J-Class versus 12Metre Class

Other America's Cup Boats
61

The Non-Prognathous rule is in refernece to No part of a keel can be forward of any part above it.

For reference, see my uploaded photo of A “Toad” Marblehead.
This style lead is prohibited. This lead is typical of Marbleheads of the Classic Era. Not Classic Marblehead Class. That does not exist. They are Marbleheads from the Classic era. around 1980.

In your drawing, no part of your keel extention is forward of any part above it, so the keel extension is within VM group (not class) rules.

62

According to VM Group (Not Class) Rules, Traditional and High-Flyer Models are limited to 2 channels of operation. That means Rudder, and Sail-Trim. Therefore, the Keel trim would be prohibited, unless it was incorporated somehow to work on the same channel as either the sail or rudder.

It depends where you go though, Some places have re-written VM Group (not class) rules locally to REQUIRE 3-channels, deviating from VM Group (not class) guidelines.

technically speaking, most Traditional or High-Flyer models were free-sailed vane gear models, so really their roots involve zero R/C channels, but the rules allow R/C for fun competition. It’s a blast to sail them R/C isn’t it?

It makes sense that both Traditional and High-Flyers utilize a maximum of two channels, since these boats were “basic” designs and 3 or more channels including jib-trim, keel trim and etc came in a higher-technology era starting with the Marbleheads of the Classic era (Not Marbleheads of the Classic Class)

For more data on the Keel fin trim tab, check out what Lester Gilbert has done here:
http://www.onemetre.net/build/TrimTab/TrimTab.htm

63

Thanks a lot,
so the sketch at post 57 showing a striped area, is not a prognathous fixture, therefore a deeper keel form could be adopted if desired to get better righting moment.
I agree on the fact that probably with a low ratio sailing area, it may not be really necessary to change the original keel shape.
Less wet area and better aesthetic appearance and all being sailing under the same conditions.

What may be a problem is to drive two or the jibs with only one servo. That means essentially, that only one stay sail can be used and no Genoa.
This is a limitation when pretending to race with the Vintage M and this include also the trim tab function that was introduced in 1970.
Similarly for the wiglets of Australia.
Cheers
ClaudioD

64

From the VM rules:

“Only the rudder, headsail and mainsail sheets may be adjusted by radio control.”

There is no limit on the number of channels or the mode of control. Jibs may be, and in some boats are, controlled separately from the main.

Rules are on the Web at:

http://www.usvmyg.org/VM/vmrules.htm

Cheers,

Earl

65

Thank you Earl,
but reading the rules :

7.2 Alternate Rigs
Alternate rigs are allowed, provided the total sail area does not exceed 800 square inches. Details of such rigs must be comparable to the original sail plan.

I shall eventually assume that 2 o 3 jib may be used in accordance with the J Class original Sail Plan configuration ?

7.3 Head Stay Height
Height of the jib head stay above the deck shall not exceed 80 per cent of the height of the head of the mainsail above the deck.

This point is of course killing the first idea to have more then 2 jibs since the stay cannot go over the 80% of main luff. see picture

This is suggesting to me that I can try to design two set-up :

One setting when racing with VM Rules and therefore one Main, one Jib , one rudder and all other functions inhibited, servo included if any.
One setting when racing with other model boats of the same America Cup origin as J class and 12Metre, where multiple Jibs, Genoa and Trim tabs can be activated.

Is a little bit complicated from design point of view but challenging.

Regards
ClaudioD

66

Huh I didn’t know that…
Well, that’s cool!

Jib Twitchers are awesome. I think I’ll install a few

67

In regards to a double-jib arangement, I wonder if that is territory anyone has ever ventured down before on a Vm.

If it came to a vote, My vote would be to allow two jib-stays, the tallest of which cannot go higher than 80% of the head of the mainsail above the deck, and not to exceed 800 square inches of sail.

68

Thanks for the vote in favor of double jib that I like it personally, but much will depends on the efficiency that can be obtained from this configuration other then aesthetics.

More probably a single Jib would be a better choice to be compatible with VM Rules. It will simplify things.

The multiple jib option, I would reserve it to the second type of set up when boats may race outside the VM Rules, but under AC regulation to be established, where J-Class and 12Metre could race together. Never seen before.

All that requires careful design approach as such to avoid that one type will always prevail on the other.

For instance, with the unique length of 127cm, all other parameters will be following the proportionality of dimensions.
This means that these parameters as Beam, Draft, Sail Area (max 800in²), will conform to the scale of that particular boat.
For the Displacement a minimum will be required and if necessary with the use of additional ballast.

I did not made any calculations yet, but I think that in general the J Class and 12Metre will be heavier than VM.

