Next Weekend II

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barts
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Re: Next Weekend II

Post by barts » Tue Jan 31, 2012 4:49 am

If you know approximate hp, rpm, length, beam and weight of boat I can crank some numbers for you; I have David Gerr's Propeller Handbook which provides several methods for selecting a proper size prop.

- Bart
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Bart Smaalders http://smaalders.net/barts Lopez Island, WA
87gn@tahoe

Re: Next Weekend II

Post by 87gn@tahoe » Wed Feb 01, 2012 8:04 am

My friends seem to find her a bit distracting...

Bart,

Could you punch in a guesstimate of 25hp and 200rpm (have not done the calcs yet) and 38'x11' (waterline width is prolly more like 10.5, as she's 12 over the rub rails)?

Thanks,

wes
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barts
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Re: Next Weekend II

Post by barts » Wed Feb 01, 2012 5:34 pm

We're going to need some idea of displacement as well....
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Re: Next Weekend II

Post by fredrosse » Thu Feb 02, 2012 12:20 am

Some very crude results based on: Waterline Length 38 ft, Beam 10.5 ft, Displacement 13 tons, 7.5 knots

Horsepower = 22.5 SHP

Propeller, (ideal size, but hull clearance constraints will often force a smaller prop)

350 RPM 33 in dia x 33 in pitch
300 RPM 36 in dia x 38 in pitch
250 RPM 41 in dia x 46 in pitch
200 RPM 46 in dia x 57 in pitch
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87gn@tahoe

Re: Next Weekend II

Post by 87gn@tahoe » Thu Feb 02, 2012 2:10 am

Oops, sorry Bart.

When they towed her down with a bunch of unused junk, like a set of doubles on the deck, a winch,giant rubber and steel fenders, a second inner plate on the entire hull, etc. she weighed 13tons, which is probably where she sits now with the superstructure, Doty compound, York watertube, and auxiliary machinery. Add a very approximate weight of 4000lbs for fuel and water and we're looking at somewhere around 15 tons
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Re: Next Weekend II

Post by dhic001 » Thu Feb 02, 2012 10:20 am

Wes,
To help you out with your calculations, Kapanui has a Simpson Strickland compound, 4.5 + 9 * 5.5 which is designed to be 30ihp at 400 RPM at 130psi. I can't remember the original prop size for it, but think it runsa 29 by 31 prop at present, which at full power does about 350rpm. She is 37 feet long, 9 foot 6 beam and 3 foot 6 draft. Weight for her is probably about 7 tons. Based on that, your engine must be at leats 30ihp, maybe 35ihp, although the revs may be down a little which would result in a larger prop.

Based on the cost of a prop for a vessel of this size, I'd be inclined to do what we've done with Zeltic, and make your own, in steel, to an efficent shape, then have it galvanised. At keast with steel, if the pitch isn't quite right, next time she comes out for a hull clean, you can whip the prop off and repitch it easily, not so easily done with cast bronze!

Daniel
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Re: Next Weekend II

Post by 87gn@tahoe » Fri Feb 03, 2012 8:09 am

Daniel,

Thank you for your input.

I would think the more efficient Simpson Strickland would be about the same power than either engine we have with their un-balanced slide valves and what not.

My father is actually considering fabricating one but he has so many irons in the fire currently with the rest of the project and trying to get her in the water by this summer (neighbors are complaining). It would be nice for him to just bolt one on and go.

If ultimately he has to go that route, then so be it. It will be significantly cheaper than buying even a used one... It's only time right?
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Re: Next Weekend II

Post by dhic001 » Fri Feb 03, 2012 8:22 am

Hi Wes,
The Simpson Strickland isn't one of their high performance models, its just a big well built compound. Its got normal slide valves, and only runs at moderate pressure and revs. At the same time, Simpson Strickland were building engines working at twice the pressure and rpm, and yet they were considerably smaller and lighter. If you need any measurements off Kapanui, say so now, as she is out for survey this week and won't be coming out again until maybe later in the year.
Daniel
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Re: Next Weekend II

Post by 87gn@tahoe » Fri Feb 03, 2012 8:53 am

What is your prop diameter & pitch?

Must be nice having summer right now...

EDIT: just saw you listed the prop dimensions previously
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Re: Next Weekend II

Post by artemis » Fri Feb 03, 2012 5:04 pm

:idea: It may or may not be overkill...

Oceanid is on "the hard" and all the machinery is out of her. Dan Martin (of Everett Engineering/Mosquito Enterprises) now owns her and has the machinery out. He might be interested in selling same. You could also check out the Burmah Queen. Jerry Ross has to scrap her and has the boiler and engine up for sale on the "classifieds" page of the NWSS website.

You can find the vital stats on both if you go to the NWSS website at http://www.northweststeamsociety.org and navigate to the >projects>boats>"boat name" and read the specs on each one.
Ron Fossum
Steamboating Magazine Editor
http://www.steamboating.org
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