Retractable Rotating Saildrive?

[Dockhead]

Originally Posted by SV DestinyAscen

Are you building a custom design? magnetohydrodynamic drive with closing bow and stern tubes!

Ha, ha. It's custom, but the budget is not unlimited!

[valhalla360]

Originally Posted by Cheechako

There was a company making retractable leg saildrives. Were used on early cats with one engine in the center instead of one in each hull. I forget the name.

Stillette, they are still in production and in use on new boats. Basically an extra long inboard/outboard arrangement.

Manuverability with a steerable leg and the ability to pull it out of the water are great.

The downside is it's 40yr old technology and they require regular maintenance or they start having problems.

Much simpler to use an outboard for the same effect.

I think it's PDQ uses twin outboards in pods between the hulls and they winch up clear of the water when not in use.

If you are set on a monohull and are custom building, I'm sure you could build some sort of wet sump with an outboard (if outside the USA and you are paranoid about gasoline, they have diesel outboards).
- Cut a circular hole in the bottom.
- fit a matching plate to the outboard so the hole is filled in but the motor can rotate.
- fit a sliding plate that can slide in place when the motor is retracted to keep he hydrodynamics good. If you want to get fancy, I'm sure you could do it with cables or ropes so you don't have to go into the engine room.

[myocean]

I think you should rather consider a retractable pod drive, not a sail drive. Thats somehow less complicated mechanically - and less heavy.
May be On Board Marine can help, a company in Hong Kong with Kiwi management.
There is as well a German engineering company which has designed a rotating and retractable mechanics based on a standard 4 kW pod drive by the elctric drive manufacturer Torqeedo.

By the way: Why exactly retractable?

[valhalla360]

Originally Posted by myocean

By the way: Why exactly retractable?

On the boat we just sold, we replaced the motor in 2007. With over 10,000miles including salt, brackish and freshwater on the new motor...

It's got the original paint still in good condition on the drive unit. The prop is always completely free of growth. Still had the original zinc. Other than a couple pumps of grease in the zerk fittings and replacing the lower unit fluid once a year (which can be done with the boat in the water) no other maintenance on the part that goes in the water.

Show me a 9yr old saildrive unit in perfect condition with that little maintenance and not completely overgrown and/or corroded away.

[Iodine]

Might be worth having a chat to these guys: www.hybrid-marine.co.uk

They're on the IoW, so not so far away for you and although they market mostly parallel hybrids, the owners own boat is (or at least was) set up as a series hybrid, so he should have some first hand knowledge of the pros & cons of the different set ups....

[Steve_C]

The now defunct African Cats - FastCat had retractable pods. They folded up against the bottom of the bridge deck. I always liked the idea, because it allowed you to use much bigger and more efficient conventional props. This could make up for some of the inefficiencies.

I always thought a great balance would be a small diesel generator and a mid-sized diesel generator that could provide a wide range of options.

Small only - light motoring, motor sailing or AC use at night or when needed.

Medium only - when more speed is needed or loads exceed Small Genset.

Both - When running full speed or for extreme uses such as motoring against high winds or currents.

I also like the thought of some redundancy.

The steerable electric pod sounds like it could be a great fit for many.

[Dockhead]

Originally Posted by myocean

. . . By the way: Why exactly retractable?

Well, this is still at the level of fantasy. But this is not for the main engine -- but for a second, smaller diesel used primarily as a generator. So it seemed right that the shaft or leg or whatever should be retracted.

Another reason is that this one won't be behind the keel, so will be vulnerable to snagging and fouling stuff while exposed. Retracting it would get it out of the way.

There are of course very good and well developed retractable shaft drives -- as used on Open 60s and many other racing boats. There's one on a Fast 40 which I walk past on my way out of the marina in Cowes. This could certainly be an option -- just give up the thrust vectoring thing, which I guess is not all that important.

This is an example:

Propulsion

It's straightforward and lightweight -- a lot to recommend it in this duty.

[barnakiel]

I have actually seen retractable saildrives.

Not sure if they were rotating or not though.

b.

[Dockhead]

Originally Posted by Iodine

Might be worth having a chat to these guys: www.hybrid-marine.co.uk

They're on the IoW, so not so far away for you and although they market mostly parallel hybrids, the owners own boat is (or at least was) set up as a series hybrid, so he should have some first hand knowledge of the pros & cons of the different set ups....

