What happened to passenger hovercraft? BBC text story

Discussion in 'Powerboats' started by DCockey, Nov 9, 2015.

  1. DCockey
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    DCockey Senior Member

  2. Ad Hoc
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    Ad Hoc Naval Architect

    I read that yesterday too. It is an interesting story doesn't give all the info but gets most of it correct.

    The new (then in 19994) HSC code didn't help much either as the CAA relinquished its role to the MCA and thus hovercraft were required to comply with the new HSC code. Not an easy task. I was on the UK committee of the new HSC code and the hovercraft group were not happy with the change of rules, understandably so too. Coupled with the arrival of the big Incat Cats, despite the tag of Vomit Comet, was the final nail in the coffin for the larger hovercraft anyway.

    It doesn't say much about SES's which are ostensibly the next generation and address the issues of noise (somewhat) and stability etc. But the heavy lift fans the cost and space requirements etc....still tend to hold them back compared to other multihulls.

    But history is littered with great products/inventions...simply looking or waiting for a market to emerge...only to fail as said market never came.
     
  3. powerabout
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    powerabout Senior Member

    When the wind blows they cant meet their timetable
     
  4. Alik
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    Alik Senior Member

    Howercraft are much more expensive to build, service, and operate. Catamarans do the job.

    BUT if amphibious capabilities are required, howercraft are still in use. Say, they are used in Russia in winter period over rivers for passenger transport. They are also used for ice rescue.

    We use table to review the possible options, evlauate them in non-emotianal manner and direct the customer:

    Priority factor Monohull Catamaran ACV Hydrofoil craft WIG
    Construction cost 1 5 4 2 2 1
    Fuel efficiency 1 5 5 3 5 3
    Seakeeping and motion comfort 1 4 5 2 4 2
    Comfort, layout, usage of space 1 3 5 3 3 2
    Service and maintenance 1 5 5 3 4 2
    Complexity of operation 1 5 5 3 4 1
    Draught limitations 1 4 4 5 2 5
    Safety 1 5 5 5 5 3
    Ice capability 1 1 1 5 1 1
    TOTAL SCORE 37 39 31 30 20
    5 – most attractive; 1 – least attractive
     
  5. daiquiri
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    daiquiri Engineering and Design

    Hi Alik,
    I have made the following copy of your table, trying to make it more readable:

    Vessel review - Alik.jpg
    The best scores are highlighted with green color and the worst ones with red.

    There are couple of scores which would perhaps require a brief explanation, because they are not immediately understandable. See the red circles and the relative alphabetical marks:

    A) You have given the same motion and seakeeping score to a monohull and to a hydrofoil vessel. I would expect the hydrofoil to behave better in a fair range of sea states, with much more contained motions and accelerations along all three reference axis.
    For the same reason, I would actually expect the WIG to have the highest score, followed by a hydrofoil, the cat and by the mono.
    I know very little about ACVs, so I have excluded them from these considerations.

    B) The same layout and usage of space score is assigned to both a monohull and a hydrofoil vessel. In this case I would expect a monohull to be in a better position, because it can carry a much higher load than a hydrofoil - although at lower speed. Small weight is everything when it comes to efficient flying on foils.

    C) Finally, I see the same service and maintenance score for both mono and cat vessels. However, a catamaran is structurally more demanding and mechanically more stressed vessel in certain areas, which in turn imply a need for a higher frequency, required accuracy and cost of maintenance.​

    It would be great if you could you write a couple of comments on the above considerations, in order to clarify the criteria of assignment of scores.

    Cheers!
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I accept that Alik's ratings are sound and sensible, as befits a good NA's
    "market" research.

    (Like you, I doubt that the market will ever emerge that will require fleets of
    large SES.)

    But if 75+ knots are mandatory, as well the ability to carry a reasonable
    amount of cargo over a reasonable range, then SES and ACV are probably
    the only viable option. Monos, cats, tris (i.e. stabilised monohulls) all end up
    too heavy, and not having the range and/or cargo carrying ability.

