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How much slippage actually occurs downwind?  Bottom

  • Thought of the day. Without pointing the boat at a fixed object and watching my gps track I wonder how much of your downwind progress happens just from the boat sliding when jibing through broad reaches.

    I know I've read it's minimal but just thinking if I was trying to make a line and pulled up the boards I wonder how much ground I'd make to leeward or if it would even be noticeable as I'm swerving around hunting for apparent wind.

    --
    Matt
    '82 NACRA 18 Square
    '85 Hobie 18 "Honey Badger Don't Care"
    '86 Hobie 18 "The Rippin & The Tearin"
    Clearwater, FL
    --
  • configure to be optimized on all points of sail.... the beauty of downwind sails and boards you can pull up and down... so I'd guess with a kite up, and boards up theres much more lateral force and much less resistance... so I think there's legit slippage... combined w/additional speed...

    other day in 15-20 winds w/o the chute I could point really deep downwind and ride the waves in, but when I steered up a wee bit (boards up) using the beach and the bows as a reference, I was slipping a good 20 degrees... and the sterns were dragging so we wouldn't stuff the bows... if the hulls were trimmed/not dragging the back, perhaps we would have slipped more? (this was on a Blade F-16)



    Edited by robpatt on Jun 14, 2017 - 12:04 PM.
  • QuoteI wonder how much ground I'd make to leeward or if it would even be noticeable as I'm swerving around hunting for apparent wind.

    you don't need no stinkin gps
    Just carry one of these suckers -
    http://www.stanleylondon.com/sextplath1.jpg
  • It's a more complicated question than just leeway (side slip). Increasing the leeway also typically decreases the VMG b/c the boards increase boat speed by offsetting the lateral forces from the sails. Increasing the SOG increases the apparent wind in a feedback loop up to the limit of driving force is balanced by the drag. Additionally, with boats with more power and deeper boards, running the boards further down potentially allows for decreased drag by flying a hull; lower drag, more speed.

    Think about it this way, prior to the Tornado being updated, the fastest way downwind was the "wild thing"; that relied on moving weight to leeward, keeping the boards down, heating it up and using the boards and apparent wind to fly a hull and go faster and deeper. If pulling the boards and letting the boat slip was faster, the wild thing wouldn't have been the revolution that it was.
  • Cool article i had read on the AU tornado site a while ago - http://www.aita.asn.au/in…d-thing-with-the-old-rig

    HOW TO DO THE WILD THING ! (WITH THE OLD RIG)



    Edited by MN3 on Jun 14, 2017 - 03:19 PM.
  • It's actually easy to see. I sail in very clear water. Get shallow enough to see the bottom, then watch where the bottom is "going" vs where you are pointing.

    --
    Hobie 18 Magnum
    Dart 15
    Mystere 6.0XL Sold Was a handful solo
    Nacra 5.7
    Nacra 5.0
    Bombardier Invitation (Now officially DEAD)
    Various other Dock cluttering WaterCrap
    --
  • MN3Cool article i had read on the AU tornado site a while ago - http://www.aita.asn.au/in…d-thing-with-the-old-rig

    HOW TO DO THE WILD THING ! (WITH THE OLD RIG)


    This will take a lot of practice to master.

    --
    Sheet In!
    Bob
    Prindle 18-2 #244 "Wakizashi"
    Prindle 16 #3690 "Pegasus" Sold (sigh)
    AZ Multihull Fleet 42 member
    (Way) Past Commodore of Prindle Fleet 14
    Arizona, USA
    --
  • Quotehis will take a lot of practice to master.

    yea - but it's really fun to watch people learn (and screw it up) :)

    PS - Many people think "the wild thing" is when you sit on the windward side and fly a hull... the are close
  • QuoteIt's actually easy to see. I sail in very clear water. Get shallow enough to see the bottom, then watch where the bottom is "going" vs where you are pointing.


    Although we live and sail here in Clearwater - our water is only clear in the later winter/early spring when all the algae dies ...
  • I didn't mean that taking the boards all the way up was a faster vmg downwind. More just imagining being say 100 yards from the leeward mark and instead of having to do an extra jibe to make it at the last minute just pulling the boards and staying hot on the wind. Like if I gained 10-20 yards of slippage to barely clear the mark I'd assume that would be faster than having to point dead downwind or add a jibe in to cross the line.

    On my H18s with sticky boards it wouldn't be a quick maneuver but on my nacra I have remote dagger board raising lines and could have the boards up in seconds.

    --
    Matt
    '82 NACRA 18 Square
    '85 Hobie 18 "Honey Badger Don't Care"
    '86 Hobie 18 "The Rippin & The Tearin"
    Clearwater, FL
    --
  • Quotejust imagining being say 100 yards from the leeward mark and instead of having to do an extra jibe to make it at the last minute

    banana - tell your tactician/navigator to get with the program and set a better lay line! banana

    QuoteOn my H18s with sticky boards it wouldn't be a quick maneuver but on my nacra I have remote dagger board raising lines and could have the boards up in seconds.

    I can't speak for an 18sq but on my boats trying to lift a foil with pressure on it is like lifting cement. possible but it's a fight and sucks!

    In my experience - small adjustments on the fly that take me off the stick or mind off the prize result in a net loss.
    i.e.
    If i have a spin out and am in racing mode, i have it heated up as much as possible, slowing down and lifting a board (or not slowing down and fighting with it for a second) would take my concentration way off the race and i would have lost any gains i would have made by a foil modification - ymmv

    now if you have a team of grinders putting oil into your hydrolic system, may be a different strategy



    Edited by MN3 on Jun 16, 2017 - 12:23 PM.

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