boat design - art or science?

Discussion in 'Boat Design' started by albentley, Mar 6, 2007.

  1. Verytricky
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    Verytricky Large Member

    Art is making a pretty boat.

    Engineering is making a boat that works.



    A true genius marries the two.
     
  2. DanishBagger
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    DanishBagger Never Again

    Tri-star

    I take it you have to be an american to think of "signing up for the military" as "becoming disposable".

    You're rewriting the meaning of the word "disposable" in order to defend the constellation "disposable fighter", although most fighters cost the farm, or actually, many farms.

    In reality, there are no such thing as a "disposable fighter" - ask around.
    And the people that sign up for such service aren't disposable either, hence catapulting seats, so they can get out alive.

    I'm thinking - I'm pretty much willing to bet that if you had the same amount of engineers and scientists working to manufacture a boat of a given design, that that boat could be much better than the civilian race-editions.

    But, and I see this as the crux between boats and planes: THe forces acting on a plane is much more predictable than that of a vessel in water.
     
  3. bfisher33
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    bfisher33 B.

    to agree with other members, Boat design is an artistic science. You have to be able to visualize the boat first, but then you ahve to make it work. Then you have to sell it. And to sell, it needs to look good. Unless its the navy. Or Exxon.
     
  4. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Firstly, I am not, nor ever have been, an academic. I just happened to work in a university maths department.

    Secondly, macaroni cheese is the staple diet for students and hydrodynamic bums here. (On special occasions it's eggs and toast slices - aka googs and soldiers.)

    Thirdly, in a recent paper, (Sept. 2006) Lawry Doctors and Chris McKesson used a 2000t SES as an example vessel. The air cushion is 72m X 17.5m and the cushion pressure is 12800 Pa. That's about 178 Pa/m. Does that seem high to you? When I last paid attention to achievable pressures, the "state
    of the art" was about 165 Pa/m.

    Regards,
    Leo.
     
  5. BMcF
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    BMcF Senior Member

    So, Leo, you are a poor peanut-butter eating marine designer like me then?

    20+ years of trying and I still can't get Larry to spell his name correctly. :p

    I have always defined/used the cushion loading 'charateristic length' as the square-root of the cushion area. Using that definition, 300 Pa/m has stood up well over time as a good threshhold or target and the SES that Chris and Lawry are talking about comes in at about 360 Pa/m using my definition. A bit high, yes, but still 'OK' perhaps. The

    In historical review, all the 'good' SES performers were at or below 300 Pa/m..some of the 'bad' ones, and there were many, exceeded even 400 Pa/m and were dogs. Looking at three of the 'best', the 40m SEMO SES ferry is at 293 Pa/m..the RNoN Skjold at 303 Pa/m..The SES-200 at 306 Pa/m.
    ( By 'best' I'm referring to where they fall on the Gabrielli curve in terms of transport efficiency..each of these three falls 'above the line')

    I have not tried to see how a loading factor based on simply actual cushion length holds up against the data.
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    They have concrete canoe races, so why not clay hovercraft.

    When you finish the real thing (or even before) I'd be happy to use it as an example for calculating resistance and wave elevations if you don't mind providing some dimensions and other variables I would need.

    Regards,
    Leo.
     
  7. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No, I'm not an engineer. It's you guys who keep us applied
    mathematicians from having to get our hands anywhere near
    high-speed machinery. Thanks for that.

    Thanks also for the rule-of-thumb cushion pressure target.
    I have seen Pc/Lc used by some Spanish and some Korean SES
    designers. Pc/Lc=165 was considered as a maximum "state of
    the art" ratio by Lindez, J.G. and Villa, F.M.G. in
    "Fast Cargo Vessel: Concept Assessment", FAST 2001, pp.51-61.

    I'm trying to put together a small set of SES designs to
    illustrate some calculations of drag, wave elevations and
    bottom pressure signatures. Eventually I would like a
    reasonable range of vessels from existing small recreational
    hovercraft and fast ferries to sci-fictional one million ton
    SES. I used to have a "bestiary" of multihull arrangments
    somewhere on the net: this would be a sort of air-supported
    counterpart.

    L.J Doctors is affectionately known as Lawry here. Come to
    think of it, I've never heard of anyone in the U.S. with the
    nickname Lawry. Perhaps Larry is the non-metric equivalent.

    Leo.
     
