Wow.
I thought I worked hard at this kind of stuff.
But, in the short time that I left this tread you’ve totally outdone yourself Claudio.
These boats look so amazingly awesome.
Welcome to the Marblehead CLASS. Inclusive of so many different designs and the total enjoyment to sail so many different shapes. Variety really is the spice of life.
Another created class will not only fail, but assist in the failure of many, many other already established and failing classes due to fragmentation.
Hense the idea here.
Take a bunch of boats of various design, and sail them all together under one roof.
I proposed the M-Class and Claudio ran with it. Others were proposed, but the M was selected.
I’d like to think the reasoning is because the M-Class is an INCLUSIVE class that allows major design variation. It is accepting of so many different hull-forms. It is NOT an EXCLUSIVE class that does not allow creative design. M-Rules are Open. not closed.
Hi Breakwater,
I like drawing and Coreldraw5 is an excellent tool once you knows how to use it.
As I said before, the displacements between the 6 selected boats having the same LOA of 127cm are rather different and I wonder if some compensations could be adopted .
This include the possibility to have similar righting moments and therefore modifying the keel dept.
The 2 JClass Ranger and Endeavour are around 4.7kg
The 2 12Metres long Keel Columbia and American Eagle should be around 5.6kg
The 2 12Metres short Keel are : Australia II 6.3kg and Azzurra 5.4kg(pending drawing confirmation).
Under the same Sail Area, the JClass may have an advantage.
At this moment in time I found difficult to introduce a Handicap Rule between them.
Cheers
ClaudioD
The Voting Standing is still as :
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The Plans available at the moments are the 12Metres AUSTRALIA II and the J Class RANGER :
To note that the shadows are in scale 1 : 1 and therefore directly printable in A4 format
ClaudioD
PS:
Added Ranger Files with Stop Image pictures taken from You Tube Video and Sail Plan.
Hi, “Claudio”
As I recall the “J-class Enterprise” had two votes, or am I wrong. I don´t understand.
Greetings.
Thank you Alberto, modification done !
Cheers
ClaudioD
COLUMBIA 1958 Files ready and attached here.
There is also a File containing several pictures that could be used when building the Deck.
There are some ancient pictures referring to the old times showing a simple Deck Layout, some others instead are referring to a recent built Deck.
Was rather difficult to find Deck pictures and layout of the Columbia. The Static Model picture is a good help.
I have made two Deck Layouts.
The Modeler is free to decide how to make the Deck.
According to the VM Rules, the drawn Sail Plan should be 51.6Dm² or 800in² , while actually is 62dm²
ClaudioD
You can make any modifications you wish, so long as you stay within these basic confines which allow the design to compete as a Marblehead of the vintage variety:
(this is not inclusive of
-50" Long
-800 Sq inches of sail.
12" Draft for a Traditional Model
16" Draft for a High-Flyer Model
1" Garboard Radius for both TD and HF.
This rule set is not inclusive of other detail points such as materials bowsprits and etc. It’s only a basic rule confine. And all it means is you can manipulate the displacements to you heart’s content so long as you stay within those aforementioned points.
Hi Breakwater,
the Garboard radius is taken at the main station or at any other place ? Close to the rudder ?
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Thank You
ClaudioD
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ClaudioD
I haven’t checked your numbers, but just a reminder that under the Universal Rule the sail area calculation was not actual area, but rated area. The mainsail area was close, but the jib was not measured. Rather, the rated foresail area was the fore triangle, that formed by the mast, deck and forestay. Actual area could be more or less, e.g., by use of the genoa-like quads.
Cheers,
Earl
Hi Earl,
The number game was made to see what would be the nominal sailing wind condition under the VM Rules with 800in² Sail Plan
The yellow sail plan is the one coming from direct scaling of the original. The striped Sail Plan is the actual with 800sq.inch (5160cm²)
The fore triangle (Jib), as you says, is limited by the fore stay and mast plus 80% of main luff.
The exercise consisted in lowering the CE and using a deeper keel lowering the Ballast CG.
According to the simple static calculations, the wind of 9.5kt is the upper limit achievable with 3.1kg ballast and 45° of hell and increased keel dept of 40mm, yellow silhouette.
3.1kg ballast is the actual retained nominal weight pending confirmation from the Hull construction for which I have allocated 1.65kg.
I do not think at the moment that I will propose a Genoa.
I would appreciate to know how these models , JClass or 12Metres do behave with the wind force since IMO 9.5kt is not very high condition !.
Thanks
Cheers
ClaudioD
This the Start for the ENDEAVOUR II design : BTW Shadows are not yet verified with the waterlines !
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The real one :
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ClaudioD
PS : Lloyd you may start with that drawing if you like !
I’d suggest running the numbers on the AMYA EC12 class and seeing what their righting moments, etc. are for comparison. If Rod Carr is following this he can tell you under what circumstances they drop down to “B” rigs. If he doesn’t respond I can ask him.
Cheers,
Earl
Reefing is for wimps 
Rod has made this EC-12 sail selection guide which I have found to be very accurate.
http://www.carrsails.com/EC12SailSelectionGuide.html
Basically you’re looking at an A-rig from about 0mph to 11mph and a B rig from 11mph to 20mph.
Although some of that depends on WHERE you are sailing. Come down to a B rig sooner if you are sailing in the rough ocean, and stay with an A rig longer if you are on a smoother small pond.
