Generic Sails

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Bruiser
Professional
Posts: 55
Joined: July 1st, 2013, 6:37 pm
Boat Make/Model: RC 27

Generic Sails

Post by Bruiser »

I have some questions regarding generic sails. You know the ones that come from sail makers where (you know, they do not know the boat that well) you have maybe 4 holes on the jib plate where the jib sheets attach. My "friend" has a jib that has 4 or 5 holes on the jib to attach the jib sheets at. The question is always which hole do you connect the sheets too?

My guess you is, you want to mirror the main sail twist, but do you do that with lead position or jib sheet trim to mirror main? Or do these holes really play a role?

Thanks,
havliii
Professional
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Joined: March 27th, 2011, 8:12 pm
Boat Make/Model: SuperCat 19, Modded SC20
Location: Fredericksburg Virginia

Re: Generic Sails

Post by havliii »

Bruiser, The holes in the plate do make a difference on changing the leech/foot tension ratio which in turn moves the draft location of the jib.
here's a link that might help http://www.uksailmakers.com/encyclopedi ... enoa-trim/
Bill Roberts
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Joined: November 17th, 2003, 9:13 pm
Location: Stuart, Florida

Re: Generic Sails

Post by Bill Roberts »

Bruiser
What I am going to tell you applies to any jib, factory made or otherwise.
I use the jib sheet tension to set the overall shape of the jib.
I use the clew corner adjustment plate to set the jib leech position and leech shape when looking up the leech.
When you connect the jib sheets to the highest hole in the adjustment plate, more of the sheet tension goes up the leech.
A leech with more tension in it will be straighter, less twist.
When you connect the jib sheets to the lowest hole in the adjustment plate, less jib sheet tension goes up the leech and the leech will tend to twist open more as you look up the leech.
Set the overall jib shape you want with jib sheet tension and set the leech, more twisty or less twisty, with the clew plate adjustment.
In general you want more jib leech twist in windy conditions and less twist in lighter conditions.
By looking at the shape of the sail, " learn what shape is fast in different conditions".
Don't bet hung up on clew plate hole position because the same hole position in different sails will give you different leech
shapes. Train your eye to recognize fast sail shapes and don't worry about hole position.
DanBerger
Professional
Posts: 280
Joined: May 3rd, 2004, 3:29 pm
Boat Make/Model: SC 15 w/ spin!, SC 19
Location: Norfolk, VA

Re: Generic Sails

Post by DanBerger »

That's interesting--I have never considered moving the clew pin based on wind. It has always been a one spot where the sail is getting equal pressure on the foot and the leech. Basically, if it is flapping on the foot, move up one hole, if it is flapping on the leech, move it down one hole. I have tied a string from the top hole to the bottom and attached the clew shackle to the rope so that is slides and auto-adjusts until it finds a happy place, then I put the shackle to the closest hole in the clew plate.

just my 2 cents.

I think I'll give moving to different holes a try this weekend!
Bill Roberts
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Posts: 515
Joined: November 17th, 2003, 9:13 pm
Location: Stuart, Florida

Re: Generic Sails

Post by Bill Roberts »

Dan, You have equal fractions of the jib sheet tension in the foot and leech of the sail when a line extension, a straight edge, of the slope of the jib sheets as they approach the sail are extended onto the sail and this line on the sail bisects the clew angle. Then 50% of the jib sheet tension goes into the sail below this line and 50% of the jib sheet tension goes into the sail above that line. When you move the jib blocks to a higher hole on the clew plate, you are pulling down on the leech more. When you move the jib blocks to a lower hole in the clew plate, more tension goes to the foot of the sail. If you have flapping foot and or leech problems and clew plate adjustment will not fix it, you have sail problems.
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