How to build a wingmast?

Discussion in 'Boat Design' started by StriderTurbo, Jan 26, 2005.

  1. asathor
    Joined: Oct 2004
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    Location: Minnesota

    asathor Senior Member

    Rotation.

    How about leaving the mast alone and rotating the Sail Track and boom?

    A more sophisticated sailtrack extrusion would not need that many supports.

    Couldn't this yield many of the benefits on a wing mast?
     
  2. W17 designer
    Joined: Oct 2010
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    Location: Vermont, VT

    W17 designer Senior Member

    I realize that this thread is 15 years old now, but as I was very surprised to see that no one else has since asked anything close to the same question since then, I thought at least an update here might help others.

    Yes, wingmasts CAN be built by amateurs and successfully too. I am equally a fan and in total agreement with Eric (Sponberg) on this, but since he has retired, it seems his website has now also sadly closed down. The strip-built Gougeon mast design was also 'taken off the market' many years back so the choices and sources have changed. It was never really a 'wingmast' anyway, being far too wide and oval.
    The good thing is that designs have improved and you can now build a professional looking (and performing) 100% carbon fiber wingmast totally at home, even without using vacuum-bagging, although that's still an option.
    Wingmasts also can, and are still being, built of wood ... using some solid timber with plywood sides plus some subtle additions of carbon fiber tapes to limit their deflection, with an over-sheathing of fiberglass for weather protection. Because of less basic material strength, the cross section will be larger and the weight slightly greater, but even reputable designers like Chris White have successfully built their own rotating wingmasts of around 60ft like this.

    My own CF design has been calculated for a more modest range from 8 to 11 metres, with a different layup defined for each length. Keep in mind that these are true wing masts ... which for me, is a mast with a fore-and-aft chord of over twice its width. In fact my designs are closer to 2.7:1, what I consider the sweet spot between added efficiency and added weight. I will try to add a photo of an example and give you a link below to read more about them.

    As far as rotating masts 'flopping around' and unnerving some sailors, I can understand where this comes from, but if properly designed and set up, the slackness will not be excessive. First, they are typically supported with only 3 stays and these should all go to one heavy-duty shackle or linkplate at the hounds. If a rotating mast is incorrectly pivoted from shrouds that are mounted on the side of the mast, then the shrouds will indeed risk to change length and that's not good. The mast should pivot about one support point and then theoretically, the effective length of these 3 stays remains fairly constant. However, used as they are on fast multihull, there is typically some flex between the hulls and this adds some slack to the rigging ... exclusively apparent in the unloaded leeward shroud. As long as most of the slack is taken up when the mast is first installed, this slack should not be of much concern as some will always be there. If it bothers an owner, one can simply install a shock cord back to the quarter, to take up the slack as it occurs. Some argue that such a rig does not allow for doubling of rigging for redundancy, but its your choice. If the original 3 stays are oversized and the end fittings well sized & installed, there are then far less parts to check and service, so finally it's '12 versus a dozen'.
    Anyway, hope this helps..... regards mike

    Try this link for more wingmast info:
    PRELIMINARY information on the homebuildable WatersWing carbon-fiber mast https://smalltridesign.com/Carbon-Fiber-Mast.html
    mike/ Waters Wing Mast leeside.jpg Mast down - ready to lift off.JPG
     
  3. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Thanks W17 for your input on your experiences. For the record, I am, indeed, retired, and my wife and I are sailing around the world in our 35’ sailboat, Corroboree, my first commissioned design that we bought back from the original owner. We have been in Australia for nearly a year, now, and will be leaving Bundaberg, Queensland, in about a month to start heading north toward Indonesia.

    You are right that I cancelled my old website, but I started a new one on retirement: www.ericwsponberg.com. I kept a lot of the data and articles available to read and download. There is a section on free- standing masts. Anyone can reach me through the Contacts page on my website. I have been consulting with a number of people around the world on their boats and rigs, mostly offering advice without doing any design or engineering. Like I said, I am retired, but I have not gone too far away.

    Cheers, Eric
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Happy sailing and safe travels Eric :)

    If you end up Japan way - drop me line.
     

  5. W17 designer
    Joined: Oct 2010
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    Location: Vermont, VT

    W17 designer Senior Member

    Thanks for the update Eric. Great to hear from you again and know you are still available when we need to tap into your experience. Happy days .. and be safe.
    mike/
     
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