J-Class versus 12Metre Class

Back to 12Metres and J-Class discussion after a year or so !

This time is to propose some plans for the J-Class as well for the 12Metre.

The list is limited to some of the boats made so far.

The 12Metre Class list is split into sections, the projects made BEFORE the Intrepid and the ones made AFTER the Intrepid.

The difference consist on the variations introduced to the Hull.
Rudder was displaced toward the transom with the use of a skeg support, the keel become shorter and equipped with a Trimmer Tab.

It should be very interesting to introduce the Trimmer maneuverability with a dedicated servo.

Actually the intent is to propose plans in both classes below the 115/120cm length.

The source of plans is the F.Chevalier America Cup Encyclopedia

I would therefore ask to select 2 plans for each series. The plans that will receive the higher number of votes will be transformed in constructional plans composed of 2 views and shadows to scale 1:1.

2 boats in the J-Class
2 boats in the 12Metre before Intrepid (long keel)
2 boats in the 12Metre after Intrepid (short keel & trimmer)

This is the List that includes the model proposed size to scale 1/32 for the J-Class and the scale 1/17 for the 12Metre Class:

Small scale outlines will be inserted in the next connection !


Here the first 12Metre side views - (before Intrepid - long keel ) :

See page 6


The other 12Metre Class side views - (short keel - Skeg & Rudder and Trim-Tab) :

See Page 6


Personally I would choose from the ‘modern’ 12Metre :

  • Courageous
  • Azzurra


For those who like to know how may 12Metres are around the World :



Unfortuately none of my 12 metres are on your list … maybe too modern :rolleyes:

My first choice would be Australia II as this was the boat that changed the game and took the Cup from the Yanks :spin: I will never forget that day, I was living in Melbourne at the time and the whole country just went wild !

Second choice is Kiwi Magic KZ-7 because it is a …well no prizes for guessing that one :stuck_out_tongue:

Wild card choice is French Kiss FRA-7 only because she was lost LVC semi-final against Kiwi Magic and I called my sailing team KiwiKiss which was joke at the time in NZ sailing circles :winking:

Cheers Alan


Of these 6 showing, I like the profile of the “Azzurra”
I look more elegant-cut stern.



From these 6 showing, I like the profile of the “Azzurra”
I look more elegant-cut stern.


Hi Alan,
Of the boats you mention, I do have only the Australia II and Kookaburra II :

See page 6

The F. Chevalier America Cup Encyclopedia was issued in 86, therefore the boats developed in 87 are not included.
Do you have the plans?
I like the idea of wiglets but the keel form is well done to catch up weeds ! hem, further is complicating the construction and probable exposed to damages after construction.


Hi Alberto and Alan,
My intention is to keep the list open for 2 months, max 3 months.

The list updating is

  • Courageous : 1
  • Azzurra : 2
  • Australia II : 1
  • Kiwi Magic : 1 (plans ?)


PS: Alberto I would appreciate if you could avoid to report the drawing outlines to avoid confusion - only text please !

Here below the side views of the 6 chosen J Class :

See page 6


PS : to note that the plans to the 1/28 scale of the Enterprise are already developed in the dedicated tread : http://www.rcsailing.net/forum1/showthread.php?5781-1-28-scale-ENTERPRISE-1930

-Hi, From 6 sailboats shown, I like the profile of the “Azzurra” It seems more elegant way of cutting the stern.
-The previous post which included drawings has been removed.


Thanks a lot Alberto

Hello Claudio,

I don’t want to mke this parochial, but can I post a vote for Australia II. Even as a child who wasn’t interested in sailing, I still stayed up all night to watch the final races. I also think you would revel in the challenge of the winged keel.


Hi Jim,
well is noted, the actual score is

  • Courageous : 1
  • Azzurra : 2
  • Australia II : 2
  • Kiwi Magic : 1 (plans ?)

I like very much the oldest 12Metre class but I would go for the Trim-Tab being a new challenge for skippers !

For Alan,
I found in my library the “French Kiss” plans that I got from F.Chevalier some years ago.


Of all the J’s, Yankee was the most modified, going through several rigs and one hull change. I documented her history in a paper for the Classic Yacht Symposium; PM me if you’d like a copy.



