Transom hung wind vane problems

[daga]

I am trying to get the self steering on a 13m 50 year old aluminium Huisman monohull working. The previous owner died some while ago and I do not know who built the steering system, may even huisman? As it is I cannot get it to hold a course for more than a minute or so in flat water and a light breeze. I have no experience with wind vanes and would much appreciate any advice you can provide, especially if you have experience with similar set ups.

The set-up is a transom hung main rudder with a trim tab on the trail edge. The trim tab has a kind of tiller on top attached via cords to the wind vane. I have adjusted the system as best I can so the tab is centred when the rudder is centred and the vane is vertical. In light conditions it holds course for a short time and then drifts off. The whole system seems free enough except that the tab binds a little at one extreme. Also, there is a little bit of slack in the vane linkages.

Q1. What is the right way to set up and adjust the system?


Q2. What should my expectations be? Limitations of such a system? Wind speeds? Wind angles? Sea state? Any comments appreciated.

[double u]

answer to Q1: send pics
a. to Q2: a good self-steering gear should steer the boat on all courses from 5kn to 45kn of wind; can't say about yours (pics?)

[daga]

Here are some photos: https://photos.app.goo.gl/4JhsSiCXPdjhPY1x6

[double u]

boat at rest:
1. adjust everything so: vane vertical (counterweight seems adjustable) - rudder centered - trimtab-centered
2. check if trimtab moves when you move windvane, friction should be low
under sail:
3. big nut on pic 1 facing into the wind
(I presume you have a plywood vane, not like in the pics )
as far as I see your system has "negative feedback": as the rudder moves the relative angle between it & the trimtab gets smaller increasing the deflection of the rudder which leads to an overcorrection of the course: the boat will oscillate wildly

[double u]

I suppose the rod going down the center of the "mast" from the vane-carrier turns the black plastic sheave with the wire, right?

[double u]

if your feedback is positiv, neutral or negativ is easy to check, btw:
at rest hold the vane in the center position & turn the rudder. If the deflection of the tab is to the same side as the rudder's: feedback positiv
tab stays aligned with rudder: neutral
tab deflected to oppisite side of rudder: fb. negative

[double u]

1 prob I see is, that the whole wheel-steering mechanism has to be turned with the rudder

[Cheechako]

"As it is I cannot get it to hold a course for more than a minute or so in flat water and a light breeze."
I doubt you will get it to hold course in those conditions. In a good strong steady breeze they work decent. Light airs they just cause frustration.

[MicHughV]

Start by giving the boat a good wash....follow up by dismantling what you can of the vane, make sure everything is clean and functioning like it should. Re-assemble and follow the directions as above.

[daga]

Originally Posted by double u

if your feedback is positiv, neutral or negativ is easy to check, btw:
at rest hold the vane in the center position & turn the rudder. If the deflection of the tab is to the same side as the rudder's: feedback positiv
tab stays aligned with rudder: neutral
tab deflected to oppisite side of rudder: fb. negative

NO DEFLECTION when rudder is turned, so neutral feedback.

[daga]

Originally Posted by double u

1 prob I see is, that the whole wheel-steering mechanism has to be turned with the rudder

Um, not quite. The lower part, under the sheave, turns with the rudder. The upper part, above the sheave, is fixed. I think the geometry of the control line that goes over the sheave and out to the trim tab is cleverly designed such that the trim tab remains in the same position relative to the rudder as the rudder turns.

[Windpilot]

Originally Posted by double u

1 prob I see is, that the whole wheel-steering mechanism has to be turned with the rudder

I'm not sure they saw your point which is very correct.
When the trim tab deflects the main rudder is supposed to turn. If you've ever tried movining your rudder say when the boat out of the water from below you would know that it takes a bit of force to overcome the connection it has to the wheel. Lots of inertia to overcome if correcting course back and forth.
When you tried it out did the wheel even turn? Could the control lines be crossed giving incorrect input?
These systems have no yaw dampening like servo pendulms do, I would not expect much better than an s track anyway especially downwind and very little steerage with at slower speeds.
But some self steering is better than none, clean things up back there and keep trying it out.

[daga]

Ah yes thanks Windpilot - it is true that the wheel turns as the rudder swings, and yes I am expecting it to weave somewhat.

We had a French sailor come by here in Trinidad and give us some further advice on setting it up correctly. He emphasised the need to align itcorrectly first and suggested increasing the pressure on the spring which is just visible in the photo of the top. There's a knob to adjust the 'backpressure' on the vane ie the pressure that keeps it upright, and we figured it was probably too light.

So we will try again in the coming days.

[double u]

the vane should be kept upright by the counterweight, & only just, not by the pull of a spring.
If the amount of friction of the wheel-steering system is too high the w/v will work only with strong winds & high boatspeeds & then weave considerably

[double u]

https://forums.sailinganarchy.com/th....196512/page-4
in principle not so much different from your system, & with positive feedback & adjustable vane:tab gearing ratio.
See what you can glean from it!