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Very large semi displacement ships

ceccherini

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I was wondering why among the many projects of military and civilian ships both very large and very fast no one seems to employ some semi planing hull design. The basic concept seems to be well understood from the second part of the XIX century and it was applied to quite large ships like the Freedom LCS and the Tirrenia Jupiter class ferries. So why there has never been any concept for a semiplaning battleship, aircraft carrier or ocean liner or at least destroyer? Is it realistic to assume that had large surface warships and passenger ships continued to evolve toward greater speed they would have adopted a semi displacement monohull design or are there some intrinsic limitations in scaling the concept to a very large size (say 50000 ton+)? It is possible in other way to built some sort of Queen Mary sized Destriero or Yamato sized Freedom?
 
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ceccherini

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Speed costs money.
That is exactly my point. Take for example the Malglaive-Hardy 1937 project for a 37 knots liner, 1350 foot in length and well over 100k ton in both displacement and GRT. It required 400k hp on 6 propellers. Or the BB-65 8 study, on the same scale but related to a military vessel. Wouldn't equivalent semi displacement designs reached the same speed with less horsepower? I'm not talking about building such a thing but dream for dream why not a planing design? What was the inherent drawback?
 

apparition13

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There have been. The RN's Black Swan sloop design from a few years ago had a semi planing hull design, but that was smaller than Freedom. Fastship was a company that proposed some cargo ships that could cross the Atlantic at 35kn full load. I believe at least one of the designs was in the neighborhood of 265 meters length. Global security has some info.


Here's a wiki article on the company.


There were also some youtube videos, but I can't find them right now.

I think these are pretty interesting designs. They wind up with a wider beam than present warships, more along the lines of battleships, which would mean more deckspace for things like vls cells. Add that to increased speed, and improved sea keeping according to some studies, and they look interesting to me. But the only way to validate the theory would be to build a full size hull and test it out, and no one has been willing to spend the money to do that research.
 
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Nigelhg

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Semi displacement boats aren't nearly as efficient at high speeds compared to planing hull type boats but generally have a softer ride. The waterline length of the displacement type hull determine their top speed which with most naval boats being large isn't really an issue. The current trend in design is towards very slim wave piercing designs for high speed, efficient and seaworthy designs- the Zumwalt DDG1000 is one of the first large vessels of this type.
 

Nik

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Didn't a bunch of such 'fast ship' concepts 'crash & burn' during 'Oil Crisis' ? Suddenly, fuel economy was 'in'...

IIRC, the same pricing change made those big cross-Channel hover-ferries uneconomical...

( Rode one, once. IIRC, it took a short-cut across 'Goodwin Sands' during 'inclement' weather, wave-heights such that you could glimpse beige banks in the troughs. The unfortunate 'Trolley Dollies' and incautious passengers went totally airborne during each mega-lollop when air-cushion blew out. Our family was sat fairly near C/L & C/G, but still took a hammering. End of that season, seat-belts were retro-fitted... )
 

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