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Old 09-10-2013, 05:10   #1
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jib size?

I opened my next sailbag, it was labeled, jib.
i wanted to check it out and make sure it was in good shape, so we went for a sail. any idea what % this jib would be? its not labeled




here is the 150% jib.


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Old 09-10-2013, 06:53   #2
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Re: jib size?

Measure it.

The I, J, P, and E, dimensions refer to the dimensions of the boat.
Sails are described with another set of terms.
The luff is always the leading edge of the sail.
The leech is always the trailing edge of the sail.
The foot is always the bottom of the sail.
The LP (Luff Perpendicular )of a Genoa is used to figure what size sail it is. Multiply the J dimension times the size sail you want, and this will give you the LP of the sail.
For example, lets say your boat has a J dimension of 12 feet, and you are looking for a 150% Genoa. Simply multiply your J of 12 feet times 1.5 to get an LP of 18' for your 150% Genoa.
Head sails that are not Yankee cut (high cut) have an LP 1'-1.5' shorter than the foot of the sail.
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Old 09-10-2013, 07:00   #3
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Re: jib size?

Gord is spot on Shoobert but for simplicity simply pull the foot of the sail tight along the deck and you can calculate its size. If its a 100% jib it will fill the space between the headstay and mast.
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Old 09-10-2013, 07:06   #4
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Re: jib size?

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Originally Posted by robert sailor View Post
Gord is spot on Shoobert but for simplicity simply pull the foot of the sail tight along the deck and you can calculate its size. If its a 100% jib it will fill the space between the headstay and mast.

oh ok. when i was putting it away it made it most of the way to the mainmast. perhaps 3-4' shy. the one i know is a 150, goes far beyond the mainmast. i will comb the log, the P,PO use to keep record of sails he used and in what wind conditions because he was a racer. he mentioned 3 jibs. a 150, a 112, and a 74. this may be the 74.
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Old 09-10-2013, 07:15   #5
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Re: jib size?

If its 3-4 feet short of the mast it is getting into a storm jib size, probably not a full hoist either. Your sails will be built of different weight cloth as well. Your bigger sail (150) will be lighter cloth than your small sail (74) Normally you'll use your larger sail in light to medium winds 5-15 knots, your 112 size might be just right for 10-20 knots and your smallest sail for winds 25+ knots. If your sailing off the wind you can carry a larger sail in stronger winds.
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Old 09-10-2013, 07:21   #6
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Re: jib size?

i do have a jib in a bag labeled "storm jib" but i also have a halyard just for the storm jib. the material on the 150 feels heavier then the one i just had up, where the storm jib feels like cardboard in the bag. very stiff.
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Old 09-10-2013, 07:26   #7
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Re: jib size?

Scoobert, were you not paying attention to Gordon?

Measure the sail yourself and don't depend on questionable records from the past. It is not rocket science. Lay the sail out flat on the ground somewhere, take a tape measure and measure the length of all three sides, plus the dimension from the clew to the luff with the tape perpendicular to the luff ( that angle doesn't have to be very exact). The latter measurement is the LP that Gordy mentioned. The "J" dimension is the distance from where the forestay hits the deck, horizontally back to the leading edge of the mast. The "percentage" of the jib is the LP divided by J times 100.

It is a good idea to do this for all your sails and keep the record somewhere. Also record the distance from the gooseneck to where the main or mizzen halyard is topped out, and the length of both booms from gooseneck to max outhaul point. This data will be useful if you ever need to discuss new (or used) replacement sails. Lastly, measure the distance from the masthead (and also the top of any lights or antennae) to the waterline... useful when approaching bridges! I wouldn't depend on anyone else's measurements on that latter one -- if there is an error and a low bridge, well, you can see what might well happen!

Cheers,

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Old 09-10-2013, 07:28   #8
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Re: jib size?

very true, i have been seeking a good measuring tape, or i can go old school, and hoist a line, and measure the line.
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Old 09-10-2013, 07:32   #9
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Re: jib size?

Can't go by feeling because as a sail ages it becomes very flexible. New sails are like cardboard as you describe, thats why your storm jib feels that way, probably never has been used.
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Old 09-10-2013, 18:45   #10
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Re: jib size?

Since without measurements we are all guessing my guess 80-90% working jib. probably 8oz or greater.
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Old 11-10-2013, 05:17   #11
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Re: jib size?

See ➥ Headsail % = (LP / J) x 100 - Cruisers & Sailing Photo Gallery
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Old 11-10-2013, 05:27   #12
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Re: jib size?

Quote:
Originally Posted by scoobert View Post
i do have a jib in a bag labeled "storm jib" but i also have a halyard just for the storm jib. the material on the 150 feels heavier then the one i just had up, where the storm jib feels like cardboard in the bag. very stiff.

Scoobert, don't just go by how the fabric feels. A worn, tired sail will handle like a lighter weight than it is. Do the math. In Florida there's no way I would want a 150% up in winter, when we tend to have more wind. However, people swear by them in the summer time (until that thunderhead pops up ...)
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Old 11-10-2013, 05:29   #13
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Re: jib size?

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Originally Posted by scoobert View Post
very true, i have been seeking a good measuring tape, or i can go old school, and hoist a line, and measure the line.

If you know how high your mast is, you can get a rough measure on the leech. You can measure the foot quite accurately. Then it's just a matter of some very simple algebra, so simple that they teach it in grade school without calling it that -- or used to, anyway. (They actually call it algebra in grade school now.)
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Old 11-10-2013, 05:30   #14
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Re: jib size?

Quote:
Originally Posted by Rakuflames View Post
Scoobert, don't just go by how the fabric feels. A worn, tired sail will handle like a lighter weight than it is. Do the math. In Florida there's no way I would want a 150% up in winter, when we tend to have more wind. However, people swear by them in the summer time (until that thunderhead pops up ...)

well i do have a roller fuller. i can always make it small in a hurry if needed.
so i will not be stuck with it up in case of a squall.
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Old 11-10-2013, 05:33   #15
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Re: jib size?

Quote:
Originally Posted by Rakuflames View Post
If you know how high your mast is, you can get a rough measure on the leech. You can measure the foot quite accurately. Then it's just a matter of some very simple algebra, so simple that they teach it in grade school without calling it that -- or used to, anyway. (They actually call it algebra in grade school now.)

its actually geometry
and the only formulas i remember anymore are for right triangles.
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