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Old 30-03-2020, 01:50   #16
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Re: Direct solar -> motor -> prop?

I am not sure that 2hp is going to move a M39. Even when becalmed there always seems to be a swell too. I spent a couple of days becalmed in Biscay some years ago. The skipper even said "take the spinnaker down because it isn't doing any good, oh and you lot can go for a swim, here is some sea soap".

We eventually found some wind and made it to La Coruna. However, a Contessa 32 wasn't so lucky. They came in to the marina a day after us under sail, dropped the sails at the last moment and did a text book mooring down a dead end of the pontoons, all very impressive. Later I asked them why under sail? They explained that they ran out of diesel 30 miles offshore and spent 3 days drifting back and forth with no wind

I have been following "Adventures of an old Sea Dog" on YT and his recent Pacific crossing, which didn't go well. The weather seemed to be constantly against him and his sails weren't in a good condition which meant an average speed of 2.7 knots. Other problems included the hull fouling up with weed.

To avoid this it might be worth adding a second hand cruising chute. Doesn't have to be anything special or even a perfect fit, but it will provide some drive in very light conditions. Do you have a boarding ladder? you might think about adding a bracket so the outboard engine can be used to drive the Moody. Here is a solution for a smaller Moody which came off the owners association. I keep meaning to copy his design.

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Old 30-03-2020, 02:05   #17
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Re: Direct solar -> motor -> prop?

Thanks for all the thoughts and suggestions. We do have a symmetrical spinny already, and expect to be making use of it.
The M39 is a big old lump of a boat and not especially easily driven- maybe there is a sort of 'stickyness' that would need to be overcome to actually start moving? I've just been using the Kiwi-Prop online calculator to see how much power you need to reach a certain speed, and it's probably overly simplistic.

I hadn't really thought about friction in the drive train, but it's obvious when you point it out. Some parts of the gearbox will be turning, and maybe the worst culprit will be the stuffing box. Balance this against the fact that it's the correct size/pitch prop for the boat, in the best place, whereas an outboard is going to have the wrong prop and in a less optimal place.
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Old 30-03-2020, 02:27   #18
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Re: Direct solar -> motor -> prop?

Steve D’Antionio’s article, “The Get-Home System: Do You Need One And What Are The Options?”, addresses this subject.
https://www.passagemaker.com/technic...re-the-options


"Get Home" Drive
https://abttrac.com/product/trac-get-home-drive
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Old 30-03-2020, 09:21   #19
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Re: Direct solar -> motor -> prop?

I saw a post somewhere where they built a fairly hefty Torquedo (or similar) into their rudder, so only the motor pod was obvious when faired into the bottom. IIRC they did it to be a pseudo azipod (Rotatable sail-drive) to help when maneuvering in tight spaces but it could likely offer some propulsion as well. Don't know if you could reverse it to generate power when the wind is good.
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Old 30-03-2020, 15:44   #20
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Re: Direct solar -> motor -> prop?

Encountered this remarkable, admirable and enterprising solution cruising the Georgia ICW at 2 to 3 knots in calm weather a few years ago. Lots of watts for the SOG. Count 'em and extrapolate up in panels or down in speed?
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