Downwind Running On A Windvane - How Do You Get It To Work?

[charliehows]

seems downwind sailing is the problem area with windvanes - i'd really appreciate to hear what people have found to work - ie sail combinations, wheel or tiller steering, servo pendulum or trim tab. I'm still trying to find a good setup for running on any point of sail from aft qtr to dead downwind - dont have much problem getting reliable steering upwind from anything from reach to close hauled but off the wind...

[oldcal46skipper]

Hi Charlie,

A lot depends on the boat underwater shape and sail trim/balance. I have a Saye's Rig wind vane on my Cal 46 and it steers a near perfect course on any point of sail. We have made several downwind passages that were so perfect I still dream about them.
In June 1990 we broad reached or ran from the Panama Canal to Mobile, Alabama, about six days, average speed 6.7 knots. Only took it off the Saye Rig when in the lee of Cuba.

In May 1995 we sailed dead downwind, two jibs poled out and double reefed mainsail set fore and aft to reduce rolling. West end of Puerto Rico to Key West.

In 1985 we had flown to Spain to meet some friends and sail back across the Atlantic with them on their F50 taiwan turkey. The owner and I are both long time sailers, cruisers and racers, but we could never get that boat to trim or sail with the wind vane,(forgot which one). The mizzen was useless, so we sailed the lighter airs with a full spinnaker and autopilot. When the wind piped up, we would pole out the 150. That boat would roll gunwale to gunwale and it had 6' freeboard. My wife coined a term, "Rhythmic rolling is reality." When he got back to the states, he sold that boat and bought a Cal 46

I am suggesting you look at the entire system, boat design, sail trim then the wind vane.

Tom

[demacsea]

We crossed the Atlantic (Canary Islands to the West Indies) some years ago using an Aries windvane on our 38 foot light displacement cutter. Sailplan was twin headsails set in the twin-luffgroove furling gear on the forestay. One sail has poled out on a telescopic pole and the other sheeted through a block on the end of the squared-off boom. In the brisk tradewinds the Aries managed well, although there was some yawing.
The problem with using a self steering gear for downwind sailing is that there's often not enough air flow over the vane. If, say, you've got 15 knots of wind coming from astern and you've got 8 knots of boat speed, then the wind vane is only going to feel 7 knots of air flow over it. This is barely enough to keep it stable - hence the problem.
There's some good stuff here about the various types of self-steering gears and how they work.

[charliehows]

yeah I'm wondering if sacrificing boatspeed by using a smaller jib would improve windvane response by having more airflow over the vane - trouble is its very hard to resist putting up a lot of sail in light airs and i just havent had the discipline to try this out yet...

[daddle]

Try heading up a little. 10 degrees. Nothing especially comfortable or fast about dead downwind.

[atoll]

best way i have found to overcome the problem of rolling is to "tack" down wind.
keeping the wind 15-20 degrees off of ddw,
this keeps a good airflow over the vane by flying twin jibs and deeply reefed main,with the weather side jib poled out.

it also stops the wind vane wandering,as you have introduced a slight amount of weatherhelm on the rudder,so the vane is only having to counter steer in one direction.

adjusting the main and poled out jib allows you to fine tune the steering once the vane is set.
any distance lost by track error is soon made up by faster sailing speed,and using morning and evening wind shifts to your advantage.(ie :corolosis effect ;cooler air at night will be more NE and warmer day time air more EAST)

[charliehows]

this is gold - i'm going to try twin jibs but i hadnt thought of using the main to ease the rolling...

[atoll]

Originally Posted by charliehows

this is gold - i'm going to try twin jibs but i hadnt thought of using the main to ease the rolling...

the reefed main also acts as the "steering sail" ,once the vane is set up and steering reasonably well,pulling in the main from its fully out position against the stays will increase weather helm and make the boat try to steer slightly higher,at which point the vane will counteract,giving you about 5 degrees of fine tuning,more speed and greater stability.

i allways use a preventer on the main so as to keep the sail in a fixed position and flat as possable.

if the wind picks up releasing the main has the opposite effect and allows the boat to run more downwind.

for reducing sail i allways drop the genoa behind the main first,and run with deeply reefed main and poled out jib.

following that for further reduction,smaller poled out jib and main,
then poled out jib only
,after that poled out storm jib,
after that storm jib no pole,then bare poles!

