AC 36 Foiling Monohulls

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

  1. OzFred
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    OzFred Senior Member

  2. CT249
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    CT249 Senior Member

    Given that probably one third or more of syndicates fail to actually get to the starting line, this may possibly be the smallest AC for years. Three-quarters of entries in 2013 never eventuated and that was probably not too far off the average.
     
  3. OzFred
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    OzFred Senior Member

    LE NOUVEL AC 75 NZ VU PAR JEAN SANS (VERSION 2.1 CORRIGÉE)
    The new AC 75 NZ seen by Jean Sans (version 2.1 corrected).
    It's in French, Google translate may help to convert to your preferred language (or use Google Chrome which can translate the page in place).

    One interesting section when looking at the power required to manoeuvre the foils:


    Point N ° 1: It takes energy to manoeuvre the two central foils and the foils equipping the saffron. It is easy to understand that the central foils will consume 90% of the energy. The solutions "cyclists" or "winchmen" no longer work. Remember that Christopher FROOME was estimated at 0.436 kW / h during the Tour de France. This is never 2 kW / h for a regatta of 5 hours. To manage to manoeuvre the central foils, it will take more than the Top Ten of the Tour de France cyclist on the deck, or in the bunkers. The AC75 NZ is no longer a "beach gear" as was the catamaran of the last AC.

     
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  4. OzFred
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    OzFred Senior Member

  5. Doug Lord
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    Doug Lord Flight Ready

    Verdier:
    Guillaume Verdier Helps Design the Future of Yacht Racing https://mobile.nytimes.com/2017/12/24/sports/sailing/guillaume-verdier-yacht-racing.html?referer=https://www.google.com/

    excerpt:
    "Bernasconi says the boat should foil at 9 knots of wind speed and be capable of hydrofoiling for an entire Cup race in the right conditions."

    excerpt:

    "The initial drawing for that project still had a keel.

    “We sat together with the client, and Ray said, ‘Hey, come on! After all we’ve learned, you’ve got to get rid of this keel. It’s looking draggy to have so much in the water,’” Verdier said. “And I said, ‘Yes, but Ray, it’s going to capsize too easily. We need some minimum stability here.’ ”

    The solution was to propose putting the weight in the foils instead.

    “That is completely counterintuitive because the foil is a lifting surface, so why put lead in a lifting surface?” Verdier said. “We need some stability before we start flying, so we make the foils like canting keels. This kind of boat existed in the past, with twin keels, so I said, ‘Let’s make a kind of twin keel but with foils, not too heavy, just enough so we can right it up at 90 degrees when we cant it the correct way.’”
    The initial drawing for that project still had a keel.
     
  6. Doug Lord
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    Doug Lord Flight Ready

  7. Doug Lord
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    Doug Lord Flight Ready

    SA article translated above(and pdf below) shows 80% of the load on the main foil 20% on the rudder foil but then says:
    "The lift on the foil associated with saffron is lower than the theoretical 20%, it would give the boat a lift, which should not be a handicap in the take-off phase."

    This loading is at takeoff and will change as the boat accelerates likely becoming neg lift on the rudder foil depending on the design.
    An AC 50 sketch done by Martin Fischer showed 75% of the load on the main foil and 25% on the rudder foil(s) at takeoff.......
     

    Attached Files:

    Last edited: Jan 7, 2018
  8. OzFred
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    OzFred Senior Member

    Another article from Jean Sans which covers racing (foiling) and navigation (floating/Archimedean) modes:


    If you don't have Chrome to translate it for you, try Google translate.

    "My previous paper of December 12, 2017 was the translation of the excellent quality video of TEAM NZ, which outlined the new AC75.
    The plans have been deducted and sized (this is the most important) from the images. Calculations were made using the very rare known parameters, namely an Archimedean displacement of about 7000 kg and a reported speed of 22 knots on a single central foil and the rear foil.
    This paper was only the technical summary of the reconstructed plans and calculations but also of my imagination.
    Indeed, the transition from an Archimedean configuration to a Foiler configuration is not easy, especially for a 75 'monohull. It is not enough to take off, it must then evolve."
     
