Benelli lift theory under question

Discussion in 'All Things Boats & Boating' started by Frosty, Dec 5, 2012.

  1. DCockey
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    DCockey Senior Member

    The "equal transit time" theory has been known to be generally wrong for decades, but is still frequently repeated. While it invokes Bernoulli's principle it wasn't created by Bernoulli. Bernoulli's principle can be used to determine the pressure distribution around an unstalled wing if the velocity around the wing is known. The difficult part is determining the velocity around the wing.

    As for "no lift without angle of attack" see daiquiri's post above.
     
    Last edited: Dec 5, 2012
  2. DCockey
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    DCockey Senior Member

    Enigma of the Aerofoil by David Bloor is an excellent review of the development of airfoil and wing theory in the first decages of the the twentieth century. Fundamental to the story are the misconceptions which were embedded at the highest levels of academia.
     
    Last edited: Dec 5, 2012
  3. Number4

    Number4 Previous Member

    Hi David,
    Can you check that link? I get the same pdf that you posted in the wing thickness thread.
    Cheers
    Adam
     
  4. DCockey
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    DCockey Senior Member

    Link fixed. Thanks.
     
  5. daiquiri
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    daiquiri Engineering and Design

    Thanks for the link, David. 600+ pages are a rather time-demanding reading, but if you say it's worth the effort, I'll see to get that book.
     
  6. DCockey
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    DCockey Senior Member

    Not light reading but a very interesting story for anyone with some knowledge of aerodynamics, or anyone interested in the history of technology. There is also a good amount of ideology, organizational politics, egos and personality conflicts including the celebrated academicians who couldn't understand why reality did not agree with theory, and the engineer who was looking for useful results but was not accepted because he did not have the "right" background. Reading the book helped me understand that some of classical aerodynamics which appears to be somewhat oblique and obtuse is the legacy of the battles of the early days.
     
    Last edited: Dec 5, 2012
  7. daiquiri
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    daiquiri Engineering and Design

    In few words, a usual dynamics of hierarchy-governed human communities. :rolleyes:
     
  8. PAR
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    PAR Yacht Designer/Builder

  9. rwatson
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    rwatson Senior Member

    You ought to read your own links Frosty -

    "Newton and Bernoulli do not contradict each other. Explanations which are based on Newton's and on Bernoulli's principles are completely compatible. Air-deflection and Newton's Laws explain 100% of the lifting force. Air velocity and Bernoulli's equation also explains 100% of the lift. For the most part they're just two different ways of simplifying a single complicated subject. Much of the controversy arises because one side or the other insists that only *THEIR* view is correct. They insist that only a *SINGLE* explanation is possible, and the opposing view is therefore wrong. "

    So, your 'friend' on the other bar stool was making this mistake.
     
  10. P Flados
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    P Flados Senior Member

    Well said.

    The above is a great summary of the "confusion" on this topic. The people that are willing to "do the research", "do the math" and generally accept facts as facts generally figure things out with explanations that work pretty good.

    Many others just get emotional and cannot stand the fact that others really do understand what they are talking about.

    Oh how the above sounds so true in so many things I deal with as an engineer and a subject matter expert in my specialties.
     
  11. tom kane
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    tom kane Senior Member

    I have got to side with frosty..there is a lot of out-of-date infomation on lots of firmlyheld beliefs and mis-conceptions about any subject now. You have to re-check everything you think you know even if what you believe in works.
     
  12. upchurchmr
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    upchurchmr Senior Member

    Tom,

    You are right, you do have to question things.
    But if you on frosty's side about aero, then you are on the wrong side.

    You also have to be able to understand what you research. Not just listen to anyone in the bar.

    There also needs to be something to the discussion more than just stirring up a fight.
    Ask yourself, what is Frosty's point? Sails should not provide force - or what??

    He just wants to stir up ****. What he got was a reasonable discussion he will never even try to understand, that is not what he wants.

    Wow, look at that automatic PC language corrector - I actually typed **** and it got deleted. Thanks to the internet god for preventing the fall of civilization,
    Waste of Time, again.

    You know I went to rate this thread. Decided to not do it. Couldn't decide if all the overwhelming reasonable, information centered posts should be rated, or the subject of the thread - didn't want to get it wrong.
     
  13. tom kane
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    tom kane Senior Member

    My penny piece was all about ckecking what the so called experts would like us to believe I have had it right up to here with bumbling experts...many experiences.. take a look around at the trail of destruction in any field.
     
  14. Frosty

    Frosty Previous Member


  15. PAR
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    PAR Yacht Designer/Builder

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