Using Auto pilot at very low speed

[baz]

Subject: Using Auto pilot at very low speed

Yesterday I was running the boat at low speed. Actually I varied the speed from neutral to the first forward indent and back again to modulate the speed between 0.5 kts to 3 kts. While doing this I had the Auto pilot set on "Heading hold".

My grandson was in the cockpit and was telling me he could hear a faint noise that sounded like metal-on-metal.

I decided to turn the Auto pilot to "Standby", and immediately the steering wheel locked up and could not be moved either way. Hmmmmm, this is not good, right? No matter, a moment or two passed and I was able to rotate the wheel freely but it did not alter the boats direction. Then a few moments later all returned to normal and the boat started to respond to the wheel inputs.

Does anyone know what was happening in this situation ? Is running the Auto pilot at low speeds as described above a big "no-no" ?

Loosing helm wheel control was quite alarming for me for the few moments it happened.

 

[scross]

I believe the Garmin autopilot system does not like slow speeds or being left on while the boat is stationary. At US CBP call in this week off Stuart Island we were on hold for over 20 minutes. At idle to hear on the phone. Got an AP error message as Our Journey rotated in the current. Turned off the AP immediately. The wheel was very stiff to turn for about a minute. Then all returned to normal.

 

[baz]

Vicki Foley and Al Thomas

Thanks for you quick response. So, it seems you experienced pretty much what I had.... and that the Auto pilot gets a real 'twist in its knickers' under the no speed and even low speed. I will try and remember to not have my Auto pilot engaged under these conditions.... although it's really quite easy to leave the Auto pilot engaged when being distracted. 😳 :roll:

 

[NorCal]

I had this when we first got out boat. Very nerve racking. Since the factory install does not have a rudder position indicator the rudder just goes hard over to one side and keeps trying to go in that direction. When it continues to go in that direction you will get the error message on your autopilot and the hydraulics are now locked up. To correct the lockup you need to turn the steering wheel in the opposite direction with all your might and it will break free. The first time I did this I was afraid I was going to break the steering wheel off.

This is another advantage of the smartpump with rudder angle indicator as the limits are programmed in the setup so the pump knows to not keeping giving more starboard once the physical limits of the rudder are reached.

So when going very slowly , this lock up can frequently occur.

 

[Wolfboy]

I had a similar experience a few weeks back. I have a 5200 series Garmin in our 2008 R-25. We were on an auto guidance route and stopped the boat to swap captains and do something else. We were in neutral long enough to drift sideways to our intended course. When I put her back and gear to resume our trip the autopilot went crazy. It couldn't figure out my direction or which way to go. It was as if I found the Alaska version of the Bermuda triangle. I didn't hear any grinding but it did push the rudder hard to one side and seem initially reluctant to let me take over the steering. I shut down the autopilot and continued for awhile steering manually. After a few minutes I re-started the autopilot and everything was fine again. I thought it was a software glitch but kicking around on the forum here I found similar issues reported by others.

On the other hand, I've been doing some trolling lately with the boat barely in gear and the autopilot on the zig zag pattern and it has been holding a course just fine. I think I was going between 1.5 and 2.8 mph according to the gps. Maybe there's a minimum speed you need to keep it happy.

 

[Navigator's Son]

I thought it was just my system, thought maybe I had accidentally hit Engage Circle instead of Follow Route. I was heading to Canada through the San Juans, trying to call Nexus. I was following a group of others who were traveling maybe at 7 knots, and I had to slow down so I could hear the phone. Suddenly my boat made a sharp right turn and held it, veering away from the charted line.

I also noticed the closer I zoomed into the map, the more "off" the boat is from holding the line. Autopilot is a fantastic tool, but nonetheless, you need to be standing over it all the time.

 

[JamesTXSD]

There are operating limits. Ever try turning cruise control on in your car when going 2mph? Or turning on the autopilot in an airplane when near stall speed? It isn't an issue with the equipment being at fault - just not designed to be used when barely making way. I wouldn't use autopilot when wide open, either - too much that can happen (like debris in the water) where you need to be right on top of controlling the boat.

 

[Whidbey Cruiser]

I just started using the auto pilot for the first time trolling at 1.5-2.5kph last weekend and it seemed to work just fine. There is a clicking sound when first engaged but it certainly did not sound like metal on metal.

I was pleasantly surprised to see the fuel economy using the trolling slow valve gear at .2 gallons per hour. I can troll for 5 hours for under $4!!

 

[ixlr8]

I have used my AP, controlling it with the remote, on my 27OB numerous times while idling around one of our local harbors and, apparently luckily, I have never had an issue.

 

[Red Raven]

The effectiveness of Auto Pilot at low speed is highly dependent on the current and wind conditions. Clearly if the current is near the boat speed over water and across or against the boats heading the AP controller is going to struggle to hold any course. I have often been in current above 1 or 2 knots without any visual indication. I often have to turn the AP off when going at a near idle speed. It is not surprising that it becomes ineffective at low speed in all but the most calm conditions with no current.

 

[baz]

Thanks for all the responses for my OP. The one thing that y'all need to be aware of is that Auto pilot can be a bit 'squeamish' under certain situations. I say this as on my R25 Classic and now the R29 CB I've had Auto pilot do things unexpectedly.

