Understanding Windvane Capabilities and Limitations

[ErBrown]

Howdy Folks,

First and foremost, this is NOT intended to dissect or second guess anyone's recent actions, but comes from comments I've read from folks who's opinion I've come to respect. That and recent events have me wanting to understand the value of having a windvane aboard a future cruising boat. For the sake of this discussion lets just assume a 40-50ft mono (nothing against Cats but we'd prefer to have the extra $ to fund our voyage for longer). I'd like this to be less of an argument about why either an AP or windvane is the only way to go and more about understanding the real world application of each.

Based on my reading both here and many cruising/circumnav oriented books I always planned to outfit our future cruiser with both a windvane and an AP. With the thinking being use the windvane when possible and the autopilot when conditions prevent it. Obviously, we need to plan enough battery and charging capacity to support weeks of AP usage as a CYA measure and I'm not at all debating the value of a good AP.

What I'm more interested in is understanding the conditions that make a windvane unusable. I've always liked the (apparent) fact that certain types of windvanes can function as an auxiliary rudder if needed. The real question I have is in a situation where your in the middle'sh of the Pacific looking at 2000 nm downwind to a small island group and 1000 nm upwind back to the mainland of the America, and lose the ability to charge the batteries (no other problems with the vessel) you're currently sailing downwind in force 5 conditions. Do these conditions alone make it impossible to use a windvane for self steering? I was always under the impression that only real limitation was downwind in super light wind but since I have no actual experience either offshore or with a windvane yet, I'm curious. Also, assuming that downwind conditions prevent the use of your windvane, is it realistic to turn slightly upwind and beat back to the mainland. Not that this would be a pleasant experience but my goal here is getting the boat to location where I can address the charging issue.

Thanks to a link provided by Salty Monkey I now have a new book on my list which I'm sure will help me understand this in more detail, but since I'm curious I thought I'd ask here as well.

Thanks,
EB

[SaltyMonkey]

There is a vast difference between a smaller boat and a larger boat and wind vane performance.

On my smaller boat w/ Monitor, had no issues at all on all points of sail. With a light vane, I could track easily going down wind or in some light wind.

My biggest gripe was wind shifts and light winds.

Contrary to what you've heard, both a GOOD AP and wind vane cost the same amount of money if you want reliability. I would want both on any boat.

[Cheechako]

You need clear air for the vane. The lighter the air the more this will be important. I'd say forget it in less than 12 knots except a reach. Steady winds are worth it on long passages, interisland stuff etc is a PITA trying to adjust constantly. Heavy water can be real dicy with the vane... boats surfs and trys to round up as it goes into the trough... accident waiting to happen. Going to weather the Dodger etc blocks the wind or cause turbulance effecting the vane. In enough wind it's OK.
All JMHO. It always felt like if conditions were perfect, steady and the same direction for hours the vane would be fine. Conditions were seldom perfect.

[model 10]

We have an Aires wind vane that used, cost way less than a good electric autopilot. Unfortunately we ended up with a Raymarine wheel pilot (+ spare.)
Perhaps it's me but I need both windvane and the electric autopilot. There are just to many times that you don't want to go where the windvane will will sail the boat well. When all is right, the windvane works beautifully but if not, the electric does OK. I don't use the Aires when motoring so there is that also.

[SaltyMonkey]

For me the cutoff in windspeed was around 6 - 7 knots. But it had to be steady, not variable direction. High winds AOK, with warps

[Paul L]

How well a windvane will work is very dependent on the boat and dependent on the skill of the operator. I had a vane on a slower 35 ft boat and it worked very well close hauled and reaching, and actually did pretty well deep reaching/running. I also had one on a very fast 37 footer and it would not last more than 2 hours without human intervention when anywhere off the wind. You've stated boats in the 40 to 50 foot range. This size is where windvanes start to fail to function well on many boats.
If you look at modern cruising boats, they tend of have a lot of crap-on-de-back. Large biminis, big dodgers, arches, solar..... all things that mess the wind up for a windvane.

