Electric propulsion for a sailboat

there are quite a few sail boats getting converted and the owners seem to be happy with them, with sail you can recharge off the prop shaft while sailing which makes it a viable option. but i can see the limitations on the system if you live in an area with strong tides and currents, where i live this is not a concern.

 

"with sail you can recharge off the prop shaft while sailing which makes it a viable option. "

Its a viable option IF you are willing to accept the drag from a pail trailed astern about 50% larger than the prop diameter .

Slows most boats down a lot unless its blowing 20K or more.

Most folks will swop distance for charge rate and tow a 8 inch diameter outboard prop (cheap to replace when taken ) with a rewound (for slow speed charging) alternator.

Some good days (24 hours) will keep a small fridge operating,

But I have doubts about 1/2 ton or more of deep cycle batts.

FF

 

so it would be better just to have a wind generator and not have the drag i guess.

 

Back again,
and the core seems to have digressed a little.

The Best way to recharge is with a genset as all else does not return sufficient capacity to the batteries if you are electric motor driven.

I have 8 PV panels that are each something like 800mm x 1600mm with 72 cells and nominally capable of 1400W delivered to the batteries (AGM), which are nice for keeping day use of all my electrics, (Nav, Galley & House), but I still need a diesel or, (heaven forbid, petroleum), genset and additional batteries for overnight passages (autopilot and chart/radar plotter).

Wind generators put out 400 to 800W and require about 15knot winds (OVER THE DECK) to achieve that. All this can be calculated and evaluated quite simply by doing some 'homework'...

 

Masalai obviously has done his homework. Every point in his post is correct. Fred, too. If you are doing more than motoring out from a dock for a weekend sail, you have to go diesel electric, or have no engines available from time to time. This means a lot of weight and a lot of expense, even using the absolute latest technology.

I never really understand the desire to drag that proverbial sea anchor behind the boat to recharge engines either.

If you weren't dragging a sea anchor (charging from props), you would get to your destination much more quickly, eliminating the need to motor. Slowing the boat down so you can motor later is robbing Peter to pay Paul.

Sailboats, by definition, already have the greenest propulsion systems available, 100% powered by the wind and zero emissions. Why not use the sails instead?

 

"so it would be better just to have a wind generator and not have the drag i guess."

Great , you have to anchor way out , to steer clear of the protection a harbor offers , and listen to the noise and live aboard a constantly shaking boat from the windmill.

As this is an area where SIZE COUNTS , you either get tiny output from a tiny unit or contend with a 6 ft diameter blade monster when the wind starts to blow hard.

Great!

FF

 

Whoops! I thought Masalai was being sarcastic about the wind generators. I've owned both wind and solar on the same boat. Wind was useless. They output nothing unless you are anchored in a windy spot and a small craft advisory is up. Solar worked much better.

 

unbelievable. 2 friends that had wind gens loved them and you could hardly hear them running. masalai wants to run the equivalent of a house full of electric appliances, i only need to charge batterys to run led's , sounder and gps, and to run the electric motor to get in and out of my mooring.

 

and to run the electric motor to get in and out of my mooring.

Should work fine for a short distance , no wind situation.

But charging a battset to actually move a boat for a couple of miles is a totally different power requirement.

FF

 

I also agree about it working fine to get in and out of a mooring.