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Thread: Twin Headsails

  1. #11
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    Quote Originally Posted by brianb View Post
    Hi Alan,

    I have often wondered about headfoils and will they blow up if the loads applied are different than the design load ?

    Brian
    OK, so here' s my thought on that.... It's a twin-groove headfoil, yes? So I can hoist two headsails at a time, one in each groove. I can then pole them out and go wing-and wing that way. But if I do that, the loads on the two headsails are trying to pry open the headfoil, and I'd be concerned that it'd come off of the forestay.

    But with this rig...two 1.5 ounce nylon sails sewed to a single luff tape, there are no forces trying to pry open the headfoil, so I *think* it should be OK.

    BTW, I had intended to fly all this with 1) twin chicken stays (basically just a line with a bit of purchase on it that will take, say 500 lbs load or something) from the mast track rings to the toerails, and not use a spinnaker net. However, if I'm gonna move the rings way up on the mast, the angle that the chicken stays work at becomes less advantageous. However, they're so easy to rig, that I figure I'll just do them anyway.

    i was also going to do all this with the main up, with a reef in it, as well. Then again, I've never tried it, so what do I know?
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  2. #12
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    Sep 2007
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    Capitola,CA
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    Just a reminder that in most situations with twin jibs/poles, it is desireable to locate the mast attachment points for the poles with about a foot or more of separation. This helps avoid damaging the poles when bringing them onto centerline..

    For those with twin poles affixed to sliders at the inboard end, the mast track undergoes extreme sideways loading, and will often work it's way loose, especially if the track attachment machine screws are just tapped into the thin aluminum wall of the mast.

    At minimum, it is best to use extra machine screws to secure the mast track to the mast. Stainless inserts are also available that can be used to strengthen threaded holes in aluminum mast wall.

    ~sleddog

  3. #13
    Join Date
    Sep 2007
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    Quote Originally Posted by brianb View Post
    I have often wondered about headfoils and will they blow up if the loads applied are different than the design load ?
    This has not happened to me using a metal foil of the Harken and Schaefer roller furlers. I can't speak to what would happen with a plastic tuff-luff headfoil.

    - rob/beetle

  4. #14
    Join Date
    May 2009
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    284

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    Quote Originally Posted by tiger beetle View Post
    The twins/butterfly sails on Beetle are sized to match a 150% jib top that I also have, which makes them huge and provides tons of power when running deep, with a lot more control than when running under spinnaker as the sails don't oscillate due to being attached down the center on the headstay furler (the two sails are sewn to a common no. 6 luff tape). The twins also work really well in super light wind despite being built of 1.5 oz nylon in a triradial panel design, as the headstay supports the weight of the sails and they will fill in 3-4 knots of wind, something a normal 1.5 kite would never do.

    I asked Hood Sails to make the twins as close to a spinnaker shape as we could get, rather than being flat boards. Spinnakers develop their power by being a hi-drag shape (a sphere develops more drag that a flat board) and the twins should operate as a hi-drag shape as well. What we wound up with most resembles a giant brassiere with a very deep centers when the luff, leach, and foot are all tight. Square footage on my spinnakers is approximately 1900 square feet, the twins come in at 1600 square feet - that's a lot of cloth to generate power.

    On the sewing end, don't sew nylon with a straight stitch, it should really be sewn with a 3-step zig zag which most home machines don't have. Synthia make be best able to speak to how good a compromise as 1-step zig zag is for nylon work.

    For pole height, the clew should be as high as possible above the water so you don't stuff the pole end in the water when the boat rolls hugely (which it will when running deep under the twins). In my case the sails are designed such that the pole butt is at the very top of the mast track, 13 feet above the deck and therefore 17 feet above the water (this is where the pole goes when running deep under kite). I would recommend you set up your twins to have the clew set at least as high as you would when running DDW under spinnaker.

    - rob
    Sorry to drag up this very old thread, but I'm very interested in how this setup worked for you Rob. I'm would like to have a similar set built, that is more of a spinnaker shaped sail. Is it still possible to tie the clews together... or does the "brassiere" shape preclude that option? What sort of apparent wind did you use this in? Were they "reefable"?
    Thanks for any input.

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