Wednesday, March 7, 2012

Autopilot - Part 3

     I've been trying to find a good spot for the autopilot computer and pump, so I spent a lot of time staring at the boat, looking around in the engine room, under the dash, and a few other spots near the helm. The pump needs to be spliced into the existing hydraulic steering lines, while the computer can be placed almost anywhere, as long as the required wiring and network connections can be made. The computer requires a power feed, input from the rudder feedback unit, wiring to the pump itself, a network connection, and bonding system connection. So, keeping it near the dashboard and main wiring harnesses is a good idea.
     After looking all around the boat, I decided against placing the pump in the engine room. There are no really good spots in a 340 down there, and service would be easier (and hopefully not needed for a long time!) if I placed the pump just to starboard of the helm station. There is an easily removable storage bin next to the helm, and there is sufficient room to locate the pump and computer in this area. It is also dry and well protected. So, I built a bracket for both items out of 3/4 plywood, and sealed it with 3 coats of marine varnish. It looks like this:

     The pump and computer are both on the same bracket, which will be screwed to the decking behind the storage bin. If I need to service anything in the future, I can simply unscrew the bracket, and slide the whole assembly out. Also, much of the wiring is already completed on the bracket, obviating the need to do it in the boat. A terminal strip is on the right side, to facilitate the bonding system connections. Both the computer, and the shield cable from the network are connected to it. In the boat, I'll connect the terminal strip to the bonding system, thus providing an additional level of RF noise rejection.
     On top of the pump, I added three isolation valves. If the pump ever fails, I can close the valves, and retain manual steering. Once in port again, repairs can be handled on my own terms. More to come....

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