10 foot SWATH

Discussion in 'Boat Design' started by amaurer, Jun 30, 2009.

  1. yipster
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    yipster designer

    sure, i wouldnt mind seeing more pics eighter but after that chance of having a second look must admid that pic wasnt even swath'ish
    to the experts here but not to the point: big swaths having pods at say 10 meter dept have twice the buoyancy?
     
  2. mydauphin
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    mydauphin Senior Member

    If it doesn't quack, have web feet or a beak, is it a duck?
    Dsikra, would say the definition doesn't specifically require those...

    I think simply a SWATH has to have a mass large enough underwater to displace the complete upper portion from wave action. That requires a certain, as some have said decouple, or distance between underwater and above water hulls.

    On a separate issues, even thought SWATH means twin hulls, certainly a trimaran or more hulls could be a Swath, so why not a crazy swath monohull.

    A swath monohull would be interesting, or how about a Swath platform with one leg...
     
  3. Guest625101138

    Guest625101138 Previous Member

    You have not looked through the previous posts. See attached images from video link posted a few pages back.

    Once you get these hulls deep enough they behave as submarines with their attendant efficiencies having little to negligible wave drag depending on depth.

    The optimised Albacore AGSS 569 repotedly achieved 33kts with 7500HP. Not too shabby for a vessel displacing 1540t. Incredibly a drag to displacement ratio of just 2%. Way better than can be achieved with even a hydrofoil.
     

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  4. Ad Hoc
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    Ad Hoc Naval Architect

    "...I think simply a SWATH has to have a mass large enough underwater to displace the complete upper portion from wave action.."

    The buoyant part under water is simply a result of what the vessel is intended to "carry", otherwise it sinks!

    A SWATH, when written correctly, is self evident
    Small Waterplane Area Twin Hull. The small waterplane area reduces the radius of gyration. The motions are directly proportional to the radius of gyration.

    For example, in a simple harmonic case:

    (virtual mass moment of inertia) + (damping coeff's) + (restoring moment) = Amplitude of said motion.

    The inertia of the waterplane area = virtual mass moment of interia components.

    So, cutting a long story short, low waterplane area, lower motions.

    These SWATHs with one leg wont go anywhere, they are just 'fun' research projects. They require lifting surfaces to control roll and picth, for example, some have small outriggers/ama's, all of which are not very practical espically when the hull is breached, or, are no better than a SWATH which can and has been built and fully operational.
     
  5. mydauphin
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    mydauphin Senior Member

    Guess I miss it rick. This thread is getting longer than 10 foot swath.
    Monohull swath probably handles like a motorcycle... Might work for unmanned 10 foot swath research vessel
     
  6. Guest625101138

    Guest625101138 Previous Member

    Yes you have it. See post #1.

    It is a good question and worthy of detailed analysis as suggested per post #59.
     
  7. weelilboats
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    weelilboats New Member

    how bout a self righting lifeboat design put your bateries on a gimbal mount in the center and your solar array on the top deck lots of surface area up there
    pluss all your electronics would be inside out of the weather
     
  8. Submarine Tom

    Submarine Tom Previous Member

    Like in Post #7?
     
  9. Squidly-Diddly
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    Squidly-Diddly Senior Member

    mono-hull "swath", how about this 'semi-submersable PT boat'

    http://strangevehicles.greyfalcon.us/VS 5.htm

    Other interesting stuff on that site includes the "Manta", a hybrid submarine-hydrofoil that also appear to have four wheels. Not sure if the wheels were retractable or just for rolling down a launching ramp.




    [​IMG]

    [​IMG]
     
  10. Paul Kotzebue

    Paul Kotzebue Previous Member

    I have some experience with small SWATH vessels, having designed four of them and logged several thousand Pacific coast miles on them.

    Yes, they are very draggy. They use a lot of fuel unless you're going real slow. They also have a relatively low GM and are tippy at the dock. Stepping on the outboard bow of a 10 foot SWATH could be a little sketchy.

    That said, a SWATH as small as 40 feet with an active ballast system and a good motion control system has phenomenal seakeeping ability.
     
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  11. aggogle
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    aggogle New Member

    "That said, a SWATH as small as 40 feet with an active ballast system and a good motion control system has phenomenal seakeeping ability."

    I know this is an old thread but what did you mean by "an active ballast"
    Peter. Aggogle
     
  12. Ad Hoc
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    Ad Hoc Naval Architect

    A swath requires a ballast system that ensures the draft and trim are constant. Therefore whether you're near light ship or full load, the draft remains the same. So to achive this you need a ballast system that is "active" and not "passive". It requires the ability to pump large volumes of water up to the tanks in a very short time period.
     
  13. aggogle
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    aggogle New Member

    Thank you Ad Hoc... Does this adjustment of draft take place once at the dock or is it an on-going process? I had assumed that the fins alone were active when underway.
    That you say "large volume pumps" makes me wounder. Peter. Aggogle.
     

  14. Ad Hoc
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    Ad Hoc Naval Architect

    You ballast down prior to going to sea. The drafts are at the dwl when you leave port, regardless of the laoding condition. Hence you need high volume pumps otherwise you'll wait for ever.

    For example, the SLICE has 4 ballast tanks, each with a total volume of around 7,000m^3. These are filled in approximately 5mins.

    On most journeys the amount of fuel you burn does not render having to reballast. But if the voyage is a long one, then you shall be required to add more ballast to offset the lost of "draft" by burning a large amount of fuel that reduces the draft from the dwl.
     
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