Lift onset, planing, and lift coefficient

Discussion in 'Hydrodynamics and Aerodynamics' started by sandhammaren05, Aug 13, 2018.

  1. DCockey
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    DCockey Senior Member

    But good background reading for anyone interested in your ideas.
     
  2. DCockey
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    DCockey Senior Member

    Why are you quoting and thanking yourself?
     
  3. sandhammaren05
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    sandhammaren05 Senior Member

    Thanks, I think and hope so.
     
  4. sandhammaren05
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    sandhammaren05 Senior Member

    The article has been updated (some errors were corrected) since I first posted it.
     
  5. Joakim
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    Joakim Senior Member

    But you still haven't corrected the errors regarding Kutta condition, onset of lift and no lift while there is backflow at the trailing edge. I hope all readers carefully examine the earlier thread linked by DCockey in order to understand the problems with these theories.

    Now you seem to add that the beam has to be finite in order to get lift or did I understand correctly. So 2D planing surface would not generate lift? Or does your usage of "finite" mean something else than "not infinite"? Or are you referring to an earlier discussion about pointy ends. You were shown that pointy end surfboards generate plenty of lift without any transom at all.

    My earlier post about this has been removed by someone. Maybe there was a valid reason for that, but I was not informed about it.
     
  6. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    Let's please try and keep the forum polite to others and stay away from jabs. Thank you.
     
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  7. sandhammaren05
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    sandhammaren05 Senior Member

    I agree completely. I will ignore irrelevant responses and will only respond to politely-posed questions.
     
    Last edited: Aug 16, 2018
  8. CT249
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    CT249 Senior Member

    May I politely ask how the claim "A boat with no beam at the stern (fig. 1) cannot plane and is thereby limited to very low speeds" can be seen to be true, when there are canoe-sterned craft that DO plane and are NOT limited to very low speeds?

    This has no beam at the stern and does over 50 knots;



    Such craft are the fastest sailing craft apart from one huge proa and kites, so they cannot be inefficient.

    This boat has no beam at the stern and can certainly plane;



    Such craft are pretty much the fastest non-foiling singlehanded monos, so they cannot be inefficient.
     
    Last edited: Aug 25, 2018
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  9. CT249
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    CT249 Senior Member

    May I politely ask for evidence for this claim from the paper?

    "Sailboats with the appearance of a transom generally have a strongly rockered bottom so that the transom is always above the waterline."

    The most popular sailboats with the appearance of a transom are the Optimist, Sunfish, Snark and Laser. None of these have the transom always above the waterline.

    The most popular larger sailboats with the appearance of a transom would probably be the J/24, Catalina 22 and Folkboat. None of these has a transom always above the waterline.
     
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  10. CT249
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    CT249 Senior Member

    Sooooo.... it seems that when the bizarrely obvious flaws in his theories are pointed out, Sandman just runs rather than addressing them. That's probably a good thing. One has to wonder how anyone of reasonable intelligence could say something (or should that be something else) as utterly and transparently wrong.
     
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  11. johnhazel
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    johnhazel Senior Member

    From the text of the link in post #1 of this thread:
    "The wet planing area ('running surface') of a planing hull should be straight, not rockered (convex) or hooked (concave)."

    On the contrary,
    It has been established a half century ago, theroretically and experimentally, that large improvements are possible compared to a straight planing surface.
    e.g. Johnson 3-term cambered planing surface
    In the last few years, MIT has made additional experiments with cambered planing surfaces that also show large improvements over straight ones.
    Stepped Cambered Planing Hull with Hydrofoils | MIT Technology Licensing Office https://tlo.mit.edu/technologies/stepped-cambered-planing-hull-hydrofoils

    The above is one example of the many problems with the document linked in Post #1 of this thread. The document has many errors and misleading statements.
     
  12. sandhammaren05
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    sandhammaren05 Senior Member

    Show me a single error or wrong statement and I'll correct it. Cambered running surfaces are not found in high performance boating for the reason that the drag is unnecessarily great. I'm not talking about hydrofoils here.
     
  13. sandhammaren05
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    sandhammaren05 Senior Member

    Put a motor on it and tell me how it runs. I'm waiting breathlessly.
     
  14. sandhammaren05
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    sandhammaren05 Senior Member

    It's in the paper. Read it. If you're asking for simulations then that would not be evidence.
     

  15. sandhammaren05
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    sandhammaren05 Senior Member

    No flaws have been pointed out. It would be good to understand the paper before shooting from the hip.
     
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