Hit n miss?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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lostintime
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Hit n miss?

Post by lostintime » Thu Feb 18, 2021 9:49 pm

I'm still slowly scrounging materials to build a steam plant, but until then I've been toying with the idea of using a 1909 associated 2.25 hp (450 rpm) hit and miss engine. My question is how much can two hp really be expected to be able to push? I'd be building a boat to use on a slow shallow river and small calm lakes, and want to slowly leisure along with a "tunka, tunka, tunka" sound but would like to be able to make hull speed.
Assuming built light, flat (or very close to it) bottom with a small amount of rocker and pointy at both ends, about what length do you think it could push?
May predictive auto spell be damned
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barts
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Re: Hit n miss?

Post by barts » Thu Feb 18, 2021 9:58 pm

You should find a total displacement of 2000 (people, boat, engine, etc) lbs to be about right; the longer the boat at that weight, the faster it will go.
Consult Skene's Elements of Yacht Design or Propeller Handbook (Gerr) for all sorts of useful formulas. Rule of thumb is 1 to 3 hp per ton of displacement.

A lightly built 20 foot hull and a couple of people should perform very nicely.

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
lostintime
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Re: Hit n miss?

Post by lostintime » Thu Feb 18, 2021 11:50 pm

Thank you, that was what I was thinking (20' length by 6' beam on the flat bottom, chined to 7'' beam at 45 degrees midship, than chined to 8' at the midship rail line, and elipsing to a vertical bow and stern, but wanted to do a reality check.
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fredrosse
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Re: Hit n miss?

Post by fredrosse » Fri Feb 19, 2021 9:00 am

The FAQ section of this forum has technical simple answers that explain all of this, sizing the engine, sizing the boiler, etc.
Launch Hulls, Power Requirement, Engine performance, Engine Steam Consumption, etc. With a properly sized propeller, (Large and slow turning) you can get by with 1 horsepower per ton of displacement, getting about 5 knots speed on a 16 foot waterline length. More power required for a bulky hull, and/or small propeller. Having some excess power for wind and waves is recommended, so you end up with 1 to 3 horsepower, exactly what Barts has recommended.

It is easy to miss the FAQ section of this forum, click on "Board Index"rather than "The Steamboating Forum" to get there.
lostintime
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Re: Hit n miss?

Post by lostintime » Sun Feb 21, 2021 12:56 am

I found the thread in the FAQs, I had remembered it but was unable to find it with the search function, since the site format change quite a while ago I've had a hard time finding threads I know existed
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