Helm Station

I have  -finally-  (almost) completed the Helm Station. From the very beginning of deciding to build Unicorn, I intended to monitor every aspect of the propeller drive motor so I can get a complete picture of how the motor is performing. The gages on the Helm Station are:

1. Voltage across the motor terminals
2. Current thru the motor
3. RPM
4. Motor housing temperature
5. Accurate low speed speedometer
6. Battery voltage

Note that the voltage and current are at the motor, not the battery. This will tell directly show how much power the motor is using. Combining that with boat speed, motor rpm, and motor temperature (and a lot of maths) I can figure out electrical losses and hence overall motor efficiency. I wanted to do this for two reasons. The first just to satisfy my curiosity, the second to have a starting point to compare the efficiency of different sizes of propellers and to see if and how much a Kort nozzle (also called a ducted propeller) as used on some large tug boats effects efficiency.

This is the wiring diagram of the electrical system not including the bow lights, bilge pump, or ballast tank pump (which have their own batteries). It took only 12 revisions to figure this all out. The power comes from a 52 volt lithium battery. The drive motor runs on 52V and is directly coupled to the propeller shaft. To facilitate forward and reverse the motor has to be bidirectional. The current meter reads positive and negative current to show which way the motor is turning.

52V is stepped down to 12V for the rest of the components. The large black thing with all the lines going to it is the main fuse block. Every component in the system has its own fuse.

This was my electrical workbench for the last couple months at its most messy.

The blue tape on one spoke of the ship's wheel is to keep track of the angle of rotation of the wheel.

This turned out to be critical.

Three confusing non-obvious pictures of the inside of the Helm.

Another picture of the guts of the Helm.

I eventually gave up trying to organize the wiring.

And here it is mounted in the boat.

Mostly completed. The last strip of wood just forward of the wheel needs to be varnished and a couple more trim pieces still need to be cut, attached, and varnished.

One gage that is not mounted on the Helm Station is the speedometer. The boat's speed is too low for a conventional speedometer. Fortunately the bass fishing industry has an amazing solution. Apparently in fishing competitions it is helpful to know very precisely how fast your bass boat is going. Some clever inventor came up with an all mechanical direct read drag-based speedometer.

The orange ball is solid steel and quite spherical. The gage is mounted on the gunwale of the boat and the ball hangs down in the water. As the boat moves thru the water, the ball is pulled back at an angle. It turns out that angle changes as the boat goes faster or slower, and that is used to measure speed very accurately! Unfortunately for Unicorn this means the speedometer gage can't be mounted on the Helm Station but the thing is so cool I couldn't resist using it. It will probably be mounted just to starboard of the Helm Station so the navigator can glance over at it to see how fast Unicorn is going.

Next up: The ballast tank electrical stuff and the wooden box that covers the ballast tank plumbing. The box will end up looking like an engine cover which of course will be totally misleading because the drie motor is really small.

p.s. I bought a table saw! Here's a couple pics of using it to slice the heavy and very hard Garapa Wood floor boards. The color in the pics isn't quite right because the sawdust was closer to yellow even tho' the boards are more brownish.