OK !
let’s see is somebody else is eventually in agreement with the scaling of all listed (not only) J Class and 12 Meters to get a LOA fixed to 127cm.
Of course I need to check other parameters like displacement and sail area for compatibility.
Basic assumption being an Open Class with few restrictions !
Cheers
ClaudioD
I’m sure you will find that most sail plans need to be modified to reach the 800 square inches of sail area as required by the Marblehead class…
But… you also will need to consider changing the scaling of a keel extension for sailing qualities over scale… So, on the face this isn’t going to be a truly scaled J or 12 50/800, It will require a little modification to sail right.
But, the nice thing is should you chose to build to the Marblehead 50/800 specs there are nearly 4,000 registered Ms in the USA alone so it’s jumping on with an already well established class.
Yes of course is a good idea if acceptable to the Marblehead !
I have to check the real sail area that can be used within the scaling factor because the Class M in Europe call for a max sail area of 0.5160m².
Now when you apply the calculating formula the Real Surface is close to 0.72m² = 1116 in²
In US, the specified Marblehead sail area is 800in² exactly as 0.5160m² specified in the Class M Rules used in Europe.
For instance a Columbia 1958 scaled to 127cm will have 0.61m² of sail area or 945in² while the Displacement will be 5.6kg without hull modifications.
Thus considering real surfaces, the 945in² is fully compatible with the real surface of 1116in² used for the Marblehead in spite of the basic rule calling for 800in².
I would appreciate other comments about scaling the J Class and 12Meter to 127cm length / 50inches
Cheers
ClaudioD
It sure would be.
It would be considered a Traditional design Marblehead, due to it’s hull-form and would fall under Marblehead class rules.
Due to it’s hull form it would be sailed with the Vintage Group. Which, by the way, is not a registered class of yacht. It’s a group that organizes activities for the Vintage era boats from the Marblehead class.
What about the fin length ?
ClaudioD
PS : I went reading the Marblehead Vintage Rules ! and, as I was suspecting,
a lot of things are forbidden as :
Sliding or adjustable keels
Centerboards
Leeboards
Bilge-boards
Bowsprits
Overhanging rudders
Outriggers, pontoons, or twin hulls
[COLOR="#FF0000"]Movable or shifting ballasts[/COLOR]
Prognathous keels ( no portion of the leading edge of the keel appendage, including the lead, may project forward of any portion of the leading edge above)
Metal fin keels
Materials with density greater than lead
[COLOR="#FF0000"]Carbon fiber or Kevlar in the hull rudder or rig[/COLOR]
Fabric or film decks
Mylar sails
Swing rigsWhen building any yacht it should, obviously, conform to class rules.
The class that presides over all Marblehead designs of any era is the Marblehead class. So, given that you could build this design with an unlimited fin length if built to USA standards, or with a maximum draft of 660mm if built to international rule.
However.
Considering the hull-form, and that it will be sailing with Marbleheads of the traditional variety, the rule set of the vintage group (not class) should be respected to allow the design to conform with other Traditional designs.
According to Vintage group (not class) rules, the maximum keel/fun depth for a Traditional model is 12 inches, as described here:
http://pages.swcp.com/usvmyg/VM/vmrules.htm
OK fine, but a J Class or 12Meter of 127cm and made with composite materials are not allowed to race or compete with Vintage Marblehead while they could do it with the modern 50/800 Rules.
In this contest the J Class and 12Meter will be looser against modern Marblehead 50/800 class as well with High Fliers.
Cheers
Claudio
Hi Claudio, your previous J-Class (Enterprise) has LOA of 1,315 mm/51.7" which is good size for this classical boat, I for one would not like to she it shortened.
For the modern 12 metre I would like see with 1200 mm/47.2" LOA as this is the current Euro AC 120 class LOA standard that seems to be ideal size for handling in Europe.
There is no-one I would appreciate either of these classics being influenced by M-Class rules etc.
Just my two cents worth.
Cheers Alan
Yes, but I am not quite sure why you would want to build a Carbon-Fiber J boat… It’s a classic hull in every way.
It would seem that the only actual limiting rule is the prohibiting of centerboards, applicable to the J class designs
This is, in essence the exact same concept as scaling the Js to fit a pre-existing class ( IACC, not M) and I like the idea.
I’m just partial to the M
Take these 12/J designs and adapt them to an existing class to make it stronger. Don’t go and make a new class. That’s the last thing anyone needs… Worldwide
Why not ? most RC J’s hulls are made of Fibreglass …ain’t they ?
Don’t agree, just because they have same LOA as other classes, does not mean they will perform the same! far from it, wake up and smell the flowers, there are more big boat classes than you can poke a stick at…that cascade down into RC classes
Hi Alan,
I just found out that a scaled J Class or 12Meter cannot race or compete with Traditional Marblehead Division due to materials restrictions and as well against High Flier Vintage Marblehead due to LWL lenght unless is accepting to loose all the times.
Limiting the LOA to 120, I’m not sure that could be racing with the AC120 due to a small detail: the Main top should be min. 60mm unless a waiver is granted.
The weight will anyhow higher then 4.5kg and the sail area could be around 55/60dm² and therefore OK also for the ballast of 2.85kg. Instead it may exploit the advantage to have and additional fin up to 42cm draft.
This may be an advantage with strong winds above 15kn.
All that need to be elaborated more in detail !
Cheers
ClaudioD
Hi Claudio,
I would not expect J or 12 to be “competing” in other classes, ideally as you point out they would need their own class specifications e.g sails, ballast etc.
The LOA I was mainly referring to handling in the sense of building and transportation.
By the same thought process, there is only one IACC 1200 that is mathematically superior to all the others, and therefore sailing anything besides that one is a gaurinteed loss.
Oops.
(Or, not scrutinize the math and have fun sailing Alinghi Vs ENTZ
I do not have made detailed calculations yet, but I’m afraid that with this scale size a wooden construction will be too heavy and hard to find an acceptable ballast ratio !
Cheers
ClaudioD
Actually, a 12 or J really does fit the bill for a Traditional Marblehead really, really well with the exception of the centerboard Rules that apply to some Js.
On paper a Traditional M will never beat a full 50" LWL High-Flyer. But, in the real world Short LWL Traditional models beat High-Flyers all the time.
It just depends on who is at the helm.
Marbleheads of the Vintage variety do not have to be constructed from wood.
There are many (And I Own one) Vintage Ms that are made from Fiberglass.
Fiberglass is not against Vintage group (not class) rules. It is
modern materials such as Kevlar and Carbon that are outlawed.
With reason- Kevlar and CF were not available during the era.
You surely could get a nice ballast ratio with a fiberglass hull.
Don’t want to stray off topic but I personally sail 3 different class boats 2 x 120cm and 1 x metre, all three have different characteristics that I like about them and that’s why I like to sail in different classes with similar spec boats.
If had to lop them all into one class rule … I would lose my interest pretty fast as it would be nothing but speed & in my opinion that is not what sailing is all about.
Thanks for wishes racing Alinghi with ETNZ … I will beat him one-day 
and if you are ever on this side of the pond there is open invitation to join us, we will provide you with AC 120 and make it a fair race so you are not disadvantaged using a M-Class 
I would be very thrilled to do nothing less! I am making a conserted effort to sail in as many Venues as possible.
But,
Unfortunatley,
Mathematically,
It’s advantage Marblehead as discussed here:
http://www.rcsailing.net/forum1/showthread.php?6388-IACC-scaled-to-a-Marblehead
LOL thanks you just proved point …different horses for different classes, that can’t be or should not be compared or competitively raced together.