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Thread: auto trim tabs

  1. #1
    Join Date
    Aug 2001
    Posts
    380

    Default auto trim tabs

    I purchased auto trim system at the lbs this jan. seems to be a great job. One question however. When making a long turn the trims obviously try to rectify the natural lean. when the turn is finished the trims over compensate leaving us leaning uncomfortably in the opposite direction until such times as the system can rectify itself. I find the odd time when starting off from stop or slow the tabs can throw a strange lean on things. My question is do you switch off the auto tabs when stationary, slow moving or making big long turns ? [img]/forums/images/graemlins/confused.gif[/img]
    Work ? don't be daft , the suns out.

  2. #2
    GC1 is offline
    Location : k up your daughters
    Join Date
    May 2005
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    3,341

    Default Re: auto trim tabs

    Try re setting them, maybe they are not set right as this has to be done by you. Go along in the boat and when perfectly level press both bottom buttons together for about 5 seconds, this memorises that 'perfect position of attitude for the gyro, when you next press the centre auto button down for 3 seconds, it will keep your attitude to that set by you.

    You can re set it as many times as you want, if it was set squint it will stay aquint, it only takes a couple of seconds. The light will start flashing fast above the set buttons when they have locked on.

    Good luck.

  3. #3
    Join Date
    Aug 2004
    Posts
    1,097

    Default Re: auto trim tabs

    [ QUOTE ]
    I purchased auto trim system at the lbs this jan. seems to be a great job. One question however. When making a long turn the trims obviously try to rectify the natural lean. when the turn is finished the trims over compensate leaving us leaning uncomfortably in the opposite direction until such times as the system can rectify itself.


    [/ QUOTE ] I have this most noticeably when running upwind, if you are slightly off the wind to port the tabs compensate, if your bow shifts through the wind then you have tab and helm working together to roll you to port for a few seconds while the tabs recompensate, not sure if there is anything you can do about it, you can disengage the ATC and reengage when the turn is complete??? This will be worse if you have the tabs fitted with the double rams as they react slower as there is twice as much hydraulic oil to move about [ QUOTE ]
    I find the odd time when starting off from stop or slow the tabs can throw a strange lean on things. My question is do you switch off the auto tabs when stationary, slow moving or making big long turns ? [img]/forums/images/graemlins/confused.gif[/img]

    [/ QUOTE ] This sounds like you may have one tab moving slower than the other, obviously both must move together when trying to pitch the bow down when starting off, if one moves faster you'll have a roll induced - is it always the same, ie start off and any roll is always to the same side? If so then you may have an issue with the valve/piping/ram/tab on the side it leans towards - if you can try some tests when the tabs are visible to make sure they move together when they are supposed to. Again they will move at half speed when both are deflecting compared to when only a single tab is moving.
    Rgds

    Simon
    Ocean Deep
    Fairline Sprint
    Volvo 4.3GXi

  4. #4
    Join Date
    Aug 2001
    Posts
    380

    Default Re: auto trim tabs

    thanks for your replies.
    each time the engines are stopped the unit is reset.
    as for rolling when moving off lets look as a sinerao.- fat man standing on port side of boat, fishing, auto trim unit lowers port trim to compensate for fat man. no fish caught so we move to a new location and plant the throttles. port trim is still fully down and causes a big roll to stb side for a few seconds untill trim compensates. My point is the unit should be interfaced to the speed so when below a set speed the tabs retract.
    Work ? don't be daft , the suns out.

  5. #5
    GC1 is offline
    Location : k up your daughters
    Join Date
    May 2005
    Posts
    3,341

    Default Re: auto trim tabs

    I have just bought the trim tab indicator unit, it shows you clearly using led lights where the tabs are on both sides. Bennett's are doing them (and all their gear) less VAT for the boat show, which is 160 or so, see here http://www.phmarine.co.uk/

  6. #6
    Join Date
    Aug 2004
    Posts
    1,097

    Default Re: auto trim tabs

    [ QUOTE ]
    thanks for your replies.
    each time the engines are stopped the unit is reset.

    [/ QUOTE ] No I don't think that is right, the unit should remember your ideal, last set attitude stored in the unit even with power off, you may have an auto tab retractor fitted which retracts the tabs when the ignition is turned off[ QUOTE ]

    as for rolling when moving off lets look as a sinerao.- fat man standing on port side of boat, fishing, auto trim unit lowers port trim to compensate for fat man. no fish caught so we move to a new location and plant the throttles. port trim is still fully down and causes a big roll to stb side for a few seconds untill trim compensates. My point is the unit should be interfaced to the speed so when below a set speed the tabs retract.

    [/ QUOTE ] yes, with no flow under the tab it won't be able to achieve the roll correction, if you plant the throttle then you can beat the system and end up over compensated until the unit reacts, but a steadier takeoff will result in the unit detecting the correction and retracting some tab before you fly. The exact responsiveness (or apparant lack of) depends on several factors, the size of tabs vs the size of boat etc. As with cruise control in a car, it has some limitations. Good system IMHO though....
    Rgds

    Simon
    Ocean Deep
    Fairline Sprint
    Volvo 4.3GXi

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