propullsion idea/design/question hybrid

[scottyt]

okay this is not really an new idea or even an old idea, its kind of a hybrid

okay i think this would be better for a cat, ie 2 hulls 2 props. basicly it would be a single diesel engine with a larger genny or alts on it. then 2 electric drive motors, one in each hull. the battery bank would be enough to run the motors for say 1/2 to 1 hour. the genny could be in one hull and the battery bank in the other for balance. but the genny should be able to put out 75 % of max draw for the motors, with the battery bank picking up the slack when really needed. this would allow most people to run the motors to get to or away from the pier with out running the engine. it also from most designs of cats i have seen would fit in much better than 2 engines.

i have done a little research out of just shear boredom. motors that put out 10 to 20 hp peak ( 10 hp efficiently ) cost around 1 k for higher end motors. the genny i did not look up.

what this would do is allow a larger cruising battery bank with the ability to charge quickly when needed. there is some loss in wiring, genny etc, it is not with out its problems.

pros:
cost might come out better
easy to fit in to a design
nice big battery bank for cruising
less wear and tear on short engine runs for dock work
fairly easy to have a small honda genny for lite electric and back up charging, with a large genny for large loads like ac
probably better fuel economy per watt hour
better reliability on larger engines
using one or both electric motors for regeneritive charging on good winds

cons:
one real power source for long term motoring ie no redundancy
the losses might add up to be too high
large genny and wiring purchase cost

[kaluvic]

Not sure what I'm missing...as you said this is nothing new.
Certainly some variations.
Here’s a link with some details on one production cat with electric drive.
Electric drive for Lagoon catamarans

[WanderingStar]

The other shortcoming is the numerous systems: generators, batteries, electric motors, take up more room, require maintenance, use space.

[kaluvic]

I guess it depends how you look at it.

I think on many cats you would have an engine in each hull plus a gen. That’s 3 diesel engines in a sail boat???

With this electric scenario you could get away with one gen only!

I looked very seriously at diesel electric drive when I re-powered my mono.
Glacier Bay has a system I like very much, but at the time they didn’t have a motor large enough.

[scottyt]

Originally Posted by kaluvic

Not sure what I'm missing...as you said this is nothing new.
Certainly some variations.
Here’s a link with some details on one production cat with electric drive.
Electric drive for Lagoon catamarans

i did not know about lagoons system

the lagoon system is just what i am talking about with a lot less battery. having enough battery to light up new york is counter productive to the space, weight and cost benefit of what i was thinking. the way i was thinking the battery would not be near large enough to run for 4 hours.

i was thinking it the same over all way lagoon did, basicly no maintenance on the drive motors plus the space freed in each hull with no engine would be great. the motors them selves are the size of a normal tranny.

well its nice to know my ideas can work

[Sailormann]

ASMO Marine

[WanderingStar]

I think the breaking point is how much motor time you require. If you use power only in and out of your harbor or marina, electric becomes practical. In that case I'd consider wind or solar charging.
When the diesel died in my 26' yawl, I thought of electric. Never got around to it, sailed engineless for a few years.