For instance from drawing already made :

12 Metre Columbia with a length of 125cm is 5.3kg,
12 Metre American Eagle with 122cm is 5.6kg
12 Metre Azzurra with 126cm is 5.2kg
J Class Enterprise with 131cm is 6.2/6.4Kg

J Class Ranger with 127cm will be 4.9kg, probably the lightest from scale calculations.

Now that the basic points are understood and defined versus VM Rules, I would like to see which are the preferences before starting a huge drawing work.

I recall, I will make drawing for the 2 boats that will receive more votes in each class

Actual standing for 12Meter is :

  • Courageous : 1
  • Azzurra : 2
  • Australia II : 2
  • Kiwi Magic : 1 (no plans available yet?)
  • French Kiss : 1
  • Columbia : 1

among J-Class

  • Enterprise : 1
  • Ranger :1

Sorry for the length !
Cheers
ClaudioD

69

The single-jib is surely compatible with the rules, so no issue there.

In regards to the double-jib arrangement… what I meant was that if it came down to a vote on whether the double-jib was “legal” I would be in favor of it, so long as either of the jib-stays were not above 80% of the mainsail head height, and the sail area did not exceed 800 sq inches.

Maybe there are actual facts why that shouldn’t be allowed by the group. but if there are I don’t know of them. I’m not a complete M-Class knowledge base by any means.

A double-jib would surely look cool on a J-class M, but maybe a single jib is more powerful?

70

Just to stick my oar in so late in the proceedings, in terms of J class builds, I’d like to see ‘Endeavour’ - although she didn’t win overall she was reckoned to be the better boat (just suffered from a poor crew) and got to have double headed rig! For the 12’s I’d go for Australia II.

Row

71

Here the sketches showing the possible dual Sailing configuration where the sail area is the same 5160cm² or 800in²

Being the forward sail area slightly different it may be necessary to have different Mast position as such to get the CE at the right place vs. the CLR.

The forward stay is fixed at 80% of Mainsail luff.

…

Earl probably may give the authoritative judgment about the sail configurations proposed, bearing in mind that outside the VM Rules the sail configuration can be different.

By that I intend to say that it may exist 2 independent setting compatibles with 2 different racing Rules as the VM Rules on one side and America Cup Rules (tbd) on the other side.

Certainly the VM Rules are more restrictive vs the Sail Area with the limit of 800in²

It may be also possible that for the “America Cup Racing configuration” (Rules TBD), the sail area being closer to the scaling factor for J Class and 12Metre class respectively including the Genoa option.

Cheers
ClaudioD

72

To recall that voting to choose a model is ongoing.

Only 2 models will be selected from each sub division, in total 6 models.

The selection will be proportional to n° of votes. In case of parity will flip the coin. (one out of two)

Actual standing :

See Page 6

Voting received from :

ClaudioD : Courageous, Azzurra, American Eagle,Columbia, Enterprise JClass.
KIW120 : Australia II, Kiwi Magic, French Kiss
Alberto : Azzurra
MIJ : Australia II
Breakwater : Ranger, Endeavour
Twister : Endeavour, Australia II

Cheers
ClaudioD

73

Personally, I Like:

Ranger for J’s She’s just a Hammer. Second place Endeavour II

Long Keel 12s, I like Columbia. Why? 1343 is my 12 Meter sail number. (S&S Design # 1343 was Columbia) Second Place Gleam. Just look at those lines. (I Like Sheptre better, but Gleam is deeper and going to be more stable)

Short Keel 12s, Australia II, Azzura. Be careful here though with the Non-Prothagenous VM Group (not Class) Rule

74

Hello,

If I can vote than there would be:
Australia II (since this was my first attemtp at RC sailing :))

and definatelly Endeavour

regards,
Lukasz Koch

75

Standing as today :

see Page 6

ClaudioD

76

Here’s the sail plan from Boucher’s 1935 M class based on Shamrock V. Note the “clubbed” jib with no jib pivot. This puts a curl in the leading edge but requires a horse to keep the leech tight.

Cheers,

Earl

77

The fore-Jib is up pretty high on the Mast, and surely the percentage of the lower + the Upper is higher than 80% of the mainsail luff…

So, Considering that it would seem that a double-jib arrangement is within VM Group (not class) rules. so long as the higher one does not exceed 80% of the mainsail luff, and sail area does not exceed 800 sq inches. Go-for-it Claudio!

78

Er, there’s only one jib. Jib stay attachment point is at about 50%. You may have been misled by the forestay, common on rigs of the period.

Cheers,

Earl

79

oops. Yes, I was. I thought the forestay was an additional sail.
It’s hard to read the low-resolution photo

Double-Jib

Ya or Nay?

80

Hi Earl,
was already controlled by radio via an electromechanical escapement or the rudder was controlled by a Braine gear ?
Thanks
ClaudioD