Chris White Atlantic 47, MastFoil

Discussion in 'Multihulls' started by bearflag, Nov 21, 2011.

  1. pogo
    Joined: Mar 2010
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    Location: Germany Northsea

    pogo ingenious dilletante


    On White's HP i can see two arrangements, one with a big V- flap ( split flap) and one with a small V-flap (flipping split flap)
    I think that one with the biggger flap has been the first one.
    This setup has to be trimmed much more, 'cause you have three interacting components.
    For easyness only upwind
    -softsail whose camber is controlled via track at the end of the boom
    --MastFoil whose amount of lift is controlled via it's positive angle to the apparent wind
    --flap, whose angle to the centerline of the Mastfoil defines again the amount of lift of the MastFoil
    A complex system, a lot of telltales are needed.
    This setup has a lot of variabilities, the margin of a mistake is big.
    With other words , for the average sailer the setup is much too complicated.
    That the big flap has been controllable over a wider range ( from 0 to about 40 degrees) shows the control arrangement in vid 40. (Note that the mizzen in the vid features the second, the smaller flap )
    https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-RnZMM5k
    https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-V3CHvnK

    Smaller flap , also upwind.
    --the MastFoil is underrotated a little --about 10 degrees positive to the apparent wind. this angle of attack is more or less universal and easy to obtain.
    At this angle the Foil itself ( alone) generates lift with little drag. It is far away from flow separation and very far away from stall.
    --at this angle the little flap can be set full . No separation, no stall , but much more lift for the Mastfil with only very little additional drag.
    This setup is much easier!
    One tacks, one flipps the flap, one rotates the foil about 10degrees to the apparent wind.
    Any Sailer can do this.
    A keen sailer has the option to fine-tune the Mastfoil on the new leg.
    pic showing flip-flap control-unit, note the two holes.
    https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-T9hbGr2
    Tacking, note that the 10degrees are given very late after the third tack , at about 2:10
    https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-RnZMM5k

    One might ask why a flap, why not rotating the foil only for more lift ?
    A higher angle of attack means earlier flow separation and much more drag.
    using a flap means lower angle of attack of the foil , only little additional drag and much more lift.



    About the kinematics , the mechanism of the flip-foil i don't know anything, sorry.
    At least one can see lever arms connected to the bigger , tuneable flaps
    http://chriswhitedesigns.com/atlantic_cats/mastfoil/update_01-12.shtml
    For other solutions please search in Google Pix under " aileron mechanism" .



    pogo
     
  2. waynemarlow
    Joined: Nov 2006
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    waynemarlow Senior Member

    Aren't we getting to the stage of this type of wing mast that to go really small as Chris has done, is almost defeating the object of a wing mast, that of high efficiency. Why not bigger and just allow it to wether cock in high winds. Even have a proper 2 stage wing setup.

    I do like the idea though of a fixed mast with a rotatable outer wing, there are just so many companies out there that could make these masts, lamp post type spiral wound tubes at quite low cost. A low load outer wing section weighs little and relatively easy to make.
     
  3. CT249
    Joined: May 2003
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    CT249 Senior Member

    How well would it weathercock? Apparently even some freestanding wing masts do not weathercock well enough to allow the boat to sit in a marina berth normally, and of course if you have a big stayed wingmast you may end up making a last radio call like that of Loic Caradec (RIP). And are the benefits of a weathercocking mast enough to make up for the staying issues?
     
  4. brian eiland
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    brian eiland Senior Member

    Remember this wing mast of his fully rotates 360 degrees around the full height 'round stub mast tube' that is somewhat free standing. It does have a forstay and a couple of backstays attached at the masthead.
     
  5. brian eiland
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    brian eiland Senior Member

    Found this photo today of the original MastFoil mast.
    First-mastfoil-ed-600.jpg


    Appears to answer 2 of my questions about the size of the original foil
    1) bigger than the more recent design, and
    2) there are some hints as to how the foil was attached.

