sea-worthy amphibious craft?

Discussion in 'Boat Design' started by jkittel, Sep 26, 2007.

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  1. kach22i
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    kach22i Architect

    I'd like to see all the concepts.

    By the time I get my model working I bet somewhere and someone will have already built a better version of it in some Skunk Works.

    Back to reality, I need to get an architectural proposal out, cheers.
     
  2. rwatson
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    rwatson Senior Member

    Yeah yeah - fling enough money at a concept and you can have bikini clad chicks carrying you everywhere in LearJets and bell helicoptors.
    How about concepts that the average boat nut can build/buy that achieve the same thing.
    Skirted amphibious catamarans are a good start, but the weight and payload for smallish craft are problematic.
     
  3. BMcF
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    BMcF Senior Member

    The one in the virtual pic I posted will carry about 400 tons payload. As for the cost...I'd be shopping for bikini-clad chicks..cheaper by far.:D
     
  4. rambat
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    rambat Member at large

    Skirt

    I would like to ask BMcF is there a reason to design fingers on the SES/Hovercraft (T-Craft) as you show? It seems the requirement is to only beach itself far enough on shore to unload the vehicles, would a simpler multi-loop skirt not do the job?
     
  5. captaintrue
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    captaintrue Junior Member

    ..dukw

    I dunno. Analysis says: its better to build a bit bigger to include a tender and tow the a wheeled multihill to the beach rather than building an 'all in one amphibious'--even if the ship has motive capability onshore, still seems more resourceful and economical to have it winch itself onto shore.

    But yet still, its probably best to quit thinking automobile (landlubber gear) in your style of wheel placement. Also, a removeable chain drive seems to be the simplest and most cost-effective way to drive the wheels.

    http://www.loyalhannadockyard.com/DUKW.htm
     
  6. rwatson
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    rwatson Senior Member

    The 'self winching' idea is an economical and efficient way to get a boat ashore - but its a bugger of a way to self launch.
    To get onto a beach, you need get a line ashore , which means someone has to go over the edge in who knows what type of sea, while the boat gets pounded on the sand, then haul a light line up to somewhere solid, or haul an anchor up the beach, then probably get a heavier line attached, and then get back on the boat to start winching if they are by themselves.
    Now we have to get the boat back to sea. Its ok if you remembered to put another anchor out before you took to land, but what if you crossed a sandbar on the way to another water body, or you are just launching the boat?
    The DUKW has more or less demonstrated that big wheels will do the job, but at severe loss of efficiency in water. Also, before a DUKW gets wet, you have to close a number of cooling ports to the engine, and change some settings in the drive chain. If you dont, you sink. This is a major problem with semi conventional drive techniques.
    Its true that a chain drive is simple and effective for many operations. However, in a marine environment (sand,salt etc) they are short lived due to the many rollers and links that it consists of. A chain that would move say a 2 tonne yacht would be pretty heavy to unfasten and store somewhere, and then you would have to wash and desalt it.
    Another potential method that doesnt get a lot of press is an Oscillation thruster. This is a series of weights driven by and engine that work like a skipper of a small sailing dinghy who 'pumps' the boat forward with sudden movements of his body, creating forward momentum. I have read stories of how this technique is used for heavy equipment that has to be moved across say swampy ground where tracks dont provide enough grip or surface area.
     
  7. BMcF
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    BMcF Senior Member

    The requirement/objective was for the beast to traverse mudflats and beaches (within reason on grade and 'flatness') with a certain degree of autonomy and considerable range. Thus, a low-speed hovercraft skirt system was designed along the lines of those already used on 'tundra platforms' and the US Army's 'amphibious' barge conversion kits. It also had to be fully retractable and that drove a segmented skirt also..but for reasons that are much clearer if I could show the craft ins 'SES mode' and I have not found a public domain shot that would suggest I'm at liberty to do that yet.

    As an SES in 'long range transit mode' the craft uses only waterjet propulsion with diesel prime movers and, of course, its lift fans. In high-speed SES mode, the air screws are also lit off. In amphib mode, only the air screws provide propulsion and steering control.

    Since the craft is both a high-speed SES and a fully amphibious low-speed hovercraft (but not at the same time), it must have the SES bow and stern seals and the ACV peripheral skirt..and use both in amphib mode.
     
  8. tspeer
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    tspeer Senior Member

    Why would you have to motorize those wheels at all? You could have a single drive wheel on a strut that was lowered from the bridge deck. It wouldn't have as much traction as you'd get from having all the weight of the boat on it, but it would be adequate if the terrain wasn't too steep.

    Actually, motorizing the main wheels isn't that difficult, either, if you go diesel-electric. Each wheel can have its own electric motor, with the genset in the hulls or bridgedeck. And with each wheel individually driven, you can steer with differential torque.
     
  9. rwatson
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    rwatson Senior Member

    Motorizing the wheels with either hydraulic or electric motors IS a great idea - just where do you get MARINIZED (rustproof/waterproof) drive unites from ?

    I would be interested in a rough sketch of "a single drive wheel on a strut" that you have in mind, to see what you mean.

    My thoughts against lowering wheels include strong enough suspension, flexible power trains and a whole host of other little problems.
     
  10. Jimbo1490
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    Jimbo1490 Senior Member

    You really will need to power most, if not all of the wheels for the thing to be practical. One traction wheel is just not going to cut it. It's hard enough to haul a boat and trailer out of a slippery ramp driving TWO wheels.

    And I think wheels are the way to go rather than walking 'feet'. The complexity and expense/maintenance of a suspension is out of the question; tundra type tires get by that problem and help with load spreading, which is absolutely essential on a soft beach.

    I have an idea that encompasses the above and more but it is hard to describe with words. Pencil sketches show the basic soundness of the concept but I've been too busy to sit for a CAD drawing lately. Maybe this weekend I'll get to it.
     
  11. captaintrue
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    captaintrue Junior Member

    * Make them (use brass, aluminum brass...saltwater friendly metals)
    * Take existing components and coat them with protective coatings?
    * Strategic use of oil/grease

    [A chain-drive could be disassembled, coated/treated and then reassembled.]
     
  12. kach22i
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    kach22i Architect

    Wheels and tracks are fine if you have something solid to grip on to. The idea situation is to go where they don't expect you, like a place really muddy or swampy or covered with thin or unstable ice.
     
  13. rwatson
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    rwatson Senior Member

    "Make them (use brass, aluminum brass...saltwater friendly metals)
    * Take existing components and coat them with protective coatings?
    * Strategic use of oil/grease"

    Not feasible to interrupt a 100 a day production line, with the custom cast components that you had to have specially poured, and they wont warrant for performance due to lack of testing.
    And you cant just coat components. Zinc adds size to parts, well outside close tolerances, and other coatings just dont cut it for long term performance.

    I have just about given up on conventional wheel/track designs due to the potential expense and lack of marine standard components.
     
  14. captaintrue
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    captaintrue Junior Member

    Fair enough. And then there are coatings which few seem to pay attention to.
     

  15. SamM1234
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    SamM1234 Junior Member

    This may be a dumb idea; I didn't really think this through. But, what about extendable support poles similar to the ones you see on construction equipment. The support poles would retract completely inside the hull when not used and would not have any moving parts/mechanisms below the water line. This would not allow the boat to move over land, but would allow to come close to the beach and raise it out of the water. So, one could still have it close by and could sleep on it not feeling the wave motion, provided it is parked at high tide. Hull cleaning and maintenance tasks could be done easier while on poles too. I don't know if the wave action would bury the pole foundations in the sand though after a while. I've seen it happen with bridge supports if not protected by big rocks.
     
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