Hybrid auxiliary propulsion (diesel/electric/hydraulic) ?s

[Seafarer24]

Let me preface by saying that I am not a big fan of auxiliary engines in sailboats, as they always seem to be the most maintenance-demanding and yet unreliable piece of equipment aboard. However, I realize others disagree and that there are significant safety aspects that engines provide so long as they work when needed to.

I do want to have a somewhat powerful diesel generator aboard, and figured that I could run some very large cables to an encased electric motor located in the bilge, or maybe even in the keel (depending on the size of the motor, obviously), and have the motor drive the prop (either directly or via a shaft). Alternatively I could fit the generator with a hydraulic pump and use a hydraulic motor to turn the prop. This does, however, add yet another system to maintain. Either way, I'm not designing it to operate without the generator running.

The boat would be 32ft long with 10,000lbs displacement, so I was figuring 15-25HP would be about right, and the (folding) prop would, hopefully, come out just behind the keel, if not out of the trailing edge of the keel itself.

A) Do you feel that diesel/electric, being directly driven off a generator, would be a viable source of auxiliary drive for said cruising sailboat?

B) Do you feel that diesel/hydraulic, being directy driven off a generator, would be a viable source of auxiliary drive for said cruising sailboat?

C) Do you think I'm somewhat nuts, am just "reinventing the wheel", and should spend more time trying to figure out how to shoe-horn a typical engine-driven configuration into the boat somewhere instead?

Oh, and if anyone knows the approximate size of a 25HP diesel auxiliary engine, that would be helpful if "C" is the favored option.

[FAST FRED]

The problem with anything BUT a std shaft is the loss of efficency with most choices.

ONLY if you have a very special reason should a lashup be considered.

Hyd is the best aboard , as it tolerates water far better than electrics.

32 ft and 10,000 lbs will only need 10 hp or so to get moving well , so the efficency losses could be tolerated ,

Why is the question.

FAST FRED

[Vega]

Originally Posted by Seafarer24

Let me preface by saying that I am not a big fan of auxiliary engines in sailboats, as they always seem to be the most maintenance-demanding and yet unreliable piece of equipment aboard. However, I realize others disagree and that there are significant safety aspects that engines provide so long as they work when needed to.

I do want to have a somewhat powerful diesel generator aboard, and figured that I could run some very large cables to an encased electric motor located in the bilge, or maybe even in the keel (depending on the size of the motor, obviously), and have the motor drive the prop (either directly or via a shaft).
The boat would be 32ft long with 10,000lbs displacement, so I was figuring 15-25HP would be about right, and the (folding) prop would, hopefully, come out just behind the keel, if not out of the trailing edge of the keel itself.

A) Do you feel that diesel/electric, being directly driven off a generator, would be a viable source of auxiliary drive for said cruising sailboat?

BOh, and if anyone knows the approximate size of a 25HP diesel auxiliary engine, that would be helpful if "C" is the favored option.

Yes, the diesel electric is a good option to you.

This is the right thread to discuss diesel-electric in sailboats:

Diesel/Electric Propulsion for Sailboats

Lots of information already

It seems odd, but a diesel electric set up, with an electric engine feed by the generator has a better efficiency than a directly connected diesel engine.

You will waste less fuel and will need a less powerful engine.

Dimensions of a 25hp diesel engine (21hp and 29hp):

http://www.yanmarmarine.com/products...0_TechData.pdf

http://www.yanmarmarine.com/products...0_TechData.pdf

[Seafarer24]

My thanks to both of you.

The "why" is space. I've been aboard a few boats in this size (one of which influenced this design) and was entirely displeased with the engine sandwhiched under the cockpit sole with almost no access what-so-ever. I'd love to locate the engine much more centrally, and have a space under/next to the galley sink that could house a small engine. However- is is not on centerline and it does not seem to be near enough space for a 25HP engine, just a little generator. I figure a small generator could still run a large electric motor, and it allows me to mount the motor with less regard to engine location.

Also, I wouldn't want an engine and a generator aboard, and engines make inefficient generators. I really do want a generator to run some computer items as I'll likely make my cruising money doing digital photography and writing along the way. I'm also going to learn more about welding and get a small tig box for aluminum/stainless and a good generator for that is critical.

Honestly, the only reason I want auxiliary propulsion is so I could market the design if it proves satisfactory to me. Well, that and transiting the Panama Canal is much more expensive if you can't make 6 knots across the lake.

I know 10HP would move the boat around for docking and when there is little wind, but that is not the condition that concerns me. Strong, contrary winds and tides combined with rough seas are what concerns me, and I doubt 10HP would then suffice.

[FAST FRED]

"Strong, contrary winds and tides combined with rough seas are what concerns me, and I doubt 10HP would then suffice."

Hull speed is all you can realistically push a displacement boat.
So with tides , if they are moving 5K against you , there is no way to go faster than 1 or 2K over the ground .

While its nice to contemplate driving into a 40K wind , the size of the waves usually requires more HP than a normal sized sail boat propellor can place into the water . Thats what those sails are for. Big wind = Big power.

The problem with actually marketing such a boat is few owners need massive electric underway and complex drive systems.

Perhaps a smaller drive engine , with conventional propulsion and a huge alternator belted off the front could charge a bat set to handle your electronics requirements.

An alternator from a bus is 12 or 24V and 300amps, with AGM batts with a great acceptance rate you might be able to get by on short but heavy charging going from 50% soc to 80% soc very quickly.(soc =state of charge )

FAST FRED

[pabble]

Check the Electric Wheel offered by Solomon Technologies (.com), or better yet contact Dave Tether who developed and brought it to market - has a new company now...http://www.electricmarinepropulsion.org/. And search here for related discussions. great idea!