Steam Launch

Hi Folks

I have started looking at building / having built a steam launch, mostly for use on the Swedish Lakes.

I have fallen in love with the concept of the 50' Edwardian Launch http://www.selway-fisher.com/Steamover30.htm and am looking at an Engine for her. In order to propel her at hull speed (8.5 kts) about 50 bhp engine power seem to be needed.

I have found this engine here:

http://www.pioneer.net/~carlich/RSE/RSEengines.html - V - 4 Single Acting Compound but I am a bit surprised at the rather high operating pressure. Especially with this pressure I am wondering whether a triple expansion engine might not be better and a double acting to boot. Question is: where could I find one? Also their boilers are a bit confusing, what kind of boiler would you recommend?

And lastly I have been thinking of running the whole boat on LPG - propulsion, cooking, refrigeration, lighting. What do you think?

thanks

Bernhard

 

Hey there;

Can't answer the first two questions, but can quote this as more or less relevant to pressures:

And, from another interest, you know steam locomotives?
In the main, they ran, and some still run preserved, around 150 to 250 psi.

There's those notes for whatever they're worth.

Hey, here's a fun steam-powered boat site:
http://www.steamengine.com.au/steam/water/gondola/index.html

Just as a novice imagining why, it would seem you'd want enough pressure to keep the cylinder moving against the torque of the prop as steam expanded inside the cylinder and its pressure declined.

 

Google;

http://www.steamlaunch.com/

http://www.prestonservices.co.uk/marine.htm

http://www.theengineersemporium.co.uk/catalogue-pages/fullsizesteam.html

http://www.steamboat.org.uk/smallads.htm

Pericles

 

I would ask the designer at Selway-Fisher. He's very knowledgeable in the correct HP engine for each of his designs. The Reliable engine is a high (relatively speaking) rpm engine. To get the best advantages of steam you should use low rpms - the larger the hull, the lower rpms. Again, ask the designer what he recommends for a propeller, and therefore the rpm.

Having said the above there is, to the best of my knowledge, no manufacturer of traditional marine steam engines in the 25 to 75 HP ranges. A complete used engine is what you're going to need and Preston's is the only place I know of that regularly has an inventory.

Depending on the engine as to the boiler pressure - if it's a compound then 125 to 175 psi. If a triple then 150 to 225 psi. Then the boiler is deduced from that. Certainly some kind of water tube. You will probably need a code boiler in Sweden, so that necessitates other things.

You couldn't carry enough propane on/in a 50' boat to operate it for more than an hour or two. A 50 HP engine will require about 3,000,000 BTUs per hour at normal cruising speed. As I recall there's about 19,000 BTUs in a pound of propane. Oil or biodiesel is your best bet.

You might contact the Swedish Steamboat Association at http://www.steamboatassociation.se/ for further info. They can probably help you.

 

:idea: I now get to eat my words. Totally forgot above a used US Navy "M" 50 HP engine. Being handled by Elliott Bay Steam Launch - http://www.steamlaunch.com/engines/AntiqueEngines.html - it will suit your needs very well; a sturdy, US Navy grade engine, excellent materials and craftsmanship. And I happen to personally know the people that Elliott Bay recommends to do the restoration work. They're GREAT!

Hope this helps.

 

Rough Calculations show only about 10 - 15 horsepower required for hull speed of 6.5 knots. Turning a prop about 24 in dia x 24 in pitch, 450 - 500 rpm. (a somewhat larger prop at lower rpm would be somewhat better).

For a reasonably efficient compound engine, only about 350,000 BTU/hr (100 kWthermal) boiler output will do OK. That would require about 5-6 US Gallons per hour of propane, somewhat less with oil firing. You would probably be better off with oil firing, and just carry the propane for the other services (cooking, etc.)