Bennett Automatic Tab Controller

Project date: 2004

This can be classified as a toy, but it really is a nice thing to have. It is an add-on to the Boat's Trim Tab system, and the basic principle is that it "learns" the attitude of the boat, then keeps the boat at that attitude by automatically adjusting the tabs.

This tab system is accomplished by the use of a sensor - sort of a solid-state gyroscope that keeps watch on the current attitude of the boat. This information is sent to a CPU which controls the trim tab switches. In this manner, the CPU will automatically adjust the tabs via the switches to keep the boat at the desired attitude. This is a simple installation, and only requires a connection to the tab switches.

The hardest thing about this project was to find a location for all of the components. The kit included pre-built wire harnesses, so I had to work with specific wire lengths, and everything had to be within a certain distance. The shortest distance I had to work with was between the trim tab switches and CPU module - about 4cable ft.



The first location to determine was the location for the CPU. Bennett recommends mounting the CPU in a flat area behind the dash. Unfortunately, the dash on this boat is sealed, and the bottom of the dash cannot be accessed like many boats. I selected an area behind a small panel atop the hanging locker in the cabin. This location was just within the 4ft limitation of the cable to the trim tab switches. The CPU has a reset switch that may have to occasionally be depressed, and the panel the fire extinguisher is mounted in is easily removeable - so it is the ideal location.

The next location to be determined is for the "gyro" sensor. This box has about 15ft of wire, so it's location was not as critical. From the instructions, the manufacturer recommends not mounting the sensor too high - as on a flybridge, because it can affect the sensing of the unit. The unit does not have to be mounted along the centerline of the boat.

I decided to mount the sensor below the helm seat, which is actually the rear berth's ceiling. The helm seat base includes two removeable storage bins that provide storage for life jackets and other essential items. There was just enough room after removing one of the storage bins for the sensor. The sensor was located in the area shown by the red circle.

The next step was to locate the control unit in the dash. One word of caution - the LED indicators may be hard to see in direct sunlight, especially if your line-of-site view is a bit off axis.

The last step is to connect everything together. The only difficult item here was connecting the CPU to the existing trim tab switches. The instructions indicated to connect the wires by color code. However, the wiring harness in the boat uses a different color code - so it was not a simple matter to match up the wire colors. A bit of research, a review of the better-than-average boat manual, and a confirmation phone call to Bennett tech support resulted in finding the correct connections.

If you will notice, when depressing the Port Tab, +12VDC appears at the PORT TAB terminal, and either UP or DOWN, depending on which direction the switch was depressed. The starboard switch operates in a similar manner. For my boat, the wiring cross reference color code to the boat wiring harness is as follows:
     - White/Pink = Yellow
     - White/Brown = Blue
     - White/Yellow = Red
     - White/Black = Green

Conclusion: The ATC system is a bit on the expensive side. The ATC system operated flawlessly, and it was really cool that I did not have to constantly adjust the tabs. The only issue I discovered was that it appears that over time, as the system automatically adjusts the tabs, eventually you will come to the "end-stop" of one of the tabs. When this happens, you have to take the system out of automatic mode, and re-center the tabs, then return the system to operation. This happens more frequently in rough sea conditions, so I suspect the tab system is more "active" during these periods. But notwithstanding this minor annoyance, the tab system is fun to use.




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