    As found a few photos that might give someone a general idea of the size of these foils.
    Chan Applies Strips.jpg
    Chan Applies Strips 3.jpg
     
  6. brian eiland
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    brian eiland Senior Member

    Taming the Powerful Sail Plans on Modern Catamarans

    I found this article interesting,...from Cruising World magazine:
    http://www.cruisingworld.com/boat-review-atlantic-47-mastfoil

    I think I have been accused of having some sort of deranged view of sailing rigs on cats as well :rolleyes:;) ,...my aftmast rig.

    I also took the mainsail off and replaced it with a pair of roller furling jibs, but I did it in a single mast configuration. Perhaps my mizzen sail is flap for the whole sail plan :?:
     
  7. brian eiland
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    brian eiland Senior Member

  8. brian eiland
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    brian eiland Senior Member

    ....as in "Think One"
    https://cdn2.hubspot.net/hub/209338/news/Ad_aerodynamics/index2.htm
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    Sorry Brian.
    I did see a Mastfoil cruising in BC this summer in Desolation Sound at Teakerne Arm. We had already anchored near the waterfall when one came in. There was wind in the channel but it was light in the arm so it powered after crossing the wind line. From what I could see it seemed cruising oriented in performance as you would expect. Steady rather than hot. From a handling perspective it seems a nice update of the staysail schooner concept. For light winds I imagine code 0s would be in order.
     

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  10. Nico Crispi
    Joined: Jun 2017
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    Nico Crispi Junior Member

    It has been a while since the last post and I hope that someone here has driven one by now and can report on it.

    I am close to making a decision on the rig of a Tri and I think one of the advantages of this design is in allowing a singlehander to be able to rapidly adjust to variable conditions like squalls. Keeping safe and easy with less rigging and maybe avoid the installation of a anti-capsize system.
     
  11. eiasu
    Joined: Nov 2011
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    eiasu Junior Member

    Hi Nicolò,
    I only read updates from Chris about some corrections of early mistakes in the first launched that now are corrected and fixed.
    I would ask Chris directely, he's always supportive and helpful, maybe can give you contacts of MastFoil owners.
    Enjoy this beautiful rig!
    I was discussing with Chris about the same, a Trimaran with MastFoils.
    Ciao, a presto
    Eiasu
     
  12. Nico Crispi
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    Nico Crispi Junior Member

    Piacere di conoscerti Eiasu.

    You may want to share, here or in a new thread, about the thinking that lead you toward a CW Tri with the Mastfoil rig.
    In my case it is equal parts simplicity, ease of sailing and safety during singlehanding.

    Nicolò
     
  13. eiasu
    Joined: Nov 2011
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    eiasu Junior Member

    Here we are,
    I am just a great fun of Chris White, such a fan that i was insulted by Peter Johnston (ex Guboat owner) on SA multihull forum who thought that I was Chris White posting with false nick name.
    I love his designs, neat, very much oriented to effectivity and not leaning to fashion or funny chooses. Reading comments from owners they are all more than satisfied, critics came only from people who never were onboard, they just don't like forward cockpit and write all kind of things.
    I find myself with your same thinking exactly in the same priority order plus performances and aesthetic.
    Ok Nicolò, feel free to ask all kind of questions, even though i also was never onboard his designs i read a lot,
    ciao buon vento
    Eiasu
     
  14. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Certainly very cool boats, I've done a passage on a Chris White Atlantic which was home built to a great standard in strip plank composite. The forward cockpit certainly makes a great space for sailing although it can get pretty wet every now and again in heavy conditions, it feels much safer than a conventional style rear cockpit with much better protection for the crew if you were pooped. The inside helm works well too my only complaint was that we couldn't spend more time sailing as the wind was a bit too light most days. Had a 13 knot average on watch one night during the graveyard watch.
     

  15. Nico Crispi
    Joined: Jun 2017
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    Nico Crispi Junior Member

    Which is probably the reason why we don't see them in much higher numbers as their great design richly deserves.
    One wonders what their retail price might be if a competent builder were to make female molds and market them in a variety of composite schedules.
    When built the West style, cost and time works against them.
     
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