  8. BMcF
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    BMcF Senior Member

    The Spanish did some good baseline work with their 'Chaconsa' SES testcraft program..but no Korean SES deisgns were ever built. There were of course, SES vessels built in Korea..but they were designed by 'others', like ourselves. As is so often the case in this bidness of 'boats what ride on air'..most of it is 'hot' air since we (the community of 'we') seldom get the opportunity to prove previous theories or expand upon new ones.

    Fast 2001..I never received the proceedings from that one. I attended the first two 'Fast' conferences (Tondheim and Yokohama) and that was about it.

    Does your program predict with or even deal with the effect(s) of water depth on ACV/SES drag? I've always had a hard time explaining to folks that air-cushion vessels have lower drag in shallow water than in deep water...and then follows the inevitbale questions about 'how shallow' and 'how deep'
     
  9. kach22i
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    kach22i Architect

    That would be great, it's kind of a cat with a front drape and seperate stern bag which I'm struggling with. I also have in model form (3 ft long) a kind of tri-hull hovercraft (one up two back) design. I'm not going to post that one, as I expect it to go straight but not turn well, I'm constanly re-thinking it.

    About Korea (old post of mine):
    http://www.hoverclubofamerica.org/forum/index.php?showtopic=1042&hl=Korean

    As Korea's first shipbuilding company with 6 decades of experience, Hanjin Heavy Industries is leading the world's shipbuilding, construction and industrial plant technologies.

    http://www.hanjinsc.com/english/sub/industry/in_01b_e2.html
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    http://www.hanjinsc.com/english/sub/industry/in_01b_c1.html
    [​IMG]
     
  10. BMcF
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    BMcF Senior Member

    Yes, the Koreans have done a lot with 'other folks' help to start with ..and have certainly expanded on the designs in some areas. I worked with some of those projects that you illustrated. HoverMarine (HM) SES designs from Tattersall and Lewthwaite..the 'baby' LCAC hovercraft developed with help from the USN LCAC design community, etc. Korea Takoma (the builders of the HM designs in Korea under license before they went Tango Uniform and were absorbed by Hanjin) was also negotiating to build Cirrus (Norwegian) 35m SES ferries at one point. And did you know that more HM-derivative SES' were produced - by far - than any other type before or since? Still quite a few of the 218s sporting around Hong-Kong and Macao, I believe.
     
  11. kach22i
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    kach22i Architect

  12. BMcF
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    BMcF Senior Member

    That was in the 80s....not a lot of information out there from that period except what little was published 'on paper'.
     
  13. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Yes, my programs can handle finite depth. Here's a plot of
    the Newman-Poole wave resistance coefficient C_NP
    for the "pure" ACV with L/B=11 I showed in a previous post,
    but here finite depth results are included.
    This (rectangular) pressure distribution has L=76.4m and
    B=6.95.

    I can also model how viscous layers on the surface of water
    (e.g. oil slicks or ice slush) affect wave-making. It's
    probably too weird to be of much use to anyone until the
    icecaps melt, partially. When specialist SES are needed to
    rescue floundering polar bears, I'll be ready!

    It's probably easier to use displacement hulls to show that
    the wave resistance in finite depth can be less than in
    infinite depth. If people don't believe computed results
    from, for example, Michlet, show them the experimental
    results in the other graph attached to this post.

    Leo.
     
    Last edited: Mar 26, 2015
  14. BMcF
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    BMcF Senior Member

    But..if I'm reading your graph correctly, it shows resistance increasing with decreasing depth...as one would expect with a 'normal' ship hull.
     

  15. tri - star
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    tri - star Junior Member

    To DanishBagger:
    you make people's heads spin.....

    Since; from at least Spartens days - all things military are expendable.
    Remember, in school, the story of the Sparten boy - who dies rather
    than to let on, to his superior that he has an animal under his cloak.

    This story told, to show how a good soldier will die, rather than break
    ranks and the incredible discipline expected in Sparta
    - of even the youngest cadet.

    Calling me an American - won't change history.
    Or insisting that the sky is green.

    Also, I'd gently suggest, that insulting Americans by inference, does
    you little credit.

    Finaly, your OWN words; support my arguement.
    - And defeats yours.
    i.e.
    "......no such thing...." disposable fighter "..."
    "......catapulting seats....out alive...."

    What else is the pilot doing when he presses the ejection seat button ?
    - But; turning his now - pilotless, Billion Euro / Dollar aircraft into -
    " disposable " scrap.

    ' Regards.
     
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