windvane steering on a cat

[owly]

One doesn't often see wind vane steering on a catamaran. It's said that due to the rapid speed changes that often occur, the relative wind changes, quickly and makes it difficult to maintain a course with a wind vane system.



I'd be interested to hear members real world accounts. It seems that autopilots are not all that rugged and reliable.... at least the "affordable" ones


It also seem like a "no brainer" to use a wind vane system but install an electronic tiller pilot in place of the vane to provide the steering force and reduce loading on the unit.



H.W.

[J.Kitchens]

You could most likely install a proper below decks autopilot for the cost of a new windvane and a tiller pilot.

[owly]

I should have done a search first.... This subject has been covered extensively, however there are very few actual accounts..... virtually everybody simply repeats the common wisdom.

The one real world account I've come across is the Utube from the Wharram catamaran Luckyfish.



I'm not a fan of electrics and electronics in a boat..... the less the better. Long distance voyaging, it seems that failures of tiller pilots are common. Windvanes too fail, but they are mechanical and can generally be repaired anywhere in the world.


The hydraulic versions consume considerable power, the little all electronic servo type work themselves to death. It seems reasonable to marry the two concepts and use the water paddle or trim tabs on the rudders to supply the needed force.


It seems to me that in many if not most conditions voyaging catamarans face, a wind vane would work fine. If one has a huge amount of sail up and is sailing the bleeding edge and surfing... that's another story.




H.W.

[Muddy Boat]

Youtubers Sailing Kittiwake also have one on their Heavenly Twins.

From the little I have read about the subject, I understand they are less suited to some (probably more performance oriented) cats due to the greater shift in apparent wind.

[Benz]

It is my understanding that the first prototype windvanes were being tested on a multihull....but it may have been a trimaran.

I think that for a tiller pilot-to-trim-tab system, you need a stern-hung rudder, or at least one where the trim tab can be easily linked to the turning mechanism. Most cats these days have tiny spade rudders far underneath, so the linkage would be hard to do.

As for a sevo-pendulum with lines led to the wheel, there's a geography issue. The dinghy davits usually are between the hulls, and the usual acres of bimini or hard top would make it hard to get clean wind just there anyway. Then the servo would be hanging in water that gets pretty turbulent in a seaway, as waves get squeezed between the hulls; it might affect the servo's motion.

If you put a unit on one hull, it won't work as well when it's to leeward; if you put one on each hull, you're buying two of them. If they're servo-pendulum units, imagine running the lines to the wheel, which is often offset! There would be spaghetti. Of course you could run them directly to the quadrants, but that's complicated as well.

If they are trim-tab emergency rudder types (like the Hydrovane), you would need to link the lazy one to the unit in use, so the rudders can turn together. Then if you figured out how to do all that, your sugar scoop transoms would be completely blocked!

I think more people don't do it because popular cats aren't designed with windvanes in mind. If you built a Wharram sort, with stern-hung rudders and a tiller bar, I think it'd be worth a try to link a central vane to a trim tab on each rudder.