Electric Motor Sailing

One of the huge advantages of the electric motor is that it can help you keep moving in very light winds. Having a fixed blade propeller is nice because you can use the regeneration feature of the motor to charge the battery bank as you sail due to the propeller spinning as it is dragged through the water. The downside to this is when sailing in light winds, you end up dragging a large 3 blade propeller through the water. 

I have found that by having the motor on just a smidge, it helps turn the propeller slowly so that it can pass through the water more easily. It isn't really pushing the boat along, rather it is gliding through the water instead of causing a lot of drag. 

While a feathering propeller is nice to have since the blades can turn to be blind to the passing water, it wouldn't allow the propeller to serve the regen function. By slowly turning the propeller, it practically reduces the drag from the prop, effectively giving the same advantages as the feathers prop. 

For example, we were sailing in very light winds with the Mainsail (522 sq ft), Staysail (180 sq ft), and Drifter (766 sq ft) flying. This gave us a total of 1468 square feet of sail area and a sail SA/D of 23.4. This is a rather large amount of sail area to have up, but in winds of 4kn or less, we were not moving very quickly due to the drag on the propeller. 

When the prop was dragging, we were only moving along at 1kn. When we put it just a touch into gear, the propeller stopped being drag and we picked up speed to 1.9kn. 

The motor is running along at just under 600 RPM and consuming minimal power, and we can make a bit more headway without dragging the large three blade propeller through the water.

We have an incredibly small battery bank since we hardly use the motor, so we can only do this little trick for about 16 hours; but that 16.5 hours moving at 1.9kn would give us a range of 31.4 nautical miles. If we were in the ocean, we wouldn't care about the added speed, because we plan plenty of time for the light air days. On the other hand, in the bay, we do like to make it to the anchorage or back to port that night, so we are willing to give it a little nudge to help improve our speed over ground. 

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