Autopilots versus windvanes

It used to be the conventional wisdom that for offshore cruising a windvane self-steering gear was the first choice with autopilots the choice for inshore cruising. In recent years numbers of cruising boats have been setting out for distant shores and places with just an autopilot as the self-steering gear of choice so on my recent cruise to southeast Asia and back I dispensed with a wind vane gear and went down the autopilot route.

Actually my wind vane gear dispensed with itself a number of years ago. At the beginning of the season I had stowed the detached wind vane on the side-deck and tied to the shrouds which was fine until the jib sheet got caught around it and upon tacking flicked it 30 feet into the air and so to the sea bottom. Later on I was motoring up a channel that was being dredged where you had to wait until the dredger dropped the cable anchoring it to the opposite bank. In the windy conditions the operator panicked and tightened the cable a fraction too soon. It managed to catch the trim tab and in an instant I lost the bottom half of the wind vane gear. When it came to my refit for the Indian Ocean trip I plumped not too install another vane gear on Tetra and to carry just the existing autopilot and a back-up.

Reasons for and against

In the past the reasons for choosing a wind vane gear went something along these lines.

·         Wind vane gears are mechanical systems and can be repaired in most parts of the world where there are simple engineering workshops.

·         Mechanical systems are more reliable than electrical autopilots.

·         The gear doesn’t consume amps and therefore you don’t need to feed it by running the engine or a generator.

·         The gear steers a course relative to the wind which means you set up the sails and away you go on trade wind routes.

The first three reasons are no longer entirely true.

While it may be possible to have some parts of a mechanical self steering gear repaired using basic engineering skills, the parts that usually go wrong are often specialised castings (often in alloy) or specific items that must be replaced by the manufacturer. I have come across cruising yachts in all sorts of locations waiting for a replacement item to arrive so that a wind vane gear can be repaired. For some home-made trim tab gears it is possible to make running repairs in most parts of the world, but these are few and far between these days and most yachts have relatively sophisticated gear which incorporate cast alloy or injection moulded plastic components.

Lu installing the Type 2 drive in Skylax's lazarette

Mechanical systems are more reliable than electrical systems when all that salt water is flying around, but electrical autopilots have come a long way since the early days and they can take a lot of abuse before they expire. In most circumstances electrical autopilots cope well these days and if you think about the conditions the autopilots on the boats in the Vendee Global and the BOC round-the-world-races encounter, then autopilots are getting pretty thorough testing in extreme conditions. There is also the question of cost which I will come to later.

While it is true that a wind vane uses nothing but the wind itself for the energy to steer a boat, modern autopilots are now relatively economical in their power consumption. A lot of other items on board are going to be using a lot more amps to run. An Autohelm ST4000 (now the S1 + Grand Prix for tiller steered yachts up to 16,500lbs/7,500Kg) uses around 0.8 amps at 25% duty cycle. An Autohelm 8000 with a Type 2 drive (mechanical wheel steered

yachts up to 33,000lbd/15,000Kg)) uses 4-6 amps. The 8000 with a Type 1 drive (up to 22,000lbs/10,000Kg) uses 1½-3 amps.  Over a 24 hour period the ST4000 will use around 19 amp hours and the Type 2 linear mechanical drive around 120 amp hours. The latter figure is an average and most well set up yachts will use a lot less – probably around half that figure by my estimate. A refrigeration unit running for 6 hours (at 6 amps) will use around 36 amp hours, a 25 watt tricolour on for 10 hours will use around 21 amp hours, and an SSB transmission over 15 minutes will use around 6 amp hours. With modern charging units, wind generators and solar panels it is not too difficult to find the amps to feed an autopilot.

While a wind vane gear steers a course relative to the wind, an autopilot copes just as well when the wind direction is relatively constant over long distances such as in the trade wind belts. When the wind angle changes or a squall comes through, both gears need to be reset and in this there is no advantage for either except that it is comparatively easy to reset an autopilot with the auto-

course button. Some wind vane gears can be extremely difficult to re-adjust when the weather is rough and can involve balancing precariously on the aft deck to reset the vane. Others can be reset via control lines from the cockpit.

There are some reasons that go against the wind vane choice.

·         The initial cost of a wind vane gear is high with a lower end gear starting at around £1100 for a 10 metre boat and going up to £3,500 for some high end gears.

·         There are some yachts which just will not self-steer with a wind vane gear. A friend of mine with a moderately designed 37 foot yacht and a well known wind vane gear just cannot get it to work. He has tens of thousands of sea miles under his belt and is the pedantic sort who doesn’t like to let a problem remain unsolved. Despite advice from others and a lot of trying it just does not work. He is not alone and there are others who have difficulty, especially in downwind situations where the apparent wind is decreased just when the maximum effort is needed.

