Understanding Windvane Capabilities and Limitations

[El Pinguino]

I'm not sure where the ideas that wind vanes can't handle down wind sailing or that they start to lose utility on larger boats come from.

'Off the shelf' vanes tend to be a bit of a compromise of the 'one size fits all' type. Mine was custom made to suit the boat... the builder/designer made his first one to suit a small proa, at the time he made mine (#20) he had a larger one fitted to his 50' steel boat.

It steers exceedingly well in light airs.... to well... as do most... the problem is that the slightest change in true wind speed, say from 5k to 2k, has a dramatic effect on the apparent wind. As your yacht carries her way and maintains the same speed the apparent wind draws well ahead and the bow falls off downwind... its the nature of the beast.

[El Pinguino]

Originally Posted by SaltyMonkey

Well, there's also the sidewinding thing if you don't set the boat and vane right

Well that's a bit of a given.

In my experience de-powering the main ( or getting rid of it completely when going downhill) is the secret.

[atoll]

Originally Posted by cwyckham

It wouldn't necessarily be centered going upwind, I don't think? You'd have a bit of weather helm, and then lock the wheel or tiller when the vane is standing upright. Then it would supply a little bit of weather helm all the time? It's been a while since I've done this.

this really would not apply going upwind,only downwind.

upwind the vane is only counteracting in one direction,
down wind it is counteracting in both,so finding the "null" point is very important.

the null point is where the sails,rudder,and servo are more or less in balance,and it is not fighting an inbalance of sail trim andor rudder trim.

[Andrew Troup]

As far as light air downwind, firstly as cwyckham wrote, a cheap, low-amps tillerpilot can be used as the input signal for a servo or trim tab on a big boat.

Failing that, a sheet-to-tiller (or wheel drum), if well thought out with a good understanding of the changing force vectors in a given situation, can be used to ASSIST self steering when going downwind in winds too light for the vane gear alone.

A much bigger vane for light airs, which can be a lightweight frame with a fabric cover, will also help, provided it is well counter-balanced.

[roverhi]

Pendulum Servo Vanes don't work as well with wheel steering. The wheel to vane drum limits the amount of throw of the rudder. Not that it doesn't work, just not as well as if the boat had a tiller. There is another thread on Windvanes on this site. One of the responders had two Columbia 50s that he sailed with Pendulum Servo Vanes without issue including a downwind run to Hawaii.

Sailed my boat to Hawaii with a WindPilot Pacific Plus steering the whole way. It was a relatively light wind sail with relative wind around 8k or less. Seas were running 5 foot swells but confused which tended to slew the stern around depending which wave from what direction was working on the stern. The vane steered without a problem, just made course corrections once a day or so to stay on the GPS's magenta line. I did make up an 8" x 4' lightweight wind vane to better sense the following wind.

The Aires on our W32 would steer the boat if it would make any headway under sail.

[cwyckham]

Here's a great video showing a cape horn servo pendulum vane being used in a southern ocean storm and downwind under spinnaker in light airs.

There's also a shot right at the end in light winds in the Atlantic that shows a stern with lots of panels and other junk and the cape horn doing just fine.

http://www.capehorn.com/PerformanceAng.htm

[cwyckham]

I'm a pretty big fan of the cape horn. Very slick installation, all below deck, customizable, and compact.

Here's a photo of a custom installation of a Cape Horn from their website. It includes all the crap you can imagine on the back of a modern cruising boat, but the wind vane is in clean air and out of the way of the davits. Very cool.

And yes, they have an emergency rudder option as well for those who fear the servo pendulum.

[SaltyMonkey]

Im toying with the idea of a Cape Horn for my next boat. I'm a bit concerned about installation complexity.

[Andrew Troup]

And in the spirit of brainstorming, here's an idea for someone bored by light conditions on a long passage, with nothing better to do:

Cheap pushpit-mounted vane input devices are (or were) available for tillerpilots, but as well as being sadly affected by wind striking surrounding boat stuff, they tended to swing around too much in light winds.
This latter was especially problematic if the boat was rolling, affecting the apparent wind direction... and this spurious side-to-side oscillation is worse still for the masthead vanes generally used for "proper" autopilots, because distance from the roll axis confers amplification.

I'm thinking of running in winds which are light and from broadly the same direction -- but (as usual with light winds) from time to time clocking around far enough to cause unwanted gybes of either main or goosewinged headsail, if steering a compass course.

At low boatspeeds, when a sail gybes: unless immediate, no amount of rudder correction will provide sufficient impetus to recover to the correct gybe. Generally steerage way is lost for good, and a sail manoeuvre will be necessary.

Another problem is that winds at the surface are disturbed by friction with the swell train. Of course it only goes downhill once the wind encounters the boat, where sources of further disturbance to direction and strength are both more influential, and more prevalent. So vane steering, whether traditional or electronic, is not the answer to this challenge.

What is needed is a stable reference for wind direction. So here's my wacky idea:

- - - -

Wind direction is more stable aloft, and windspeed is generally greater.


If there's enough wind to fly a kite (not a spinnaker, but a kid's plaything):

Perhaps the tillerpilot's compact windvane, intended for pushpit mounting (like the one in the pic) could be mounted in the point of the pulpit, ahead of the forestay, on a simple improvised pivot mount with a hanging weight to keep it level. The vane would act as a sensor, NOT of wind direction directly, but of the direction of the kite string, streaming forward.

