Mainsail measurement and voting

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Re: Mainsail measurement and voting

Post by Shu » Sun Nov 14, 2010 1:20 am

In order to have something established now in preparation for Weymouth, I agree we should go with the revised UK proposal. However, as George points out It can result in the rig violating the fundamental height of sailplan rule, so we should consider revising the rule after the Weymouth worlds.

I think we really need to bite the bullet and measure the mainsail on the rig. We can dispense with the measurement of the mast in a straight position, and instead measure the max height of the mainsail. This can be done in a prescribed manner, such as putting the mast at max forward, or most upright rake, putting the main at max hoist, pulling on the cunningham until wrinkles disappear then releasing cunningham.

The tricky bit is establishing the baseline from which to measure. This should be a line parallel to the waterline which intersects the mast at the shearline. One method would me to take a point 1.25" above the bottom at the transom (most I-14's have a design waterline near this point), and a point 2.5 or 3 inches above the knuckle of the bow. The knuckle could be established by a tangent from a point maybe 6" or so aft of the stem. A line could then be stretched between two points maybe 2.5 feet above these two waterline points and the distance then measured perpendicular from the line up to the max height of mainsail and down to the intersection of mast and shear.
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Re: Mainsail measurement and voting

Post by Shu » Sun Nov 14, 2010 3:32 am

Here's a diagram of what I propose for post Weymouth. We would need to keep the straight mast measurement too, or else everyone's rigs would be obsolete (too short) (my 25' mast in this diagram measures about 24.7')
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Mainsail Measurement.JPG
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Re: Mainsail measurement and voting

Post by rand » Sun Nov 14, 2010 6:41 am

I used to maintain that the top of the main should not exceed a 90 degree project from the bolt rope. But...

Why don't we just measure the area of the sail? Surely we can come up with something that won't allow for extra unmeasured area if the main projects above the band. And doesn't require measuring on the mast (I speak from experience having to measure a hundred of these things at a worlds…)
Rand Arnold
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"A Bumblebee Called Kate"
(former US President, former US Measurer)

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Re: Mainsail measurement and voting

Post by Shu » Tue Nov 16, 2010 3:20 am

Yeah, and the head board is not to be more than 102 mm (4 in) measured at right angles to the luff. Somehow in our excitement to adopt fat/square top mains we made the spurious distinction between a headboard and a batten holding the head out in board-like fashion.

I think the British proposal does measure the added sail area, regardless of the shape. However, by our current measuring convention (measuring mast height only), the sail can project above the 7626mm (25 ft) max height of sailplan prescribed by rule 12 (a) (i)
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Re: Mainsail measurement and voting

Post by george » Tue Nov 16, 2010 1:49 pm

Nothing spurious about distinguishing headboard from top batten. they are different things. as it happens we don't use headboards any more so really there's nothing to worry about.

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Re: Mainsail measurement and voting

Post by george » Tue Nov 16, 2010 2:05 pm

My comment about the new rule allowing sails to exceed 7626mm was not meant to be interpreted as a problem. The problem is exactly the same if an angle is used instead.
Ways of defining and measuring the height of the sail have been circularly discussed for the past 4 years and got nowhere. Complicated methods as described above look fine on paper, but imagine having to do that at events, or every time you change your rigging? And still it doesn't actually identify how the sail behaves once sailing. We have too much unnecessary legislation already (i think!).

angle or area rules are sensible as they are very simple and clear to define. i prefer area, as discussed above (plus what is the poing of unmeasured area when the rest is measured?).

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Re: Mainsail measurement and voting

Post by Shu » Wed Nov 17, 2010 3:26 am

George,
I would disagree that a headboard and top batten are different. Ok, they are different, but their purpose is the same, to extend the top of the leach aft. I was not around when the headboard limitation was written into the rules, but clearly the intent of putting a limit on the headboard size was to limit the unmeasured sail area above G3. We just got around that by sticking a batten out there instead. I'm not trying to be difficult, just trying to point out how I think we got into this predicament.

I think the method I described above can actually be done quite quickly with a few simple jigs, but certainly not as quickly as pulling a tape from the shear/mast intersection to the top band.

To avoid such a method, and to keep it as simple as possible, then we should stick with a sail measurement formula that measures all the area (UK proposal). And if we don't want the aft end of the sail sticking way up, an angle limitation is fine. But we need to recognize that the first sentence of 12 (a) (i), "The sail plan shall not exceed 7626mm above the top edge of hull and gunwhale assembly in way of the mast." will be meaningless, and should be replaced with a simple measurement, consistent with current practice, establishing the lower edge of the top band. Then the rules will be consistent with each other, and with the way we apply them. Now I'm off to Dinghy Anarchy to see what your response is to my latest query about progressive depowering. :)
-Steve
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Re: Mainsail measurement and voting

Post by Caprice » Wed Nov 17, 2010 7:11 pm

hi, i ahve a serious dude about mainsail measurementes, i have the only i114 in argetnina so i can compare my mainsail with another, so i would thanks a lot if some one could post me the leech, foot and luff lenght of a Penny od, and a new rules mainsail.

thanks!

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Re: Mainsail measurement and voting

Post by Caprice » Wed Nov 17, 2010 7:13 pm

and also jib measurements please.. and i would like to know how wide is the head of your mainsails..

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Re: Mainsail measurement and voting

Post by aem27 » Wed Nov 17, 2010 9:41 pm

Caprice wrote:hi, i ahve a serious dude about mainsail measurementes, i have the only i114 in argetnina so i can compare my mainsail with another, so i would thanks a lot if some one could post me the leech, foot and luff lenght of a Penny od, and a new rules mainsail.

thanks!
The answer is whatever fits the area rule., but roughly 2m for foot, 1m for head and 7m for luff length. Main area 12.7 and jib 5.9 sqm.

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