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AP26 Simrad Autopilot not holding course

Discussion in 'Electronics' started by CSkipR, Dec 30, 2011.

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  1. CSkipR

    CSkipR Member

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    Haven't used the boat in several weeks and went out all day yesterday offshore fishing. The autopilot in the auto position would not hold a steady course as it would sometimes drift off course a few degrees. Not major degrees but 4-5. Seas were 2' or less. Looking at our trail behind the boat it was pretty squirrly. Need ideas as to what I should I check for? Thanks
  2. K1W1

    K1W1 Senior Member

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    Hi,

    Start with something simple like slack in the link between the feedback unit and the rudder(s)
  3. Norseman

    Norseman Senior Member

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    Magnet or tools close to the FluxGate compass..?
  4. Swamp fox

    Swamp fox Member

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    Is there an advanced autopilot mode that accounts for drift/current? I have a Furuno Navpilot with the option of standard/advanced mode to hold a compass course. In the advanced mode, it keeps the course you set while correcting for drift. (This is different than nav mode.) Just a thought.
  5. dennismc

    dennismc Senior Member

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    If you have a NAV mode that steers by an off course setting, say .02 nm this will help the pilot steer a tighter course than by compass , that's been my experience with a Simrad AP45.
  6. CSkipR

    CSkipR Member

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    K1W1 - no slack between feedback and rudder

    Norseman your suggestion might be the answer. Where is the fluxgate compass normally located? In the lazzarette with the rest of the autopilot accessories? When we went out fishing yesterday I clamped visegrip pliers on a fitting located in the lazzerette to be able to stop/start water flow drainage from the livewell. Do you think that may have caused it.

    Thanks, Skip
  7. dennismc

    dennismc Senior Member

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    That may have increased the fluxgate offset degrees, doubtful would start course S ing but you would know how to check that out.
  8. Ozzie

    Ozzie Member

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    Usually it's located closer to the center of vessel.
  9. NYCAP123

    NYCAP123 Senior Member

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    If the problem were the location of the fluxgate compass this would have been a problem from the start. It could be having a problem, but I think that Dennismc hinted at your actual situation. Auto setting will continually try to keep your bow facing to the directed destination, however it will not correct cross track error. So you could easily end up considerably off your course line in any kind of sea and the result of the continual bow corrections will be "our trail behind the boat it was pretty squirrly". The Nav or track setting will hold you on your course line (or more correctly, correct to bring you back to your course line and then counter-correct to straight you out on that line).
    While we're on this subject a lot of people don't seem to realize that an autopilot reacts after the fact. It is not intuitive. In a heavy sea with a smaller boat one needs to go to manual stearing or they could find themselves broaching when they come down the wave's face into the trough. Once followed a 43 Ocean out of Hilton in about 14' seas. One minute I'd be looking at his bow rail and the next looking a his mate puking off the stern, then back to the bow rail, until I told him to go manual.
  10. Capt J

    Capt J Senior Member

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    None of the above. The compass is usually mounted either in the bilge under the salon floor or that foward access hatch in the floor, or it is mounted in the brow of the flybridge, but that's not the source of your problems.........

    You have the sensitivity turned up too much in the head unit....causing it to oversteer back and forth, this sometimes has to be adjusted on some boats depending on it's running angle/fuel load etc.......I forget what it's called in the simrad's menu, and I don't have a unit in front of me......but you get to the menu (I think by pressing stby 2x in a row).....and then get to the sensitivity/gain or whatever simrad calls it and dial it back 2 notches usually....sometimes 1 notch does it........and it should track straight again......
  11. NYCAP123

    NYCAP123 Senior Member

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    Good info cap, but I still think I'd go to trac first, to confirm there is a problem, prior to adjusting the setting since it was working fine before.
  12. Capt J

    Capt J Senior Member

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    It'll do it on track as well......because it's oversteering past center. I've had this problem on several yachts with a Simrad AP, and I can bet money it's in the setting for the sensitivity or reaction.....that's what it has always been.....the Simrad unit adjusts compensation every 40 seconds.....so it oversteers, then 40 seconds later oversteers back.......
  13. NYCAP123

    NYCAP123 Senior Member

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    Not saying you're wrong. If the setting was right to begin with, before I'd mess with the settings I'd take it out and put it on trac first. If it is the settings it will in deed do it as well, but if it doesn't, he was just working in a breeze or current on auto instead of trac.
  14. AMG

    AMG YF Moderator

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    If your autopilot is not connected with a GPS or other speed sensors, you must select the speed, HI or LO yourself. Another issue could be air in the hydraulic pump...

    A good start anyway is to have a manual, you can download it here: Downloads for AP26 Autopilot | Simrad Yachting

    Attached Files:

  15. CSkipR

    CSkipR Member

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    Okay lots of good info here Capts. Let me clarify that I was using the autopilot in Auto not in Nav.
    AMG - I do believe the autopilot was set on LO previously not sure how it would have changed and not sure what difference that makes. Will read up.

    Thanks again will keep everyone posted once I identify the cause.
  16. CSkipR

    CSkipR Member

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    AP 26 Simrad

    AMG,
    Well it turns out it was a simple correction. The autopilot is connected to GPS but when this problem occurred we were just running a straight line on Auto. Turns out a friend who was running the boat had inadvertently pressed the auto button and the autopilot had moved to the Hi position creating an oversteer problem at high speed.
    Thanks to all for your information.
    Nice to find out it was something simple and didn't cost anything to fix for a change.
    Skip
  17. AMG

    AMG YF Moderator

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    Yes, and it is always nice to find such problems before getting a technician onboard!

    When it comes to electronics behaving strange, I usually turn them off and restart to get them to work properly again....
  18. Bill106

    Bill106 Senior Member

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    setting adjustments

    It sounds like there still is room for improvement in the pilot calibration. Simrad, like many other pilots, uses two sets of steering parameters high and low speed and switches between them based on speed from a connected (and configured) GPS or paddlewheel input. Most often the self learning mode does a good enough job when done by the manual instructions but the manual also says to do it at a slow speed. The unit then extrapolates high speed parameters from that data but the correlation isn't always linear.

    I've found on many high speed boats, especially ones with power assist steering, it helps to do the autocal routine at cruising speeds instead. Simrad recommended this to me years ago when we had similar problems when manually inputting different parameters didn't seem to help. You absolutely have to have plenty of open room to do this and make sure you are holding on tight as it may very well jink the boat violently at first. Also make sure it is configured and recieving GPS speed data so it knows what speed you are travelling at and will reprogram the high speed parameters accordingly. You may also have to adjust the low/high transition speed if it differs much from your planing speed.