Auto Pilot/GPS

[sailaway78]

Blame this post on my curiosity, or my enjoyment of starting an argument, but I have to ask. There have been a couple of posts recently on tying the auto pilot together with the chartplotter, so the auto pilot can run from waypoint to waypoint. My question is this. Can anyone actually explain any benefit to this hookup. In my area, there are lots of twists and turns inside the bays. Once you get over into Mississippi sound, and Mobile bay, you can run some longer straight runs, but there you can just punch up the course and go. Offshore, pretty much the same thing. If on a run from say, Pennsacola over to Tampa, a straight shot, I don't run on auto pilot a lot. When inside I use it mostly to steer the boat if I need to go below, or up on deck for something. When offshore, I use it primarily to maintain course when I am single handing and need to sleep. Is there any actual benefit to having the GPS/autopilot wired together, or is this just another one of the toys we all must have.

 

[Terry Cox]

Yes! Our PNW cruising grounds are filled with ...

hazards; some well marked, others not. The night before I most always plot our course to the next destination on our Garmin 178C chart plotter. Then I track the course to verify sufficient hazard clearance to our destination. That way I know with reasonable accuracy that we will have a safe journey to our next anchorage.There are caveats. Many times the wind direction will not allow me to follow a plotted course. Other times it will. I like the idea of the AP following directions from the GPS when the point of sail allows. Either way I keep a close eye on the system and chart data to make sure a safe journey. TerryP.S. I would consider the GPS to AP link a feature function rather than a toy. Similar correlation to a car's speed control system. I like the speed up or slow down feature to help maintain a safe distance. My wife hates it and instead disengages the system whenever she wants to change speeds.

 

[Stu Jackson]

Speed and direction are two very different

things.We have kept our "system" integration to zero.It keeps our head "outside the boat", improves awareness and avoids dependency on instrumentation. Our GPS tells us where to go, reviewing the charts indicates potential hazards in between, and the AP steers or we do.That doesn't mean that integrating the systems doesn't work for others, it just seems to me that integration means that awareness and vigilance shouldn't be reduced because the equipment is working together.We've all heard the story about the motor boater who set it on autopilot and went below...I just have a feeling that some, even if just a tiny few, may depend too much on the systems, rather than the basics.There's no right or wrong, your boat your choice, but we prefer simplicity.

 

[Tim C350 April IV]

Arrival at Waypoint vs. Heading hold

There is a difference. Say desired destination is 5 nautical miles from current location, bearing 270. Setting the Autopilot to hold course 270 and then going below for 1 hour while the boat is moving at 5 knots will result in the boat being 5 knots away from the starting location and at the desired destination, providing (underlined and bolded PROVIDING) that there is no wind or current affecting the boats travel. If there is a 2 knot current running at 180, where will the boat be at the end of the 1 hour? It will be approx. 2 nautical miles south of the desired destination. That's called Cross Track Error.Linking your autopilot to your GPS, and setting the desired waypoint, and allowing the GPS to provide the autopilot with updated steering instructions to account for the actual current or wind affects that the boat is experiencing - in essence, the GPS is watching the actual cross track error being experienced and then provides adjusted steering instructions to compensate - thus maintaining that straight line course that you desired.Simply put. An autopilot alone can keep the boats nose pointed at the selected heading. An autopilot linked to a GPS can keep the boat travelling along a selected path inspite of the effects of winds and currents.Good Luck!Tim BroganApril IV C350 #68Seattle

 

[sailaway78]

Some differences of opinion and methods

There seem to be two distinct opposites of opinion here. Those who are going to let the auto pilot do the work, and those who would rather do it themselves. Tim, if as in your example of five miles to the waypoint, that is roughly an hour. Why do you want the auto pilot to steer this for you. The vast majority of the time,more likely 100% of the time, if I am five miles from a waypoint, I am more than likely fairly close to an obstruction of some kind. Be it a shoal, a piling, an anchorage or whatever. I do not want the auto pilot steering this course. If necessary to go below, or on deck, the auto pilot can do this for a couple of minutes, but basically I will be at the wheel. On longer passages, offshore in particular, when single handing, it is a necessity in order to get some sleep. I just don't understand why, when day sailing, or anywhere inshore for that matter, anyone would trust their boat, and possible their life to an electronic magician.

 

[Don12364]

Luddites All

Sometimes you DO want the autopilot to guide the boat EXACTLY along the rhumb line when in the vicinity of hazards. That way you can be sure to miss them.We autopilot much of the time with GPS steering us from waypoint to waypoint and half a boat's length accuracy. We use routes and waypoints used proven previously to be safe. Some would say it is boring and I would agree - but on a bad night the feeling of comfort is wonderful.We use a large screen laptop for navigation rather than one of those itsy bitsy chartplotters so we can really see where we are. Of course every waypoint is properly named using the keyboard and courses etc correctly calculated by the nav program to include the set and speed of the tide at that moment. Even the latest chartplotters cannot aspire to this.

 

[Stu Jackson]

Donalex really nailed it

It depends on what you prefer but also where you sail.With large currents affecting your course, most (not all) APs tied to GPSs will REACT rather than be PROACTIVE.Point A to Point B with a current at 90 degrees to your course would, with a "simple" system, keep correcting and result in a curved course as it keeps correcting to get to Point B, but WILL get you there.If, however, there is an obstruction to the curved side of the course that you need to miss, either you have to offset that in your "simple" setup with, say a middle waypoint (or series of waypoints) OR you need the "smart" software that will compensate for the offset which it can ONLY do if it's "smart" and knows the offset from the current ahead of time.Many different ways to do it, having nothing whatsoever to do with Luddites, just sailors with many different ways of getting from A to B.With a SMILE!

 

[BobW]

Both are tools....

and making them work together - while properly supervised - lets me concentrate on 'managing' the boat and its course, rather than having to focus on steering.I LOVE helming my boat. Recently I went on the 'sail the America's Cup boat' in San Diego, and standing at the helm, feeling the incredible responsiveness of the wheel... indescribable.But when I'm going somewhere - in our cruising grounds, anywere from 10 to 70 miles away, I don't enjoy steering for long periods. Sailing in the Pacific Ocean, there isn't much chance of hitting something, so we set the A/P (which is hooked up to the chart plotter) and relax.That doesn't mean we go below and trust it. We just let it steer, while we navigate and manage the boat. And yes, that means being aware of where we are, what forces are acting on the boat, and knowing whether the AP/CP combination is getting us where we want to go.On the other hand, Nice N Easy, having done some powerboat runs out of western Louisiana (Calcasieu River), I know what it's like dodging some infernal obstruction every few hundred yards, and why you ask.Cheers,BobWs/y X SAIL R 8