Autopilot Confusion

[colemj]

Originally Posted by goboatingnow

Most when set into motorboat mode will execute full authority turns of any degree including 180 s

Dave


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OK, I will take your word for that since I have never set up a pilot in motorboat mode - only sailing mode.

I assume in that mode that full authority can be turned off or modified if wanted?

Mark

[colemj]

Originally Posted by Pelagic

Thanks for fixing for me Mark.
I can only admit that I am less of a sailor when everything stays on automatic Nav.

But, I am not one of those purists, I love all the modern Nav equipment that I get to play with on Super Yachts but have learned to keep the watch keepers (including myself) engaged in manually adjusting for leeway to keep alert.

Also certain experiences can lock you in to the value of feeling the boat on ocean passages.
A couple of them did that for me:

1 Mid Ocean, one afternoon, I turned off the adaptive pilot to hand steer and something felt funny. We found no problems with the pumps or steering, so back on Autopilot and had an uneventful passage. First opportunity, we dove on the hull and found that one of the rudders had completely disappeared. This was traced back to a recent dry-dock failure to secure the rudder flange with the proper lock nuts.
Now on each watch I always hand steer for a little while, just to feel the boat.

2 Similar experience where in rough conditions off the Australian Coast, the mate told me he had to apply lots of leeway to keep her on track to next waypoint. “Northing Tests” confirmed that both Gyros that had just been serviced in Sydney, were failing in a strange way. Altered course back inside reef towards Townsville and all was fine.
Since this was a possible warranty issue, I had service tech from Radio Holland meet me in Townsville. Turns out their Sydney Tech had failed to top off fluids after assembly and the spheres were hitting the sides in rough conditions creating a variable gyro error in rough conditions. Both Spheres were damaged and luckily replaced under warranty.
Point is…if autopilot had simply been steering to a waypoint, we would never have picked up on that compass problem.

Each to their own!

I'm sorry, but I just do not understand how a failure to do basic inspection and testing of recently repaired components is reasonable cause to completely negate the use of a common operating mode of an autopilot. In the first case, that was a problem whether the AP was steering to a waypoint or not. In the second case, a compass problem would very certainly cause a problem if the AP was steering to a waypoint - where do you think the chartplotter gets its bearing from?

Both arguments are non-sequiters.

Mark

[Pelagic]

Originally Posted by goboatingnow

Couldn't agree LESS , the job of helmsman is a lowly position, unsuitable for any skipper. The role of the skipper is to command the vessel, evaluate the situation and make decisions as appropriate. Turning wheels is for monkeys or electrics.

There should be no diminution of responsibility by using an autopilot. In fact an AP aids in situational awareness

Dave


Sent from my iPad using Tapatalk

Agree with you Dave that there is no reason to NOT use an autopilot but as I said on the compass thread, my training is probably my biggest navigational asset along with what’s between the ears.

Unfortunately with those certificates comes a multitude of case studies where a mariner relied too much on the AP and a programmed in waypoint to do its job.

As a watch keeper I enjoy the freedom of using an AP, but as a mariner I want to adjust the AP regularly during my watch to get a sense of external forces. As the captain, I insist the other watch keepers do the same, so I never connect the GPS- AP-Nav waypoint sense.

There are other case studies where the captain relied too much on using the AP when operating in dense traffic, approaching a harbor, in Fog, or in tidal currents… so there are rules and warning for me on that…. But for the average pleasure boater, they don’t appear to have the legal requirements for that situational awareness if ever an event went to court.

[Pelagic]

Originally Posted by colemj

I'm sorry, but I just do not understand how a failure to do basic inspection and testing of recently repaired components is reasonable cause to completely negate the use of a common operating mode of an autopilot.

Little different on a Super Yacht where 2 certified engineering crew/ reputable navy shipyard and Lloyds inspector missed it. No excuse other than they/we are only human, but I was pissed!!


In the first case, that was a problem whether the AP was steering to a waypoint or not.

In a way True, but I had a feeling we were adjusting more than normal to stay on track.
It was only when I went off AP to test, that I sensed something different in the feel of the ship.
If the adaptive pilot had been steering to waypoint, I would never have noticed as it would have self adjusted and rudder action is silent on the bridge


In the second case, a compass problem would very certainly cause a problem if the AP was steering to a waypoint - where do you think the chartplotter gets its bearing from?

