Chris White Atlantic 47, MastFoil

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

  1. cavalier mk2
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    cavalier mk2 Senior Member

    It reminds me of El Tigre ? I think it was, the Spronk staysail schooner used in the charter trades. That 57 had a lot of help capsizing....more of a seamanship issue. The only fool proof boat would be a sandbox in the desert. I wonder how they compare with a walker wingsail ? Marples new diamond rig solves some of the same problems though I agree with the comment on outrig.org about using more of an inverted kite shape to increase area.
     
  2. brian eiland
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    brian eiland Senior Member

    The rigging doesn't look that complicated to me :?:

    Its attempt to split the sail areas up and get a lower sail plan...much like most ketch rigs sought to do.
     
  3. brian eiland
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    brian eiland Senior Member

    Yes schooner rigs like ketches break that sail down into smaller sails spread out at lower heights.

    I don't think this was a 'seamanship issue'. It was more of a case of a very sudden burst of wind which just can't always be anticipated, nor designed for. **** happens sometimes.

    Atlantic 57 Cat Capsize recently
     
  4. pool
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    pool Junior Member

    It surely does to me!

    You will want to make absolutely sure nothing goes wrong with that upper set of spreaders on the aft mast - any minor failure up there will very likely have that rig collapse.

    Also, a wishbone overhanging the cockpit seems to be more of a complication than no boom at all.
     
  5. brian eiland
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    brian eiland Senior Member

    Attached Files:

  6. brian eiland
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    brian eiland Senior Member

    Lets be sure we are talking the same rig design.
    Here is Chris' weblink to his lastest rig design:

    http://www.chriswhitedesigns.com/atlantic_cats/mastfoil/index.shtml

    I don't see any depiction of the "spreaders" on that aft mast. And I don't see any wishbone boom on his rig ??
    I do see a single forestay to his aft mast and two shroud-backstays like most 3-point multihull rigs.
     

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  7. brian eiland
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    brian eiland Senior Member

  8. cavalier mk2
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    cavalier mk2 Senior Member

    The seamanship point was the reminder to fight complacency. They didn't think the coming squall was any different from the norm so the didn't do anything until after it hit. In the account I read I think they said they weren't on deck after noticing the approach of "another squall". While **** happens they had warning a squall was coming and could have kept from tipping the outhouse with a different set of procedures. Safety can seem boring and can slow you down but a little excitement goes a long way....Being able to feather a rig on any point of sail is a great feature, I have my canoe set up that way and it makes life without the "training wheels" easier.
     
  9. catsketcher
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    catsketcher Senior Member

    I am getting a little off topic but I can't see how anything but a narrow band of theory can lead anyone to say jibs are more efficient. In practise fast boats have big mains - the mainsail plan is elliptical or something approaching this which is efficient, you can put battens into them - efficient again, you can even have the mast bend - gust response built in so that the camber changes as the wind increases and you can couple this with a roachy main that flicks off in gusts as well. A whole bunch of good stuff.

    Contrast that to your normal jib - pinhead triangular sail plan - inefficient, forestay sag - inefficient - greater forestay sag in gusts leading to fuller sails - reverse gust response very inefficient but you don't have a mast in the way. So if you ignore all the points above you can call a main inefficient but only of you only look at wind tunnel tests of jib versus main metal shapes. Obviously in the real world large jibs are slow, which is why no race boats have them.

    Now I like jibs - I have them on all my boats. I like a screecher for downwind running as kite are a pain under autopilot (a symmetrical on a run is great) and the average multi has a main that can't be let off enough. But do we get rid of the main? I say no but then others who have sailed heaps say yes. John Hitch got rid of them on his last cat and it sailed well. I don't even mind Chris White designing such a boat as he has - it looks interesting. I just can't see how anyone can ignore all the evidence of every fast race boat which has a big main and look at one small piece of tunnel testing. If jibs were so great then every race boat would have big ones and they don't. The only time they got big was in the rater or IOR days when genoa overlap was unmeasured.

    So put one on your boat for all the obvious advantages but don't try to say it is more efficient.

    BTW - jibs aren't always safer. In the squall that capsized the White 57 they were careful not to dump the genoa as they did not want it to flog and get the sheets into a rope ball. I understand this point exactly. A dumped genoa is a much nastier beast than a dumped traveller on a fully battened main - or a main tamed by a wishbone - but that is my own prejudice showing there.

    cheers

    Phil
     
  10. brian eiland
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    brian eiland Senior Member

    Sail Aerodynamics, Legitimize the Jib/Mainsail Interaction

    Phil,
    There are lots of interesting discussions about this headsail/mainsail 'sail combination' subject thru out that 'Sail Aerodynamics' subject thread I referenced. I'll just repeat two of mine:




     
  11. brian eiland
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    brian eiland Senior Member

    MastFoil Aerodynamics

    I've made a posting about this new rig concept over on that Sail Aerodynamics subject thread. It should be interesting to see what replies come up, as there were quite a few really knowledgeable people contributing to that subject thread (Tom Speer, etc)

    Back to Chris White's new rig, the subject of this thread. Did all of you take notice that his 'mastfoils' were two element foils themselves??
    "Why does the foil have an articulating trailing edge flap?
    Because a flap adds lots of power to the foil with very little additional weight and complication. Reaching and running the flap is set at a significant angle (approx 40 degrees) to the main foil which increases the overall camber of the foil and can nearly double its power. Sailing upwind only a small amount of flap angle is used but it helps create additional lift with very little drag"


    This is an important and distinguishing feature of his design. This imparts a much greater contribution to their effectiveness, both alone, and in support of that headsail located in front of each MastFoil.

    This unique design deserves more analysis before being tossed to the trash pile by the 'traditionalist'.
     
  12. CatBuilder

    CatBuilder Previous Member

    I'd agree completely.

    I read through everything I could on this new design. If it works as he's suggesting, he's got quite a solution to the typical problems of handling sails on a performance cruising catamaran.
     
  13. pool
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    pool Junior Member

    sorry for not being clear enough:

    my reference to complexity was directed towards both the twin masts on a 47' cat and the aft mast rig with its spreaders and wishbone, as cited in the previous posts.

    in comparison, the A-frame mast with 2 boomless rollerfurling sails would be a much simpler and not less efficient solution for a large shorthanded performance cruising cat
     
  14. brian eiland
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    brian eiland Senior Member

    Video reference on Twin Wing Mast Rig

    Hi Eiasu,
    Wasn't it you who just recently brought up this reference VIDEO discussion over on Sailing Anarchy?

    Mention is made of his new mastfoil rig, and its also a little revealing as to what thought processes likely led to this new mastfoil rig.
     

  15. eiasu
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    eiasu Junior Member

    yes kind of me it is .. was ...
     
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