Buttocks

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

  1. DogCavalry
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    DogCavalry Senior Member

    A tad! Don't go making me disappointed in my dream boat before it even exists.
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Ooops, sorry :(
    The 32' ally landing craft (for US$195k) is a nice dream boat for sure, in that something like this would probably cover the requirements in your SOR fairly well - you could build a small cabin on the back, and it has good deadweight capacity for transporting people and some cargo.
    The hull form seems to be relatively simple - would it be feasible for you to build something like this in plywood?
    It might even be easier than building a sea sled type of hull form? :)
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    "Go fast" is the problem. There is a world of difference, between 20 and 30 knots (the figure you have mentioned) in terms of boat type, size, powering, and running costs, to get similar comfort and load carrying ability. I think you need to nail down what the difference would come down to, in $ perhaps more than anything, between a 20, 25, 30 knot cruise speed, Of course you lose time on the job, with longer transit times, but may pick up with lower running costs, better comfort, etc. Getting belted around on choppy water could also impact on productivity of the workers, I really can't see a cheap boat of any kind working out, with the loads you envisage.
     
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  4. DogCavalry
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    DogCavalry Senior Member

    You are right, Mr E. Anything cheap is worth what you paid for it. As I said, the shop and all the wood are free to me. So for the simple hull, it's glass and epoxy. I've been looking at powering options, and that's all so steep that my best option may be to buy a suitable used boat and cannibalize it for Marine diesels and transmissions, bilge pumps etc.
    As far as running time, 5 passengers on board at a typical employer's cost of $40 an hour. Even considering my own time as worthless, which I emphatically don't, that's $100 a day for a slight increase in trip time. I could buy a lot of gasoline for $100 a day.
    Please read the articles I mentioned. There will certainly be less banging around in a sled than any of the Ianding craft seen so far.
     
  5. DogCavalry
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    DogCavalry Senior Member

    Damned by Faint Praise, issue 100 of Woodenboat, May/June 1991
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Have you looked into this, from that article ? "The new Sea Sleds being built today by Dr. Salvatore Iannotti in Florida, designed by Johan Valentijn,"
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

  8. DogCavalry
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    DogCavalry Senior Member

    Insofar as that's possible. They seemed to have no more sense than a goose. Boats had a hard time making speed. The outboard just wasn't delivering power. So they ****** with it until it was something else. Then they went out of business. In 1914 Hickman could see that the water down the centre of the transom was so aerated it was worthless for propulsion, so his patent drawing for the sleds, and the surface piercing propellors, showed twin props. Embarrassed to have the same number of chromosomes as those guys.
     
  9. DogCavalry
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    DogCavalry Senior Member

    Okay, that was mean of me. But honestly. If the whole concept works because it traps air and foam in the middle of the tunnel, getting lift back, and trading viscous water drag for air drag, why would anyone expect a prop to work in the middle?
     
  10. DogCavalry
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    DogCavalry Senior Member

    It surely is, anf thanks for pointing that out for me, Mr Efficiency
     
  11. DCockey
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    DCockey Senior Member

    Is there any verification?
     
  12. DogCavalry
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    DogCavalry Senior Member

    Well, it certainly turned the bow waves inward, and rode over them, leaving almost no wake, but a trail of foam.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    I guess heavily aerated water lessens frictional drag, but also creates a less than ideal working environment for propellors.
     
  14. DogCavalry
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    DogCavalry Senior Member

    Hell yeah. Truer words were never spoken, my friend.
    Consider that in a deep v hull, inboard engines must be as low as possible. That squeezes them together, putting props close together. As low as possible in an inverted v, puts them well out against the topsides. Widely spaced props give nice control in tight spaces, if the operator is good with his throttles.
     

  15. DogCavalry
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    DogCavalry Senior Member

    Good with his throttles... That won't be me any time soon. Practice will be necessary.
     
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