Little different on a SY set up. For adaptive pilots/ IMO Radars and Sat TV/Communications we use the special step feeds from the 2 Gyros (one is back up).

For the other many B&G type yacht Nav Instruments repeater that feeds the many stations (crew mess/Galley /Owners cabin/Engineers and Mates Cabins/My cabin etc.. we then would use Flux gates.

Not sure about yours but our Chart plotter calculates SOG/COG/ETA/DTG and Own ship Posn. from the GPS to the waypoint. You are correct, the Ship’s Head would have been wonky on the chartplotter display (if connected to the Gyro) but it is not a display we usually show on the Chart plotter screens (They are distributed to all the TV’s as a “Navigational Channel)

When AP is operating it just shows the “Set Heading” but when I was told by Mate that he was really having to adjust more than normal to stay on waypoint track in those condition, first thing I looked at was the bridge gyro repeater. It seemed too lively for those conditions.


Both arguments are non-sequiters.

Mark

Happy to agree to disagree and leave it at that, but in both cases not having AP connected to a waypoint was what first alerted us to a problem.

[DotDun]

Originally Posted by Pelagic

Agree with you Dave that there is no reason to NOT use an autopilot but as I said on the compass thread, my training is probably my biggest navigational asset along with what’s between the ears.

Unfortunately with those certificates comes a multitude of case studies where a mariner relied too much on the AP and a programmed in waypoint to do its job.

As a watch keeper I enjoy the freedom of using an AP, but as a mariner I want to adjust the AP regularly during my watch to get a sense of external forces. As the captain, I insist the other watch keepers do the same, so I never connect the GPS- AP-Nav waypoint sense.

There are other case studies where the captain relied too much on using the AP when operating in dense traffic, approaching a harbor, in Fog, or in tidal currents… so there are rules and warning for me on that…. But for the average pleasure boater, they don’t appear to have the legal requirements for that situational awareness if ever an event went to court.

The thesis of your argument is on the knowledge of the skipper, you seem to be trying to extend that somehow to a piece of machinery.

I'll be the first to agree with you that someone who doesn't have the capability to skipper a vessel without an autopilot, shouldn't be skippering any vessel. But that's not a negative on the autopilot. An autopilot, just like any computer, performs repetitious mundane tasks that humans become bored with very quickly. It's a tool to assist a skipper/helmsman with his/her duties, not unlike a compass or electric head.

[Pelagic]

Originally Posted by DotDun

The thesis of your argument is on the knowledge of the skipper, you seem to be trying to extend that somehow to a piece of machinery.
:

No only that formal Marine College training over the years accumulated in about 8 months of full time courses and lectures on the limitations and dangers of certain practices with electronic aids.
At the end of it you are expected to have a higher awareness than the average boater. How you apply that is really up to the individual.

[bobconnie]

Gee I guess I sorta knew my AP has a lotta stuff I don't use!! But had no idea of the stuff it might do !! LOL All Ive ever used one for is to stear a course Ive already plotted somewhere else !! And the wind!! works for me !!

[Pelagic]

Same here Bob. Just because a piece of gear can steer from waypoint to waypoint without human intervention. It doesn't me you should use it

[Jim Cate]

We do not routinely use the linked GPS route to guide our AP, but on one occasion I found it extremely useful:

When cyclone Xavier popped up very unexpectedly in mid October, we were anchored near Santo Vanuatu, which was directly in the predicted path. We set out toward Port Sandwich (arguably the best cyclone anchorage in Vanuatu), about 75 miles dead to windward, with a building gale force wind. Not a fun day, and we arrived off Port Sandwich around midnight, pitch black and a circuitous entrance to get through. Normally we would have hove to and awaited dawn, but with a cyclone breathing down our neck, that seemed undesirable. We had a set of waypoints for the entrance, ones that had been used successfully by a trusted friend. With some misgivings, I programmed them as a route in the GPS and told the AP to follow the dots. With some fear we motored very slowly into the dark. Not having to steer myself, we had two sets of eyes to peer into the gloom, and to watch the Probe (forward looking sonar). The pilot hit every WP dead nuts on, turned briskly onto the new course and soon we were safely in the outer anchorage where we gratefully dropped the hook.

One could criticize our decision, but under the circumstances I was damn glad to have the GPS option, and it worked very well indeed for us.

Oh... Xavier went somewhere else... but waited until we had stripped the boat of canvas and sails before doing so. Timing is everything...!

