12 Metre design

Discussion in 'Sailboats' started by phum, Oct 14, 2009.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'll leave the forum to asses rather then tolerate this type of ridiculousness anymore.
     
  2. apex1

    apex1 Guest

    Well Paul, I know the reason of such design (which does´nt make it better). And I must confess I have only sailed one of such boats with that rudder outcut. That boat was a goat to maneuvre under motor. Hence my comment. And I know of several older designs with the prop well on the right side, to prevent the lack of maneuverability.

    Regards
    Richard
     
  3. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Well, PAR and Paul B. seems to be entering the canting-keel zone in their debate. Phum, the low cost of the 2.4mr enable you to test various bustles. The modded Mariner bustle shows great potential. Only light downwind, say 1-2 m/s seems to harm it. Probably to much water must be draged along. By increasing the mainsail (and reducing the jib) the performance is nu much better. Still the differences is small to the most common 2.4mr the Norlin mkIII. Sailing the latter boat type you can tune against identical boats which seems to be more important than optimizing the Mariner mooded bustle.
    Another problem is tacking with boats having big bustles. To get the wave-pattern to develop as desired it takes longer time with such bustles. One has to remember that the 2.4mr is a small boat about 4 m long, and allmost all waves are big in comparison.
    Regards,
    Booster
     
  4. Paul Kotzebue

    Paul Kotzebue Previous Member

    What's also nice about the prop on the side is you can use a folding prop. Although a right hand prop should go on the left (port) side. My favorite full keel propeller installation is what Kettenburg did on the PCC's and K38's. The shaft poked out on centerline just aft of the rudder post. You could install a folding prop, no aperture in the keel or rudder, and you could pull the shaft.
     
  5. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Hi!
    The steering of boats with bustles can be different from other boats. Who doesn't remember the reports from Fremantle. Stars&Stripes usuallay started to lee of Kokaburra. Stars&Stripes was reported to have "long legs", not pointing that high as Kokaburra but speeding. Stars&Stripes sailed "around" Kokaburra. Conner tried to keep the bow under high pressure and the steering was said to resemble that of a drunk.
    Regards,
    Booster
     
  6. booster
    Joined: Apr 2009
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    booster Senior Member

    Hi!
    Well, a good portion of bustle may be helpful, but compare the draft of Stars&Stripes at 2.96m to 2.64m of Kookaburra. This must mean that Stars&Sripe has a draft penalty under the R-rule. Perhaps this was more important than the bustle discussed previously.
    Regards,
    Booster


    Stars&Stripes US-55
    Length overall (LOA): 20.23m
    Length waterline (LWL): 13.92m
    Beam: 3.81m
    Draft: 2.96m
    Sail area: 164.70m2
    Displacement: 28.180 tonnes
    Mast: 25m


    Kookaburra III
    Length overall (LOA): 20.52m
    Length waterline (LWL): 13.86m
    Beam: 3.80m
    Draft: 2.64m
    Sail area: 162.90 m2
    Displacement: 28.200 tonnes
    Mast: 25m
     
  7. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Stars&Stripes US-55

    us55.jpg
     
  8. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Kotzebue!
    What is your analysis of Stars&Stripes US-55 vs Kookaburra III? The basic dimensions are similar but the draft. Seems that one already before the first race could tell that U-55 must be faster. Iain Murray (Kookaburra chief designer) said something about the boats looking so different that someone must have done something wrong. Later poor calibrations of measurment-devices at the tank tests was found to be the explenation.
    Regards,
    Booster
     
  9. Paul Kotzebue

    Paul Kotzebue Previous Member

    Booster,

    Are you sure about the draft dimension? It could be a misprint or misinformation. If S&S has a draft penalty she would have to give up length or sail area compared to Kookaburra. Yet that does not seem to be the case based on the dimensions you gave in an earlier post.

    The only way to evaluate the relative characteristics of the two boats is to compare rating certificates. However, I doubt very much that S&S took a draft penalty. It is a very expensive penalty (3 x excess draft added to rating).
     
  10. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

  11. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Hi!
    I have discussed the subject above with the signature MYD on this site. Yes, he has seen the information about draft penalty earlier. Some years ago he was in contact with someone in the design team of Stars&Stripes US-55Britton Chance, Jr., Bruce Nelson and David Pedrick. Probably it was Pedrick, MYD recalls. What came out from that contact was that US-55 was said to have no draft penalty. The boat was nothing special, but every detail was 100%.

    Seems to me that it was special anyway, in having every detail 100%!

    Regards,
    Booster
     

  12. booster
    Joined: Apr 2009
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    Location: Sweden

    booster Senior Member

    Rating certificate site?

    Hi again!
    Yes, as pointed out by Kotzebue one must have the rating certificate to see if there is a draft penelty or not. Regarding the 2.4mr in Sweden we have a site there one can study the rating certficates.

    http://www.svensksegling.se/Avdforbatteknik/Matbrev/Sokgiltligtentypsmatbrev/

    Perhaps there is a similar site for the 12-meter yachts?

    Regards,
    Booster
     
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