    I found that (1200 tonne) Cats and Tris are generally limited to about 55-60
    knots; SES are good for up to 75 knots, and ACV are the only option for 80
    to 100 knots.
    "Hydrodynamics of advanced high-speed sealift vessels",
    http://digital.library.adelaide.edu.au/dspace/handle/2440/37729
    Those speed and weight limitations are roughly in accord with work by
    Kennell and others who looked at large high-speed sealift vessels back in the
    late 1990s.

    The "100 knot Navy" objectives are very tough!
    1 million tonnes delivered to any coast in the world within 28 days, and
    250,000 tonnes delivered in the first 7 days.
     
  7. BMcF
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    BMcF Senior Member

    I don't disagree with that. But note also that the powering requirements for a 50-knot SES are still well below that for a "payload equivalent" cat or tri operating at the same speed.
     
  8. daiquiri
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    daiquiri Engineering and Design

    Me too. I am just trying to better comprehend the rationale behind such comparative tables. I've never made one, so I am an ignorant here.
     
  9. BMcF
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    BMcF Senior Member

    Good catch. A state-of-the-art hydrofoil with flight control will exceed any other vessel type when it comes to motions and ride quality.
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    Agreed. But being the only "solution" also does not mean it is game changing option. The market for such a vessel is somewhat limited at best.

    Looking at the Japanese TSL, at LOA 140m, speed 44knots, carrying 925tonne with 2 x 25,000kW GTs, and 4 x 4000kW lif fans, is no small power requirement.
     
  11. BMcF
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    BMcF Senior Member

    The TSL was a failed attempt to leverage a bunch of technology that was "handed over freely" but not nearly well enough understood by those on the receiving end. Put another way..the TSL is one of MANY failed attempts to utilize SES technology by those whose understanding of it's limitations and critical parameters was....inadequate, at best.

    I'm on record as declaring the TSL-SES "DOA" not less than 3 months after key parameters of that vessel became public record.
     
  12. Ad Hoc
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    Ad Hoc Naval Architect

    You and I both know, yards never seem to listen to the designer and think they know it all simply because they suddenly have a bunch of dwgs in their possession, ergo, 'we' know what we are doing :eek:
     
  13. Alik
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    Alik Senior Member

    Thanks for You comments. This table is from paper on small passenger craft design which was presented at Marine Design 2014 in UK.

    One should treat this table in connection with particular project, not as general comparison. For particular project priorities and scored could differ. The scores I gave are for high-speed small passenger craft, i.e. about 50 passengers.

    A) Seakeeping - hydrofoils are strictly wave limited craft, as well as WIG. At certain wave conditions they have to crawl on their bottom. For WIG - they have limit of take-off wave height. And pls note that we are comparing vessels of the same size.

    B) Most of passenger craft are defined by volume not by mass of cargo.

    C) On our small passenger cats, I don't see much difference in service compared to monohulls operated at nearly the same speed.
     
  14. daiquiri
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    daiquiri Engineering and Design

    Thanks for the reply, Alik.
    So what is missing in that table is the context - sea state, overall dimensions and speed. Which sounds reasonable.

    Talking about hydrofoils having to "crawl on their bottom" in certain sea states, a comparison with sailboats comes to my mind. A bare sailboat hull will have very pronounced rolling motions in wavy seas. Hovewer, adding the keel and rudder improves considerably that behaviour, because they act as stabilizers. When moving under sails, the roll period becomes very long, because of the additional stabilizing contribution by sails.
    Wouldn't the same happen to hydrofoils, when compared to bare-hull monohulls? At least intuitively, they should have a more favorable RAO than monohulls, due to stabilizing effect of both struts and foils.
    Any opinions on this?
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Hovercraft seemed to create a few noise issues that got people excited, that I recall.
     
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