A sail is not a wing

Discussion in 'Hydrodynamics and Aerodynamics' started by Sailor Al, Feb 7, 2021.

  1. Glueandcoffee
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    Glueandcoffee Junior Member

    also at higher (closer to 1) mach speeds.
     
  2. DCockey
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    DCockey Senior Member

    I doubt they even thought about it. The Wright brothers were from Dayton, Ohio where sailboats were not to be found (unless there were some very small ones on a park lake or similar) and my understanding is they were much more emperical than theoretical.
     
  3. Glueandcoffee
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    If you cut some portion off of one of the wings on a glider and added a lead bulb to the end of it you would be left with a n odd looking but somewhat functional version of a sailboat.
     
  4. Glueandcoffee
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    Glueandcoffee Junior Member

    Maybe if they had thought about it they could have flown longer than the wingspan of an A380.
     
  5. gonzo
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    gonzo Senior Member

    History tells us that most of the experimentation happened in the Outer Banks, where there were large amount of sailing boats and ships.
     
    Will Gilmore and CT249 like this.
  6. Howlandwoodworks
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    Howlandwoodworks Member

    Was that just the first flight?

    Free-Floating Rationales (Daniel Dennett) have gotten us a long way but Newton theory of gravity was 1670's and the Wright brothers flight was 1904-05.
    Newton's law of universal gravitation is usually stated as that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
    Fg=Gx(M1xM2/r2)
     
    Last edited: Feb 23, 2021
  7. Glueandcoffee
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    Glueandcoffee Junior Member

    My bad. Yeah first flight was just 37 metres. Longest flight was 260 meters
     
  8. Howlandwoodworks
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    Howlandwoodworks Member

    jehardiman, Top drawer stuff.

    There is no lift only attraction: Newton's law of universal gravitation.
    There is no attraction only the curvature of spacetime: Einstein equivalence principle
    Let's use a thought experiment used by Einstein to illustrate the equivalence principle but the windowless elevator is now an airplane. If you are climbing at 3 g’s vs banking at 3 g’s how would you know if you were you were climbing or banking without a window or instruments. You would only feel 3 g's in the back of the set, either way.

    We still use Newton's law of universal gravitation because it works on the local level.

    1905 they flew complex maneuvers and stayed aloft for 39 minutes.
     
  9. Glueandcoffee
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    Glueandcoffee Junior Member

    Also as wrong as it is to say a sailboats only purpose is to sail upwind I think its equally wrong to say a glider or planes only purpose is to gain altitude.
    Both are just vehicles to get from a to b. The altitude difference between highest and lowest airport is only 4.7km. There are runways 700meters longer than that.
     
  10. Glueandcoffee
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    Glueandcoffee Junior Member

    Even after spending months on a school project about the wright brothers I never knew about that.
     
  11. Howlandwoodworks
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    Howlandwoodworks Member

    It's OK, I don't really know anything about Newton or Einstein. I am just a old woodworker.
     
  12. Glueandcoffee
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    Glueandcoffee Junior Member

    And I a humble carpet fitter.
     
  13. CT249
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    CT249 Senior Member

    The Wrights were actually very scientific, in most uses of the term. They started by asking the Smithsonian for all the information it had on flying. Wilbur used Lilienthal's coefficient of lift tables when designing gliders, and they were despondent when the 1901 glider seemed to show that the tables were wrong. They then adopted a very scientific method of working out the lift and drag of various wings in their wind tunnel.

    Dayton actually had a strong canoe scene around the time, with around five clubs on the river. The Dayton canoeists were also keen on Open Canoe sailing, and of course at that time sailing was strong in canoes generally. Dayton was, and still is, a stronghold of Open Canoe sailing. So the Wrights may well have been aware of the sport, particularly since the Americas Cup and other events were reported across the USA. Their hero Lilienthal used the term "sailing" rather than "flying", incidentally.
     
  14. gonzo
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    gonzo Senior Member

    The Wright brothers were inventors and didn't have a lot of technical background. For example, they couldn't follow all the math and physics theories about flight and airflow. Therefore, they built a box with a window on the side, set an oily shop rag on fire and put a house fan in front of the contraption; they invented the wind tunnel. The smoke let them see what the airflow actually did, which was completely different to what the theories of the time predicted.
     

  15. CT249
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    CT249 Senior Member

    I'm late to this discussion, but it appears that your reasons why the wing analogy is wrong are often invalid.

    A sail CAN create useful lift when jumping or waterstarting a windsurfer or (more controversially) perhaps when an assymetric spinnaker is (allegedly) presenting a nosedive. A sail that is creating lift in this way does not suddenly start to act in a different way to a "normal" sail, nor are its aerodynamics or the way it is trimmed or used dramatically different from when the same sail is used in a more normal fashion. A foiling Moth also uses the lift of a sail when heeled to windward.

    If we think of a sail in a similar fashion to a wing, we don't have to suddenly introduce new concepts as we change from one mode to another while windsurfing or Moth sailing.

    Similarly, heel is not always adverse. In windsurfers (especially longboard windsurfers), scows and catamarans the fastest performance is often obtained when the hull or hulls are heeled. A sail in such a situation is not generating adverse heel, and in some specific situations in a case even leeway is not adverse. A sail on a cat downwind doing the "wild thing" is not generating "adverse" leeway and heel, but leeway and heel that are positive, in terms of increasing performance.

    Again, it seems unhelpful to use analogies that would suddenly require us to change the analogy when we are doing nothing more than re-trimming during a gust or course change. If we're sailing an F18, we shouldn't changing from thinking of the rig as a sail, to suddenly thinking of it as a wing when we are trying to lift a hull, and then changing our model back to sail once again as soon as we are overpowered as the gust increases.
     
    Last edited: Feb 25, 2021
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