Solar electric cat

[Peter]

At times, pretty often, a headsail can provide all the push you need. Sometimes more than you need. Far more push than 7 kW can provide. And even a headsail alone can get you upwind reasonably well. 7 kW is going to struggle to push a boat that big into any kind of breeze.

The problem with a mast on a powerboat is that it creates a huge amount of windage especially when going to windward. Also in this case it will amost always be shadowing the solar array. A much better solution, if you could make deployment and retrieval simple and easy would be a kite. This will provide downwind assistance, or in some cases total power downwind, yet does not shadow the solar array when not in use or add to the windage.

[44C]

To be honest, with only 7 kW available, I don't see this boat motoring to windward.

[patrickza]

I love this idea, but I'm a huge fan of electric power (here's my 85km/h bicycle: https://www.youtube.com/watch?v=nu0IHH8EAvQ).

I'm wondering why instead of going for two electric motors and a diesel genset, why not instead go for one electric motor and leave the one yanmar in place. That way you can still sail all night, and don't need to convert diesel to electric to motion, but just diesel to motion. Surely that will be more efficient, and cost less considering you already have the diesel.

I'm sure you've already seen the solarwave: http://www.electricseas.org/profiles...g-with-the-sun

I read about it a year or two back, and they'd actually never used their generator after 3 years plus cruising!

[2whitehulls]

I love this idea, but I'm a huge fan of electric power (here's my 85km/h bicycle: https://www.youtube.com/watch?v=nu0IHH8EAvQ).

I'm wondering why instead of going for two electric motors and a diesel genset, why not instead go for one electric motor and leave the one yanmar in place. That way you can still sail all night, and don't need to convert diesel to electric to motion, but just diesel to motion. Surely that will be more efficient, and cost less considering you already have the diesel.

As I was reading through this discussion I was thinking exactly the same thing. Also, an electric motor could be attached to one of the existing saildrives.

[Parker]

Hi Patrickza,

I did consider that option as it would have been significantly cheaper, but with fixed three-bladed props, dragging on while running the other is (literally) a drag. I do like to use both motors for maneuvering, and I didn't want to be starting a diesel every time I wanted both screws.With two electric motors, the efficiency is such a flat curve (good efficiency at low through high RPM) that running both motors at low power beats running one motor and dragging one unpowered prop.

[Parker]

Hi 2Whitehulls,

The Yanmar SD40 sail drives use one of the Yanmar motor mounts to stabilize them, and the dual rubber gasket system is somewhat problematic. I could have coupled an electric rive to the Yanmar sail drives, but considering their age (2002 boat), I opted for the new sail drives from Oceanvolt with their robust mounting system.

[Parker]

If I have to power into a headwind, I can run both 17KW gensets and get 15 KW from each sail drive for 30 KW power. She should run into head seas and head winds if necessary.

[Bobate]

So do you have any numbers or videos yet for us? I see you splashed her in the water. Can't wait to hear your thoughts on her performance. I know we are very happy with ours. Yours project was overkill but you will find that out as you learn to cruise electrically.

[Bobate]

So in your video your doing 6 knots for 6 kwh basically. I'm trying to put that into amps... https://video-sea1-1.xx.fbcdn.net/v/...mp;oe=59F3C5F0

So roughly your turning prop for 60 amps a side. But your bringing in 3 kwh of energy so your turning prop for 60 amps. Great job. I can't wait until you get more water under the keel and more trips with it and you learn the finer points of powering your boat for even greater efficiency. You can probably do 4 kts for next to nothing.