Gas power for sail

[ErikG]

Thanks Stuart!

Any close up pics or additional info?

So, showing my ignorance in the coice of props and powering them.
The gearbox is used to bing down the revs and bigger prop for thrust and folding I guess...
What kind of gearbox?

This actually sound pretty simple... Maybe I should try to find an old cheap outboard to try it with. The really cheapass version would obviously be to use the existing prop as well, and just create a watertight seal... Though a bit draggy... But could be done just to test it.

Winter project if I can find a cheapass engine.

[ErikG]

BTW

If anyone happens to be in posession of a service manual for a smallish (4-10hp) outboard I'd be happy to get one Brand i irrelevant, just need to get a few ideas of how to do this.

[Skippy]

Is it possible to hook a small gas engine onto a standard straight prop shaft? That sounds ideal in terms of weight and CG, and better than a saildrive for simplicity.

[water addict]

off the track a bit, but has anyone heard of rotary engine use on sailboats? The rotary's power to weight and power to size is unbelievable compared to typical gas and diesel auxiliaries. I wonder why no-one has developed it for the marine market - or maybe it has been done and is not a good solution? just curious.

[gmiller]

Has anyone tried to adapt the hole for saildrive as a well for outboard? I have just made a bid for an etap with no engine and would like to put that expense off for a while , the saildrive is still there but condition is unknown . and i don 't want to mess with the transom. Thanks for any advice Geo.

[cyclops]

The Mazda's are in boats with inboard shaft drives. I have seen several in Clayton , N Y.

[mackid068]

Really? Mazda rotaries? How fast do you think a rotary of equivalent power to a gas would get the boat to hull speed?

[cyclops]

You have to remember 1 very important thing about small ( cubic inches ), light weight, high horsepower engines. They can NOT move any real boats up to speed quickly. They are more like a 3 point racing hydroplane. Lots of scream and slow acceleration. Cubic inches throw boats up to speed quickly and maintain planing speed in turns.

[Vega]

Diesel-electric propulsion???
From the Malo site:

"Why is Nigel Calder’s new boat for sale?
...
The primary reason is that in the three years it has taken to design and
build ‘Nada’, two technologies that have the potential to create the
greatest changes in boat systems in more than 30 years have more-or-less
matured. These technologies are diesel-electric propulsion and distributed power systems. ..... For research and development purposes Nigel and Malo Yachts would now like the opportunity to build the same boat, including all the modifications made to ‘Nada’, but incorporating these new technologies.
This would make it technologically the most advanced cruising boat in the
world......"

What are they talking about? What is a Diesel-electric propulsion and a distributed power system? why are they such a big deal?

http://www.maloyachts.se/

[cyclops]

Malo quality is all hype according to boat owners who have to close water cocks on the port side to prevent flooding in hard turns. Old recurring problem. And they are going to Diesel - Electric power???? Wear rubber boots in the heads.

[marshmat]

Skippy- Yes, it is possible to do straight shaft with a small gas motor. Practical Boat Owner had an article on how to do it in issue 398 about 5 years ago, you might be able to find it at http://pbo.co.uk/pbo/home.htm It's generally superior to a kicker outboard, but not as good as a larger inboard for motorsailing. (I'm assuming we're still on displacement sailboats here?) There are still a few small, but beefy, low-hp marine petrol engines available that work well for this. Low-displacement 'lawn tractor' motors don't fare so well though.

Wateraddict- Yes, Wankel rotaries can be and have been used in boats. There are a few companies that do Mazda conversions or new builds for marine use. They're only suitable for high-speed applications though; the engine architecture encourages a very high RPM and so they have very little torque at low speed. They behave much like turbines, and nothing at all like piston motors. A Renesis 654cc twin-rotor, for instance, needs to turn 5,000 RPM before you get substantial torque out of it- but from there, it pulls hard up to around 9,000. So you end up needing about triple the gearing as you would with an equivalent diesel if you're using it in a boat. Great if you want to run 60 all day but miserable when puttering around at 8kts.

Vega- by "diesel electric" he is referring to a multi-part powertrain, where you have a diesel engine spinning a generator, an electric motor on the propshaft, and a bank of batteries and controllers between them. You can thus putter around on batteries alone in the harbour, or cruise on the diesel; you also have the battery as backup when the engine craps out. Also, you get a shallower shaft angle and more advantageous engine placement. The greatly enhanced versatility comes at the expense of a bit more weight, a fair lot more money, and about 5-7% in peak efficiency. I can't figure out what he means by "distributed power", unless he's thinking of something like a solar array/diesel hybrid.

[Vega]

Originally Posted by marshmat

Vega- by "diesel electric" he is referring to a multi-part powertrain, where you have a diesel engine spinning a generator, an electric motor on the propshaft, and a bank of batteries and controllers between them. You can thus putter around on batteries alone in the harbour, or cruise on the diesel; you also have the battery as backup when the engine craps out. Also, you get a shallower shaft angle and more advantageous engine placement. The greatly enhanced versatility comes at the expense of a bit more weight, a fair lot more money, and about 5-7% in peak efficiency. .

That's interesting. It looks like the hybrid motor technology developed first by Toyota in cars. Nobody has believed that at first, but they are obtaining some net results. So net that now they are preparing to put almost all their cars with that kind of motors, even the sport roadster MR2. And they manage to increase horsepower too, (both motors can work at the same time delivering more power) without significatively increasing weight. They manage to lower cosumption by 30%. In a boat it looks even more promising, because a boat uses a lot more electricity than a car and authonomy is much more important.
It looks like distributed power will be the distribution of the electric power generated by the diesel motor to where it is more needed : To charge the two different set of batteries (boat and motor), to be used directly for running at the same time the electric and the diesel power and certainly for a lot of other situations.

Nice move.

[mackid068]

Diesel-Electric? Aren't those often used in cruise ships and large vessels?

[marshmat]

Almost all cruise ships are powered this way, only they don't usually have the battery bank that is common in smaller vessels. The majority of the world's midsize submarines also use variations of the system.

[mackid068]

Midsize-like the Russian Kilo class, I assume? They're diesel electric.