Tracking Performance

Quitsa

Quitsa

Furuno Super Fan
I have a 711C on my 38' twin Diesel sportfishing boat with an SCX-20 as the heading and GPS data source. When steering a course to a waypoint in NAV mode at planing speeds, the autopilot will generate a pretty big cross track error -- 20 yards or more -- before initiating a course correction. My course track ends up looking like big sweeping S curves around the course line. If I switch to Auto course mode using the bearing to the waypoint as the set course, it steers far more tightly around the course line, usually deviating by only a few yards. I have XTE set to "precision" in the NAV mode and the self-learning is on full auto.

There would seem to be something in my settings that is affecting the NAV mode steering but I can't for the life of me figure out what to change. Any suggestions for what I should look at?
 
Can you try to run NAV mode on Economy instead of Precision and see if it performs better? I know it sounds counter intuitive but I have seen it work better on some vessels once or twice.
If that does not help, run the rudder test that is in the diagnostics menu and post a picture of the results. Run the test in the water with the engines running and gears in neutral.
 
Same setup on my 43' sportfish and I've occasionally seen the same 20+ yard deviation on plane in ECO mode but it seems to be pretty rare, normally tracking pretty close. Haven't been able to put my finger on what causes those occasional 'detours'.
 
Same with my 46' sportfish. Precision is the only mode that runs a straight line for me, but I always end up with a hard "S" on every turn because of it trying to get back on the course line. The only correction that I have found is to tap the restart after the turn is mostly complete. Economy is a slow deviation, almost always to port, but never seems to correct itself eventually throwing an XTE alarm. I have yet to figure out what "Course" is for, it just seems to do whatever it wants in that setting.
 
gtstang462002 said:
Same with my 46' sportfish. Precision is the only mode that runs a straight line for me, but I always end up with a hard "S" on every turn because of it trying to get back on the course line. The only correction that I have found is to tap the restart after the turn is mostly complete. Economy is a slow deviation, almost always to port, but never seems to correct itself eventually throwing an XTE alarm. I have yet to figure out what "Course" is for, it just seems to do whatever it wants in that setting.
Click to expand...
Course is a little more complex but you are kind of correct. haha It will make a new course after you dodge something, rather than returning to your original route line. Essentially like manually pressing restart after you move the boat off course for whatever reason.
 
FishTech said:
Course is a little more complex but you are kind of correct. haha It will make a new course after you dodge something, rather than returning to your original route line. Essentially like manually pressing restart after you move the boat off course for whatever reason.
Click to expand...

I think there are a couple of issues getting mixed up. In auto mode, there is a setting for "course after remote." It gives you a choice of "present course" or "previous course.: In Nav mode, I think the only option after dodging to avoid the sharp turn back to the course line is to hit "restart" on the navigation bar on the plotter so it reclaculates the course from the current position and sends that to the autopilot.

As for the steering accuracy issue, one setting that I might play around with is the "response" setting. I have it set to auto now. It would seem that if it were set to a high number manually, it would shorten the response time to a XTE and keep the boat closer to the course line.

The other thing I notice is that the autopilot really does not like the trim tabs. Using the trim tabs will really mess up the steering accuracy unless I turn off the autopilot and make sure the boat is running straight at zero rudder with the trim tabs deployed.
 
Under Nav Mode there are three options for the type of Nav Mode you would like to run. Course, XTE(Precision), XTE(Economy). My previous post was describing the behavior of "Course" Nav Mode. This is similar to the way Auto Mode has an Advanced Auto setting that behaves differently.

Response would be a good setting to start making adjustments with. You could also switch Deviation Level to manual and try a lower number.

Trim tab adjustments will annoy an auto pilot. It is changing the steerage characteristics of the vessel, which is what the processor has spent all of its time learning. Keeping Sea State on Full-Auto should help it get past these adjustments as fast as possible.

Also ensure that nothing is selected in the NavPilot for STW. I have seen paddle wheels jam up and confuse the pilot. "SOG says 20 knots while STW says 0 knots"
 
Stupid question, where is the response setting at. I have been through the entire menu structure and must be missing it somewhere.
 
It turns out that the response setting is the key. I changed mine from auto to manual and used the highest setting. Running in rough conditions using lots of trim tab, which in the past produced the worst performance, the boat tracked like the proverbial arrow in NAV mode. The deviation stayed within 5 yards and was even better than that much of the time. The display was showing 0-1 yard deviation for sustained periods.
 
Certainly the pump will be working more often. The main negative associated with having response too high is over-correcting.

Generally speaking, when response is too low, if you looked at a bird's eye view of your track overlayed on your route, you'd see long, sweeping "S's" where the autopilot 'waited too long' to correct a course deviation, over and over. When the response is too high you would see short, sharp "S's" where the autopilot was adjusting rudders/engines too much for slight deviations between HDG & CTS. With response set properly you will hopefully see neither. In tough conditions (wind/current/seas), high gain or response is preferred. High response in calm or moderate conditions may cause your steering to be overly busy with frequent and unnecessarily large changes in heading. Not-so-great autopilots benefit from the user regularly adjusting response to account for conditions (this is what 'auto' is supposed to do).
 
I was off shore this weekend and noticed the large deviations again and remembered this thread. Changed from ECO to Precision and also began to play with response level. Selected a new waypoint and the boat started to turn...and turn and turn and turn. Damn, I lost the high pressure steering:mad:. 75nm run home with manual steering is not fun.
 
Ever since I changed the response setting from auto to the highest manual levels (8 or 9), my boat will stay with 8-10 yards of the course line no matter how rough it might be. If it's calm, it often stays within 5 yards. Much much better.

I am sure it is very boat-specific.
 
gtstang462002 said:
When all is right, precision hold you dead on the course line.
Click to expand...
I LIKE that RPM gauge in your data box, great idea!! I just added engine gateways last week and have been toying with the Dual Inboard page to get it just right. I hadn't even thought of a gauge in the data box and that would be so much better than the 3 box screen I was trying.

BTW,I assume that there is a limit to the number of data boxes on the dual inboard page. No warning, just disables the option to add anything new.
 
Bayhouse said:
I LIKE that RPM gauge in your data box, great idea!! I just added engine gateways last week and have been toying with the Dual Inboard page to get it just right. I hadn't even thought of a gauge in the data box and that would be so much better than the 3 box screen I was trying.

BTW,I assume that there is a limit to the number of data boxes on the dual inboard page. No warning, just disables the option to add anything new.
Click to expand...
Yeah, I noticed that limit also. I am slowly working my way through converting all of my old analog gauges to NMEA2000 and adding fuel flow sensors. My goal is to get another 9 inch TZT3 and use that in place of my old analog gauges on the dash while running. But while trolling it would give me an additional screen to use for fishing at my helm.
 
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