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Old 06-06-2018, 13:38   #1
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Downwind Self-Steering Woes Continued

A while back I made a post about my struggles with my Navik windvane on a downwind course, wing-on-wing in moderate swell. On that passage, I decided to use my tiller pilot and figure out the self-steering issues later.

Comments on that thread seemed to suggest that the issues I faced might be related to the light relative wind and large swell.

On a recent passage, I tried again. This time the winds were stronger, and the relative wind definitely wasn't an issue (though I attached a streamer to the windvane anyway). I also engaged the windvane while still in protection of the island, so the swell was small.

I fiddled with the tension of the lines for about 15 minutes before I gave up. The weaving was unacceptably excessive and probably would have caused a dangerous jibe if the main were up. I had the main down though, because it was too much sail for the conditions, and the genny was easier to handle by itself.

Here's a video that shows the windvane in action and gives you an idea of the conditions:
https://youtu.be/fke4qBUdCGA

Any advice for windvane gurus out there?
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Old 06-06-2018, 14:01   #2
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Re: Downwind Self-Steering Woes Continued

Hmm... looks like the vane is going full-over from one stop to the other with nothing in between?
Could the solar arch be blocking wind in the middle? (One reason I hesitate to build an arch.)
Could the counterweight be unbalanced?

edit: I don't know the Navik, but on my Sailomat, I'd adjust the damping lever, to make the rudder movements smaller.
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Old 06-06-2018, 14:01   #3
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Re: Downwind Self-Steering Woes Continued

It's no answer but in those conditions I've found a tiller pilot steering the wind vane itself will steer in those conditions better than the wind.
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Old 06-06-2018, 14:35   #4
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Re: Downwind Self-Steering Woes Continued

I really can't help since I haven't really tried using my Navik downwind.

The manual says:
Quote:
Running Downwind
- Set the wind vane along the centerline of the boat, spinnaker strie aft [*].
- Lines slightly loosened
- Main sali [sail] boom lashed. Jib boomed.
- Adjust attachment of Unes [Lines] to tiller to limit the tendency to yaw.

*this is a terrible translation of the french "pénon vers l'avant" which I think means "pennant forwards".
This seems to suggest that a bit of slack in the control lines is desireable, maybe you have the control lines too tight?

Another thing I have heard of is using a piece of string or bungee cord up by the vane to limit how far it can travel from one side to the other so you don't get such dramatic swings.

As I said, I haven't tried either, but maybe something to try next time ... I'm very interested to hear what you come up with.
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Old 06-06-2018, 16:21   #5
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Re: Downwind Self-Steering Woes Continued

I don't have a Navic but I have done a fair bit of downhill sailing with my trim tab on aux rudder setup....

What I see here....

Maybe too much headsail... when the ship's head comes to port the genoa will try to drive her onto a beam reach if it can get away with it.... so the Navic over-reacts ... and then one thing leads to another and then another....

The Navic is applying almost full rudder ..... I think you need damping lines on your tiller.

On my setup the aux rudder has a short tiller arm ... damping lines to port and starboard normally set so that maximum rudder that can be applied is in the order of 4 or 5 degrees or less... ( In the pic she is at anchor so one line has been hauled right home to keep the rudder clear of the ladder..)

In your case I would fit lines from tiller to cockpit coaming clam cleats so they could be released quickly.

Think of how much rudder you would be applying in those conditions.... your Navic is behaving like a first time helmsman who has never been on a boat before..........

Hope this helps,
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Old 06-06-2018, 16:27   #6
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Re: Downwind Self-Steering Woes Continued

When a wind vane struggles is when it is overpowered (too much sail) or when the sail plan isn't balanced.

Look at your speedo and see how fast you were going then roll in 25% of the jib. Bet your still doing the same speed and the Navik handles it. Looks to be overpowered.
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Old 07-06-2018, 14:36   #7
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Re: Downwind Self-Steering Woes Continued

I have had Monitor, Pacific Plus, Aries, and Navic vanes, I find they work best when you can balance the boat to where she nearly sails herself, then engage the vane.

Watching your video the wind (from the flag on the stern, appears to come from off the port quarter, closer to a run than a broad reach.

I do not think you are overcanvased at all. Your jib is a bit oversheeted, naturaly because if you let it out more it would collapse and flog around as the boat turned in a more downwind direction. But this also makes it want to head up quick when she rolls to Stb or even heads up a little, thus deflecting the vane blade fully causing the helm to come hard over, she heads off, boat slows, goes down wind vane corrects and the oscillations continue.

Always remember speed is stability (until you surf… )

My recommendations to correct this is to get that jib out on a pole so you can adjust it to the wind (ease it out)without it collapsing or being over sheeted.

