Thinking of building a self steering wind vane?

[KellysEye]

>The posts seem to be about servo-pendulum systems which don't have a rudder, but a pendulum oar or blade. On the whole the oar and vane are generally remarkably indifferent to boat size: in many cases the same system can steer anything from, say, 30 to 60 feet. What varies most (essentially because of greater freeboard at the transom) is the length of the pendulum shaft. Larger boats obviously generate higher steering forces (and need them) simply because speed through the water and thus over the pendulum oar is greater.

To me that post does say size is important even with Servo Pendulum kit.

 

[DownWest]

Yes,but, boat balance is very important. A quite small SS (Navik?) can helm a medium sized boat, if the sailplane is set up to give light helm loads for the point of sailing.
Those old QME ones used to work quite well except down wind. But very much a cheepy version of a real system.
DW

Enjoyed Dijkstra's book, still got it somewhere....

 

[fishermantwo]

Look at the The Amateur Yacht Research Society The Amateur Yacht Research Society. Publication 127 is on self steering. They also have numerous publications on self-steering in Catalyst - their journal. I couldn't find the one I was looking for on the upside-down gear. Horizontal pivot vane with the pivot at the top. It was quite convincing and simple. Claim is that power increases with angle of heel whereas with the bottom pivot it decreases. Think it was a Dutchman called Alkema or something like that who invented it.

Jan Alkema is a regular contributor on http://www.cruisenews.net/forum/viewforum.php?f=62

You can argue the pros and cons there!

 

[fishermantwo]

>The posts seem to be about servo-pendulum systems which don't have a rudder, but a pendulum oar or blade. On the whole the oar and vane are generally remarkably indifferent to boat size: in many cases the same system can steer anything from, say, 30 to 60 feet. What varies most (essentially because of greater freeboard at the transom) is the length of the pendulum shaft. Larger boats obviously generate higher steering forces (and need them) simply because speed through the water and thus over the pendulum oar is greater.

To me that post does say size is important even with Servo Pendulum kit.

Its all about ratios and these are standardised over all the production and homebuilt units these days. The same unit will fit on and operate a large range of yachts, the only difference is the mounting height above the water on the transom to maintain the correct ratio.
The power generated from a servo system on a yacht doing 4 knots is enormous and I would recommend not getting in the way of a tiller!