The issue on my R25 Classic was far more serious for me. At times when holding a heading I would use the two soft buttons to change heading by 1º. When using the the Auto pilot in this way when the boat was a few months old pressing one of these buttons caused the Auto pilot to suddenly steer the boat to starboard as if it was acting on the MOB feature. This was an ongoing issue that stopped me from using the Auto pilot until Garmin technician came to the boat several weeks later. The Garmin technician spent 5 hrs with me on the boat while cruising about and each time I pressed the soft button to change 1º to starboard while Heading hold was active the boat performed the MOB. The Garmin technician was watching me carefully and he tried the same thing but could not cause the Auto pilot to do the MOB. He thought I must have a 'magic finger'. 😉 No matter, he got on the phone while we were on the water and spoke to Garmin's Auto pilot software guru in Sweden. After some 10 mins it was decided there was an unintended software glitch causing the issue and in short order the onboard Garmin technician change a few settings per instructions from the guru. This fixed the issue for me.

You can read the exploits for this R25 Classic Auto pilot issue I posted in June 2009 here
http://www.tugnuts.com/viewtopic.php?f=5&t=556&p=4223&hilit=circle#p3716

Software has its limitations as does hardware. WE all need to know how to address these weird happenings and do our best to avoid them and know how to resolve them least we get ourselves into serious trouble.

I use my Auto pilot very frequently, but with my past experiences with it I'm always on the 'alert' and the odd unusual sounds that the Auto pilot's mechanism can make is a sure sign something is not right.

Jim: I would never ever use my AP inside a harbour or any place in close quarters to other objects.

 

[aintmissb]

I think this is obvious to most contributors to this thread, but one reason an AP doesn't work well at low speeds is that these boats don't steer well at low speeds. There is not enough water going over the rudder and the rudder is too small. I would rephrase this as saying, "anytime your boat is hard to steer by hand, it will be at least as hard for the AP to steer it".

 

[bill46]

I have used heading hold at 4-5 MPH many times without issues.

 

[baz]

I have used heading hold at 4-5 MPH many times without issues.

...and so have I. 🙂

 

[ixlr8]

I think this is obvious to most contributors to this thread, but one reason an AP doesn't work well at low speeds is that these boats don't steer well at low speeds. There is not enough water going over the rudder and the rudder is too small. I would rephrase this as saying, "anytime your boat is hard to steer by hand, it will be at least as hard for the AP to steer it".

I wonder if that is why I have so far had no issues with the AP at idle speeds with my Outboard powered boat, but the inboards have issues.

 

[baz]

I think the most basic issue the AP has is when its left engaged (especially with Heading hold set) with engine in Neutral. The AP then starts to 'hunt' and will obviously have a hard time. It possibly is an end-case for the AP software and difficult if not impossible to deal with regardless of the boat having a traditional rudder or an outboard motor.

 

[Tuggernaut]

The auto pilot will def work better at low speeds on an outboard vs inboard on these boats. As described above, the inboard version of these boats has a small rudder and not enough water flow over the control surface. For an outboard your rudder and prop are both turned giving you actual directional thrust. Obviously with the engine in neutral on either type of drive will lead to control problems. It's important to realize the limitations of your equipment and the current sea conditions before relying on automated systems. I think people hear autopilot and assume the vessel will run itself when in reality it's simply a task management tool.

 

[Fisho]

Great thread and some good advice. My 21EC has the Lowrance/Simrad Autopilot running through cable steering. All larger boats will use hydraulic steering that has a few different complexities. The 21EC does have a large rudder and good keel that makes the autopilot more effective I suspect. I use my autopilot all the time, maybe 90-95% of the time while cruising at all speeds. I agree that at WOT better to not be on autopilot for obvious reasons but for all other circumstances, even at idle speed works ok within limits. At slower or idle speeds (when trolling) wind and currents can be an issue. For the most part I use the autopilot to follow routes I have programmed, often with 100-200 waypoints, taking me through channels, between channel markers, away from rock bars etc etc. The only problem is sharp turns which are problematic. In these cases I just disconnect the autopilot in the sharp turn and reconnect a few minutes later once into the smoother curves and straights. But the golden rule is when using autopilot you must keep a careful lookout since the smoothing algorithms, the variable GPS signals and winds can put you on a slightly different course than a previous cruise. Remember the autopilot operates in real time and recalculates the route from waypoints using the algorithms and GPS signals afresh each time. For the most part the autopilot at cruising speed keeps the boat within 10-20m of the route I have programmed and often within 5-10m. Using the autopilot to just hold a heading at any speed is almost foolproof but again I prefer not to use at WOT. Simply autopilots are brilliant but you must calibrate them carefully according to the manufacturer, have them set up appropriately for your particular boat and understand their limitations since there is a lot going on between the chartplotter, the particular chart you have and it’s accuracy, variable GPS signals, winds and currents and all the electromechanical components that transmit the signals to the rudder. From my experience most autopilot issues arise from poor calibration and poor autopilot settings. They are however brilliant. Enjoy.