Autopilot Confusion

[Pelagic]

Thanks Nigel you have put it in perfect perspective

The decision ultimately remains with the skipper.

I only wanted to note certain concerns

I think if singlehanded I would enable the Nav function for the situation you described.

[RaymondR]

Hi Neptune's Gear,

The computer or GPS or chart plotter tells the autopilot whether of not it's on track but it is the autopilot's internal processor which steers the boat. It appears that since both the autopilot and the device sending it the XTE, waypoint arrival and other nav data have processors and one of them could probably do all the work. So you one could either put a nav program in the autopilot or put the vessel control program into the nav computer and have it control the steering mechanism.

[colemj]

Originally Posted by RaymondR

Hi Neptune's Gear,

The computer or GPS or chart plotter tells the autopilot whether of not it's on track but it is the autopilot's internal processor which steers the boat. It appears that since both the autopilot and the device sending it the XTE, waypoint arrival and other nav data have processors and one of them could probably do all the work. So you one could either put a nav program in the autopilot or put the vessel control program into the nav computer and have it control the steering mechanism.

The problem with that is how cumbersome it would be. The autopilot would need the equivalent of a chartplotter screen, input and memory storage to be useful and the chartplotter would need the large power supply of the autopilot to power and control the drive unit. The only reasonable way this could be accomplished is to break it into distinct units - where you have a chartplotter in one unit and an autopilot drive in another. Which sounds familiar…

In your example, you are only thinking about the software necessary. The hardware is what makes it a no-go.

BTW, many chartplotters have complete autopilot control software incorporated into them. However, they only control the same brand/generation of autopilot.

Mark

[Neptune's Gear]

Raymond, that is what I meant by the AP "Brains" in my previous post. But I have to agree with Colemj above, you could certainly add the software at the PC/plotter side. BUT you still have to have the hardware, and a decent power source to actually control the rudder. (the hardware). I guess you could do this, but I'm not aware of anyone who does. You could use a mosfet based switching system to tell the AP pump/Motor to go to port or starboard, but you also need to bring info from a rudder angle sensor back to the device to confirm movement. This is pretty much what an AP computer does (plus a bit more of course).

[RaymondR]

Hi folks,

One of the problems we who live entirely on solar and wind have is power consumption. I spend a fair bit of time dreaming up schemes to limit power consumption and begrudge every small quantum I have to use particularly when underway at night or for an extended period of overcast skies.

Since I have taken up the much more enjoyable pastime of electronic navigation (General Montgomery said that he never fought a major battle during WW2 where the area of operations was not at the junction of four maps and paper navigation on a small boat is just as problematic) I sometimes find I have the computer the GPS and the autopilot on line all at the same time. I know they only pull an amp or two each but an amp here and an amp there and pretty soon you are talking about a real power draw.

To avoid the power draw I often find myself switching on the computer just to satisfy myself as to where I am then switch it off because I think it is drawing too much power. Then repeat the process 15 - 20 minutes later.

If say OpenCPN had the autopilot program included and all I needed was a port/starboard control signal on a data line from computer to the H bridge controlling the wheel drive and a USB fluxgate and GPS I would gladly rig the boat that way if only for the sake of the redundancy.

Addressing the autopilot with nav capabilities.

If the autopilot had a GPS engine connected internally all it would require to be programmed by a computer or slate would be a data connection, bluetooth, WiFi or wired. One could then do the route planning on the computer, transfer the waypoint and route data to the autopilot then switch the computer or slate off or to sleep until you needed a position check.

I'd bet a good bottle of wine that we will see this from the commercial guys within a couple of years.

[Andrew Troup]

I agree with Jim, Nigel and Pelagic.

I think NAV is a great facility, provided you don't overuse it, and provided you don't underuse it.

I would certainly set up a route in circumstances as described by Jim - I think it's a great way to use the technology - but I would want to have already become well familiarised with the procedures.
And to have scoped out the pitfalls under more forgiving circumstances.

And, like Pelagic, I see a lot of value in "flying the plane" for a portion of every watch.

And not just for the excellent reasons he gave: if I have to be there, keeping watch, I personally (and rather untypically) find it less boring if I am taking part in the process of sailing the boat.

In bad weather, it helps me sleep when off-watch, if I've "done a few rounds" with a punch-drunk helm.

Plus it can be fun, and instructive, trying to steer 'like an autopilot'.

In other words, making up and testing rule-based algorithms.

Two of the best I've come up with both relate to reaching and running in hard weather.

Under one routine, I adjust the phase, and the 'profile', of my steering correction relative to the run of the sea, until the boat stays under the mast.

(By "profile", I mean the waveform of my correction. It might for instance have a sudden onset and a slow decay (usually works better) or a slow onset and a sudden decay. By phase, I mean shifting the timing, sometimes almost 180 degrees out of phase with the 'natural' tendency)

Under the other routine, which works best on high performance sailboats, I monitor the attitude of the boat in pitch rather than heel, by comparing the pulpit against the horizon. A simple mental image of a hoisting rope, attached to the bow, running up to a pulley in the sky, and then taken to one side of the wheel, sometimes (often) works a treat, keeping the boat under the rig almost as well as, and with less mental effort, than the other (more powerful) routine.

Where this sort of practice really pays off (apart from racing, with a spinnaker, on the hairy edge) is when someone has to go up the mast in bad conditions to effect a repair.

But it also makes life on board more pleasant for those below, and more interesting for the person on the wheel. Watches seem to pass quicker when you're learning, and I would rather it was me doing the learning than the autopilot.

[colemj]

Originally Posted by RaymondR

If the autopilot had a GPS engine connected internally all it would require to be programmed by a computer or slate would be a data connection, bluetooth, WiFi or wired. One could then do the route planning on the computer, transfer the waypoint and route data to the autopilot then switch the computer or slate off or to sleep until you needed a position check.

I'd bet a good bottle of wine that we will see this from the commercial guys within a couple of years.

Again, many chartplotters do just that now, and have been for several years. Our Furuno CP can be put to sleep while still routing communications. Alternately, a free-standing GPS can take route input, send data to the AP and use little power doing so. You won't gain any power savings by putting those functions into the AP.

None of this is rocket science and all of what you suggest has been capable for at least a decade. The reality is that it does not make much practical or marketing sense for the manufacturers. If it did, the market certainly would be flooded with these units because, like I said, doing this isn't rocket science and has been capable for many, many years now.

(BTW, I like dark, chewy Zinfandels… )

Mark

[colemj]

Originally Posted by Andrew Troup

But it also makes life on board more pleasant for those below, and more interesting for the person on the wheel. Watches seem to pass quicker when you're learning, and I would rather it was me doing the learning than the autopilot.

To each their own - personally, neither of us feel our watches pass quicker or are more interesting or life is more pleasant when we are hand steering. We find just the opposite - the AP is there to make our life more pleasant and the watches more interesting and quicker. Both of us would rather read a book or fish or cook or watch the waves and flying fish or look at stars, or, or, or….

Mark