12 Metre design

[PAR]

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

[apex1]

Originally Posted by Paul Kotzebue

Apex,

That rudder is typical of auxiliary sailing yachts built from the 1930's through the 1960's. I've sailed on many boats with that type of rudder. They did not maneuver well under power, but you went real slow in tight quarters. It was just about as easy to maneuver those boats under sail as under power. The idea was to hide the propeller behind the keel under sail. The aperture extending into the rudder allowed the propeller shaft to be removed without removing the rudder.

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

[booster]

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

[Paul Kotzebue]

Originally Posted by apex1

And I know of several older designs with the prop well on the right side, to prevent the lack of maneuverability.

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.

[booster]

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

[booster]

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

[booster]

[booster]

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

[Paul Kotzebue]

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).

[booster]

Kotzebue!
Thanks for your analysis. No, I am not sure about the draft. As you say it can be a misprint or worse, but occurs twice:

http://www.americascup.com/en/acclop...4888&idRubr=74

However, I have been told about the US-55 draft penalty about a year ago by the signature MYD on this site. But I didn't realize it was that big. I have asked MYD to comment here.

Regards,
Booster

[booster]

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

[booster]

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/Avdforba...entypsmatbrev/

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

Regards,
Booster