A long narrow "U", bent from brazing wire, could be clipped to the little vane, the opening facing forward and upward, with the kite string passing through between the tines.

This would allow for changing altitude of the kite, and it seems to me the improvised pivot, arranged as a fore and aft gimbal (if the kite string was tethered in line with the gimbal's axis), should cancel out the effect of rolling.

However I have the feeling that, at least in the case of the original Autohelm 1000, there was a cunning system of feeding back tiller movement in the form of a rotation of the mast of the pushpit vane to prevent overcorrection.

Without something to simulate or substitute for that, it may be that my idea is clutching at straws, certainly for any boat which is not naturally directionally stable downwind.


Having spent many happy hours flying a kite from a sailing boat, I know that in light winds it is generally necessary to sail upwind to get enough apparent wind to get them launched, but a well proportioned, lightweight kite, once it's well aloft, will often stay aloft even if you then bear away to a run, provided it's done progressively.

If you're really sick of handsteering and need to get some rest and the kite won't quite stay aloft, it wouldn't necessarily be ridiculous to tow a drag device to provide enough apparent wind to keep things working, whether it be this, or a sheet-to-tiller, with or without a traditional windvane.

It's surely preferable (and more comfortable) to keep sailing, even a bit more slowly, in the right direction, than to have to heave to or lie ahull in order to sleep.

[ErBrown]

Thanks for all the responses folks. Great video cwyckham and Ocean Girl thanks for the story, cool stuff. I've been thinking it would likely be a hydrovane or Cape Horn when the time comes. I really like the ability to mount the Hydrovane off center, but will definitely have to check out the compact Cape Horn model.

The link to Evans' systems page was great and surprisingly enough (not really, obviously a great source of info) I really agree with his statement that some form of windvane, for me, is required equipment when the time comes. I'll very likely have an AP as well, but it's good to see all the comments about success with a windvane down wind. From other recent threads I was thinking I was being naive in thinking thinking problems where the exception and not the rule there.

Again great info, please keep em comin'

-Erin

[cwyckham]

Originally Posted by ErBrown

Thanks for all the responses folks. Great video cwyckham and Ocean Girl thanks for the story, cool stuff. I've been thinking it would likely be a hydrovane or Cape Horn when the time comes. I really like the ability to mount the Hydrovane off center, but will definitely have to check out the compact Cape Horn model.

The link to Evans' systems page was great and surprisingly enough (not really, obviously a great source of info) I really agree with his statement that some form of windvane, for me, is required equipment when the time comes. I'll very likely have an AP as well, but it's good to see all the comments about success with a windvane down wind. From other recent threads I was thinking I was being naive in thinking thinking problems where the exception and not the rule there.

Again great info, please keep em comin'

-Erin

Check out the Cape Horn website. Tons of good stuff there. It has been mounted off center many times.

Sorry if I'm sounding like a bit of a Cape Horn salesman. I've used one for an 8 day passage down the coast from Victoria to SF and it worked well for us. I'm strongly considering one for my own boat, eventually.

I certainly share SM's concerns about the install compared to bolting an oil derrick on the back of my boat for a Monitor (the other model I would consider). The end result is so slick, though, I think I'll have to man up and go for it. They offer an install team to come do it, but I'd already be paying $4k for the unit, I'll have pull up my big boy pants and drill a huge hole in my transom all by myself.

[SaltyMonkey]

Originally Posted by cwyckham

I'll have pull up my big boy pants and drill a huge hole in my transom all by myself.

Gad i nervously wanna see that

[Andrew Troup]

Interested to see the Cap Horn video showing Jean du Sud's circumnavigation; I flicked the link to my sister.

She had to turn back temporarily from a trip to Antarctica with a French family, because a small child on board was not responding to antibiotics .... they doubled back to the Chatham Islands, and Jean du Sud was anchored in Waitangi, en route around the world.

On the subject of Cap Horn, I very much like the 'built in' nature of the linkage between servo oar and quadrant.

I'm going one stage further in the direction of total integration of the vane gear on my project yacht. The manual steering will be by vertical tiller (ie whipstaff) in the centre cockpit, hinged (so it can lay down into a slot in the cockpit floor, completely freeing up the cockpit) to a longitudinal shaft, which passes aft from the cockpit through the aft cabin (dividing around the watchkeeping seat, permitting inside steering with the feet, say if the windvane needs a helping hand to avert a broach, or to dodge a floating object)

The shaft carries on through the lazarette emerging just above the waterline, where a clevis detail (vertical thru slot and horizontal cross-hole) enables it to carry the servo oar directly.

A "quadrant" aft of the transom on the same shaft, is just a Y, with the shaft disappearing "into the page" at the bottom of the Y.

The top extremities of the Y have connecting rods across to spherical joints at the top aft corner of each transom-hung rudder. (Port arm of Y connects to starboard rudder, and vice versa, to provide Ackermann action)

The twin rudders are not strictly transom hung: while external, they're set forward into "notches" in the stern scoop, keeping the connecting rods in the plane of the transom. This also means the servo oar can swing past them.

So the quadrant and the servo oar head fitting are effectively one and the same.

[SaltyMonkey]

OK you got me. Are you saying like pedals in an airplane?

[Ocean Girl]

Gotta know how to trim the sails properly, or you definitely need an autopilot