SWATH resistance predictions using Michlet

Discussion in 'Hydrodynamics and Aerodynamics' started by Leo Lazauskas, Mar 13, 2012.

  1. Leo Lazauskas
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    Leo Lazauskas Senior Member

    They are fascinating from a wave resistance aspect, too.
    Are there any in service now, apart from the Lockheed original?

    One feature I thought interesting was the ability to add another strut+pod
    between the aft pair. Has anyone tried this sort of modification on a full-size
    SLICE?
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    There are 2 in Mexico, Tenez and Lider are their names.

    SLICE x 2.jpg

    You mean have 5 strut/pods?
     
  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Yes. I have a short report touting that as one advantage of SLICE.
    To carry extra cargo, operators can "simply" drop in another strut and pod.

    Personally, I imagine that it is not as easy as all that.
    There will obviously be knock-on effects on resistance and motions, and the
    cross-structure would have to be able to cope with the additional loads.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Correct.

    Their myopic gain, in buoyancy, for increase payload capacity marrs the myriad of losses it would suffer from, by the adding of a hull/pod.

    For starters, it would only effect heave and pitch and only marginally at best.

    SWATHs are not really designed for high payload as %'age compared to other multi hulls. SWATHs do one thing and only one thing well...seakeeping! As soon as you add other things into the equation it slowly degrades and compromises the seakeeping. SLICE is a classic example. Probably best seakeeping vessel ever made, yet at what cost!....very very expensive, slow, (for its size) the gear boxes are unique to that hull and have a lead time of 12 months....so you'd better have a spare, which means $1-2million dead cash etc etc....see what I mean? Hence a decent SOR is required first. As "normal" SWATHs can do much better, all round that is.
     
  5. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Apart from that, the structure must be strong enough to cope with the
    occasional addition of the 5th leg. That means carting around additional
    structual weight most of the time.
    It just doesn't smell right.

    I'll be interested to see the powering required for a 50 knot SWATH and
    how much it can carry.
    Bill McF: Are you free to disclose rough estimates of full load displacement
    and powering?
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    There is the obvious too...which is over looked.

    Looking at the pictures of Lider/Tenez,...er...where can you fit another hull?

    Ahh..extend the main deck...oh..a redesign! :eek::mad:

    I'd be interested in the displacement and powering too at 50knots, see how it compares to ours at 40knots.
     
  7. Leo Lazauskas
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    Leo Lazauskas Senior Member

    To be fair, the modification I saw was for a working vessel with a moonpool in
    the centre. I'll try to find, scan and post the article here.
     
  8. BMcF
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    BMcF Senior Member

    Unfortunately, I'm not. NDAs in abundance and all that. I can tell you this much though, so you don't think you are missing out on the 'mother load' of any paradigm-shattering envelope-busting data :D:

    The prototype is very small, less than 20m LOA...and attempts to achieve the higher design speeds have not even been made yet.

    Stay tuned...and I do appreciate you posting those papers; every bit of information regarding a "high speed" SWATH design is usefull to us at this point in the effort. And goodness knows, getting anything out of John is worse than pulling teeth from a lion..:p
     
  9. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Here's another one from 2009 on resistance prediction of high-speed SWATH.
     

    Attached Files:

  10. Ad Hoc
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    Ad Hoc Naval Architect

    Thanks Leo.

    Technically, this isn't a SWATH at all, just a rounded hull form with a shape that looks at first like a SWATH but is in reality just a catamaran with a lot of shape.
     
  11. DCockey
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    DCockey Senior Member

    Leo, are the singularity strengths of one hull of a multihull vessel in Michlet altered by the presence of the the other hulls, or are the singularity strengths of one hull what they would if that hull was the hull of a monohull vessel?
     
  12. Leo Lazauskas
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    Leo Lazauskas Senior Member

    The latter, David.

    I have been thinking of what to do to improve the model, but it is not as
    simple as just modifying source strengths. In finite depth, finite width
    towing tanks, bores can form between hulls, and solitons can shoot out
    ahead of the vessel. That's tough to model! I have all the mathematical
    work needed to include Havelock vortices in some models, but I don't have
    much incentive (or time) to implement it all.

    There are also some viscous interference effects when demihulls are closely
    spaced. I am trying to include that in Flotilla. (It would be messier in
    Michlet which can have up to 5 demihulls in any arrangement.)
     
  13. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Attached is a short article about the SLICE.
    It seems that the ability to increase passengers from 250 to 400 by simply
    adding a 5th pod has yet to be realised.
     

    Attached Files:

  14. Ad Hoc
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    Ad Hoc Naval Architect

    A classic example of a press release. More spin than substance.

    There are only 2 SWATHs in the world that have successfully achieved 30knots or more on a regular service time table, SLICE is not one of them.

    The hull form is also not capable of 30-35knots, well unless you can find GTs that don't consume so much power it doesn't take up all the available space for fuel nor weigh the boat down that its over weight to begin with!!
     

  15. Submarine Tom

    Submarine Tom Previous Member



    Now why does that last sentence sound familiar?

    lol

    -Tom
     
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