.

As a hint, it's inventor does not agree with the maxim "if it looks right". You'd know who he is?

ps. To other subscribers to this thread - sorry.