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Weather Helm/Lee Helm -What's The Diff?

Discussion in 'Sail Trim with Don Guillette' started by Don Guillette, Apr 26, 2018. Add this thread to a FAQ

  1. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    3,275 posts, 413 likes
    Starwind 27
    US Barnegat, NJ
     


  2. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    3,275 posts, 413 likes
    Starwind 27
    US Barnegat, NJ
    Right, isn't that how a roll tack works? :waycool:
     


    Gene Neill likes this.
  3. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    3,275 posts, 413 likes
    Starwind 27
    US Barnegat, NJ
    Ok, that, too ;)
     


    jon hansen and Jackdaw like this.
  4. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    200 posts, 99 likes
    Hunter 170
    US Tampa
    Windsurfing has tremenous appeal. Fits on roof rack, beach launch, perfect for days over 15 knots great for hot weather. Seems perfect for my off season. My experience is with snowboarding so the crossover should be easy.

    The part that confuses everyone is that stupid CE picture of wind fore and aft of the CLR. Those books should be burned.

    Everyone first sailing class (after the obligitory bowline lesson) shouldbe the instructor blowing on a pinwheel, then cutting all but one petal off and blow on it again. The sailboat is doing that 100% of the time there is wind.

    Next lesson is tying a string to a mast about 1/2 way up RC mast and the student pulls the string in different directions (lift force) while the model is held near the keel joint.

    That would show just about every essental force in sailing for entry level.

    The key is the difference between the forces of the wind and the floation and the location of ballast versus flotation. Those two distances determine the center of the pinwheel.
     


  5. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    200 posts, 99 likes
    Hunter 170
    US Tampa
    This is easy to explain and understand.

    Imagine yourself as king neptune. You see keelboats racing above you and rise up. You grab a fin keel by the bulb and hurl it like a dog toy as far as you can. (Crew is tethered, they'll be ok)

    The boat spins very lopsided. If you slow time, you would see that the boat is spinning around a single point near the rear keel hull join. That point is following a smooth arch tbrough the sky, regardless of lopsided spin. I think that point is the center of mass (COM).

    When floating that point should be directly below, in line with direction of travel.

    When the boat is heeled over any amount that COM is shifted to the opposite side.

    Heres the next point. If you apply a force to get the boat moving it ideally should be in a perfect line between the destination and the COM. Kerbal space program on a playstation 4 shows this easily. Any misalignment generates rotation and centrifugal forces.

    If you have sails up the lifting/pulling force is way above the COM pulling some degrees away from your destination off to lee. Since the lift force is not the same as your destination and not in line with your COM. There is rotation around the COM.

    If you are under power and heel with rail meat, it should be less noticeable since the prop is very close to the COM and in line with your destination. The rudder if applied, then provides a force not in line with your destination so there is rotation around the COM. If the prop or applied rudder force is below the COM the boat turns in. If the prop or applied rudder is above the COM you turn out.

    Next time you are out with crew try to see if there is a difference between under sail and under power.

    Fast power boats turn inwards since tbe COM is above the prop(s), keel boats turn outwards since the COM is just below the prop and rudder.
     



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