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J dimension discrepency

Posted: Fri Mar 14, 2014 2:18 am
by Bob McGovern
Hello Balladeers: I've been taking actual measurements of boat, rigging, and mast to prepare detailed sail specifications, and I noticed what seems to be an error on the official Sailplan as published by Albin Marin AB. They list the J dimension (front of mast to forestay fitting, perpendicular) as 3740mm (12' 3"). But my measurements say J=3430mm (11' 3"), a full foot smaller than published! That is a huge difference in sail design terms. :shock: If you use the 2m scale printed below the official drawing, you get J=3500mm+/-, which is rather closer to my measurement than to their published distance.

Does anyone else have a measured J dimension for your boat, just to verify that I am not crazy? (Most of the other published measurements on that drawing seem very close to reality.)

Re: J dimension discrepency

Posted: Fri Mar 14, 2014 9:35 am
by TamTam
Hi,

we measured it last year, when we ordered new Sails. Our measurement says 3,57m (about 11`8").
I guess every Ballad is unique, because the building standards in the 70ies were not as high as today:-)

Re: J dimension discrepency

Posted: Thu Apr 03, 2014 3:50 pm
by Bob McGovern
Browsing through the One Design rules of the Ballad Handbook this morning, I found the official J measurement:
Das Maß zwischen Vorstagsbefestigung am Rumpf und der Vorderseite
des Mastes (J-Maß) ist 3500+/- 25 mm. Doppelte Vorstagen sind nicht
erlaubt.
It has been some years since German language classes, but I read that as:
The distance between forestay fitting on the hull and the forward side of the mast (J-distance) is 3500 +/- 25mm. Double forestays are not permitted.
Which is at odds with the sailplan drawing in the Ballad Handbook by 240mm. :lol: But fairly close to what I measured, if we allow for the rubber blocking. Okay, next question: Our upper black band is only 7" or so below the top of the mast. Official sailplan drawing locates it 18" (452mm) below top. That seems excessively low, but maybe it is needed so the headboard clears the backstay? Also, official mainsail luff length is 32'-0" (9750mm). There is no way a mainsail that tall fits on our mast under the official black band, unless the boom is about 30cm above deck. (Which is about where the previous owners had it, rendering the vang useless.)

If we move the boom gooseneck up to just below the wide mast slot (anyone know the correct lower black band height?) and accept the drawing's 452mm upper black band location, that indicates a mainsail luff of 31' (9450mm -- not 9750), a full 1' shorter than the sailplan. The existing mainsail is indeed 31' unstretched. Can anyone verify that dimension is right? We like the higher boom anyhow, as it will permit a reasonable spray dodger and make vang/Boomkicker attachment easier. But I would like the headboard to go as high up the mast as possible, for light wind performance.

Danke!