Most of the undesirable overpowered action on an EC-12 comes when the boat is not wing-on-wing downwind where it can make wild broaches. (Like the real ones!)
Either way- the A rig stays on the boat untuil it is forced off.
In your example the arrow pointing vertically passes Marblehead Vintage Group rules.
the arrow pointing from right to left is illegal per Marblehead Vintage Group rules as there is a hollow gap between the 2" disc and the garboard.
Now, is that an actual lines plan or an example? If it’s an actual plan that station could be faired to match the garboard radius rule without trouble or really much design change at all.
Hi Breakwater,
thank you for the answer, I was suspecting that the Garboard “discus” was extended to all the shadows. As a matter of fact this check shall be done directly on the plug and carry on some surface fairing at that level since is not sufficient to modify one shadow only.
Hi Earl,
would be nice to do the same calculation with the EC12 but I do not have all the infos I need at the moment and in particular the ballast weight.
I was reading that the EC12 DSPL is 24lbs while the ballast “could be” 18lbs and the construction left with 6lbs.
If this is the case, then the ratio Ballast / Hull is already 75%, probably the highest ratio I know with RC models.
Under these conditions, I think that the J class and 12Metres will have at this scale factor some difficulties to cope with that Ratio.
As an example shown above the Columbia do have a DSPL of 5.75kg and applying the ratio of 75%, the ballast shall weight 4.3kg and the remaining 1.45kg dedicated to the full construction.
I’m skeptic about unless some volume is obtained with a deeper keel and at the same time increasing the righting arm.
Personally I do not like the idea to “deform” the original shape, but apparently this is what it is done all the times and for good reasons !!
With the VM Rules unfortunately I cannot insert a fin blade with a bulb when in the water and remove it once at home.
I will take the Columbia drawing as a basis for Keel design modification and see what happen !
Cheers
ClaudioD
The EC-12 should be built at 24.5lbs total. 19lbs of that is generally lead, and 5.5lbs the remainder of the build.
The only class rule being that an EC-12 must float between 42" and 43" on the LWL.
So, There is some wiggle-room in the weight of your build. A heavier boat will have a longer LWL, where a lighter one might float at the lower marks on the LWL Rule.
In regards to your concern about righting moment: The EC-12 is a tender boat that requires skill and delicate hands to sail it.
And that’s why I love it.
The righting moment of an EC-12 is the complete and polar opposite to that of a Dropped-keel Modern Marblehead. The EC-12 can stuffer knockdowns or broach if you don’t plan ahead and manage the sheets and rudder. The Marblehead with it’s massive High-Aspect ratio will stand up straight in anything you throw at it.
Because of this, the EC-12 takes a LONG time to accelerate up to speed. And if you goof- It takes a LONG time to decelerate. When It’s at hull-speed it’s like a freight train.
The Marblehead is the polar opposite. It will Accelerate at the snap of a finger. It will also stop-short because it doesn’t have the mass to carry. I.E. watch an M that can’t carry through a tack and gets stuck in-irons.
The Traditional era Marblehead Class boats fall more inline with the sailing qualities of the EC-12. And, The EC-12 is one of the finest model yachts that this hobby has to offer. It’s just a totally different trip than you are accustomed do.
There is absolutley no reason to put a removable drop-keel on an EC-12 to manage the low righting moment. You manage this with sheets and rudder. Therefore there is absolutley no reason to put a removable drop-keel on a Traditional M.
Just be tender on the sticks with a tender boat.
Hi Breakwater,
My RC model culture is coming from the modern Class M that I practiced for several years up to the moment I start designing other models like the AC120 and finishing with Vintage models on one hand and super performing model as the Esterel 123.
Now I’m back to the wel desired Vintage and searching for a captive formula. Probably with your help and the Earl one I think I’m getting close.
I spent the last hours to calculate the static righting moment of the EC12 (for what I managed to discover on the Web) and the counterpart 12Metres Columbia of 1958.
Of course one has a LOA of about 60" and the other stay with 50".
An important parameter is the LOA/LWL ratio.
This ratio justify partially the increased available volume for the the EC12 among the fact that the LWL is 1070mm against 835mm of the Columbia. Of course the Columbia have longer overhangs an nice to see on the water !
Surprisingly ! the two boats appears to have similar behavior against the wind force, see drawings :
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Observing the data, it came out that with 45° of heel and Rig A, the Columbia can go up to 10knots of wind speed and the EC12 can go up to 10.5knots.
The Columbia weight is 5.75kg with 4.0kg ballast (theoretical design) and the EC12 weight is 10.8kg with 8.2kg ballast (tbc)
The use of a deeper keel will allow to gain 1.5 knots of wind speed.
Having said that, the derived JClass, as already seen with the Ranger 1937, will be less performing and a deeper keel will be a better option.
This what I can say up to now ! unless everything is wrongly calculated (as someone suggested already), but in this case it will be wrong for both cases and the “relative” comparison remain valid.
Cheers
ClaudioD
umm thanks… you do know i am married… and this boat has just been saved… now she who must be obeyed… needs dinner and a movie…
i have been looking for drawings of endeavour and endeavour II for a long time. so to start the arguements here
I think Endeavour II is the super J . and not ranger. just look at that pointed bow. IT WANTS TO GO FAST… so yes IT will be built.
hehehehe…