Originally Posted by IanClarke
Thanks for all of your responses. Mark ( Colemj) I do take your point :-) I was only joking about the number of three out there. But you are correct, if the number out there is low, it should be telling me something, and the relevance of a 30 foot cat to how a 50 foot cat will work could be limited. The size of the hydra vane rudder compared to the current
rudders on the boat is a concern, especially in heavier seas.
I think the actual number of cats who have windvanes really is three.
The points about acceleration being an issue are true, but not the real problem. The real problem is getting steady airflow to the vane on a St. Francis 50 (or most other cruising catamarans).
Even out on a hull on a beam reach, the airflow is swirling in direction and continuously changing strength. The big cabin
is the problem - even with steady winds not coming over them, they create venturies and eddies that disturb the air quite a ways behind and outboard
I suspect you would only have a reasonable chance of one working if you were on a beam to broad reach in strong winds - and only from the side you have it mounted.
And then you have the whole issue of running control lines and losing the access of one of your sterns.
You can talk to the manufacturers and they will tell you how successful their products will be on your boat. But I don't see a St. Francis 50 being steered successfully by a wind vane.
You already have a backup rudder, so I don't see why you are concerned about that. Main steering
failure shouldn't be a problem because the AP is connected directly to one rudder. For <$2,000USD you could install a drive unit on the other rudder and the AP could drive either one in the event of a rudder failure of either side. This would only cost ~$500 if you have hydraulic steering
. Or just install the mounts and move the drive unit in the rare event of a rudder failure.
For those unfamiliar with this boat, this is the challenge: