A Displacement-Only AC Class?

Discussion in 'Sailboats' started by Earl Boebert, Sep 24, 2007.

  1. Earl Boebert
    Joined: Dec 2005
    Posts: 376
    Likes: 46, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    I tried this over in the 2007ac.com forum with out much success, so here goes again...

    I'm in the process of writing an article on the history of model yacht rating rules prior to radio control, sort of a "Men Against the Rule" for toy boats :) I'm particularly interested in how the rules and the materials of the day resulted in "type forming," that is, all the boats ended up looking very much the same.

    In Germany in the 1920's they had a displacement only rule, that is, the sole limit on the boat was how much it weighed. Since a free-sailing boat has to be able to go anywhere in lake or pond, there was a de facto limit on draft.

    So let's say that in some alternate universe the America's Cup folks replaced the fifty or so pages of rules with one that said: A monohull of 30 tonnes maximum displacement, human power only, has to sail the AC32 course in Valencia. What would you design, and how would you anticipate the rule would result in type forming? The model rule converged surprisingly rapidly -- I'll describe that after this thread runs its course.

    Cheers,

    Earl
     
  2. Doug Lord

    Doug Lord Guest

    Ac Usa Flyer One

    Earl,the key to your rule, in my opinion, is the MAXIMUM limit on weight. It allows extremely lightweight boats as long as human movable ballast is used.
    I'd like to see a boat like this around 60' LOA with a 50' beam . Buoyancy pods would be shaped so that they did not look like a hull nor function like a hull. 15 to twenty crew(good at running 50' in 4 seconds). Since the whole thing is so light it would probably be possible to engineer a "human power" system for the 5000lb canting keel; otherwise a very minimal fixed ballast bulb incorporated into the retractable strut/foil.(Self-righting is not a rule requirement so a minimal keel with buoyancy in the maximum outboard portion of the racks should keep it sailable.)
    Designed to foil in 10k or less wind. Should whup heavy seahugging leadbellies pretty convincingly.
    60' monofoiler/ human powered ballast version
    http://www.boatdesign.net/forums/attachment.php?attachmentid=12546&d=1176896587
    ------------
    The USA FLYER ONE would reflect the basic technical details of the 60' ocean racing monofoiler proposed below with people replacing some or most inanimate movable ballast:
    60'+ or - 20' Ocean Racing Monofoiler Design Discussion - Boat Design Forums
    Address:http://www.boatdesign.net/forums/showthread.php?t=15143
     
  3. Earl Boebert
    Joined: Dec 2005
    Posts: 376
    Likes: 46, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    Well, this didn't exactly set the forum afire :) Anyhow, as promised, here's a typical German displacement-only boat, in this case a 4.5 kg design from the early 1930s. It appears that in model yachting at least, class rules that do not place an implicit (through a LOA limit) or explicit (through quarter beam penalties) limit on the LOA/LWL ratio type form into these light displacement scow/skimming dish designs. Presumably the reason is that downwind planing/surfing advantages overcome any loss in upwind speed. It's interesting that this seems to be the case even in free sailing, which was conducted as match racing, each pair of competitors sailing what amounted to drag races, once to windward and once to leeward; a windward win got you three points and a leeward one got you only two (loser gets nothing), thereby placing a premium on speed to windward.

    Cheers,

    Earl
     

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