MASTFOIL RIG: Mainsails Be Gone

Atlantic 47 under sail

I spent a day hanging out with multihull designer Chris White a while back and came away all buzzed up over his latest idea. The basic concept, as you can see in the image from his website up top, is pretty simple: two jibs and no mainsail. What isn’t immediately clear from the photo is that those aren’t conventional pivoting wing masts behind the sails. The masts in fact rotate through a full 360 degrees and have controllable flaps on their trailing edges, so that they too can act as sails and create lift at any wind angle.

 Chris calls them MastFoils and has various patents pending. What he told me was that he expects a MastFoil rig to be just as fast as a conventional full batten main and jib going upwind and faster than a conventional rig going downwind (yes, you can fly spinnakers and gennakers and such off a MastFoil, too). Plus, there are all sorts of incidental benefits when it comes to anchoring, close-quarters maneuvering, and heavy-weather sailing.

Of course, the most obvious advantage is that a rig like this should be exceedingly easy to control.

MastFoil spar

A MastFoil in all its naked unfinished glory. The foil, comprised of carbon skins over foam, rotates around a carbon-fiber pole supported by three stays at the top. The foil itself carries no structural loads

Atlantic 47 rendering (fwd)

Computer rendering of Chris’s new Atlantic 47 catamaran flying a MastFoil rig. The self-tacking rig is controlled from the forward cockpit, a standard feature found on all Atlantic cats (and copied on Gunboats)

Atlantic 47 rendering (aft)

Rendering of the same A47 cat from the aft quarter with sails off

This ain’t just some conceptual pipe-dream here, people. As of a couple months ago, five boats with these rigs have already been commissioned; one of them is already sailing north from Chile, where Atlantic cats have been a-building of late. One of the new rigs is also going on a sweet custom 41-foot design that Chris has developed for a client in Florida.

MastFoil 41 rendering

The MastFoil 41, as Chris calls it, is a light, very simple performance cruising cat designed for a woman who likes to cruise the Bahamas alone with her two standard poodles

MastFoil 41 interior

The MastFoil 41 interior. Chris tells me he’s been waiting his whole career to draw a catamaran with just one head in it

You can read a lot more about the MastFoil rig and about Chris’s career as a designer in the May issue of SAIL, which should be on newsstands any day now, seeing as how it’s mid-April.

Chris White w/sextant

Chris in his younger days, navigating with a miniature sextant designed by his grandfather

Searunner trimaran

Sailing his first boat, a Jim Brown Searunner tri he built in his parents’ backyard

Meanwhile, I’m crossing my fingers that I get a chance to sail a MastFoil-rigged boat before the year is out. I’m seriously thinking this could be a major breakthrough.

(All photos and images are courtesy of Chris White)

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3 Responses
  1. Richard D Elder

    Hmm. Torsional loads on the foil fairings– wind velocity and direction at masthead is as much a 15 degrees and 20% different than at deck level.

    Friction of foil fairings over carbon tube must be substantial. Any wind loading should lock it up and make it impossible to rotate. Are you sure that the entire mast and fairings are not designed to rotate together?

    What is the world coming to? A Chris White catamaran (the 41) without an open air mast pit? (LOL)

  2. Charlie

    @Richard: You’re right… there probably is some torsional loading on the foils. I wasn’t smart enough to ask Chris about that. But I’m quite sure the foils rotate on fixed tubes. I believe bearings are interposed, but I’d have to go back and check all my notes.

    Re the 41: as I recall there was a height restriction on the mast (due to a bridge near the owner’s home), so Chris put more area in the mast foils to compensate.


  3. Richard D Elder

    hi Charlie
    hmm— bearings would impose point loadings on the fairings unless the fairings were very rigid/stiff/heavy. Be interesting to know how the design actually works. Till then I’m still a fan of a 3/1 single rotating wing mast–carbon or carbon over 1/4″ cedar.

    Enjoy your site.

    ps; a friend tried to shelter in Culebra during the infamous Cat 5 a number of years ago. His tale would make your hair stand on end.

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