AC 36 Foiling Monohulls

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

  1. CT 249
    Joined: Dec 2004
    Posts: 1,695
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    I assume it means something else in French?
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,478
    Likes: 287, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    The reference is to the tip and shaft of an uptip foil or any foil with similar geometry.
     
  3. CT 249
    Joined: Dec 2004
    Posts: 1,695
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    Hey Doug, now that you're popped up, can you answer the question?

    Are you going to make more sneering comments when people like me trust the articles you post?

    Do you think we should stop trusting articles you post, which is what I did when you made your sneering little "corrections"?

    Do you have the honesty and good manners to apologise for making your posts when all I did was rely in good faith on an article YOU linked to?

    Why should we trust you, when you sneer at people who rely on articles YOU post?
     
  4. Earl Boebert
    Joined: Dec 2005
    Posts: 363
    Likes: 42, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    Here's a couple of diagrams from a recent article in La Stampa showing the extent of the redesign. Not exactly a minor tweak.

    Cheers

    Earl

    Screen Shot 2019-05-30 at 3.46.46 PM.png Screen Shot 2019-05-30 at 3.47.11 PM.png
     
    OzFred and Doug Lord like this.
  5. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    It seems Malta is out:

    Royal New Zealand Yacht Squadron (RNZYS) shared a post:
    The Royal Malta Yacht Club have officially withdrawn their Malta Altus Challenge team from the 36th America’s Cup.​
     
  6. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    That is a substantially bigger arm, better than 50% more in cross section? No doubt the new one is based on results of testing and breaking the first, it must have been way underdone.
     
  7. Earl Boebert
    Joined: Dec 2005
    Posts: 363
    Likes: 42, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    Speaking as someone who has reviewed many engineering projects (good, bad, and ugly) I would rate this as a pretty epic management failure. That arm development was on the critical path for just about everything: concept validation, schedule, and safety. To allow a team to burn money (and more importantly, calendar time) and come up with something that appears to have been so spectacularly inadequate says to me that somebody high up wasn't paying attention. This degree of inadequacy should have been caught in a design review, not after fabrication and test.

    Cheers,

    Earl
     
  8. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    I think Alessandro Franceschetti, Head of Structures, Luna Rosa would agree with you. Here's what he said in Technology: Foil Arm testing for the America's Cup:

    "So after the first generation of the one design we have gone through a full review, from design inputs to design methodologies, from manufacturing techniques. And the second generation is actually an outcome of a revolution within the structure of this component.

    "We have changed the way we are building it, we have changed the way analyse it and we have included in the design process more details and more accurate inputs in order for the designers and builders to make sure that we accomplish successfully this milestone."
     
  9. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    Luna Rossa Prada Pirelli (aka LR) have launched their test boat: AC36: And then there were three – AC75 test boats that is.

    For the record, sources close to LRPP say that the first sail with their new test boat "went well."

    They capsized it on their first outing. No doubt a planed test of righting the boat… ;-)
    [​IMG]

    The best view so far of their foils.
     
  10. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    A few more pix of the Luna Rosa test boat: Luna Rossa’s new AC36 test boat – It Floats, it Foils!
    [​IMG]
    Seems it foils, no double–skin main, unusual helm position.

    It seems to me an important part of helming is knowing what the crew is doing and watching the sails during manoeuvres to get the timing and apparent wind angles right moment to moment. Putting the helm in front of the crew means the helm is just steering and the crew have to get everything spot on without any help from the helm. Effective communication will be very important.

    Can't wait to see some video.
     
    Doug Lord likes this.
  11. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    A video from Luna Rossa reveals the arm redesign added 50% to its weight, it's gone from 300kg to 450kg.

     
  12. Earl Boebert
    Joined: Dec 2005
    Posts: 363
    Likes: 42, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    Ouch. Either the new one is seriously overdesigned or the old one missed the mark by an appalling margin.

    Cheers,

    Earl
     
  13. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    I think the old one was supposed to handle at least 200% of the estimated maximum load but broke at 180%. It was then decided the new one should be 300%. Clearly they learned a lot from breaking the original.

    To be fair to the original builders, they were working to a predefined weight (245 kg) and maybe they did as well as anyone could have given that limit. Some attention should be given to the writers of the spec the builders were working to, and how they came up with the original values. Maybe too much was expected of CAD to model the real world, particularly given the unique nature of the part.

    The fact that they're now working on 300% means there is serious doubt in somebody's mind as to the accuracy of load estimates and respect that reality doesn't always match the computer simulation.

    TLDR;
    I watched a documentary on Frank Gehry, the famous architect. His models were really crap—bits of paper and cardboard rudely folded and stuck together. Someone asked him why he didn't make better models, he answered something along the lines that perfecting the the model detracts from the real job—perfecting the building. He used models only just good enough to understand an aspect of design, never to model the entire building.
     
  14. OzFred
    Joined: Nov 2015
    Posts: 444
    Likes: 41, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member


  15. Earl Boebert
    Joined: Dec 2005
    Posts: 363
    Likes: 42, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    I'm inclined not to trust static flex load as the sole criteria in an environment like this. Believing that a big flex load margin automatically protects you against torsion, vibration, and harmonic effects can lead to nasty surprises, e.g. the Lockheed Electra. It would be interesting to know the degree to which instrumentation of the INEOS and NYYC test boats informed the design of the new arm. And as far as models go, I used to remind my students of Alan Turing's introduction in the last paper he wrote: "This model will be a simplification and an idealisation and consequently a falsification."

    Cheers,

    Earl
     
    Konstanty likes this.
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.