Wednesday, February 7, 2018



During the winter, the January-February months at about 34 degrees latitude, provide a low sun for the solar modules atop the boat. Even on a very clear sunny day at this latitude in Wilmington, NC, the electrical capture rate is low. In the summer the sun light is more directly over head, yielding a much better rate of electrical collection.

The winter sun test was to help us understand how to find and use the balance point between incoming sun energy to simultaneously replenish the drive motor(s) usage under water travel conditions.  Except for the three motors being used for exit and entry to the slip, just one motor was used, with the other two dragging in the water. Later, the two draggers will get lifted, just not this time out.

It is quite ordinary to use math to indicate usage in watt hours but those numbers do not give the captain a realistic feel of how tide, wind, clouds, humidity and seasonal sky position directly effect boat control. Just as with a wind sail boat, a solar sail boat takes practice getting use to the interplay of the many facets of power usage.

On the road (um) on the river again to probe a bit deeper into how the boat handles and refuels with a winter sky.


Our battery bank system is comprised of standard flooded lead acid batteries of deep cycle design, similar to a car battery but having the ability to provide a longer duration of power than a car battery's brief high load for engine starts. We have finally gotten a good sunny winter day with low wind with reduced tidal flow in order to set a base line of drive power needed to make the boat move with control and maneuvering capability.

Once out of the slip/fairway and into the river, there are no protections from wind and the mix of river & tide flow. Eddy currents near and around the marina and especially at the center of confined bridge water flow tend to shove boats around, requiring the capain to increase the drive power to offset swirling water conditions.

We found that a speeds of 3 to 5 miles per hour were needed to keep the boat on desired headings in average river & tide conditions, require 300 to 500 watts of continuos power.
In order to keep the batteries from being depleted, the solar modules atop the roof had to replace such an amount. That amount was provided, allowing operation that although comparetively slow for other boats, was suitable for rudimentary navigation.

Around the bridge, very squirrely currents require a bit of steering. Awaiting the closure and reopening is rewarded with an addition of energy to the batteries. We were definitely not rocketing along at 3 to 5 mph but there is no range limitation. If you are retired, as we are, time is more than money, it is fuel.

Taking a close view of the underside of the Cape Fear Hilton railroad bridge on the return leg of our brief sojourn.

Awaiting the bridge opening, having a snack, reading, taking pictures or conversing makes use of the  sun. Quite amazing that a few minutes with a large enough solar array, will top off the battery banks. After a quarter century of collecting the sun's energy this way, the fact that we are actually doing such is still impressive to me.

The bridge and the batteries are up, continuing the equilibrium of power in, power out.

There will be only a few more nice days such as Tuesday February 6, 2018. These videos will serve to remind us of how we got out and back, at what level of energy, distance, time and ease of control.

Heading back to the slip with grins and more knowledge about solar sailing.

Once back in the slip we just became another 40 foot boat. However, until you have piloted such a boat, just using the sun, no fuels, no wind, no sails, no noise and no smells, you will have missed the power of nothing.

More to come.

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