How Does Autopilot Work?

[Alaskan Sea-Duction]

In the search for my retirement boat, I have found a lot of them have an autopilot. Never having a boat with one, how does it work?

 

[C lectric]

Usually quite well.

Of course they can develop problems like all devices but if a decent unit for the vessel was chosen and set up correctly it should perform for many years with minimal service or problems.

On a trawler or any boat that will spend a lot of time running slow an AP can be a godsend. It can free you from constant, tiring steering corrections and keep you closer to your desired course.

You must still, of course, maintain a proper watch. Collisions and groundings are not nice.

SOme can be tied to a GPS for track control but even without that it will make long, multi hours, muti day runs easier.

It will take some experience to learn how to get the best out of it.

In rough seas some units can do better than operators particularily if the rough stuff goes on for a long time. However, it cannot anticipate a slew from a large wave, it can only react once the boat starts to slew so be carefull.

 

[LarryM]

Most marine autopilots provide two basic modes of steering the vessel, AUTO and NAV.

The AUTO mode is used to make the autopilot steer the boat automatically on a set course. A compass sensor in the system provides directional information to the autopilot. When engaged, the autopilot uses the current boat heading as the set course until disengaged or overridden.

In NAV mode, the steering information received from the external GPS or chart plotter alters the course to direct the autopilot to the destination waypoint. It can also follow a route consisting of multiple waypoints. It uses waypoint and cross-track information from the navigation source to follow the selected route. This has the added advantage of being able to compensate for wind and current.

There are additional adjustments to match the autopilots response to the vessel's handling characteristics and to compensate for sea conditions.

More sophisticated systems offer advanced features and modes for specialized functions like fishing or MOB, but in normal pleasure boat use, the AUTO and NAV modes are the most common.

That is about as simple is I know how to describe autopilot usage. Hope it helps.

Finally, always keep a good watch when the autopilot is engaged. No matter how well it steers your boat, it cannot see.

 

[C lectric]

Or did I misread your question , jumped to a delusion, and you meant literally 'How does it work' rather than ' How well does it work'.

Fooey, Oh well here goes again. I'll leave the other post alone.

Generally they use a compass, a modified magnetic moving card type with a sensor or a flux gate, which has no moving parts and can be hidden, to send the electronics a signal to show it the difference between where the vessel is actually headed and where you want it to go.

The electronics then direct the hydraulic pump unit through a hydraulic cylinder to control the rudder for corrections.

In some smaller units an electric motor may directly move the steering wheel, a belt, to effect the rudder control.

There are other types but these are the most common on typical pleasure vessels.
Man, that's simplified.

 

[Pau Hana]

Basically, an autopilot system allows the vessel to follow either a pre-plotted course or hold an unplotted course with minimal human interaction. The system usually consists of the course computer, a fluxgate compass or heading sensor, some type of drive mechanism, and a control head unit.

The course computer can interface with your plotter to receive direction commands.

Whether the autopilot is following a preplotted course or is simply holding a course, an autopilot is a great tool for easing fatigue and keeping the skipper fresher and more alert.

 

[Peter B]

Yeah, and after doing one unbroken 120nm leg just after new year, including having my pilot seat break under me, (no, I'm not that heavy, it's just...well...old...that's all)......
I WANT ONE...!

 

[ARoss]

Yeah, and after doing one unbroken 120nm leg just after new year, including having my pilot seat break under me, (no, I'm not that heavy, it's just...well...old...that's all)......
I WANT ONE...!

Based on the age of your boat, unless you did a steering upgrade you probably have the old chain/rod steering system in the vintage CHB/Marine Traders. Here's a link to an old thread where several of us discussed wheelpilots (usually installed on sailboats). Mine's still going strong.

Hmm. In rereading that thread, I see you were looking for an autopilot back then too! You need to "git er done"


http://www.trawlerforum.com/forums/s3/5-most-useful-improvements-your-boat-1585-2.html

 

[BaltimoreLurker]

Hmm. In rereading that thread, I see you were looking for an autopilot back then too! You need to "git er done"


http://www.trawlerforum.com/forums/s3/5-most-useful-improvements-your-boat-1585-2.html

And e-Bay is your friend for stuff like this. That and a Google Alert. It's amazing what eventually turns up.

 

[LarryM]

If I remember correctly, your Sea Ray 300DB has Morse/Teleflex cable (push-pull) steering with a tilt steering wheel. The steering cable connects directly to the rudder arms. If so, you can probably use either a Comnav 1420 or Si-Tex SP-80, both of which are available for cable-drive steering. These autopilots replace your existing steering drive assembly (behind the dash) with an integrated autopilot drive unit that connects directly to the steering cable. They have a separate control head or remote. I'm not sure if they are available with a tilt wheel, so you may have to go with a fixed steering wheel angle. I would definitely check with the manufacturers for recommendations on your specific application.

Raymarine makes a 'Sport Pilot' that bolts directly to your existing steering system. They are generally used on smaller boats, but if your steering load is light enough, this could be an option.

I doubt that a belt-driven 'wheel pilot' often found on sailboats would work because of the steering wheel size and angle in your SeaRay.

From experience in a prior boat, I can tell you that one of the most important aspects of this installation is to make sure that your existing cable steering is in PERFECT condition with MINIMAL slack and friction. You should be able to turn the wheel with one finger. This would be a good time to install a new, high-quality steering cable.

Beyond that, I would check boating publications and boating forums for more information on autopilots for cable-steered boats. Specifically, try to find feedback on this type of autopilot installed in boats similar in size and hull form to your own.

If your boat happens to have hydraulic steering, you have many more choices, Simrad, Furuno, Raymarine, Garmin, Comnav, Si-Tex, and on and on.

My advice is to take your time, do your research and install it properly. I mostly single-hand my boat now and love the freedom afforded by a solid, reliable autopilot.

Good luck.

 

[Brooksie]

Autopilot is a great safety device too (if used correctly) It can give you time to check navigation and prepare food on long passages, I have even set my oven timer and taken 1/2 hr nap under radar proximity alarm on an all night passage.
One boat has a Bendix CS21 chain & sprocket type 25 years old and still works great the other has a Robertson 3000 hydraulic also old also works great so good experiences all around here with autopilots.

 

[Alaskan Sea-Duction]

Thanks everyone. No I am not putting AP on the Sea Ray (has manual hydraulic steering) as I am not adding anything new to it. When looking at Trawlers I have seen AP on most and wondered how they work. I know understand how, will just need to play with it when I get it.