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

    Just that it is a bit frustrating for us that he never comments on the functioning of his foils, is he happy with, or worry with, how they work in the various speed vs sea state conditions ? During this round the world, he was often in conditions where the limitation of speed is due to the sea state height and angle vs boat speed and route, where foils can improve and/or reveal fragile, we have no info on this scale one experience.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Thats a great point!
     
  3. Dolfiman
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    Dolfiman Senior Member

    Macif still in the trade wind which are rather strong with 20 to 25-28 knots, so the sea is a bit rough but Francois Gabart maintains the rhythm with an average 30 knots (and only 1h sleeping time) during the last 24h. On the video from 00:40 one can see the leeward foil in action. The next challenge is the Azores High, now exactly centered on the Archipelago, "to get around at the best by the west (absolutely no wind in its very center), an about 10h affair" dixit JY Bernot, "then got the west wind in the north of the High but which likely cannot accompany him to the end so the very end is predicted a little slow".
    Video : [Vidéo] Le récap' du 39è jour en images - Macif Course au Large https://www.macifcourseaularge.com/actus/video-recap-39e-jour-images/
    Cartography : Cartographie - Macif Course au Large https://www.macifcourseaularge.com/cartographie
     
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  4. Doug Lord
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    Doug Lord Flight Ready

    Great video but I wish there was more time spent on the foil to be able to study it a little........Better than nothing though.
     
  5. UpOnStands
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    UpOnStands Senior Member

    Has the leeward foil been partially retracted so the foil is more for displacement assist and heave damping than full-on foiling?
     
  6. Doug Lord
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    Doug Lord Flight Ready

    The foil appears to be partially retracted but I have no clue why. Logic seems to indicate that you'd want the foil down as far as possible to prevent it from breaching the surface -which is draggy.
    In the video, the tip is clearly breaching the surface......
     
  7. cavalier mk2
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    cavalier mk2 Senior Member

    I don't know Doug, deeper is always more drag. Shallow the trade off is temporary loss of lift in a breach and when waiting for flow reattachment but in those instances there is actually less drag as it is running in air or aerated fluid versus the solid stuff with a long arm. Be fun to get the data and plot the tradeoffs.
     
  8. UpOnStands
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    UpOnStands Senior Member

    Could be more for comfort. Retracting the foil means that speeds are lower and boat movement not so violent. If day racing you can accept the shocks of driving fast in rough water but after 38 days it would be tough.
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    Part of that equation though is the airflow over the sailplan. Shock loads make it less efficient as abrupt changes hurt the airflow over the aerofoils/sails. The human condition might be a good barometer for averaging the forces to maximize the drive.
     
  10. Dolfiman
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    Dolfiman Senior Member

    Could be also to minimise vibrations, a partially retracted foil has higher frequency eigenvalues less sensible to excitation by waves encounter frequencies : may be some combination speed/waves are not possible with a fully deployed foil.
     
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  11. Dolfiman
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    Dolfiman Senior Member

    The Azores High contour is underway with a speed that remains high, around 26 knots with 10-12 knots of wind. J-Y Bernot "we try to take advantage of the contour winds without being caught by the lack of wind in the central zone". Next days forecasts are still uncertain in terms of speed, it seems that two scenarii are on the table : either a large anticyclonic bubble is being formed off the Bay of Biscay with no other option that to cross it at low speed, or to catch wind of a Low coming from the North-West. So, about 3 to 5 days to finish.
    Video : [Vidéo] Le récap' du 40è jour en images - Macif Course au Large https://www.macifcourseaularge.com/actus/video-recap-40e-jour-images/
    Cartography : Cartographie - Macif Course au Large https://www.macifcourseaularge.com/cartographie
     
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  12. OzFred
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    OzFred Senior Member

    So "worst case" is he loses one day of about a 6 day lead. What an amazing achievement, surely it will be quite some time before this record is broken.
     
  13. philSweet
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    philSweet Senior Member

    Yes, in addition to the phenomenal performance of boat and skipper, they seem to have had a bit of a Goldilocks passage. Is there any record for the shortest route sailed around the world? The 'don't break anything' route would be a good option now. I would totally understand that decision. 9+ hours sleep today. He's gotten more sleep than I have in the past week.o_O
     
  14. rwatson
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    rwatson Senior Member

    macifpng.png I'm watching for the sudden Port tack just before the Azores. Its like being in the race myself
     

  15. Dolfiman
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    Dolfiman Senior Member

    He is doing what we called in french "une aile de mouette" , in English " a seagull wing", a typical sailing optimisation around an anticyclone . Description by Jean-Pierre Dick :
    "This is a nice term (which I find poetic) of our offshore jargon. The boats sneak under (here it is above) the Azores anticyclone and slowly follow the gyration of the wind. The goal of the game is to get downwind closer to the anticyclone central zone without being stopped by the calm in the center but especially to take advantage of the radius of curvature of the air flows to gain ground towards the goal. When the wind softens too much, you change tack by jibing".
     
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