RCU Forums - 48" J-boats

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I'm in the middle of getting 4 of these boats shipped from the Christchurch New Zealand model club. They're all spoken for, but I'm more than willing to share contact info, etc. With any luck, they'll be here in time for Mystic races (I live an hour from Mystic) and I'll bring down a hull or two....

Re J Boats; I'd like more info

Hi Bob;

Greetings to you from the 'Oven'.

I'd like more info on these J-Boats; & by Js, do you mean replicas of the old America's Cup J Boats of the 1930s? Please email me info/data/contacts, I'd sure appreciate it. Best regards from sunny and real hot Phoenix,

Joe Nagy. email: [email protected]

Hey Rob,

Let us know what the cost on these 48" J's run with the shipping. Another classic design boat for us EC12 afficienados with out big trucks to haul the AMYA Jboat.

Rob,

One other thing, Any sail dimensions? The website referenced above is unreadable even when zoomed.

I just calculated them the other day at my desk (working hard as always)...based on my scribbles, it looks to be about 600-700 squares. They allow 3 rigs. We're waiting on Paypal at the moment while they figure out how to do the transfer. I'll keep you guys updated.

Rob,

Are you sure? 600 to 700 sq inches would be a one meter sail area. I would guess, as the J, both full size and AMYA carry a lot of canvas, it would have to be at least 1000, if not upwards of 1200 or greater. Have you tried sailcut and input your dimensions, it will give you a read on total sail area per sail. My guess is it acutally falls about the same as an EC12, (1200) even given the smaller LOA.

Yeah, I did (well, not Sailcut) but talked to Earl oh-crap-can't-remember-his-last-name and he owns one of these that he hasn't finished. We had the same debate in the club...let's see - a 96" J carries around 3500-4000 squares, so a 48" should carry 2000, right?

Earl BOEBERT said that they're light, skinny boats and the sail they're carrying was adequate. Of course, we thought about sticking an EC12 rig on just to see what would happen :)

The main dimensions are (in mm - you do the conversion)
1450mm luff by 480 mm foot. That's HxB/2, right? Even with a huge roach, that main isn't getting very much bigger.

57" high by 18" boom div 2. The jib is 45 x 14. That's all she wrote.

WOW!!!

I just plugged in your numbers. I come up with a 524Sq in sail area.(pretty small on a full keel boat with an LOA of 48inches, and at a guess LWL of 40) Given 50% roaches, at 10%of luffs.
Unless this boat has no ballast, she carries far to little sail. Based on the photos, she has a (my guess a 10 inch keel).
If she isn't carrying full lead there this may explain the small sail footprint. With the design, she should easily carry almost 10 lbs of poured lead. She seems by my amatuer calculations to be forfeiting close to 400-450 inches of sail area. Wonder if this was done for ease of sail. Hopefully one of the experts from rcsail will opine, but she looks grossly under canvassed based on her LOA and available ballast area.

If Earl is saying the sails are is correct, then I've got to wonder if the beam is too narrow, and the lead is insufficient in the hull considering the draft that appears available. I would think that a boat this size with this depth of keel should easily handle close to 800-1000sq inches with a poured lead ballast. Seems underpowered to me.

Earl- please - tell me where I've calculated incorrectly.

I can't do those calcs, but it *will* be a skinny boat with not much waterline. The all-up weight (minimum, I guess) is 6.5 kgs, or 14+ pounds. That's not a whole lot of weight, and even the EC12, at 59" (what's the waterline on those things?) carries about 1000 squares on a 23 lb. hull.

My Star 45 carries roughly the same sail, but it's 3" wider and hard-chined. 'Member - an EC12 is a scaled-down 60' (or so) boat, right? The J is gonna be a scaled down 130' boat, and the beam will be commensurately narrower.......

Hey Rob.

AN EC12 can carry up 1200sqin in an A rig as measured,(plus roaches). Normal lead weight runs 19lbs. 2.5 for hull., plus mast sails and rigging
FIGURE 24.5LBS TOTAL ON A MINIMUM 42 TO MAX 43 WATERLINE, LOA of 58inches

This J boat seems light for overall displacement, and even lighter with sail area. That depth of keel seems to me like it's not being put to good use.

I came up with 855 squares for both the main and jib excluding any roach. 57.0865 x 18.8976 /2 + 45 x 14 /2. At these numbers it's not that bad. If you add another 2" for the roach on both that would add another 170 bringig it up to slightly over 1000. For a light shallow draft hull that's not bad at all.

Steve