Electric boat was a term that, when I first heard it, was like putting aluminum foil in your mouth. It jarred in my mind as an association of elements, utterly unsuited to exist in proximity; namely electricity and salt water. It was a decade ago and I was watching the process of a pioneering installation. An old and tired diesel was removed from the a wooden sail boat similar to my own while the bilge area was stripped clean and re-painted in white enamel. When all was clean and bright a tiny and I thought 'puny' electric motor and its control apparatus was installed in its place.
Electric boat; I couldn't believe it. I thought the Owner to be barking mad. What was he thinking?
But I've since changed my mind. The source of this conversion to electric boat for lakes enthusiasm, comparable to Saul's conversion on the road to Damascus, was a video I witnessed recently of a catamaran powered by two fold down outboard legs, with motors mounted in the respective propeller pods; that is to say the bit that folds down into the water. Although I'm a classic boat nutter, I was agog watching this video and sold on the idea in all of a nanosecond.
The boat electric thing and cats it seems, is a marriage of great convenience. Firstly having the deck area of suburban household roof at one's disposal, presents no problems either of practicality or aesthetics, when it comes to where to plant the solar panels. If your budget will run to it, it's possible mount enough panel capacity on a cat's deck, to power a small city if you're so inclined. On a mono-hull on the other hand, you're limited in terms of opportunities for placement and to my eye, they mostly look hideous. But multi hulls are highly sensitive to weight, meaning that when you pile on weight, performance drops sharply.
This is where mono-hulls and old sail-boats have one great advantage. Many old wooden sail-boats have supplementary internal ballast; namely pigs of lead in the bilge. For an electric boat conversion in http://bestonpaddleboats.com/electric-lake-boats-for-sale/, the lead pigs are replaced by the batteries so that the net weight increase is likely to be negative. Ballast is no longer just dead weight.
Secondly; there's the fixed prop vs feathering prop issue. Unless you opt for a fabulous and fabulously expensive; Hundested variable pitch & reversible propeller, there's an issue with electric power on a mono-hull, in that you generally need a fixed prop setup if you want to charge the batteries under sail. It would be a great pity is this re-charging capability were to be lost.
I'd love to fit an electric power unit to my 72 year old wooden sail-boat monohull, but I don't want a fixed prop. The three bladed affair currently in situ creates so much drag that you can feel the eddying of the water on the rudder under sail. It must account for of a knot under sail, which must translate to 20 odd nautical miles in twenty four hours.
If you can simply fold the entire prop and shaft up out of the water to lay flat against the hull, it solves several problems all at once not the least of which is the problem of accurate engine alignment in a confined space. The second problem is the presence of a stern gland which is a pain in the fundamental orifice. The third problem is the prop itself. A feathering prop coupled with a diesel, is a solution to drag, but I have seen big problems caused by jammed mechanisms and when they wear, they rattle. So a feathering prop to my mind is just another damned thing to go wrong.
Having the ability to remove the entire apparatus from the water when under sail is magnificently elegant. It neatly eliminates the drag factor when sailing while having the ability to remove the prop from the water eliminates also the complications of anti-fouling in the tropics and the incredible problem of keeping salt water intakes clear of marine growth. This is the bane of sail drives and the main reason I gather, why sail drives have acquired a reputation for unreliability among charter fleets.
And when you're sailing and the batteries, need a boost there's the opportunity to down the drive leg and generate power to the batteries via the spinning prop.
So a folding electric power leg is feasible and aesthetically no problem on a cat, but how can it be done on a monohull?
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