AC 36 Foiling Monohulls

Discussion in 'Sailboats' started by OzFred, Sep 13, 2017.

  1. OzFred
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    OzFred Senior Member

    It seems the foil arms have been delayed a little longer with no explanation. In the meantime, a promo for the Sardenga leg of the America's Cup World Series (ACWS), scheduled to be held from 23 to 26 April 2020, has been released:

     
  2. Earl Boebert
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    Earl Boebert Senior Member

    Some speculation over on SA that the new design is labor and material intensive (it looks it) and that is cause of the second delay.

    Cheers,

    Earl
     
  3. OzFred
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    OzFred Senior Member

    “That which can be asserted without evidence, can be dismissed without evidence.” - Christopher Hitchens

    Or as Illy might have said: "Ok, but then what?" :)
     
  4. Earl Boebert
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    Earl Boebert Senior Member

    Well, of course. I labeled it as speculation, or as old-time intel analysts used to call them, a "tipper." Worth nothing in itself, but could lead to something if followed.

    The really important thing is they project appears to have burned a great deal of their schedule slack in the Rev. 1 fiasco and so any schedule slips from here on in will be more or less painful.

    Cheers,

    Earl
     
  5. Earl Boebert
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    Earl Boebert Senior Member

    Indications of/speculation about further delay from Tom Ehman at Sailing Illustrated. In video:

    https://www.sailingillustrated.com/home/category/America's-Cup

    At ~1:16:50 he states (without evidence, and therefore by Hitchens' Law etc. etc.) that the foil arms will be delayed until end of August or into September. FWIW and all that jazz. He also says (similar disclaimers) that work on Stars and Stripes has not resumed.

    Earl
     
  6. Earl Boebert
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    Earl Boebert Senior Member

  7. OzFred
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    OzFred Senior Member

    Just stumbled across that on SailWeb, which is a rehashing of the Tom Ehman article at Sailing Illustrated. Seems the LRPP surrogate was pretty much a scaled down version of the real thing.

    The continuing foil arm delay means syndicates may now be up to 6 months behind schedule, we should have seen some AC75s in the water by now.
     
  8. Earl Boebert
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    Earl Boebert Senior Member

    Tom Ehman (usual disclaimers) reports that the delivered foil arms are having to be repaired by the teams owing to surface delamination.



    Discussion starts at ~1:03:30

    Earl
     
  9. OzFred
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    OzFred Senior Member

  10. OzFred
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    OzFred Senior Member

    American Magic's first hull being delivered…
     
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  11. OzFred
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    OzFred Senior Member

    I have no idea about the original source of this image, but it's apparently the NYYC boat. It seems ugly to me, but I guess it's beautiful to some…
     

    Attached Files:

  12. Dolfiman
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    Dolfiman Senior Member

    I presume the hull should be mostly aerodynamic due to its mode of functioning, and Airbus is in the backdrop.
     
  13. OzFred
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    OzFred Senior Member

    Interesting comments in Sail World by American Magic’s wing trimmer Paul Goodison on the dual skin mainsail:

    It’s really unusual from any other boat where you can practically look at the sail and know how to trim it. Now, we have an independent leeward skin of the mainsail, which is the most important side to get right. The problem is, you can’t actually see it—visually.

    These boats have a lot more righting moment than the AC50s—and less power relative to the righting moment.

    The one big challenge with this type of boat will be the takeoffs. In 7 knots of breeze, if you sheeted the sails on, the boat would capsize because there’s so little righting moment available at that speed. … The way the foil geometry works, as soon as you heel over, you lose a lot of righting moment very fast. So it’s about trying to accelerate with a flat boat, and this is where the big top-panel inversion and the deeper cambers to start the acceleration come in. Then, very quickly, you have no [shortage] of righting moment.

    Sailing World: Intel on the AC75’s Twin-Skin Main, 27 August 2019

    So it appears there's a lot of work and design choices to be made to get the best out of the dual skin sail. It sounds complicated, with lots of moving parts so while it might be a good choice for the AC75 as a wing alternative, it doesn't seem that practical for everyday use or even other classes of racing boat.
     
  14. OzFred
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    OzFred Senior Member

    The launch of ETNZ's AC75 posted on Sailing Anarchy:

    http://forums.sailinganarchy.com/up...ideo.mp4.46ef18e0a447e6f883e47acd5ba8ee1a.mp4

    Live Sail Die article on YouTub:



    Also a story and lots of pictures on Sail World:

    America's Cup: Images from the Emirates Team New Zealand launch

    The starboard foil is flat, port is anhedral. Some interesting shapes below the waterline, seems to me they're trying to stop it being too sticky in light winds, perhaps at the cost of some stability. But these boats were never going to be very stable anyway, so maybe it doesn't matter.
     
    Last edited: Sep 6, 2019
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  15. Doug Lord
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    Doug Lord Flight Ready

    While the foils are different both have upturned tips-very interesting......
     
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