D shape or semi oval advances wing systems shape for double mainsail

Discussion in 'Multihulls' started by Boy Griffioen, Jan 24, 2022.

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D or Oval

  1. D

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  2. Oval

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  1. Boy Griffioen
    Joined: Sep 2017
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    Boy Griffioen Junior Member

    I want to build a 11m mast for my boat (mini650 454) I'm posting this here because in the monohull section there is not much talk about wingmasts and softwings.
    I really like to make a double main wingsail and I can't find some solid information on the choice of mast shape. A D section mast seems to be used most (AC75, @Gary Baigent 's Frog and others) And with the right control lines i guess you can trim the wing thickness with crossed control lines on the sail battens and with the addition of the outhaul and downhaul i think you can shape the foil pretty good. The only difference with the AWS wingsail mast of wich i made a drawing myself. you can counter rotate the mast to make the foil thicker independent of the leading edge shape of the front of the wing. But they also speak of control lines on the battens so i guess counter rotation alone is not enough. And the leading edge foil shape seems not to be fully optimal on the "flat" side of the main it will make a slight angle from the mast to the sail surface. Why would one choose the one over the other. I cannot find enough info on the sail trimming to give the answer myself. But info on this is also nice!
    mastprofiel mk2.jpg
     
  2. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    The shape you want is probably a parabola along the lines of a naca section.
    I’d be posting this in the aerodynamics section.
     
  3. Erwan
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    Erwan Senior Member

    AFAIK
    Wing section thickness is usefull for structural reasons, not for aerodynamic efficiency

    Thick sail is good to minimize drag, and it is important to minimize drag when you have a lot of apparent wind, and you have a lot of apparent wind with foiling vessels.

    Going do decksweeper mainsail might be more rewarding than thick sail if the boat is not a foiling one

    Fair winds
     
  4. Gary Baigent
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    Gary Baigent Senior Member

    The late Frog with double luff main; boat was smashed on mooring ... but I still have the 2 mains.
     

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  5. Erwan
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    Erwan Senior Member

    Does it mean you lost the boat??

    Condoleances
     
  6. Gary Baigent
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    Gary Baigent Senior Member

    Yes - most of it went to the tip; however I saved the main beam and am completing Frog 2 - which is a radical catamaran. Never learn?
     

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  7. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Gary. Please keep us informed about your proposed cat. Your designs and builds always are interesting.
     
  8. Erwan
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    Erwan Senior Member

    Is it what people used to call "Resilience" ?

    Wish you the best for your MK II

    If you have a look at calculations regarding induced drag of the main, I feel confident you will wish to go decksweeper.

    Fair Wind & Epoxy Works

    Cheers
     
  9. Gary Baigent
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    Gary Baigent Senior Member

    Agreed. Reduce disturbance at mainsail base. So obvious - but tricky to implement especially on Frog 2. However helm could lie down in shallow cockpit. And then you reduce area of vision. Can't have everything?
    Here's Dave Knagg's foiler of near 40 years ago.
     

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  10. Boy Griffioen
    Joined: Sep 2017
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    Boy Griffioen Junior Member

    I will share about my crazy idea :) Yes it is intended for a foiler. But not a standard configuration.
    My idea is to have a monohull but you could see it more as the centre hull of a trimaran. A bigger version of a moth without hiking wings would also be a good description.

    The foils under the boat have to be able to either push the boat up but also be able to pull the boat down. On the tips of the wing (not drawn yet) I want to have a lifting foil and maybe some floatation.
    If the concept works the wingtip foil pushes the wing up and the vector of the wind and the foil wants to pull the boat out of the water. If the force surpasses the weigth of the boat there is some extra power by pulling the boat down with the foils.

    I think this is a better idea than the https://www.flowmotion.nl/UK/applications/aeroskimmer.htm because with this catamaran still wants to heel and when it does the wing gives it even more heeling power.
    In my view a very dangerous boat, but fast none the less.

    I think my force vector is more forgiving because the spar wich attaches the wing is hinged the boat does not want to heel a lot. The balance between the weight of the boat, the wingtip foil and the main hull will create a balance and preferably a level ride.

    Here is a very crude mockup of the idea.

    WhatsApp Image 2022-02-11 at 10.34.11.jpeg
     
  11. Erwan
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    Erwan Senior Member

    Hi Boy,

    Should investigate the web and search for the C-Cat OTIP, quite similar rig concept on a cat, but the mast is attached with front & lateral stays, and the pivoting axis of the wing is at the top of the tiny rotating teardrop mast.

    Before OTIP, one of the guy tried a deltaplane wing on a Tornado plateform. I was there for the first experiement, on a lake near Paris, with no wind, so nothing conclusive, later, it was reported it could achieve marginally better performanve windward but in the light as long as the cat did not fly a hull.

    The guy above mentionned travelled to Australia for the ICCC, so you could try to ask Linsday Cunningham the father of Australian C-Cat, or Barry Marmion, who was crazy enought to give an A-cat to this guy, who destroyed it in a few minutes.
    The guy was pretty chubby, so easy to recognize, it is not the standard in the A-Cat serie.
    It is the same guy who prompted Mattia Esse to put on the market beach cats with a crazy hull shape including a transversal channel on the bottom of the hulls.

    In conclusion, in France among our sailing geeks there are many good engineers, and an handfull of freaks.

    Fair Winds
     
  12. Erwan
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    Erwan Senior Member

    A precision to an apparent contradiction
    According to CFD a thick wing section is more draggy than a thin one especially in a turbulent BL environment.

    When mentionning Thick sails, in opposition to thick wing section I mean a rotating mast with 2 sails like the AC75 or a mast sleeve like windsurf rigs or Mothsbwhere the "thickness" is helpfull to minimize separation and therefore drag.

    Apologize for seeding the confusion.

    Cheers
     
  13. Boy Griffioen
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    Boy Griffioen Junior Member

    This OTIP looks quite similar to the Aeroskimmer. Should work very good but with a good gust it's not safe. The force vector that i would like to achieve is more like the Sailrocket. But tackable.
     
  14. Boy Griffioen
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    Boy Griffioen Junior Member


  15. Erwan
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    Erwan Senior Member

    AFAIR it is exactly what happened, a "good" gust lead to a "good" capzise which in turl lead to a "good" race ending for OTIP
     
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