34th America's Cup: multihulls!

Discussion in 'Multihulls' started by Doug Lord, Sep 13, 2010.

  1. groper
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    groper Senior Member

    No, i dont they are bedding anything... the same twisty behavior was also very noticeable on BMW Oracle`s 90ft tri - which appears to have many similarities to their AC72, more so than their AC45`s... their 90ft tri also appeared to trim very bow down aswell... not sure what their design approach is, but its clearly very different to team NZ...
     
  2. petereng
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    petereng Senior Member

    BOR90 (USA17) was used 3 times so definitely hadn't bedded in! I'm sure bow down is not what they want! Has anyone any comment on why the new Oracle AC72 is called USA17 yet the AC33'rd tri was USA17? Is this for good luck? Or did they cut the old one down :) ?Peter
     
  3. Doug Lord
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    Doug Lord Flight Ready

    34th AC on Foils!

    =================
    Peter, I'm hanging in here-trying to digest the exhilerating AC developments.
    Just a great time to learn!
    At this point I tentatively think Oracle is flying manually by pivoting the daggerboard in the lower bearing. I don't know how they do it but I think they do it.
    I think TNZ is using what is, basically, a surface piercing foil system that doesn't require direct angle of incidence control like I think Oracles system does. And the one video where they stuff the bow points out a possible problem with ventilation-typical of some surface piercing foils-especially those w/o fences.
     
  4. petereng
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    petereng Senior Member

    Hi Doug - There is no point in the inboard end of the foil to be surface piercing. If you mean the "free" end of the board. Obviously the hull end is piercing too. Any lift generated near the surface just wastes foil area. It would ventilate badly. The "dihedral" produces a steadier more stable lift then a perfectly horizontal foil. A dihedral produces a lift "bucket" area vs a small balance point.

    The rules allow the daggerboard and the rudder to have two axis of control. I'm interested in whether the control is manual of electronic. There is no express rules against electronic control (I'll have to read through the rules again) so you could just hook them into a gps height control. Does anyone know about this side of the problem?
     
  5. Doug Lord
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    Doug Lord Flight Ready

    TNZ surface piercing lifting foil

    Yeah, the inboard tip may not be above the surface but it could be with enough speed. The curved lifting foils in trimarans like ORMA's and MOD 70's are designed as fully submerged foils. Even disregarding the tip the TNZ foil is acting like a surface piercing foil and would be subject to ventilation. You can see the "crash" that I believe was caused by ventilation in the video,next post.

    click-
     

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  6. Doug Lord
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    Doug Lord Flight Ready

  7. tom28571
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    tom28571 Senior Member

    Ditto. I appreciate your willingness to get out there and take whatever anyone throws at you. Right or wrong, its always interesting and often enlightening:idea:.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    34th AC on Foils!

    ============
    Thanks, guys. It's a fantastic time to be alive!
     
  9. Gary Baigent
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    Gary Baigent Senior Member

    People underestimate the loads and important work the rear beam undergoes, concentrating more on the main beam.
    The wide and aerodynamic chord on Oracle's rear beam may be there besides less drag, but mainly an attempt to help stop platform twist - which so far doesn't seem to be working that well.
     
  10. Corley
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    Corley epoxy coated

  11. Doug Lord
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    Doug Lord Flight Ready

    34th AC on Foils!

    Corley, I saw those on one of the threads on SA as well. Problem is that, contrary to what the article says, they are in no way like the foils on Hydroptere. Hydropteres foils pivot close up under the crossarm and when retracted are out of the water. These(in the article) rotate about a pivot on the bottom of the hull and a substantial portion of the foil would still be in the water when retracted. So far I see no advantage with this sort of system.
    The article also states the the "S" type foil used by TNZ is the only "style" seen so far. Wrong-Oracle's slightly angled "L" foils have been used successfully on AC 45's and are entirely different than the TNZ foils.


    Pictures: 1) Hydroptere.ch with main foil retracted, 2) Hydroptere with retracted main foil. Both have the foil pivot above the waterline.
     

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  12. Corley
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    Corley epoxy coated

    I agree Doug it does not look like an optimal way of mounting the foils at all. L foils and a T rudder seem to be a better overall proposition.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    34th AC on Foils!

    Note: if the "F" word used in joyful exuberence offends your sensibilities turn the volume down before playing this video!
    ---------------
    Some guys were out sailing today in NZ when low and behold tnz's foiler shot by them-must have been really cool!

    http://www.youtube.com/watch?feature=player_embedded&v=jRHkrCiQYhg
     
  14. Doug Lord
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    Doug Lord Flight Ready

    34th AC on Foils!

    TNZ from Sail-World: what an incredible boat! Look at the picture of the boat going downwind. You know its downwind because of the sheeting angles of the leadbelly in the picture-wow!

    click-
     

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  15. groper
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    groper Senior Member

    Doug, are there any videos of the #5 oracle ac45 foiling? i cant seem to find anything but still photos???
     
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