·         The gear clutters up the stern of a yacht which these days is cluttered up enough anyway with aerials, a swimming ladder, barbecue, life-saving devices and quite likely some fenders and ropes.

Making a choice

I think the old axiom of ‘if you can afford it, get both’ still stands. Most people have got so used to not steering a yacht on long or short passages that whatever works is good news. If you cannot stretch to both a wind vane gear and an autopilot, then the choice is more difficult.

On the trip from the Mediterranean to Malaysia and back in 1996-97 on Tetranora (31ft long keel around 7 tons) I took my trusty Autohelm 2000, now the ST4000 with added ingredients, which was already 7 years old and had a lot of miles under its belt. As backup I took an Autohelm 2000 all-in-one unit. The old 2000 lasted until the return trip back across to Sri Lanka when its motor packed up. There was a minor problem on the way when I cracked the end casing trying to remove it from the bracket on the aft deck, pure clumsiness on my part. Frank my crew mended this in Aden with a moulded epoxy casing he made up – he even bought a can of black spray paint so it looked a neat job. The new 2000 lasted until the Red Sea when it to expired and on inspection it was found that sea water had got inside and corroded the electronics making it impossible to repair.

You might surmise from this that the electric autopilot option was not the right choice. In fact I still believe it was and had I bought a new ST4000 instead of the ST2000, there would have been no problem. The new ST2000+ has also been beefed up with new silicon compression seals on the pushrod and most importantly a Gortex patch on the ‘breather’ under the body of the case. I suspect it was the latter that allowed water in as on the all-in-one 2000 I used there was no Gortex patch. Incidentally the old 2000 (now the 4000) was repaired in Turkey by the simple substitution of a new motor (cost around £40) and is again doing sterling work. Over 15,000 rugged miles a wind vane gear may have broken down.

On above decks systems one item that always gives trouble is the deck plug and socket. A good plug such as the dri-plug is adequate when there is just a bit of spray, but with any solid water coming on board all deck plugs just curl up and die. I had to replace the cockpit deck socket four times on this trip alone, although to be fair there was a lot of water coming on board for the first half of the trip.

To provide the amps for the autopilot I installed two solar panels on the bimini and at no time was I ever short of battery power. Mind you Tetra is an energy efficient boat to run without a refrigerator consuming all those amps, and in the Tropics I’m talking about a lot of amp hours if you want cold drinks. Other yachts I’ve talked to running autopilots only have often used both solar panels and a wind generator and have not experienced any lack of amps. On one Atlantic crossing a 45 foot yacht with an old American ‘windbugger’ could not get near the locking mechanism to stop it producing amps and had to resort to turning everything electrical on, the stereo, all the lights, anything that consumed power, until the gale died down a bit. It must have been an eerie sight in mid-Atlantic to see a yacht all lit up like a Christmas tree blaring out loud music in a gale. Newer models have a different mechanism so that this problem doesn’t arise.

There is also the question of cost. At today’s prices two ST 4000 gears would cost around £1200. Other comparable autopilots are around the same sort of price. The cheapest wind vane gear on the market would cost around the same as two of these autopilots and there is no backup if it breaks down. Moreover you will have to helm when motoring if you buy just the wind vane gear. You can set up a small autopilot to work the trim-tab ‘back the front’ as it were, when motoring, but this involves an additional cost buying a small autopilot.

On a small wheel steered yacht it occurs to me that there is no good reason why you couldn’t mount something like the ST4000 or similar down below on a small tiller bracket out from the rudder stock and have a small access hatch somewhere to engage or disengage it. This keeps the autopilot out of the elements with the only disadvantage being that it might be difficult to disengage in an emergency. On some yachts there may not be sufficient room to mount the autopilot at the distance specified from the rudder stock.

Whatever you get, make sure it works. On seven tenths we had two ST 4000+ units which were not up to the job of steering her downwind in the trades. On Sylax we have an 8000 unit with a Type 2 linear drive that after 18,000 odd miles is going well.

I can remember all too well what it was like to helm night after night on long passages in seven tenths. There are some who still do it, but they look shattered when they arrive. Self-steering of whatever type allows you more time to check your navigation, trim sails, keep a good watch and make lots of cups of tea. One thing that is important with an autopilot is not to trim sails too precisely when on passage. If the sail trim is a bit sloppy it allows the autopilot to get back on course without too much effort spent fighting the force of the wind in the sails when off course. When downwind if there is a lot of wind around I will often put a reef or two in the main which makes it easier for the autopilot to cope and in cruising mode doesn’t knock the average speed too much. And it is easier on the nerves if you are already prepared for any increase in the wind and easy enough to shake out if it all goes quiet.

2007 slightly adapted from an original draft from 1997.

 Fixing the 4000ST+ on seven tenths - yet again.