AC 36 Foiling Monohulls

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

  1. Doug Lord
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    What do these results have to do with AC 36 foiling monohulls? More new foilers are being designed to be able to efficiently fly in very light air, however most existing(but not all!) foiler cats are not. I hope that the new AC boats will be able to effectively fly in 5-6 knots of wind.
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    The Gonet Monofoiler finished in 58th place out of over 160 boats in its very first race in extremely light air. Of the total entries about 28 did not finish. Meaningless result for the Gonet and totally irrelevant to the subject of this thread.
    http://www.ycg.ch/wp-content/uploads/2018/06/YCG-Geneve-Rolle-Geneve-2018-Lestes-M1-M2.pdf
     
  2. CT249
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    CT249 Senior Member

    The results are relevant because they provide more evidence that the speed increase created by foiling is normally not as great as it is in Moths, which are particularly well suited to foiling. That is in turn relevant to the potential speed of the AC75s and also to the trickle down.

    It's important when discussing the possible performance and trickle-down that we notice when foilers don't perform as well as hoped. We tend too often to get press releases when they perform well (which is of course quite often, in some cases) and silence when they don't. That does not give us the true information about their all-round performance.

    One of the most important things in any design development is identifying weaker areas, rather than simply the strong points. To ignore weaknesses is to ignore reality and close off potential areas of improvement.

    Claims about what can be done with light air performance in the future may turn out to be as accurate as the earlier claims that someone would build a mass-market foiler have turned out to be.
     
  3. Dolfiman
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    Dolfiman Senior Member

    A depleted uranium keel was used by Tabarly on Pen duick VI in 1973, for the first Withtbread round the world race, that made a lot of ink flow. But it was more for financial reason that ET advocated this solution, as the CEA (French institute for Atomic Energy) proposed to offer the uranium and this avoided the purchase of 15 to 16 tons of lead. The keel density when machined was no greater than conventional ballast as uranium was embedded in a resin web. ET declared : "a small economy that costs me a lot", as IOR rulers soon declared that this ballast was not in accordance with the regulations, and it was necessary to change it.
     
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  4. markdrela
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    markdrela Senior Member

    You should realize that there is always a threshold wind speed below which foiling will be slower than displacement sailing. The simple reason is that the ideal-foil wetted area increases as 1/V^2, while the ideal-hull wetted area stays more or less fixed. What the threshold speed is depends on the boat weight, type (mono or cat), amount of sail, foil type, etc., but the threshold is always there.

    For example, for a well-designed human-powered boat it's about 10-12 knots boat speed. This also requires at least 200 Watts, which is why a recreational foiling pedal boat is impractical for a majority of people. I haven't run the numbers for a large sailboat.

    PS
    Since A Sahlin is here, I should comment on the HP boat more...
    The 10-12kt and 200W estimate assumes you have a clean hull (like a rowing shell or good kayak) to allow takeoff, which adds significant weight. Wing-only HP vehicles like the Trampofoil are lighter and can foil efficiently at lower speeds, but these cannot float and hence are not practical for e.g. taking a long tour around the pond.
     
    Last edited: Jun 4, 2018
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  5. Doug Lord
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    Thanks, Mark....
     
  6. Doug Lord
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    Last edited: Jun 4, 2018
  7. CT249
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    CT249 Senior Member

    Yes, it's completely illogical to say that foiling isn't sailing. The clearest proof would be the many classes that can use foils. Various classes from original Windsurfers and D2 boards to foiling Lasers, 18s and Optimists use mostly the same gear as the "seahugging" versions, often sail pretty much in the same way, and spend a lot of time sailing normally. A Laser with Glide Free foils in seahugging mode is clearly normal sailing. To claim that it becomes something else as soon as the hull clears the water is obviously wrong and illogical.
     
  8. Doug Lord
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  9. OzFred
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    OzFred Senior Member

  10. Doug Lord
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    Doug Lord Flight Ready

  11. Doug Lord
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    Sardinia Challenge--- from Scuttlebutt Europe:
    America's Cup: Sardinian team clarifies Challenge status
    A spokesman for Sardinia Challenge has clarified claims in a media statement issued by the team last Wednesday.

    Superyacht magazine publisher, Colin Squire, who is based in Suffolk, England says a miscommunication within the team led him to the impression that the Challenge had been accepted by the Royal New Zealand Yacht Squadron.

    Instead, Squire claims that the team have been in contact with the RNZYS and have been told verbally that if they submit a Challenge by the June 30 deadline, "it will be accepted".

    "I was under the impression when I wrote the media statement that the Challenge had been accepted, and it is now apparent that I had misinterpreted the conversation [with team head Renato Azara in Sardinia]. It's awful - I would never in a million years send out something that I knew to be incorrect, but it appears that Renato has been given the verbal assurance that when he submits the Challenge at the end of the month, which he is aiming to do, they [presumably RNZYS] will accept it. That was a misinterpretation on my behalf, it came about through a language issue."

    "He has been four or five months trying to get the Challenge together, and we can only sit and wait."

    Although he has run many stories over the years on the America's Cup, Squire says he has never been involved in the Challenge process and wasn't aware of the strict procedure involved where a notice of challenge is issued, the defending club receives it, puts it through a vetting process and then decides if it complies with the Deed of Gift and Protocol and whether or not it will be accepted.

    A key point will be whether the yacht club meets the validity tests in the Protocol and Deed of Gift and in particular if it holds an annual regatta on an arm of the sea. -- RIchard Gladwell

    /www.sail-world.com/news/206408
     
  12. Doug Lord
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    American Magic--
    America's Cup activity returns home >> Scuttlebutt Sailing News https://www.sailingscuttlebutt.com/2018/06/14/americas-cup-activity-returns-home/?utm_medium=email&utm_campaign=Scuttlebutt%205103%20-%20June%2015%202018&utm_content=Scuttlebutt%205103%20-%20June%2015%202018+CID_801857e8449fa1095d39848965ce4871&utm_source=Email%20Newsletter&utm_term=Full%20report
    ==================
    Excerpt:
    New York Yacht Club American Magic (“American Magic”), the U.S. sailing team challenging for the 36th America’s Cup, will have a dedicated construction facility and build a pair of state-of-the-art racing boats in Bristol, Rhode Island.

    The return of America’s Cup activity to Rhode Island shores is expected to strengthen the local marine industry, attract additional design and engineering talent to the state, and continue a storied boatbuilding legacy in the town of Bristol.
     
  13. Konstanty
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    Konstanty Junior Member

    That's my shot at AC36.
     

    Attached Files:

    Last edited: Jun 19, 2018 at 4:06 PM
  14. Doug Lord
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  15. OzFred
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    OzFred Senior Member

    The latest prototype? https://www.sail-world.com/photo/208901

    [​IMG]

    Wasn't 1 April a couple of months ago?

    I think this highlights just how dangerous the AC75 configuration might be in the wrong hands. Or even the right ones.
     
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