Ultim Tri Macif round the world in solo

Discussion in 'Multihulls' started by Dolfiman, Nov 4, 2017.

  1. Dolfiman
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    Dolfiman Senior Member

    Macif / François Gabart started this morning his round the world tentative to break Thomas Coville record (49 days !) , you can follow him through this web site (but in French) and the Facebook (with English translation). On the home page, you have the boat dashboard with the speed (presently 32,7 Knots) and the advance or delay with regard to Coville record.
    Accueil - Macif Course au Large http://www.macifcourseaularge.com/
     
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  2. Doug Lord
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    Doug Lord Flight Ready

    Thanks for posting this, Dolfiman. I wish them luck!
     
  3. rwatson
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    rwatson Senior Member

  4. Dolfiman
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    Dolfiman Senior Member

    Translation of François Gabart first message yesterday, after the first day :
    "I'm off Portugal after a day of racing, first incredible day, with a pretty incredible crossing of the Bay of Biscay at full speed. There was not a lot of wind, but not too much sea either, but it was especially the angle that made the speed. It had been a long time since I had been so fast on 12 hours, I had regularly tens of minutes at more than 40 knots. I may have broken the boat record at 46 knots, I would have to take the time to check. "
     
  5. UpOnStands
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    UpOnStands Senior Member

    Unbelievably fast across Biscay. Just half day needed.
     
  6. rwatson
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    rwatson Senior Member

  7. Dolfiman
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    Dolfiman Senior Member

    François Gabart message this morning (8 Nov.) :
    "Always under big gennaker with the small jib (J-3) in the role of staysail. I had the mainsail high and it was not easy because the boat forced a lot... I prefer when there is more wind because with a reef in the mainsail, the boat can go fast without effort... Actually, I struggled with gusts of wind ! One of them was very short and yet it caused me a big wind failure: from 20 knots to 10 in a few seconds ... "
    + the following comments of the web site :
    "Fortunately since his third jibe off the Canary Islands, François Gabart was able to tumble south to pass 250 miles in the west of the archipelago of Cape Verde around midnight. And if the disturbance of the volcanic relief did not take place at this distance, the loner did not have a very simple night to manage: the fleet of sailboats that participates in the Mini-Transat was precisely on its way between the Santo Antão island and the Antilles, most of the competitors just overflowing this mark course ... The sunrise was therefore a relief for the skipper who no longer had to stay glued to his radar or standby in his cockpit to avoid collision !

    Macif enters now the doldrums by the longitude 32° door, by hoping there is there a small corridor of wind dixit J-Y Bernot his router.
     
  8. rwatson
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    rwatson Senior Member

    An hour behind at 5d 2h 16:35
     
  9. Dolfiman
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    Dolfiman Senior Member

    In François Gabart 10 nov. message :
    ""You have to find the balance to be able to stay in support on the central hull, but it's not so easy when you go fast. I cannot stay on the central hull all the time and I'm still not comfortable sleeping like that. It's starting to come, it will take training again. But my sleep is damaged, despite fatigue. I still managed to take a few naps."

    Is it not in this case that a foil on central daggerboard, when adjusted to provide a small downforce, which can add passive safety when the singlehander is sleeping ? In case of gust of wind with a move to more heel, the inflow incidence on this foil increase instantly and can provide an extra RM which adds to the one due to the weight. And moreover in steady state condition, this foil RM component is in squared speed boat, can increase in parallel with heeling moment in squared apparent wind speed. I am right ?
     
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  10. Doug Lord
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    Doug Lord Flight Ready

    Fantastic quote, Dolfiman-something I've been saying for years! At least I've pointed out numerous times that one of the advantages of a daggerboard foil is the ability to generate downforce for extra RM..... Done 100% automatically on the Fire Arrow.
     
  11. TANSL
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    TANSL Senior Member

    I hope you know how to excuse my ignorance but, if it were not for that, would not it be enough with central foils?
     
  12. Doug Lord
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    Doug Lord Flight Ready

    I'm not sure I understand the question? For a daggerboard hydrofoil to work to increase stability it needs to be able to lift vertically and develop downforce as needed. I know for sure that is possible on Maserati and Gitana 17-not 100% sure about Banque Populaire but a high probability that their foil is also adjustable.
    Of course , on the Fire Arrow Test Model it works 100% automatically.
     
  13. TANSL
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    TANSL Senior Member

    The force developed by a daggerboard foil, which is at a certain distance from the axis of rotation of the ship, not only produces the elevation of the assembly but also gives rise to a righting moment (moment of the force with respect to the axis of rotation). If the foil is located in the center, very close to the axis of rotation, that righting moment is very small, but the lifting force can be the same. therefore, the only extra effect that the daggerboard foil achieves is the RM. If someone had not been looking for that extra effect, the daggerboard foils would not have been used. It is not a surprise that the designer has met.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Daggerboard foils or at least one pair have been used in the past that only lifted vertically with no AOI adjustment possible and, of course, no downforce. Using an adjustable mainfoil that provides both vertical lift and downforce was pioneered for the first time in history on a trimaran main hull on the Fire Arrow Test Model almost 5 years ago and then last year on the MOD 70 conversion- Maserati. This year it is used on Gitana 17 and maybe Banque Pop.
    It should be noted that on the test model the downforce can double the total RM......The daggerboard foil is capable of enormous downforce and, because of that, presents an engineering challenge on large trimarans. The force on the daggerboard is multiplied by the distance from the center of lift of the daggerboard hydrofoil to the center of lift of the lee ama hydrofoil resulting in a very large moment.

    Downforce.png
     
    Last edited: Nov 11, 2017

  15. rwatson
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    rwatson Senior Member

    Exciting to see he has made up ~100 NM, by turning East sooner. I find the strategy based on prevailing winds fascinating.
     
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