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  9. Dolfiman
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    Dolfiman Senior Member

    Many thanks, very interesting, Jean Sans also posted previously technical notes on ratings, foils , foil assist Imoca 60 ... :
    Technique | UNCL https://www.uncl.com/courses/technique/

    A bit too long to propose you the full translation, sorry, just note that "Safran" is the immerged wing part of the rudder, not Saffron as proposed by google translate. And "Bras + foils" means "Akas + Foils" . "Dessalage" is another term for capsize , mostly use for dinghies when crew are able to right up the boat by themselves.
     
  10. Doug Lord
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    After studying these pivoting arms it occurs to me that the position of the pivot might be improved if it was raised to the sheer line as opposed to being at the chine where it will be immersed. It could be effectively sealed like a canting keel but that wouldn't be necessary if it was raised?
     
  11. OzFred
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    OzFred Senior Member

    That would introduce a whole new set of engineering issues, such as "navigation mode" would need the struts to be more curved to fit around the hull and I expect it's a less structurally strong for the range of loads (particularly torsion) than deeper in the hull.

    It also exposes the mechanism so compromises the appearance and challenges traditionalists even more than the bike riders on the ETNZ AC50.

    But I'm sure they're considering all options, and maybe that's one.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    It seems to me that to be anywhere near cost effective for the participants these boats -especially the "swing" foil system- will have to be one design. If that's the case it is very disappointing because there are MUCH simpler(and equally effective) ways to do a monofoiler than with ballasted swing foils! If they give the teams the latitude to design their own system we could see real monofoiler development with "trickle down" potential.
    The more I've looked at the TNZ renders, the more convinced I am of the incredible complexity of the foil system. That seems like it will have to result in a one design foil system which is too bad. A simpler , less costly system and open design would potentially result in some trickle down tech which I don't believe will happen with the current version.
    -------
    The current version is just way too complex and if you remember the design development saga of AC 35 that started out with the AC 62 and went to the 50 there is hope that at some point the new version could be simplified to be less like a War of the Worlds invader.

    NZAC ONE-
    1) main foils: carbon ,unballasted and fully retractable for light air and
    and in-the-water boat stowage. Foils as shown below allow light air takeoff(5-6mph wind). If that isn't desirable they could be smaller.
    Surface piercing foils=automatic altitude control.....
    2) If racks were legal-and they probably should be-then this -as is- would be close. Otherwise they(and the buoyancy pods) could be eliminated(requiring a wider hull). Racks protect the boats and crew in the event of contact.
    3) Keel ballast could be reduced by making keel cant but, to me, that is mostly additional complication that isn't required for foiling.
    4) Rudder + T-foil sliding in a cassette could be rotated to use the "normal" top of the rudder as a light air rudder which would remove the drag of the t-foil.

    NZAC ONE     9-25-17  dl 002 - Copy.JPG

    NZAC revised deck plan     1-12-18 001.JPG
     
    Last edited: Jan 12, 2018
  13. Gary Baigent
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    Gary Baigent Senior Member

    Quit your endless postings of your wacko fantasy creation - ETNZ won't be using your sketches, in fact at this date, the new boat will have been near finalized - and your scribbles would never have been considered. You need to accept that savage reality.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    ====================
    I'm afraid the savage reality is that like Larry starting with the AC 62 last time , TNZ has picked a design that will be very hard to get built unless the critical components are one design and even then it will be a monumental project for each team. Going one-design with critical components would be unfortunate because the "design contest" that is the AC will be diluted to parts that don't matter much. I hope I'm wrong but it looks like a massively complex contraption with the great potential for all kinds of disaster.
    That level of cost and complexity is not necessary for a viable, fast, monofoiler.......

    NZAC--AC_75_15841.jpg
     

  15. Konstanty
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    Konstanty Junior Member

    Cost it's no problem. Vibrations and low stiffness and resistance for the wind this is a problem.
     
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