Planning an electric motor install in a launch.

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burgundyben

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I've bought a 16ft Fairey Faun* launch and I'm planning an electric install.

I want it to do about 6 knots max, 4 knots cruise, this means about 2.5kW motor, batteries and a VFD inverter to a 3 phase motor. I think.

It will need a shaft install with a particularly low friction, friction will kill battery range. Plus, its unlikely that the motor will have angular contact bearings, so some method of managing the thrust.

Some wild guess numbers/thoughts are, 3/4" shaft, 10 inch prop, 1000rpm, small fabricated P bracket with a short phenol cutlass bearing, timber shaft log glued into the keelson, lip seal shaft gland in a flexi mounted housing and some method of managing shaft alignment/adjustment or flexi drive (but a flexi drive must sap power) and finally, photo'v cells for re-charging when not in use.

I might try and DIY cast a small bronze P bracket, always wanted to do some casting at home, maybe 3D CAD the bracket and 3D print the pattern to sand cast, or look at the cost of DMLS a P bracket.

Thoughts?






*Actually bought a very rough Fairey Falcon sailing boat, same hull as the Faun, substantial amount of woodwork repairs/re-configuaration to do, but let's just gloss over that and pretend its not happening.
 
so one hours motoring is 2.5KWh of electricity you are going to need stored.

That's 4 decent car batteries worth of power. But you never discharge a battery fully, so realistically 8 decent car batteries worth per hour.

I hope you are planning short trips, or the boat can handle a lot of batteries acting as ballast.
 
burgundyben said:
I've bought a 16ft Fairey Faun* launch and I'm planning an electric install.

I want it to do about 6 knots max, 4 knots cruise, this means about 2.5kW motor, batteries and a VFD inverter to a 3 phase motor. I think.

It will need a shaft install with a particularly low friction, friction will kill battery range. Plus, its unlikely that the motor will have angular contact bearings, so some method of managing the thrust.

Some wild guess numbers/thoughts are, 3/4" shaft, 10 inch prop, 1000rpm, small fabricated P bracket with a short phenol cutlass bearing, timber shaft log glued into the keelson, lip seal shaft gland in a flexi mounted housing and some method of managing shaft alignment/adjustment or flexi drive (but a flexi drive must sap power) and finally, photo'v cells for re-charging when not in use.

I might try and DIY cast a small bronze P bracket, always wanted to do some casting at home, maybe 3D CAD the bracket and 3D print the pattern to sand cast, or look at the cost of DMLS a P bracket.

Thoughts?
Click to expand...

Hi Ben,

Just some thoughts.

By the time you have fabricated a thrust bock a small Aquadrive may prove more cost effective.

I would go for a 48 Volt brushless Lynch motor and traction batteries.

Rather than buggering casting a 'P' bracket fabricate it in stainless, far easier.

Good luck
 
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Latestarter1 said:
Hi Ben,

Just some thoughts.

By the time you have fabricated a thrust bock a small Aquadrive may prove more cost effective.

I would go for a 48 Volt brushless Lynch motor and traction batteries.

Rather than buggering casting a 'P' bracket fabricate it in stainless, far easier.

Good luck
Click to expand...

Thanks. A Lynch motor is £3600!
 
burgundyben said:
Thanks. A Lynch motor is £3600!
Click to expand...

I know someone who has converted a 26' sailing boat to electric auxiliary power. He uses a Lynch motor, and yes, it cost a bomb. Range is awful limited, even with something like 400Ah of lead-acid, but a nice battery manufacturer has just given him lithium-ion batteries to test, which is nice.
 
Thought of a Torqeedo on the back?

torqeedocruise2.0rs.jpg
 
Whitelighter said:
Id have thought lead acid is a non starter. Lithium of some sort is the way to go, with solar panels to extebd range
Click to expand...
Poor old Ben is struggling to come to terms with cost high efficiency electric motor you will end up demoralising him completely!

We have been using lead acid traction batteries in launches since late 1890's suggests he stick with it.

Lithium Iron say 20kW giving a usable 18kW costs about £500/kW plus around £500 for a charger, this is the factor which blights electric/hybrid cars once they get older.
 
Hmm,

Well as a real world example I know someone who has dumped their lead acid in a cruising boat for 700ah lithium which 18 months ago cost $4,000 (£2500). Don't forget all of the power js usyable unlike lead acid where only about 60% is usable, so you can reduce your power need
 
Whitelighter said:
Well as a real world example I know someone who has dumped their lead acid in a cruising boat for 700ah lithium which 18 months ago cost $4,000 (£2500). Don't forget all of the power js usyable unlike lead acid where only about 60% is usable, so you can reduce your power need
Click to expand...

Also don't forget that the number of charge/discharge cycles is limited, usually to somewhere between 500 (Tesla Power Wall) and 2000 (MasterVolt Leisure). It wouldn't matter much for occasional pootering, but really rules out Li-ion for daily use as things stand. Tesla cars are lovely, but you need to find £50k for a new battery after 500 charges ... that's a hundred quid per charge, which knackers the fuel efficiency calculations more than a little.
 
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