Moth on Foils: 35.9 knots(41.29 mph)

Discussion in 'Sailboats' started by Doug Lord, Apr 11, 2006.

  1. Doug Lord
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    Doug Lord Flight Ready

  2. OzFred
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    OzFred Senior Member

    You do not understand it. For production Moths, unless the boat is modified way beyond manufacturing settings (including significant modification of the strut and flap hinge), a Moth wand can't be setup to cause that kind of crash because the flap can't come up far enough.

    Certainly NONE of the crashes in popular YouTube videos (e.g. Moths Crashing in Super Slow Motion) show anything of the sort, they are all a consequence of mainfoil ventilation.

    That point has been relentlessly driven home, yet you continue to defend the indefensible.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!

    No, from what I found out, you're just flat wrong.
     
  4. OzFred
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    OzFred Senior Member

    That's it? All you can do is say "you're wrong" because you have no proof to support your position: zero, nada, none.

    You can't even show what settings or modifications are required to recreate such a crash, nor can you actually reproduce one or find someone to do it for you. You don't even know what the limits of the flap up/down angels are.

    Yet there are many, many YouTube videos showing the contrary and real life people who actually sail the boats saying, in your words, "you're just flat wrong".
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!

    Again for the last time:


    =======================

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    From "technologika":

    http://www.teknologika.com/mothblog/wp-content/uploads/2009/10/Magic-Wands.pdf
     

    Attached Files:

  6. OzFred
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    OzFred Senior Member

    Endlessly repeating the same thing without addressing the counter arguments you're presented with isn't constructive argument, it's denial.

    Yes, gearing can be adjusted to make flap movements more or less aggressive, but it's impossible to reproduce a classic nose–dive crash caused by ventilation by using flap alone. In 8 years of sailing a Moth, sometimes with gearing and settings as extreme as I can get them, never once have I come close. Not only that, it's a practical impossibility to do so for reasons already explained.

    You've taken some (unpublished) statements and come to an incorrect conclusion. The evidence is plain for everyone to see, yet you persist in dogged refusal to accept the obvious.
     
  7. Doug Lord
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  8. OzFred
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    OzFred Senior Member

    Yes, ventilation.

    That's when air around the main foil causes turbulence and affects lift. In most cases of spectacular nose dives, it's because the main foil comes too close to the surface, or breaches it. It can also occur from air traveling down the low pressure zone on the leading edge of the foil, generally initiated by the wand paddle wake (see Wand/foil interferance, Waterloo Bay 2013-06-02).

    This has been explained to you before, in great depth, from post 1542 onward.

    In the Moths Crashing in Super Slow Motion video at 1:50 you can even see the splash from the main foil as it breaches the surface and re–enters the water. The wand has been fully forward and nowhere near touching the water for many frames and the boat hasn't even started to descend due to action by the flap.

    But the moment the main foil breaches the surface and ventilates, all lift is lost and the boat goes "down the mine". Note that this is roughly a 1g descent, there is zero downforce from the flap (which became irrelevant to this event once the flap was fully up).

    There are many, many such videos, none of which support your wand/flap hypothesis. I've not heard of anyone supporting it, whether they sail a Moth or not.

    I don't know why you continue to post flat denials of a reality that is plain for everyone to see.
     
  9. Skyak
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    Skyak Senior Member

    A couple of items from the UFO thread

    -In videos of the UFO foiling it often runs with the wand dangling vertical above the water

    -we were discussing how to make the moth more tolerant of larger waves like the conditions in the video below -a spring in linkage between the wand and the flap with a damper between the flap and the boat could tune out those breach/crash problems.
     
  10. OzFred
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    OzFred Senior Member

    There are already such systems in use, but they aren't particularly sophisticated. The return spring tension is adjustable, and some boats with a "stopper" also adjust its tension.

    Don't ignore the role of the sailor in all this. There is no Moth system that will allow you to just sail wherever without regard for waves. Once the chop gets over about 0.5 metres (noting that some waves can be up to 3x average height) the crew needs to sail for the conditions.

    If you're sailing a lot with the wand clear of the water, likely you need to increase gearing so the flap moves a bit faster with respect to wand movement. Also try less AoA on the main foil so the flap has more chance of doing something and isn't overpowered by the rest of the foil. Both can be adjustable on the water while sailing.

    Having lots of adjustments will help you find the right settings. Once you have them right for particular conditions, likely you won't move them much. But different conditions require different settings, even up and downwind settings can be quite different. Probably the best single adjustment is wand length, as it simultaneously adjusts ride height and gearing and is simple to operate.

    But this should be discussed elsewhere.
     
  11. Doug Lord
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    Doug Lord Flight Ready

  12. Doug Lord
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  13. Doug Lord
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  14. Doug Lord
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready


  15. Doug Lord
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    Doug Lord Flight Ready

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