Reefing a headsail??? - Page 4 - SailNet Community
Old 01-10-2013
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Quote:
Originally Posted by deltaten View Post
Thanks Rich;

I'm having some trouble digesting the text stating; " The LP defines the sail size in terms of percentage increase beyond the J measurement as in the following examples." with the chart immediately below. It shows, under the "LP" column, a direct correlation to unit "J" past the "I" line.
It appears that roller furlers need the "LP" figure to relate the amount of sail exposed, as that's the direction of reduction; but regular (geometric term) foresail calcs rely on straight "J" numbers.
Am I missing something??
Doesn't the "IJ" fore-triangle calc describe a geometric area potentially filled by a headsail at 100% (not necessarily the actual measurements)? As I was led to believe, the increase in percentage was a function of the amount of the (base/"J") jib triangle passing the mast (height/"I") of the theoretical/geometric right triangle??
Its really VERY SIMPLE once you define 100%LP dimension that equates to the "J" dimension. Once you arrive/calculate (or do this 'graphically') all further dimensions will be directly proportional (ratio'd). Eg. a 120% LP will have is 'foot dimension' at ~120% of the 'J' dimension. .... you just have to first establish the 100% LP dimension in relation to the J dimension, .... first.
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Ummmm... yessssss.. 592 ft/2 is more than entire sailplan PLUS the wetted surface of the hull !
So then, the discussion is the manner in which I calculate the jib ....OK; but the OP was about reefing. Does it matter if I wanna reef a 150% genoa or a 145% genoa?. Any way ya slice it, it's still too damm'd big ta suit me... being a novice and all

Tastes great....less filling!
For all intents and porpoises... same-o, same-o. I don't feature being knocked down; whether it's a 150 or a 140. JUst hafta wait and see what the learning curve is... *THEN* get knocked down! LOL

thanx guise
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Old 01-11-2013
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Quote:
Originally Posted by RichH View Post
Once you arrive/calculate (or do this 'graphically') all further dimensions will be directly proportional (ratio'd). Eg. a 120% LP will have is 'foot dimension' at ~120% of the 'J' dimension.
Hm... this is essentially saying, "If x is an altitude of a triangle, then an adjacent side is also x." That's only true if that side is perpendicular to the side that the altitude is perpendicular to. I think the angle at the tack of a jib is usually less than perpendicular.

There is a proportionality, but only in the component of the measurement perpendicular to the luff.

Okay, to anybody still confused about LP, it's just the width of the sail. Just imagine stretching the sail out with the luff along the ground and the clew held up off the ground so the sail is flat. The LP is now the height of the clew off the ground.

s/v Laelia - 1978 Pearson 365 ketch

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