Cheers,

Jim

[Pelagic]

Interesting decision Jim and I am glad it worked out. Don't know that channel but I am sure with your experience you had considered all the pros/cons.
In truth, that is one of the scenarios where they advise you to hand steer ie slow speed/tight quarters/large course changes/currents/gusty winds?
I uderstand your faith in proven waypoints but not that the AP would have stayed on track better than your hand steering and ability to crash stop if a bow lookout saw a fish net strung across the chanel.

[Neptune's Gear]

Ok, back to the OP's question.
The AP will steer to a compass course, or, if it is a suitable type, and connected to instruments, also to wind angle.
IF you add a NAV source (GPS Navigator, Plotter, PC with suitable software etc) the the AP can steer to a waypoint or a route.
In your situation, using opencpn, you can use the pc as a nav source, OR you can upload the route from opencpn to your GPS and use that as the nav source. In that situation you can then turn the PC off. This is the same system that I have.
If you switch the output from the PC and GPS to the AP, you can use either as the Nav Source. We use a simple on/off/on switch to do this. My AP likes 3 decimal point accuracy in the XTE to steer well. If you need further info, have a look on my website and or send me an email...
Also, to the other posters, we use "follow route" often with the AP. It allows automatically for set and drift. Alarms are set if XTE is too much. We also regularly switch to manual steering, but a good gauge of issues on auto is how much rudder is applied to sail straight!
Cheers
Matt

[RaymondR]

Bit of drift here.

I do a fair bit of single handed coastal cruising in areas strewn with rocks, reefs and other hard places and even when I occasionally hand steer it is on a track between waypoints. Unless it is just a short run across the bay I pretty well always plot a route and enter it into the GPS.

I now use OpenCPN for passage planning and hand enter the waypoints into my 1992 Magellan GPS. I have a computer loaded with OpenCPN and use a puck USB GPS which I use to occasionally check where I am and on really paranoid days may even get a chart out of the locker and plot positions (Does not happen very often though)

I have found from experience that doing things this way keeps me from being distracted by problems which might focus my attention away from course keeping and have had a couple of near misses with just putting the autopilot on a course and then getting distracted with fixing gear problems etc.

I have not seen any autopilots with nav capabilities, the ones I have seen have all required data from a chart plotter or GPS or computer, not enough buttons on them for entering waypoints etc but it probably won't be that long before someone incorporates either chart plotter functions in an autopilot or autopilot functions in a chart plotter.

Pondering on the above it would be a good add on for OpenCPN. I seem to recall that my slate specs said it had a GPS, accelerometer and rate gyro already in it and interface motor driver gadgets from the USB port are probably available already.

I seem to recall that the NMEA0183 protocol is a unidirectional protocol derived from RS422 and NMEA 2000 is bidirectional derived from RS485.

[Neptune's Gear]

Raymond, I don't follow - OPENCPN can already control your AP....
Even if the AP "Brains" were part of OpenCPN (is that what you mean?) , you still need the physical abilities of the AP - a computer cannot physically turn the rudder! It does instruct the AP what to do now - APA,APB etc....
Matt

[DotDun]

Originally Posted by Pelagic

Same here Bob. Just because a piece of gear can steer from waypoint to waypoint without human intervention. It doesn't me you should use it

Agree, those that don't understand what it's doing shouldn't use it.

[nigel1]

Pelagic is referring to skippering a super yacht (and no doubt not his own), and has ultimate responsibility for the safe navigation of that yacht, that is what the owner of the boat is paying him for.
The watchkeepers, although responsible for the safe conduct of navigation throughout their watch, may not have the same sense of responsibility towards the boat, after all, it's not their boat.
Like Pelagic, I get to study all the major maritime mishaps around the world, and you might be surprised at the number of casualty's that have resulted from setting an AP to steer to a waypoint.

On the other hand, when it comes to our own boats, which we have worked hard, and saved hard for, if we elect to have the AP steer to a waypoint, we will have had made all the proper checks before hand, and will continue to monitor the passage.

Like Jim said above, I have used the AP to steer to a WP when I am single handing. Last time was threading my way way through the sand banks to a known safe anchorage at night. The area is also strewn with pots. I felt my time was better used to keeping a look out rather than concentrating on the compass card. Rather a soft grounding than a a rope around the prop on a winters night.