Thanks! That's a hot tip.

This thing of theirs:



is very much how I visualize my wing engine!

[beiland]

Originally Posted by beiland

What I have in mind at this moment is how I might adapt thie Vetus Rim Drive unit to be my single primary propulsion propeller.I would like to mount it in the aft portion of the wingdeck of the vessel, and make it steerable upon demand, and also retractable when sailing.

Perhaps I did not describe this thought of mine properly?

If you imagine just replacing the prop on the end of this Baltic retractable leg with the Vetus rim drive unit.
Baltic Yachts introduce a retractable propulsion system! - Ocean Of News

Then instead of driving the prop via hydraulics, the rim drive prop would be driven with electric current.

Isn't that what you were looking for, Dockhead?

[Cottontop]

Originally Posted by Dockhead

Thanks! That's a hot tip.

This thing of theirs:

Attachment 133386

is very much how I visualize my wing engine!

Steyr has a similar parallel setup:

http://www.steyr-motors.com/fileadmi...DS_digital.pdf

[joeboxer]

Alibi has a retractable propeller

[Rapanui]

A slightly simpler solution than some of the ideas floated would be to have an electric motor driving the prop shaft of a conventional Diesel mechanical drive via say a belt drive and one way clutch so that propulsion could be by electric drive or mechanical drive using the main propulsion engine. We built high speed patrol craft ~40 kts which had just such electric propulsion on 2 of the 4 shafts enabling the vessel to patrol indefinitely on generator power alone. Ok, you would not have the vector drive capabilty of an azimuth thruster, but the arrangement could optimise nicely with the variable pitch propeller you intend to fit. In fact, the electric motor could be a simple constant speed non-reversing motor with such an arrangement.
The addition of a large LiFePo battery and large charger could make it a hybrid system and also reduce generator run time even with large consumers such as heating or air conditioning. Carefully designed, you could also operate without loss of capability with either of your main engine or generator diesels u/s.

[Dockhead]

Originally Posted by beiland

Perhaps I did not describe this thought of mine properly?

If you imagine just replacing the prop on the end of this Baltic retractable leg with the Vetus rim drive unit.
Baltic Yachts introduce a retractable propulsion system! - Ocean Of News

Then instead of driving the prop via hydraulics, the rim drive prop would be driven with electric current.

Isn't that what you were looking for, Dockhead?

It looks very cool.

But the Baltic Yachts system is made by Hundested. I suppose it would be simpler with electric drive, but more efficient with direct mechanical drive. And since they don't make an electric one, it would be totally custom ($$$$$).

The Hundested system is something really massive and probably not suitable for this. The Open 60 system appears to be like 10x less bulky, so much better it seems to me, for this purpose.

[Dockhead]

Originally Posted by Rapanui

A slightly simpler solution than some of the ideas floated would be to have an electric motor driving the prop shaft of a conventional Diesel mechanical drive via say a belt drive and one way clutch so that propulsion could be by electric drive or mechanical drive using the main propulsion engine. We built high speed patrol craft ~40 kts which had just such electric propulsion on 2 of the 4 shafts enabling the vessel to patrol indefinitely on generator power alone. Ok, you would not have the vector drive capabilty of an azimuth thruster, but the arrangement could optimise nicely with the variable pitch propeller you intend to fit. In fact, the electric motor could be a simple constant speed non-reversing motor with such an arrangement.
The addition of a large LiFePo battery and large charger could make it a hybrid system and also reduce generator run time even with large consumers such as heating or air conditioning. Carefully designed, you could also operate without loss of capability with either of your main engine or generator diesels u/s.

Thanks. Something else to think about. I guess this would be a lot simpler than a retractable drive. Minus would be lack of redundancy in drive system, but I guess that could be a small price to pay.

Edit: After thinking about this a bit more -- I don't really see the point of electric drive, but a mechanical link (toothed belt?) from the secondary diesel to the shaft could be really good. Really simple and efficient, and shouldn't be too expensive. I think this could be a good idea. As you said, with the manually variable pitch Hundested prop, there shouldn't be a problem that the prop will be large compared to the power of the secondary diesel. I guess it might even be rather efficient.

Nice idea.