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Old 07-12-2013, 11:22   #1
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Jib Sheet Strength Calc

I need to order new jib sheet and don't remember my genny dimensions off hand to calculate sheet strength. I own a CAL 35 which is 35'. Anyone know off hand if I should order 7/16" (7100lbs) or Sta Set or 3/8" (5100lbs). Or should I splash out and get dynema?
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Old 07-12-2013, 12:32   #2
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Re: Jib Sheet Strength Calc

For Cal 35, I= 47.13 J=15.6 P=39.48 E=12
Sheet load for a working jib at 35 knots is about 2000 lbs. I think 3/8" Sta-Set is strong enough but 7/16" would be easier to handle. I wouldn't get Dynema for a sheet.
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Old 07-12-2013, 14:00   #3
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Re: Jib Sheet Strength Calc

The formula is
SL = SA x Vē x 0.00431

Where:
SL = Sheet Load in pounds
SA = Sail Area in square feet
V = wind speed in knots

I always recommend dyneema, typically endurabraid (tapered). It is lighter, stronger, lasts longer, you don't need expensive shackles, and depending on line costs less. Sta-set is hard to recommend anymore, for any reason.
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Old 07-12-2013, 14:02   #4
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Re: Jib Sheet Strength Calc

What Ziggy said. I have a 33 foot IOR old racer/cruiser boat with a 15 foot J measurement, meaning it's probably likely that my No. 1 1535 genoa is the same area or slightly larger than yours. I went from 1/2" sheets to 7/16" to get a better fit on my equally ancient jam cleats. Given that I was able to tear out a genoa track with the old 1/2" sheets at 28 knots (admittedly the deck needed work before and certainly after this incident), I would neither worry that the 7/16" aren't sufficiently strong nor that Dyneema is needed for a sheet. Anything smaller that 7/16" is going to be hard on your hands unless your hands are unusually small.

I love Dyneema for halyards, outhauls and guys, however!
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Old 07-12-2013, 15:05   #5
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Re: Jib Sheet Strength Calc

Quote:
Originally Posted by Stumble View Post
I always recommend dyneema, typically endurabraid (tapered). It is lighter, stronger, lasts longer, you don't need expensive shackles, and depending on line costs less. Sta-set is hard to recommend anymore, for any reason.
It is true that Dyneema is lighter and stronger. It may be true that it lasts longer. At West Marine, 8mm Endurabraid costs $2.60/foot; 7/16" Sta-set is $1.71/foot. You should never use shackles on a jib sheet, regardless of the rope it's made of. A knot tied to the clew is much safer. But Dyneema does not hold knots very well because it's very slippery. For that reason, Endurabraid has an outer cover of polyester, but I believe the core can still creep inside the cover. And 7/16" diameter rope is going to be a lot nicer to handle than 8mm (5/16").

If I were racing I would probably consider Dyneema, but I would not recommend it for jib sheets on a cruising sailboat.
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Old 07-12-2013, 15:13   #6
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Re: Jib Sheet Strength Calc

7/16" StaSet or equivalent double braid from other mfgs. More than strong enough, easy on the hands and not too bulky. Save the expensive low stretch stuff for halyards or ultra lightweight sheets with the cover stripped. Even then would go with 3/8" diameter for core and cover. Anything smaller is a killer on the hands.

Went with 7/16" on my 35' boat. Replaced the worn out 1/2" double braid that was nice but took up too much space when coiled in the cockpit. Tried 3/8" for a 150% genoa but it was just a tad too small for comfortable handing.
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Old 07-12-2013, 15:34   #7
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Re: Jib Sheet Strength Calc

Consider dynema with a cover.Product

I use the 1/2 in for sheets with a eye splice at the end and a Colligo soft shackle to connect. Easy to undo, and no big clunky knot to go thru the rigging.
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Old 07-12-2013, 16:07   #8
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Re: Jib Sheet Strength Calc

Forget calcs... You want something that is easy on the hands...3/8 is impossible harsh... start at least at 7/16 and go up. I cant imagine handling dyneema for jib sheets... maybe I've not been exposed to the right type...?
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Old 07-12-2013, 16:10   #9
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Re: Jib Sheet Strength Calc

Click the link on my previous post and you will see . . .

Samson MLX is a great line.
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Old 07-12-2013, 16:15   #10
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Re: Jib Sheet Strength Calc

I guess I'm just back to the same issue... it's really not about strength (who wants to handle 3/16 dyneema cord even if it is strong enough?) Is stronger than you need with very low stretch good or hard on hardware? just sayin...
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Old 07-12-2013, 16:34   #11
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Re: Jib Sheet Strength Calc

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Samson MLX is a great line.
I don't doubt it. But 1/2" MLX costs $3.66/foot and does not really have much advantage to non racer. If you have a surplus of money, go for it...
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Old 07-12-2013, 17:36   #12
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Re: Jib Sheet Strength Calc

Ziggy,

Sure endurabraid gets expensive if you use it like you are suggesting, but almost no one does. Stripping sheets allows you to keep the cover where needed and just the core on the working portion of the line. This allows you to buy a shorter section of line, which depending on the piece can be cheaper than sta-set.

It is also pretty common to use amsteel as a core and splice on a tail from the retired line that was taken off. Since all the cover does is provide bulk for handling it doesn't really matter so long as the cover is in somewhat reasonable condition.
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Old 07-12-2013, 17:58   #13
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Re: Jib Sheet Strength Calc

Unless you are racing, regular common old garden variety 7/16" poly rope will do just fine. Shop around your local chandleries for the best price on Sta Set, XLS or whatever.
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Old 07-12-2013, 18:18   #14
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Re: Jib Sheet Strength Calc

I usually just check the WM or Defender catalogs. 40' boat, jib sheet, 3/8" or 7/16", OK good. That's what I'll buy.
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Old 07-12-2013, 18:41   #15
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Re: Jib Sheet Strength Calc

If online buying is the way to go then the best current deal on 7/16" Sta Set is at Jamestown for white only at $1.00/foot. I don't know their freight charges.
New England Sta-Set White Polyester Double Braid
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