mainsail rule question

Moderators: Shu, rand

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Post by Guest » Fri Nov 13, 2009 5:16 am

15.c.i. "No part of the headboard of the sail shall exceed in height the lower edge of the black band". No mention of 90 degrees.
15.c.iv. mentions 90 degrees as the direction of measurement for the width of the headboard.
As far as I can see all references to the extent of the top of any part of the main or sailplan are distance above the top edge of the hull and gunwale assembly in way of the mast.
So does "above" mean a straight line distance from this top edge at the mast, which could have a slope upward and aft? Or does above mean height, as in vertical elevation relative to this top edge at the mast?

Good grief, I'm starting to sound like a lawyer. :?

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Shu
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Post by Shu » Fri Nov 13, 2009 5:19 am

That was interesting; the forum didn't require that I log on prior to posting. For those wishing to flame away, that last post is mine.
Steve Shumaker
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Post by Guest » Fri Nov 13, 2009 9:03 am

most mains don't actually have headboards now so you can almost ignore that bit!
p.s. this is george, posting without having logged in

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rand
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Post by rand » Fri Nov 13, 2009 2:40 pm

Shu wrote:That was interesting; the forum didn't require that I log on prior to posting. For those wishing to flame away, that last post is mine.
Fixed, looks like the default permissions for a new forum is wide open, good to know!
Rand Arnold
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(former US President, former US Measurer)

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Shu
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Post by Shu » Sat Nov 14, 2009 3:20 am

Thanks Rand. Glad to see one of the moderators knows what he is doing :oops:
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Post by RolloP » Mon Nov 16, 2009 3:34 pm

I've come to this post a bit late. "In way of the mast" is a quaint phrase we have inherited from the past. It refers to the intersection of the mast and the sheerline, and it is from this point, at right angles to the waterline, that the 25ft max main height is measured from the sheerline. There was a time with wooden masts, that were bolt upright in the boat, when the max rig height happened to be along the front edge of the mast and that the lower egde of the top black band donated where the max height was.
Masts today are well raked as well as having significant bend with the sail rigged. The result is that the 25ft max height does not have a fixed reference point, and so is difficult to measure accurately. Further more, the sail measurement is separate from the mast height, in that the mainsail "A"(luff) measurement is a declared number measured from the mast between the boom and top bands band. What this means is that the sail leech can be above the mainsail head and black band, but must not be above the 25ft "in way of the mast ". Simples !

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Post by cam » Mon Nov 16, 2009 10:17 pm

Well done rollo , exactly what I needed .
Thanks .

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Post by Shu » Tue Nov 17, 2009 11:48 pm

Makes sense and is simple in concept. May be difficult to measure/verify. Sounds as if this interpretation would require the main be measured on the mast/boat with minimum rake and minimum bend. Do-able, but what do our measurers say?
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Post by RolloP » Fri Nov 20, 2009 5:10 pm

The situation we find ourselves in is that a mainsail can be measured within Class rules as can a hull and mast, but when they are put togeather there is the possibility that the 25 ft sail max height is exeeded.
This has come about because the unmeasured area at the top of a mainsail is being exploited for "free" sail area, and there is no clear way that denotes when the 25ft limit has been exeeded. At present this "free" area is approx. 0.7m2.
My proposed rule change is to include the 0.7m2 in the overall sail area, i.e. measure the true sail area, and measure the 25ft on a mast (as we do at present ) with no upper tension i.e. straight, so the mainsail luff shall not exeed 25ft.(as at present).
This has the benefit of maintaining the status quo, with no advantage nor disadvantage being conferred to new or existing sails. The only downside is that there would be no restriction on the height of the mainsail leech, but at least the mainsail area could not increase.
There may be aerodynamic advantages (reduced tip vortices) from having a raised mainsail leech, if so, then as a development Class, we should be able to explore and benefit from this effect. (The fact that it would make the 49er rig look old fashioned again is immaterial.)
The height of the leech would find its own limit provided the Class keeps the One sail per event rule.

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Post by aem27 » Tue Dec 08, 2009 5:15 am

Thanks Rollo, that's the clearest explanation I've seen yet. The only points of contention I see now are:
1. Are we ok to ignore the term headboard? As the reinforced area at the head of the main could exceed the 102mm width restriction.
2. How would a protest hearing determine if a boat had at any stage of a race exceeded the 25' maximum height? I hope this never happens.

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Post by RolloP » Wed Dec 16, 2009 5:01 pm

Yes, I think references to headboards can be ignored as they are not fitted on modern mainsails. They come from a time when the mainsail did not have full length top battens and were restricted to prevent offering extra support to the mainsail leech.
Looking at the I14 "Measurer's Manual" I was given in 1976, the waterline with reference to the max. rig height is defined as " ... that of a boat sailing in normal trim to windward in a medium breeze on smooth water.Typically, the waterline passes through the transom end of the keel with the bows immersed a few inches", i.e.twin wiring upwind, on the cusp of depowering. In other words it is the designed waterline and not the
waterline in light winds, as we now do, when the crew is perched as far forward as possible.
I think this is a sensible approach. As with most things in life it comes down to the application of Common Sense which unfortunatley,on occasions, seems to be a remarkably rare commodity !
If the mainsail leech is no more than a few cm above the mast band - in normal sailing trim - then I would hope that would be deemed acceptable.
The Class has taken steps to address the problem, so hopefully there will be no protests on this matter.

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Re: mainsail rule question

Post by george » Tue Mar 16, 2010 5:53 pm

Hi all. I thought this was all settled, but I see that the rule change re mainsails has been delayed. What is the concern raised by the World Council?

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Re: mainsail rule question

Post by Colin Smith » Sat Mar 20, 2010 7:26 am

See reply to George's other post in the "general" forum...

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Re: mainsail rule question

Post by george » Mon Jul 12, 2010 5:06 pm

Anyone know if this problem has been resolved?

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Re: mainsail rule question

Post by aem27 » Wed Jul 21, 2010 11:02 am

Not yet. It's with the Aussie's to propose a new rule. Otherwise the British proposal will become law.

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