[model 10]

If you look at modern cruising boats, they tend of have a lot of crap-on-de-back. Large biminis, big dodgers, arches, solar..... all things that mess the wind up for a windvane.[/QUOTE]

We were having some trouble with the windvane one day and found the Life Sling was messing up the airflow over the vane. Usually you don't need clear air very far fwd for the vane to do OK.

[highseas]

Windvanes work much better on fullkeel boats.To me it makes no sense mounting a windvane that still relies on main rudder to steer boat.If your going to hang a big clunky thing off the stern it had better work independently from main.A slightly bent/jammed rudder shaft would be a disaster otherwise,and emergency tiller is useless.

[model 10]

Originally Posted by highseas

Windvanes work much better on fullkeel boats.To me it makes no sense mounting a windvane that still relies on main rudder to steer boat.If your going to hang a big clunky thing off the stern it had better work independently from main.A slightly bent/jammed rudder shaft would be a disaster otherwise,and emergency tiller is useless.

That sure cuts down your choices. I don't think most windvane users would agree with you. Maybe if you sailed a Hunter or Catalina..

[highseas]

Agree with what?

[SV Windrush II]

My issue with a Wind Vane is I have a 24 ton full keel schooner, and my aft deck freeboard is about 6 feet high. Not sure if it would do me any good.

I have a AP installed to work with my hydraulic steering which works good but just concerned about battery life. I have three Grp 31 AGM batteries onboard. I plan on 400 watts of solar panels and one 600 watt wind machine. I do not really want to depend on my diesel to keep the batteries charged if all possible, although I have 200 gal on board.

Any Advice?

[cwyckham]

Originally Posted by highseas

Windvanes work much better on fullkeel boats.To me it makes no sense mounting a windvane that still relies on main rudder to steer boat.If your going to hang a big clunky thing off the stern it had better work independently from main.A slightly bent/jammed rudder shaft would be a disaster otherwise,and emergency tiller is useless.

Servo-pendulum is much stronger and more effective from what I understand. They're the only kind I've used. I've used them on a Valiant 40 and a Westsail 32. I loved them on both.

[cwyckham]

Originally Posted by Cheechako

You need clear air for the vane. The lighter the air the more this will be important. I'd say forget it in less than 12 knots except a reach. Steady winds are worth it on long passages, interisland stuff etc is a PITA trying to adjust constantly. Heavy water can be real dicy with the vane... boats surfs and trys to round up as it goes into the trough... accident waiting to happen. Going to weather the Dodger etc blocks the wind or cause turbulance effecting the vane. In enough wind it's OK.
All JMHO. It always felt like if conditions were perfect, steady and the same direction for hours the vane would be fine. Conditions were seldom perfect.

I can't tell from your post if this is theoretical or if you've used one in these conditions.

I also don't feel that your typical monohull has any issue with heavy weather use of a windvane. They don't surf too quickly, and if the wind is blowing 35 knots and get a surf up to about 9 or 10 knots, it isn't going to bring the apparent wind too far forward.

Also, remember that a servo-pendulum will tend to act against any gybe, quite independent of wind angle. The stern slewing around pushes the paddle hard over and spins the wheel in the opposite direction.

[highseas]

Originally Posted by cwyckham

Servo-pendulum is much stronger and more effective from what I understand. They're the only kind I've used. I've used them on a Valiant 40 and a Westsail 32. I loved them on both.

But what good is servo when you lose your steering/rudder?Trimtab systems have plenty of power if built right.Not so nice for backing,but boats are usually going forward.

[model 10]

Originally Posted by highseas

Agree with what?

Just about anything you said. You need a full keel? What difference does the keel make? I can think of but 1 vane gear that does not need a your rudder so you have few choices there. But, if you loose your rudder like some boats seem to do, (Hunter, Catalina ) having an independent system would be pretty nice.