Buttocks

Discussion in 'Hydrodynamics and Aerodynamics' started by DogCavalry, Sep 30, 2019.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I notice that some query the cavitation issue as one that held the sled idea back, but I would say that at least for single engine installations, it would have been a source of trouble. Twins, it may still be a problem, but if you are going to use twins, I say a cat would be a better idea.
     
  2. DogCavalry
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    DogCavalry Junior Member

    You really love cats!

    I really love sleds. I’m beyond hope or reason sir. I’ll have a sea sled, or die, pining for one. Since I’m doomed anyway, I’ll make the best that my hands and brains, and tiny budget will allow.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    All the rescue services, water police etc use cats here, and for good reason

     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I do like your quixotic ideas, but probably because I'm not footing the bill !
     
  5. DogCavalry
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    DogCavalry Junior Member

    Lol! Fair enough.
     
  6. bajansailor
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    bajansailor Marine Surveyor

    These Noosa Cats are very impressive indeed.
    I was on a mini-walkabout in Oz 20 years ago (from Sydney to Cairns and back on the buses) and I stopped off in Noosa for a couple of days, and wandered in to the Noosa Cat yard to say hello. They were very helpful and interesting to talk to, and I came away armed with a stack of brochures (these were pre-internet website days) even though they knew that I wasn't in the market for buying one of their craft.
    Noosa Cat Australia https://noosacat.com.au/
     
  7. DogCavalry
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    DogCavalry Junior Member

    So here's the best photo I've seen of this action
    Note there's no bow wave. I do see a large rooster tail from the large 1928 surface piercing propellors. I also see a tiny stern wave. Looks like lateral flow down the tunnel and under the transom rolls the stern wave inwards. Fascinating.
    26-0.jpg
     
    Last edited: Oct 10, 2019
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd be leery of dynamic instability with a sled. Especially if lightweight, and high powered. Corkscrew rolling isn't unheard of in lightweight cats, it would likely be more pronounced with a sled, driven hard at an angle to head seas. What may save the day, the driver has already backed off after bone-jarring landings ! But it is a factor, and may explain a few mysterious capsizes of asymmetric power cats, that had more "shape" down the tunnel, than outside it.
     

  9. DogCavalry
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    DogCavalry Junior Member

    This particular sled will never be lightweight, or high powered. Think of a tradesman's lorry loaded with bits and pieces, half a dozen lads in heavy practical boots, their tools, 25 sheets of 15mm plywood, and a dozen bags of cement.

    A sled gives more speed at any power to weight ratio, or at least that was the professional opinion of George Crouch. It also is completely level, when landed on a beach, like a cat. And I think they're cool.

    There's nothing in the literature to expect slamming. In fact the literature suggests the opposite. But I aim to find out.

    j
     
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