Autopilot vs windvane Will it sove my problem?

[Steve Laume]

Larry, I belive we probably have the same set up with some of the same problems. I have a ST4000 wheel drive that works very well most of the time. I have come not to trust it too much though. Some times it will be steering along just fine and then start to steer off course. As it gets farther off it seems to turn harder in the wrong direction. I have always disengaged it and grabbed the wheel before determining how far it will go and what it will do next. At first I thought maybe it was low battery voltage. I believe it has since happened when this was ruled out. Bad connections? Our flux gate compass is located forward of the step in the vee berth. We keep a spare anchor up under the center of the vee berth and it could have an influence. I do not really understand what a flux gate does. It is the random inconsistency that is so troubling. When the trust is gone the whole thing becomes pretty worthless. Anyone with any ideas, Steve.

[Peter Drake]

The basic fluxgate compass is a simple electromagnetic device that employs two or more small coils of wire around a core of non-linear magnetic material, to directly sense the direction of the horizontal component of the earth's magnetic field. The advantages of this mechanism over a magnetic compass are that the reading is in electronic form and can be digitised and transmitted easily, displayed remotely, and used by an electronic autopilot for course correction.

To avoid inaccuracies created by the vertical component of the field, the fluxgate array must be kept as flat as possible by mounting it on gimbals or using a fluid suspension system. All the same, inertial errors are inevitable when the vessel is turning sharply or being tossed about by rough seas. To ensure directional readings that are adequately stable, marine fluxgate compasses always incorporate either fluid or electronic damping.

Fluxgate compasses and rate gyros complement one another nicely. The fluxgate provides a directional reference that's stable over the long term, and the gyro adds accurate short-term corrections for acceleration and heeling effects. At high latitudes, where the earth's magnetic field dips downward toward the magnetic poles, the rate gyro data can be used to correct for roll-induced heading errors in the fluxgate output. It can also be used to correct for the roll and heel-induced errors that often plague fluxgate compasses installed on steel vessels.

From Wikipedia, the free encyclopedia.

[Ben Thomas]

I would locate the fluxgate as low and in the center of a vessel as possible, avoid either end especially the bow.
I have mounted the fluxgate under sole on L shaped mount to keep it vertical aft of step onto main sole at companion way steps just above the bilge. Originally mounted on fiberglass bilge pan aft end below bilge access hatch on my CD 30. I was concerned about proximity to engine and other electrical influences but there has been no adverse effects on fluxgate, steady readings that are consistent with recently swung compass at binnacle.
There is still a lot of motion at this location but it is (smoother) different than the abrupt changes bow receives.

I think it would be worth it to test a different location, (more stable).
Worth a try. Keep us posted. Ben

[L.DeMers]

Steve,

Exactly our symptom also. In our case, the fluxgate compass is located in the forward wall of the cockpit footwell. This is a new location for it, and I suspect (now) that it is too close to the engine mass.

I suspect that your fluxgate is too close to the anchor under the v berth. It would make sense that the iron of the anchor would affect one heading more than another too, as it is probably at the edge of it's influence on the compass, so it's affect is not distributed evenly around the compass. Hard to explain it, but I think this is what had us chasing the boat onto course a few times. It sure did keep me awake though!

Larry

[Cathy Monaghan]

Hi Larry,

I am by no means an expert on the subject, having only sailed on one boat with a wind vane. It was a Monitor by Scanmar International. But even being a "newbie" in the use of wind vanes I can say that the experience on that boat has made me a firm believer in the need for that piece of equipment, especially for a short-handed crew, while passagemaking. It is, in a sense, an additional crew member.

I took me serveral days to really learn how to use the thing. But the most important thing in getting the boat to steer on course with a wind vane is to make sure that the sails are balanced. You have to get the boat to sail a straight line pretty much on her own by adjusting the sails before the wind vane can be deployed. Of course wind speed and strength will change as you continue on which means that you'll be kept busy adjusting both the sails and the wind vane. If you don't keep the sails balanced, she won't sail in the direction you want to go no matter how much you adjust the wind vane. And I'll say this much for it, you won't have to worry about the watch falling asleep in the cockpit since in addition to "watching" they'll be messing about with both the sails and the wind vane. So before setting out on a long passage, I'd recommend some practice first.

On the particular boat I was on, the wind vane didn't perform very well in winds below 15 kts, but it worked like a dream in stronger winds. So when the wind died down we disengaged the wind vane and used the autopilot instead. So you really need both pieces of equipment onboard for any offshore passagemaking with a shorthanded crew.

For the Cape Dory 30, and this is just my uneducated opinion, so take it with a grain of salt, I think the Monitor would be too bulky. I think I'd look at one of the many other wind vanes available.

Try researching the following:

Sailomat
Hydrovane
Navik -- manufactured by Scanmar, the same folks who make the Monitor.
Cape Horn
Voyager Windvanes
Windpilot

There are lots of other wind vanes but most are better suited to larger, heavier boats with bigger transoms than your CD30. I like the Sailomat in concept because it can be mounted off-center (so you won't lose the use of your stern-mounted ladder) and can be installed on any transom no matter which way it's angled, and it's strong without requiring a bulky cage-like attachment to the boat.

My opinion is just 2 cents, but I hope the links will help.

Have a wonderful new year,
Cathy
CD32 Realization, #3
Rahway, NJ
Raritan Bay

[L.DeMers]

Hi Cathy,

Sounds like good advice. I have stayed away from windvanes because of the weight. But lighter units are available as you say. One windvane that two friends now have is this one.
http://www.voyagerwindvanes.com/Voyager/windvanes.aspx


Still a lot of weight on the stern though...

Maybe learning to drink coffee and investing in Mountain Dew is the least expensive answer for now.


Larry

[Matt Cawthorne]

Larry,
I use a Wind Pilot Pacific. It works really well. Last summer I sailed all the way to Cape Breton, Nova Scotia with it, and most of the sailing was down wind. There were a few times when we had to hand steer, but usually it did just fine. Sometimes the main sail must come down to make it sail down wind. The times when we did have to hand steer it was because I was tired and did not want to do a sail change in the middle of the night. Wind Pilot makes a lighter version that may be OK for your boat. I made some modifications to my unit to make it work better. If it is not gusty, I can sail in less than 2 knots of apparent wind on any point of sail. The sails need to be adjusted when the wind strength changes. If the wind strength changes often, you have to tweak sails often.

Matt

[L.DeMers]

Matt,

Congratulations for making such a voyage and returning safely. I trust the CD36 was up to the challenge? That is a sail with many unknowns, so it must have been interesting. I would like to hear more about it Matt.

I am following the same path, but on freshwater, at least for now. Superior has enough territory that is far from any civilization and mostly untouched by man, that we can make a couple 100 mile passages and be in a cruising area that is unequalled. Hundreds of uninhabited islands, wildlife galore (eagles, wolves, moose, elk etc....), and have challenging sailing/navigation due to the _many_ rock reefs, and enormous boulders that dot the area , as well as good wave size when SW winds are running (5-10 ft are fairly common. The SW wave train has a period of around 3-4 sec, so these waves are steep).

What was the scenery like once you got there? How many miles did you put on the boat? What worked best on the boat?

Cheers,