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Wow, look at this sail twist!

Discussion in 'Sail Trim with Don Guillette' started by Brian S, Feb 16, 2017. Add this thread to a FAQ

  1. Brian S

    Brian S

    Joined Nov 9, 2012
    2,068 posts, 92 likes
    Oday 192
    US Lake Nockamixon
    Here's a picture of the F4 foiling catamaran (an evolution of the old Gunboat G4 which flipped in Antigua a few years ago...) It's reportedly "at 30 knots" which I assume is boat speed, not TWS or AWS. Note how the main and the jib are mostly sheeted for close reaching, which makes sense as the apparent wind angle moves forward at high boat speeds, yet the tops of the main and jib are SIGNIFICANTLY twisted off, implying they are bleeding of a lot of power due to higher true wind speeds. Based on the sea state, with white caps, this makes sense. Also, note the true wind angle looks somewhere around 145ยบ or so, based on wave direction.

    Twist.jpg

    Photo from: http://sailinganarchy.com/wp-content/uploads/2017/02/image1.jpg
     


  2. kappykaplan

    kappykaplan

    Joined May 1, 2011
    485 posts, 19 likes
    Pearson 37
    US Lusby MD
  3. Gene Neill

    Gene Neill

    Joined Sep 30, 2013
    1,539 posts, 248 likes
    Catalina 22, Albin Vega 27
    US Orange Lake, FL
    New desktop wallpaper. :)
     


  4. rgranger

    rgranger

    Joined Jan 19, 2010
    3,700 posts, 279 likes
    Hunter 26, Hobie 16 26
    US Smith Mountain Lake
    You could probably ski behind that.....
     


  5. Meriachee

    Meriachee

    Joined Aug 1, 2011
    1,321 posts, 143 likes
    Catalina 270
    CA Edmonton, Ab Wabamun - on the orange ball
    Looks oddly like the hulls are upside down.
     


  6. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    6,097 posts, 629 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    They're not going 30 knots with that sail trim. The apparent would be so far forward they would look more like an iceboat. Think about the vector math, and the wind speed that would have to be there to have the sail fill at that angle with 30kts boat speed.
     


    Last edited: Feb 16, 2017
    Brian S likes this.
  7. Brian S

    Brian S

    Joined Nov 9, 2012
    2,068 posts, 92 likes
    Oday 192
    US Lake Nockamixon
    Ok, yeah, they musta meant "sailing in 30 knots." I dunno, that sea state looks pretty tame for 30 knots, doesn't it? Looks more like Beaufort force 5 than force 7 to me. Still, pretty cool they are busting along at very high speed (look at the spray around the foils) with that amount of twist.
     


  8. thinwater

    thinwater

    Joined Mar 26, 2011
    1,364 posts, 60 likes
    PDQ Altair 32/34
    US Deale, MD
    ^^ I'm with Jackdaw. I had a cat that would reach at over windspeed.

    If the wind is 12 knots sustained with higher gusts (guessing), and the true wind angle is 155 (looks pretty deep to me), and app wind angle is 50-60, they're going 150-170% of wind speed, but not much more. I'd buy low 20s at times. I'm sure they seen 30s.

    My old Stiletto would have had the chute up, app wind about 70 degrees, and about 15-17 knots in 12-15 true. This is faster than that.
     



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