When you took her by hand, it was probably easy to sail until the boat healed to stb and then you would have to give a good amount of rudder to catch her swing to port and bring her back, then as she started to go a bit much downwind a bit of ruder, wait a moment and she would come back. The vane does not wait, it just stays over until the wind rights the vane. Also when she heels to stb and starts to round up the apparent wind speed increases blowing the vane over, more downwind the apparent wind decreases having less effect on the vane so she goes too far.

I do not recall on the Navik, can you adjust the tilt the blade a bit downwind? This decreases the sensitivity of the vane.

Anyway, balance the boat, play with the vane, and you will get her to steer. And she will steer better with a bit too much sail than with too little.

Hope this helps,

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Old 07-06-2018, 15:09   #8
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Re: Downwind Self-Steering Woes Continued

I have a home made SS windvane similar to a Monitor. On the tiller I use two cam cleats to secure the control line and on the tiller I have 3 turn points for the control lines so that I can change the ratio of response to the tiller. In your video the control line goes out to the end of the tiller. I use that position when sailing close hauled for long periods where I need little input to the tiller.
For sailing downwind I use a turning point much closer to the rudder post that gives less power but a much faster response time. Your windvane is working fine just responding slow so it appears to be wandering.
Make up a couple of temporary turning points down the tiller near the pivot point for your tiller pilot and even shorter and try that.

At the end of this video you should be able to see the SS loops the control lines run through.
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Old 07-06-2018, 15:37   #9
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Re: Downwind Self-Steering Woes Continued

I've had 5 different Self Steering systems including a Navic. Had a Hydrovane and when you have one of them they tell you that you need to become a better sailor or it won't work..... and it's true. You have to get the boat balanced first before you engage it then there won't be a problem except in very light downwind situations.
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Old 07-06-2018, 16:35   #10
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Re: Downwind Self-Steering Woes Continued

I have a Flemming which I rarely use.
I found it doesn't like the boat being over powered.
Sail balance is essential.
I rake the wind vane (angle it) which seems to adjust the sensitivity or gain if you like. Also when sailing downwind I rake the wind vane forward since the wind is coming from behind. I don't know if you can do that with yours. Also I have three different vanes a light weather long blade, medium heavier blade and a shorter heavy blade. When setting it I always consider the situation of my boat turning around the vane not the vane turning around the boat. In the video your windvane seems to flop from side to side then gives maximum correction.
Is the rolling of the boat causing that or is too much gain in the system?
I also have another electronic autopilot a Navico that can be attached in place of the windvane another alternative since it reduces battery drain by the fact that the self steering system steers the boat the navico only keeps it on course.
I suggest sailing on other points of sail such as Close hauled and reaching see how it works. Maybe think about a smaller vane? Dampening it down somehow.
To me it's a bit of a black art. I'm no expert and I've never run into anyone who offered much advice.
Remember Robin Knox Johnson had the self steering smashed off the boat in the Southern Ocean finally he learnt to trim the sails and found Suhaili sailed herself the rest of the way around the world.
Eric Hisscock didn't have one and they hove too at night. But they did sail with some arrangement of twin headsails that steered the boat by pulling on the tiller. They said it rolled a lot but they as we all do adjusted to that.
A different world today.
I also have a Raymarine tiller pilot with which I can select the masthead wind indicator to input to. The gain is adjustable and so is the rudder response so even with all that adjustment too much gain the boat snakes around too little it slowly wanders off course.
Good luck
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Old 07-06-2018, 16:52   #11
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Re: Downwind Self-Steering Woes Continued

There must be some other explanation.

I have a similar boat with monitor wind vane, and it can steer downwind in basically any conditions. I have crossed 3 oceans using mine, and sailing in lots of different conditions. I can sail on only a headsail, or only the mainsail, so obviously being balanced is not required.

1) You need to be able to change rope attachment to cancel weather helm
2) The boat will steer an S course, but what is unacceptable? For me, I don't want to luff the sails or gybe. Typically the vane steers +- 15 degrees.
3) You need a light air vane. The wooden ones are not ideal, even 15 knot wind.
4) You should limit how far the vane can rotate in light air to prevent excessive oversteering.
5) The oar itself should be light weight and efficiently shaped and large enough to make power. This is critical for light air performance.
6) The linkages should have little slop or play in them, and minimal friction. This is also critical.

In light wind it can be a challenge, but I can use mine down to 3 knots. Today with autopilots costing < $100 which can steer a lot straigher than a wind vane using minimal power, and even work below 3 knots, I would save the wind vane for windy days. I have plenty of autopilots. These allow you more sailing options, making it possible to run wing and wing closer to the wind etc.. autopilot complements windvane like windgen and solar, but yes, you can use either or.
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Old 07-06-2018, 17:25   #12
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Re: Downwind Self-Steering Woes Continued

Saying your boat will sail in 3 knots is a little misleading. I see 3-4 knots downwind but the wind is blowing 8-9 knots.
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