Pivoting Mast Catamaran?

Discussion in 'Multihulls' started by tasman sailor, May 11, 2011.

  1. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    Hello

    I am currently studying in year 12 and have elected to draw and design aspects of a boat mainly delving into more hardware and technical side of rigging. I was thinking of drawing a Moth but was as you would expect, hard pressed to find any proven plans of the foiling designs but if someone had some loose guidance say a link for the class guidelines i could perhaps design my own however i'd say the simple ability to develop this class without looking at materials and really technical dynamics wouldnt be suited to a year 12 student i then moved through ns14s and cherubs untill arriving at an idea for a catamaran.

    the course calls for a design component and i was wondering if it would be possible to design a pivoting mast for a catamaran. I think that if you could adjust the stay length (relatively) along the beam plane you could increase the efficiency of a boat class that already relies on sailing at an angle with one hull in the water the other as ballast. So if i could shorten the windward stays going upwind and lengthen the leeward ones accordingly say to allow for a 25 degree angular shift to keep the mast vertical and perpendicular to the wind and water. Problems arising would be i think retaining a sideways stiffness for the mast and whether the boat could handle the pressure of winching the sail to windward. perhaps it could pivot and the be locked of through tacks.

    So im going to need some plans of a catamaran to work with an old class like the maricat might have some, if anyone has a link. Still cant figure out if this will work so all opinions are welcome. Ideally i could get some plans for a DNA cat F16 stealth or tornado one of the high performance cat classes but thats unrealistic, i suppose but it is just a year 12 project if anyone can point me in the right direction.

    I think you may need to offset the increased efficiency with some ballast water pumped to windward hull perhaps to scale with efficiency to keep the boat in equilibrium. does anyone no of ballast systems like this being used in a dinghy.

    typed in a rush ha
     
  2. tspeer
    Joined: Feb 2002
    Posts: 2,299
    Likes: 267, Points: 83, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    Canting masts are used in the ORMA 60 class, and the trimaran USA 17 had a canting mast.

    The masts on these boats typically sit on a ball that allows the mast 3 degrees of rotational freedom. This is necessary because of flexing of the structure, rotation of the mast about its axis, and to adjust the rake (fore-aft tilt) to tune the directional balance, in addition to allowing the mast to be canted to the side.
     
  3. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    i didnt know how they adjusted rake on those, have there been any applications on smaller boats? i was thinking of relying on natural rake, bend from mainsheet and retain the vertical stiffness in other direction
     
  4. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    just saw canting rudders, thought there were only dual fixed ones like the 70s
     
  5. Doug Lord
    Joined: May 2009
    Posts: 16,662
    Likes: 332, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Your first idea on the Moth was a good one because, from a technical standpoint, it is one of the only boats capable of "veal heel" which cants the mast to windward as well as moving the CG of the hull physically to weather.This can result in a 30 to 40% increase in righting moment essentially "for free" since after the crew reaches his/her maximum hiking position they can initiate "veal heel" with no further crew movement required. It is a technique unique to bi-foilers- -only bi-foilers are capable of veal heal-it's not just weather heel. See below for Bill Beaver's excellent paper on the Moth. There are lots and lots of Moth references on the net including plans etc. http://www.moth-sailing.org/imca/faces/news.jsp be sure to search the "Mothosphere"...
    Good Luck!


    Here is some relevant stuff:

    http://www.wingo.com/chriswhite/tiltrig.html

    http://seahorsemagazine.com/9802-feb/tri.htm

    Proposed movable ballast system for a dinghy: http://www.boatdesign.net/forums/sa...isabled-physically-limited-sailing-37048.html

    Pictures: Astor 18 sliding tramp movable ballast system, second to last-BMW-USA17 canted mast, last- Merlin Dinghy with canted mast-click on image for better view:
     

    Attached Files:

  6. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    Great

    okay so i wasnt intending to cant the mast to windward to gain lift as the foiler guys do, but instead to keep the mast perpendicular to the water to retain maximum sail area to the wind. The catamaran with the sliding tramp looks genius are there any further links? I think i will still go with the catamaran and will need the plans to an, A class, one of those Marricats or something like that to work off if there are any resources around. Otherwise i can call the Nation Maritime Museum of Australia its just a school project. also after looking at your developments im amazed how inventive they are. Is the Aeroskiff 16 the only full scale development you've done, how did it go?
     
  7. Doug Lord
    Joined: May 2009
    Posts: 16,662
    Likes: 332, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ================
    Thanks. No-see my gallery. It didn't work too well-(but did foil)-primarily because the hull design(bow) was poor for the intercoastal and increased takeoff speed a lot. It was a great learning experience. Using the same basic hull(new bow+2') ,foils and rig on my new experimental platform.
     
  8. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    ah, wow, how are you building these boats, is the red consistent with the moulding material or a theme ha, also what advantage do the curved centerboards have, im going to work off a mosquito plan
     
  9. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    curved centerboards on catamarans that is. Also did the moulded lee boards in the Tantra? Work as efficiently as a traditional up, down?
     
  10. Doug Lord
    Joined: May 2009
    Posts: 16,662
    Likes: 332, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ========================
    Seemed to work fine. Best comparison was with the US one where the two were essentially equal upwind. The molded in leeboards were asymetrical and toed in.
    See the "Aerodynamics and Hydrodynamics" forum for more on curved foils. http://www.boatdesign.net/forums/hy...lifting-foils-monohulls-multihulls-37508.html
     

  11. tasman sailor
    Joined: Feb 2011
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: yas

    tasman sailor Junior Member

    OKAY, so now i need to figure out sail loads in order to calculate block ratios any info? and wondering if you can get manual winches that are geared to winch continuously clockwise and anti-clockwise.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.