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Square Top Mainsail, Shaping with less Mast Bend  Bottom

  • Wondering if anyone has tips for shaping a sq top mainsail for a Nacra 5.2. The mast wants to bend to the shape of the original Dacron main sail luff, whereas the Slo Sail square top is a much straighter cut along the luff. So in a close haul, even with tight diamond wires, the top third of the mast (beyond the diamond wires) bends a bit. Are people compensating by not rotating the mast as much?

    1985 Nacra 5.2
    Corvallis Oregon
  • The diamonds are not going to control the mast stiffness above the wires. For ideal wind flow across the mast and main you want the direction of the mast basically pointing towards the wind for proper flow. If you were to limit mast rotation it would seem the mast would be more rigid as you forcing it to work from the major axis (thicker section of aluminum) when applying downhaul and mainsheet tension. The only time I limit mast rotation is when depowering (I run prebend setup). When the mast is not facing the wind direction correctly it's not as efficient (thus depowers). When you sailing next time limit the mast from rotating as see how the performance changes.
  • I run a slight prebend with my prindle 19 and i have about .75 to 1 inch of bend. I find with my setup the more i rotate the mast till it aims at the shrouds the more power i make, and then when i start derotating and pulling downhaul it bends the mast more and flattens the sail more.

    the guy to talk to on this one is TXTuma here or go find him on facebook

    Captain Chris Holley
    Fulshear, TX
    '87 Prindle 19 "Cat in the Hat"
    '74 sunfish "1fish"

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