David,

I think it is to ask for a lot from a self-steering gear to control a boat which is not course stable in the first place. My limited experience with windvanes was mostly on my 23’ Malena. She had a big skeg in front of her rudder and was definitely course stable. As a result, my Belcher vane, Otto steered her straight as an arrow right downwind with mainsail and jib to either side. Another boat I sailed was a Maxi 95 with a (Wind Pilot?) windvane driving its own aux. rudder. With the main rudder locked, this worked very well even downwind in high seas.

In case a boat is directionally unstable, I would first correct this, instead of trying to build God into the windvane. On Weaverbird, with that powerful wind vane system already operating, I would simply add an auxiliary rudder on the transom. This rudder would normally be locked on the CL, or offset a bit to trim out any weather helm. It would thus act as a steering feather or skeg, making your bird want to fly straight.

As a bonus you get a spare rudder in hot standby in case the deeper main rudder gets knocked off. Many mayday calls could have been avoided if yachts were fitted with an easy to use spare rudder.

Arne

Malena with the Belcher type OGT Mk II windvane ("Otto"). No feedback remedies needed on that course-stable boat.

Just one more question before heading on to the harbour:

Is the Dueta directionally stable in the first place, or will she flick into a sharp turn if one lets the tiller go?

Arne

PS: I just found the string of photos of the vane in your album, which lifted much of my mental fog....

Good question! I tried it, and found that the vane became unstable to windward. The main reason for making the mounting in the form of a clamp-on to a round tube was that I wanted to be able to try the effect of these various angles.

Arne,

1) Right

2) Yes, it would be an idea to have a variable inclination of the vane axis, on any experimental gear. I did this on Fantail's gear, coming to the conclusion there that the usual inclination of 15° - 20° was about right for a conventional pendulum gear. In this case, 0° seems right in theory, and I'm talking about adding a few degrees only so that the inclination doesn't go negative. There doesn't seem to be a need for a wide range of variation, it seems right to try to think of an easy way to achieve 0° - 5°.

3) Right. The blade is antifouled and remains in the water. I have seen no Ill effects in previous gears. A bolt-on or clamp-on blade could be made, at the expense of more complication in the construction.

I'm being asked whether I'll be writing out a full specification and list of parts. That's difficult, as the design evolved with the intention of using all the various bits and pieces of material and fittings that I've acquired over the years, and other people will have a different pile of junk to work with. But here goes with an indication of the major items that I used:

Seasure dinghy rudder hangings: 3 rudder pintles + 3 rudder gudgeons, 25mm wide, 2-hole fastening. 1 transom pintle, 1 transom gudgeon. The gudgeons with bushes are better, but the bush holes are slightly too tight and need easing.

An Antal 10x7 low friction ring to turn the primary linkage lines outwards.

About 5 metres of 63mm x 25mm strong and stable* hardwood will be enough to make up the servo blade and servo carrier.

The mounting on the the boat will be dependent on the form of the transom and rudder.

3 discs of 9mm ply, 250mm diameter, 1 disc of 9mm ply, 100mm diameter, and 1 disc of 12mm ply, 200mm diameter, to make the vane turret and its base.

Short lengths of 80mm diameter GRP tube to make the vane drum and the mount on which the vane turret rotates.

2 tubes 750mm x 10mm diameter and 1 tube 500mm x 6mm diameter CFRP to make the vane frame.

A piece of 5mm diameter st st rod and some plastic bearing material for the vane axis.

Offcuts of 9mm ply to complete the vane drum assembly, and for the triangular "tiller" at the top of the servo blade.

Some light polyester cloth for the vane sleeve.

A lead counterbalance weight.

4mm Dyneema + 2 micro Clamcleats + 2 small parrel balls for the primary linkage lines.

6mm yacht braid for steering lines and course adjustment lines.

A strong lacing eye for the ends of the steering lines.

A short stainless steel bar to redirect the course setting lines at the front of the vane turret.

Epoxy and paint.

I've put some more photos into my album on the vane gear, with some explanatory captions.

* the phrase is not copyright, it can be employed in a more meaningful way here than in the political circus ;-)