Looked high & low and can’t find anything on Kiwi Magic only the site that I posted earlier, great news about French Kiss :smiley:

Cheers Alan

Personally, I would love to see a Ranger, or Endeavour II Scaled down to 127cm (2cm under 1/32) Or Columbia scaled up to 127cm (2cm above 1/17)

Because at the length of 127cm, the boat can be measured in the large, existing Marblehead class and due to the hull style could be sailed with the Vintage Group

Columbia (or any of the 12 Meters for that matter) would be a better option for your build, as the scale is not so drastically reduced as the J boats. What I mean is the final result of a 1/17 boat will sail better than a 1/32

Hi Breakwater,
You may have a point, but…

Let says that all J Class and 12Metre be scaled to the same length : 127cm LOA.

Of course, the 12Meter will offer a little more comfort during construction.

The point is, using the LOA of 127cm, the LWL, that is what count when discussing about racing, will be in the order of 83/85cm and thus some 40cm shorter then a Vintage Marblehead. In this case are needed different classifications.

Actually I reckon that in US there there are several classes built around J Class and 12Metre design, while in Europe are much less :

1 - http://www.officialjclass.org/…220 cm long and 35kg average …Open to all J Class
2 - http://www.theamya.org/boats/newport12/…182cm long and 18kg…One Design
3 - http://www.theamya.org/boats/ec12/…152cm long and about 10.5kg…One Design
4 - http://www.theamya.org/boats/us12/…116 cm long and 7.2kg…One Design
5 - http://www.theamya.org/boats/canterburyj/…122cm long and about 6.5kg…One Design

Now I would I fill uncomfortable suggesting to US modelers another choice allowing to choose the model they like.
Of course the “One Design” offer a big advantage, all boats are built to the same base and only one design is developed.
This make also easier to deal with the single Rules.
The Open Class, as I wish to do, requires several design drawings scaled from real yachts. The “Rules” shall be more detailed
Common design parameters at first glance :

  • the LOA +/- 3cm
  • weight +/- 500g
  • Sail area +/- 5dm²
  • Draft with two options: deeper keel or added retractable/adjustable fin/bulb to be compatible with the wind forces. (prosthesis)

Let get further !

Actually, not quite on target (and certainly not being argumentative… your work is A+)

Many Marblehead designs do not use the full LWL of 50". In-fact, most, if not ALL Marbleheads from the Traditional era do not use the Full LWL. The Most popular design from the Traditional era, the Madcap is a great example, and the hull style is similar to that of a J or a 12.
It is not untuil the High-Flyer era that Marblehead design was changed to encompass a full 50" LWL… which, yes, is a different classification. These boats in general are faster, not only because of the LWL extension.

See John’s Marblehead here for an example of the:

Also inspect many Traditional M plans on this page, including the first of which (Cypher) listed having a 40" LWL:

First, The Marblehead class is an international class of Yacht, so yes the Marblehead does exist in Europe. However, most in Europe are sailing Marbleheads of the Modern Variety with carbon/ Kevlar composites (such as the Starkers or Skapel) as opposed to the Traditional, High-Flyer, or Classic Varieties.

Yes, there are several USA classes that encompass Js and 12 Meters. The J class being the only limited development class, and is HUGE because of the scaling factor (again, see where 12s are a better option for the build)
All other classes are One-Design. That is doing wonders for class organisation (especially the EC-12, which is very healthy) but also stinks because the 12 Meter was, in reality, a developmental class.
At 48" It’s at least my wonder why the Canterbury J wasn’t made 2" longer to dual-rate as a Canterbury J as well as a traditional Marblehead.

The M class is nice, as it can encompass any design that is 50" long, and carries 800 square inches of sail. ANY of the J boats, or 12 Meters could be encompassed as an existing class, instead of making a new one… we all know there are far too many classes.

I don’t want to dampen your enthusiasm on the build. It’s just an observation that these classic yachts could be rolled into a pre-existing international class.

In the end it’s your build, and you are very welcome to do whatever you wish, but, selfishly I would love to see all of these Js and 12s on the pond together at one time racing under 50/800 rules.

I wish I knew how… I would start the task of sketching the lines plans to all of the Js and 12s to Marblehead size.
There is atleast 1 known J-boat scaled to 50" Marblehead size. It is a Boucher M design, essentially a semi-scale “Shamrock” J boat hull scaled to 50" and available here:

If you don’t wish to make a boat at 50" long, no issue… but I may contract you to draw the lines plans for several 50" Js and 12s, or teach me how you make such wonderful lines-plans, and so darn quickly!