[Jim Cate]

It is also possible to construct a light air vane for your system. Depending on the specific design of your rig, a larger area but similar weight vane made of "doorskin" veneer or other very light material can increase its response to the small apparent wind speed downwind. You may have to change the counterweight as well... some are adjustable.

Not hard to do, and it worked for us down to about 4-5 knots apparent.

Cheers,

Jim

[Andrew Troup]

+1 for poling out a smaller headsail (say a #3) to windward and sailing a bit higher than DDW. Ideally on a telescopic pole or a penalty length spi pole.

This headsail acts like the leading panels on a spinnaker to scoop airflow round into the big headsail and keep it pulling hard and consistently, instead of filling intermittently and adding to the rolling.

The big sail acts like the rest of the spi, except stabilised and flatter cut.

Better still if you can improvise an outrigger for the leeward clew of the big headsail, to stabilise things further. Beware of dipping it in the ocean, though, if it's a low cut sail. If there's a reefing eyelet futher up the leech, you could possibly pole to that.

And the main should be prevented forward (or to the rail, subject to provisos about strength and fuses) and the mainsheet snugged, so once again the sail is stabilised, this time along two edges.


I reckon the way to really nail downwind trim in preparation to engaging the vane is to try as hard as you can to get it sailing with the helm locked in position. (at least, in mild conditions - of course, this is when it's hardest ,because the boat travels at nearly wind speed)

A well as experimenting with trim: If you have a centerplate or aft daggerboard, use it to move the center of lateral resistance as far aft as possible. If you have control of mast rake, let the masthead go as far as it will go forrard. Trim the boat down by the stern, unless it's already bordering on too much that way. Keep the rudder and keel clean! (and of course the vane gear needs to be in tip top condition, bearings all refurbed, scrupulously clean, ball-bearing blocks on control lines etc...)

And of course Jim's excellent suggestion about upsizing the vane for light airs ...

You might also be able to supplement the vane's influence on the helm by using some variation on "sheet to tiller", transferring changes in sheet tension to either the servo oar or the helm itself.

The thing about trying to to it without the vane on every possible occasion, is that you will gradually piece together a picture of how the sails and the wind and the seaway interact, ideally one which is both deep and nuanced -- this might tip you towards a good solution.

If nothing else works, some modern autopilots do an amazing job downwind.

[Andrew Troup]

For anyone thinking of sticking with (or going to) twin headsails, I've read good reports and seen compelling footage of the "Twistle Rig" solution.

The appeal, for me, of twin sails on the one stay, would be when they're set on a twin-groove roller headfoil. I like the idea of a single line reducing the sail area to any desired extent while keeping it balanced across the boat throughout.

This rather novel setup (which doesn't require purchasing any proprietary items) promises to virtually eliminate rolling DDW.

Google if interested.

[charliehows]

i have a big vane and matching counterweight - havent tested it yet. also my furler does have twin tracks - i'll think about a 2nd hand light jib to run up it - generally at sea i use my 2nd forestay with hanked on sails so having a 2nd sail on the furler might work as a custom downwind sail. just have to think through how to tack it so the genoa stays on the lee, swap the ropes in the blocks i guess...

[charliehows]

wonder how the mizzen would work instead of the main - wouldnt have to reef it but it is further back so might bugger up helm balance...

[Andrew Troup]

I should clarify that my previous post on the Twistle rig relates to using twin running sails only

(unless possibly with a reefed main or trisail sheeted amidships, purely as a roll damper)

- I have theoretical reservations about the latter course of action, as it seems to me it might overpower the vane steering if the boat were to yaw enough to get some serious (reverse - leech to luff) flow happening on the main

As for how to gbye when using unequal sized headsails on one stay: that's a disadvantage of that setup, for sure. I always try to set it up in view of expected wind shifts or course changes so I can get by simply by gybing the main, rather than the headsails, or fudge a bit by running slightly by the lee if that's sufficient, for short periods (with a decent preventer, of course.)

It's a big help, when doing this, if a decent length second pole is available for use bearing out the clew of the bigger headsail: if it's to windward, a long-enough pole becomes essential.

[Tales]

When using two headsails we set the leeward one flying on the spinnaker halyard.

There is very little gap at the forestay and it's really quick to drop if you want to reduce sail or gybe.

Also when we want to reef the main it's convenient to heave-to with the poled out jib backed. Everything under control and the second headsail will pull you back on course when you want to continue.

It's all very civilised!