Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old May 01, 2005, 07:44 AM
RGinCanada is offline
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I wonder how well cavitation was understood at the time? I was surprised to see the skewed blades. Wasn't it nearly 60 years before they came into vogue?
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Old May 01, 2005, 09:13 AM
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All the best ideas seem to have been 'reinvented' at least once - castor oil, canards, round bilge fast hulls, high aspect ratio rudders/low aspect ratio rudders, biplanes....

....and wasn't there an early prop driven steamship converted from a paddler which had skewed blades? I can't recall the details but have a picture in my mind of a renovated ship in drydock - riveted prop, painted red with a metal band around the tips to hold it together. The important thing being what must have been difficult to engineer, thin root blades with the main area being behind the trailing edge of the root.

I don't really understand props too clearly, but like most modellers I really appreciate the look of such shiny, beautifully sculpted bits of metal.

Old May 01, 2005, 10:44 AM
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Cavitation


This, again, from my Father, Charles, who is unable to post at present but thought it might be interesting to the discussion:

The first time cavitation became a real problem (the phenomena was known but little understood) was upon launch of Cunard’s “Mauretania.” At trials, with speed at not quite 20 knots, the ship shuddered so badly that those on the bridge were shaken uncomfortably. The screws were the latest in design of the period and not defective at all. Cavitation had turned the steel hull unto a giant tuning fork.

This was an infant science. Wooden and steel hulls do not resonate at the same frequency and although screws had been tried on wooden hulls, it was already known that wooden hulls would not support the raw power needed to push screw-type propellers. Although Parsons had done pioneering work by using high speed photography with intense illumination in a glass-walled tank and had actually observed that a rapidly revolving propeller creates such thrust and resulting suction that the water behind it is literally vaporized. The vapor appears at the trailing edge of each blade as an elongated, spiral bubble. Water rushing in to fill the vacuum hammers the blade surface and can, in a short time, pit and weaken the material.

Cunard had constructed small prototype electric launch prior to constructing the “Mauretania” and while this aided in the placement of the screws, it was of little help in predicting the intense vibration that eventually plagued the ship. Short of inserting a diver with a suicide wish into the water as the ship passed, there was no way at that time, to observe propeller performance while underway.

The ultimate solution was to strengthen after hull members following trials and a new set of redesigned propellers were put into the works, although not delivered until a year later after one of the original propellers fell off at sea. The new props solved much of the problem, greatly reducing vibration. It is a testament to her design that she made eight crossings on three screws while waiting for the replacements.

Brian
Old May 01, 2005, 02:25 PM
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Yes, he could have used larger propellers with more blade area to fix the problem.
Old May 01, 2005, 03:26 PM
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The British Admiralty used 176 ft. HMS Rattler a converted sloop to test propellers. In 1845 they actualy had a tug-of-war with her half sister, 164 ft. HMS Alecto sidewheel steamer. Alecto got a head start but when Rattler's engine got going it was no competition, Rattler easily pulled Alecto stern.
Old May 19, 2005, 01:11 PM
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I've just received my plan of Turbinia from Nexus.

Really, it's a side and top view drawing with eleven hull sections plus views of the various above-deck structures - all full size for the model.

The plan is by David Metcalf, and is for a model 50 inches long with a maximum beam of 4.5 inches. Displacement suggested is 9.75lbs. Suggested motors are three Cyclone 20 or similar with scale prop layout (three per shaft).

I think colouring will follow the vessel as she is now, so I may try and scrounge some of the paint they used to match.

Looking quite exciting now.
Last edited by Tony Oliver; May 19, 2005 at 01:13 PM. Reason: finger trouble
Old May 19, 2005, 02:26 PM
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Please keep us updated Tony! This looks to be an unusual and exciting project!
Old May 23, 2005, 01:52 AM
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Hey Tony,

Have you seen the photos of the Surry Park MBC in Victoria, Australia. Go to the www.modelboatmayhem.co.uk site -> Galleries -> Australia and then Part 2.

Its a nice looking model.

Cheers
Old May 23, 2005, 04:18 AM
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I hadn't! - but I have now!

Thanks for the link.

Nice looking boat and very encouraging. I particularly like the reference to it going too quickly to get a good photograph. Sounds exactly what I'm aiming for.

They've even got a version of the rowing boat I built too.

Fine upstanding fellows, you Aussies!
Last edited by Tony Oliver; May 23, 2005 at 04:19 AM. Reason: finger trouble
Old May 31, 2005, 05:41 PM
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Amazing just amazing
Old Jun 11, 2005, 07:05 PM
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Hi Tony,

I noticed in the June edition of MMI, that John Mandell from the Looe MBC exhibited his Turbinia at the Liskeard boat show in Cornwall.

Isn't it amazing how you never 'see' things until you become aware of them (does that make sense?) Like when you buy a red sports car and suddenly 'see' red sports cars everywhere.

Cheers
Old Jun 12, 2005, 04:11 AM
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:0

How right you are!

That happened with my Flower - never seen a conversion other than those which came up on a search. Even while working on it I must have seen a dozen or so at various events.
Old May 11, 2007, 12:37 AM
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Hello Tony,

I saw that your hull is made of glasfibre. Is it self-made or do you buy it. .and how long is it?

At this time I look for parts to build the "Turbinia". A well-made steam turbine I already found...

Many thanks, Ottmar
Old May 11, 2007, 03:18 AM
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I've bookmarked this topic for future viewing. Steam turbine??? This is gonna be a good one!

Chuck
Old May 11, 2007, 08:05 AM
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Turbinia? Chuck, don't you have enough projects already?


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