Autopilots--basic question - Page 2 - SailNet Community
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post #11 of 23 Old 02-27-2011
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I've used an autopilot for longer passages with apparent wind angles. It works fairly well if you have consistent winds, as you often find off shore. Balancing the boat's sail plan is key to getting it to work well.

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Originally Posted by ccriders View Post
A few weeks back it was asked if anyone had experienced how an autopilot performed when coupled with a wind sensor. No one seemed to have direct experience to offer. Can you elaborate on this statement? Did the autopilot get into a disagreement with the wind vane? Was it confused by the wind/water combination? Was it a hull/sails configuration issue? Was it an adjustment problem?

Autopilots are expensive enough for a basic system and can get really expensive for one that talks to other devices. But add in the other devices and it gets so expensive one would really want it to work of advertised.

Your observations will be appreciated.
John

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post #12 of 23 Old 02-27-2011
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my AP has a "wind vane mode" that I really like. Pick an angle of apparent wind and it will steer to that angle, meaning you dont have to trim the sails again once you have them right, so long as the wind stays the same. If the wind shifts more than a few degrees it beeps and asks if you want to accept the course change. Best of all for singlehanding, is the autotack feature of the wind vane mode. It will tack the boat through a preset number of degrees (default is 100 degrees but you can change that), meaning that once you hit the button you are free to handle lines without having to worry about steering the boat until you are ready.

It has worked very well for me so far, but as SD says it is more useful the steadier the wind is.
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post #13 of 23 Old 02-27-2011
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sck5- what pilot do you have? My old Auto 7000 crapped out so I'm in the research phase. Thanks.

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post #14 of 23 Old 02-27-2011
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Auto tack is a cool feature and I find it works reasonably well. I find it typically over-steers the tack to be sure to catch wind on the other side. Just be sure you are pointed about as high as possible, before you engage it.


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post #15 of 23 Old 02-27-2011
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Well the ST60 and X5 (raymarine) seem to work fairly well, it will say BEEP BEEP BEEP when the wind shifts more than 20 deg and you have to reset (press both buttons).....it is one reason I bought it.

I love to sail, coming from a Swordboat capt's loin one would think I'd of caught the bug long before now! Oh well, this ones for you Bisque...(My Father may he RIP)

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post #16 of 23 Old 02-27-2011
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We use ours primarily on long passages. As CD said offshore there tends to be more consistant direction so it holds a course well.

Its great for holding a course into the wind when raising the sails when you are singlehanding also. I prefer the feel of the wheel and the motion of steeering the boat most of the time however on the Bay.

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post #17 of 23 Old 02-27-2011
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Not to hijack but ... does the AP work well while motoring with sails down ?just courious....

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post #18 of 23 Old 02-27-2011
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If the sails are trimmed right and the boat is well balanced, it should sail to apparent wind without an auto pilot. As the boat leans it rounds up slightly and then levels off. As the wind lets up, the boat straightens up and rounds down. While I've not had the boat on a large lake, I've sailed for over a mile with the tiller cleated. The boat found its own course based on wind. I have heard of tieing off the main sheet to the tiller. using a bungee cord as a counter balance to the tiller.

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post #19 of 23 Old 02-27-2011
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Quote:
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Not to hijack but ... does the AP work well while motoring with sails down ?just courious....

Yes.... to a compass heading

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post #20 of 23 Old 02-27-2011
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Quote:
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We've found that if you tune the AP for, say, motoring in calm conditions at hull speed, she's too insensitive to handle the heading under sail in some chop or waves, esp close hauled.

For a long sail, off the wind, I might bother to retune it, but mostly we use it for setting and dousing sail, long windless days, and for short term departures from the wheel..

After all, as coastal cruisers if we're sailing, we prefer to steer anyhow.
Ditto here. I've had a lot of experience with PID controls in manufacturing processes, and the concepts are exactly identical. The "proportional" part of PID is your gain setting, the "integral" part is referred to as "AutoTrim" by Raymarine, and sums up the cumulative error in your bearing or track, gradually increasing the amount of correction to bring the boat to the setpoint. You can basically tune these parameters for motoring or for sailing, but not both. And even when tuned for sailing, it may be unreliable unless you're REALLY GOOD at balancing the sails, because conditions can push the boat off its course in ways that your own senses will detect, but the AP will not. (For instance, you will immediately notice a change in heel and subconsciously adjust - but most APs will not detect this at all.)

To summarize, most modern APs have three modes:
  • "Standard" bearing mode, where you press a button the AP locks onto the bearing (from its integrated compass) and keeps the boat pointing in the same direction. Actual COG can/will vary as current and/or wind push you in a different direction that you're pointing. This is the most commonly used mode, because it requires no interfacing - though to really use it you need to tune the controller parameters.
  • Track mode when interfaced with a chartplotter, where you set a waypoint and activate a course to the waypoint. When you press a "track" button (or similar) to activate, the AP starts out pointing your boat toward the waypoint, but as current or wind push you off course (increasing XTE - cross-track error), the AP will change your bearing to eliminate the XTE and keep you on course. IMO this is best used when motoring - under sail, this could cause you to point higher into the wind than your boat is capable of, or worse, to broach. But apparently many people do use it for long-distance cruising.
  • Wind Vane mode when interfaced with an electronic wind sensor. When activated the AP calculates your bearing relative to wind, and keeps you there. Supposed to work like a real wind vane.

How many of you have an actual wind vane? I have a friend who bought one a couple years ago, and has mixed results.


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