Boat trim flaps remake. Help needed.

Discussion in 'The Projects Forum' started by Jacob J, Jun 24, 2013.

  1. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    Hello all

    I have a boat with lenco trim flaps on it, but it is only the electronic cylinders which are working. I have tried hooking them up to the 12v battery I have on board and they work very well.

    The control box or the buttons that originally was used doesnt work anymore.

    Ive thought of the following for a simple and cheap solution:

    I take two sets of spdt relays and hook them up like this:

    To activate the relays I use some low amp momentary push-buttons and also take the power for those from the battery.

    Are there any concern in doing so? Any improvements you could suggest?

    I have thought of how I could make some indicators, like and RED LED that turns on when those flaps reach there full extend, but have no clue atm. how this can be done.

  2. SgtWookie


    Jul 17, 2007
    That's a good start. Don't forget a properly sized fuse. Use your switches to ground one side of the relay coils. Use a 1k to 2.7k resistor across each relay coil to provide a current path when you release the switch, or the switch contacts will get burned.
  3. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    Okay, the fuse should be on the main wires going from the battery to the power rail, from where I draw the power to the relays right?

    I will place my switches on the ground side of the relay coils. May I ask what the purpose is of doing that instead of the positive side?

    Any thoughts on the LED indicator? I have thought of something like measuring the amps and get something out from that. My thought is, that when the flaps extend or retract all the way to the end, something happens to the power consumption, either it gets higher or lower, can't realy figure.
  4. SgtWookie


    Jul 17, 2007
    The fuse should go in the positive supply wire, as reasonably close to the battery as you can. Wiring between the battery and fuse will NOT be protected by the fuse, so you don't want that portion to be very long. Lead-acid batteries are capable of several hundred (or more) amperes of current during a short circuit, and under such conditions will cause even heavy-gauge wire to become red hot and melt, likely causing a fire.

    You may use an automotive-type circuit breaker instead; these will usually reset by themselves after a cool-down period.

    Switching the ground side is safer for the switch. I'm on my phone and don't feel like a long explanation.

    If you put an LED or lamp across the breaker, it will light when the breaker is open, if you have a separate fuse for the relay coils.
  5. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    Okay. Thanks to the help from you guys I now have fully functional trim tabs on my boat. Now I would like to take this remake a step further.

    It is possible to buy an original switchpanel with trim indicators in it. That is a very nice feature and I to would like to be able to see the position of those flaps.

    How can I make that happen? Any suggestions? Maybe it is enough to just be able to tell the flaps extremities and maybe it can be done by measuring a spike in current if such a thing happens when they can't get any further up or down?
  6. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    What about making a metal rod that is attached to the trim tabs and that runs through a metal hole that is fixed to the boat. Then attach a wire to both the rod and the metal hole and measure the resistance between those two measuring points? Could that be a solution or is that too unreliable?

    Another thought is something with a timer in it. I take a time reading of how long it takes for the actuators to go from one end to the other. I then make a setup that reads how long I push the button and makes and LED come on when that time has gone. This system tho seems to be very unpredictable and I guess it wouldnt work in the real world.

    The only thing I have found out about the switch panels with indicators you can buy, is that you need to calibrate those too. So maybe those are also a timer system...?

    Here is the calibration procedure for benette trim tab switch panel with indicators:

    Make sure that both trim tabs are in the full up position. When you power up the TPI the port and starboard displays will
    begin to flash alternately, indicating that the system is not calibrated. Press and hold both buttons on the TPI
    simultaneously for about 3 seconds. Both the port and starboard lower yellow LEDs will begin to blink. Using the Trim Tab
    controls run both Trim Tabs to the full down position (Bow Down on the control). Hold the control longer then
    necessary to ensure that both Tabs go fully down (this will not harm the system). A few moments after the Tabs are all
    the way down the upper port and starboard yellow LEDs will begin blinking. Again, using the Trim Tab Controls, run both
    tabs to the full up position. Make sure the tabs come all the way up. The upper yellow LEDs will then light up solidly
    indicating that the TPI is calibrated and ready to operate. If you wish to re calibrate the TPI at any time simply bring the
    Tabs to the full up position, hold both buttons down and repeat the calibration instructions."

    Further reading in this manual indicates that those trim actuators have build in sensors in them:

    But my lenco actuators should also be able to use that panel, so I am a bit confused if they have such sensors..
    Last edited: Jul 10, 2013
  7. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    This is the information I've got from lenco on their switch and control box:

    The control box for the indicator switch counts pulses from the motor to determine where they are.* No calibration is needed at all."

    Can anyone of you tell me what this means and if it is possible to duplicate?
  8. cork_ie

    Active Member

    Oct 8, 2011
    I am not familiar with Lenco Brand trim tabs. From what I have read online they are electrically actuated.
    Bennett use hydraulic cylinders operated by pressure from a seperate electro-hydraulic pump. Bennett have the option of sensor coils built into the hydraulic cylinders. Bennett are a reliable respected brand but the position sensors often fail after a short while ; salt water and electrics do not mix well, especially if continuous flexing causes damage to the insulation.

    Some other more modern units determine their position in the display panel/switch unit by measuring the little back emf pulses generated by the armature in the hydraulic powerpack motor. Assuming that there is no air in the system, then number of motor turns, while relevent solenoid valve is operated will give a reasonably accurate tab position.I assume it is possible to use this principal with your Lenco Units.

    I would assume you will need some form of circuit to count the number of motor pulses & motor locked current in fully extended and locked position. This would need to be stored in some form of memory. I have insufficient knowledge on how to do this but I am sure someone else here can help. Some electric window systems in motor vehicles also use this principal.

    Just for your information Bennett motors have wound fields - not permanent magnet and there are two field wires to reverse direction.

    As far as I remember Bennet Colours are:

    Orange = Switch 12V/24V +
    Blue = Pump in push mode = Tabs down
    Yellow = Pump in retract mode = Tabs up
    Red = Port Solenoid Valve
    Green= Starboard ValveRed
    Black = Pump connection Battery - (may or may not, be ground)

    Switch Connections.............................. Desired response
    orange ( + ), blue, red...............................Port trim tab down
    orange ( + ), blue, green...........................Starboard trim tab down
    orange ( + ), blue, red, green ....................Both trim tabs down

    orange ( + ), yellow, red........................... Port trim tab up
    orange ( + ), yellow, green....................... Starboard trim tab up
    orange ( + ), yellow, red, green................. Both trim tabs up
    Last edited: Jul 11, 2013