fairlead position and leech tension

wumhenry · #1 (**permalink**) 07-09-2007

Which way should I move the fairlead to stop flapping in the genoa's leech: forward or aft?

sailingdog · #2 (**permalink**) 07-09-2007

If the leech is fluttering, that means the leech needs more tension, so you would slide the fairlead forward, to increase the tension on the leech. Also, you might want to check the leech line on the genoa, if it has one.

nolatom · #3 (**permalink**) 07-09-2007

And if neither of Sailingdog's suggestions work, then depending on the sail's age, it may just be overstretched and blown out around the leech. In which case, go see your sailmaker to see if some leech panels can be replaced, or whether you need to replace the sail.

SEMIJim · #4 (**permalink**) 07-09-2007

Further to nolatom's point: It may do no good, and may actually harm performance, to move the jib sheet blocks (those aren't actually fairleads) forward on their travelers simply to stop the leach flapping if the reason is a blown-out sail. I saw this demonstrated over the weekend, during sailing class. We'd been on a broad reach at some point. Now we were on a close reach. I was examining the jib and wondering why it wouldn't fly right. Main looked good. So, eased the jib a bit. (When in doubt, let it out.) No good. Trimmed it. No good. "What the hell?," I'm thinkin'. Finally wandered over to the lee side and saw it right off: Nobody'd pulled the starboard jib sheet traveller back. Had the helmsman point 'er into the wind, eased the sheet, brought the car back. got back on tack and trimmed the jib Now all was well. The leach was fluttering, but the sail shape looked better, the tell-tales were flying , the helmsman reported the boat felt better, and we had another knot or so of speed.

Jim

sailingdog · #5 (**permalink**) 07-09-2007

If the sail is just old and blown out, there isn't much that can help it.
My suggestions were based on the sail being in reasonably good shape.

SEMIJim · #6 (**permalink**) 07-09-2007

Quote:

Originally Posted by sailingdog

If the sail is just old and blown out, there isn't much that can help it.
My suggestions were based on the sail being in reasonably good shape.

I assumed that. (I'm sure nolatom did, too.) But the OP may not have known that.

Jim

wumhenry · #7 (**permalink**) 07-13-2007

Quote:

Originally Posted by nolatom

And if neither of Sailingdog's suggestions work, then depending on the sail's age, it may just be overstretched and blown out around the leech. In which case, go see your sailmaker to see if some leech panels can be replaced, or whether you need to replace the sail.

It *is* old. Glenn Halsey, of Halsey Sails Annapolis, looked at it last year and said I'd be lucky to get another season out of it, even with repairs. I don't know for sure whether it's blown out at the leech, but I have to rate that a likely possibility.

sailingdog · #8 (**permalink**) 07-13-2007

If Glenn is saying you'd be lucky to get another season out of it... it is probably more than just blown out...

labatt · #9 (**permalink**) 07-27-2007

The loft says "You'll be lucky to get another season out of it" and all I hear is "Check back with me next year"

RichH · #10 (**permalink**) 07-28-2007

Moving the fairlead forward will increase tension on the leech and stop it from fluttering .... but this may not be the answer you are looking for.

First, you have to determine if this is a 'shape' problem or a trimming problem. For trimming, the 'test' is to slowly bring the boat up to the wind and begin to 'luff' the boat (the luff begins to shake). Then notice if the top section of the LUFF (forward edge) OR the bottom section of the luff begins to luff first. If the top section of the luff 'breaks' first then move the fairlead car FORWARD and conversely if the bottom/lower section 'breaks first then move the fairlead car aft .... you watch the LUFF and NOT the leech. Keep testing and adjusting until the ENTIRE luff 'breaks' **all at the same time** when you slowly luff up to wind. This adjustment wherein the LUFF 'breaks' ENTIRELY the same will insure that the 'shape' is good and *matches* the wind conditions that you happen to be sailing in at the time. Different wind-strengths and different sailing angles will change this shape so when in doubt simply head up slowly and watch for which section of the LUFF 'breaks' first, etc. .... you want the LUFF to break simultaneously all along its entire length.

Once you have determined that the shape (as above) is correct, then notice if the leech is still fluttering. If the basic shape is correct and the sail is leech fluttering: 1. increase the leech cord tension (if you have a leech cord). 2. ease the genoa **halyard** tension until the fluttering stops, 3. move the fairlead car 'just a wee bit further forward'.

All these 'adjustments' are made when you have 'proper' backstay (forestay) tension. An overly 'tight' forestay will automatically 'reshape' the genoa/jib leech (exit) section making it 'tripped' (loosened) and such will have a tendancy to leech-flutter (corrected by leech cord tension adjustment).

Its really BETTER to do this with tell-tales applied to the leech and near the luff of the sails as the tell tales are VERY sensitive to correct ariflow across the sails. For a comprehensive (technical) go to www.arvelgentry.com ---> 'magazine articles" ---> then look at:

"Checking Trim on the Wind, November" 1973
"Achieving Proper Balance, December 1973
"Sailing to Windward, January 1974
"Are You at Optimum Trim?", March 1974

These articles by Arvel Gentry are the 'seminal' sail trim (etc.) articles that set the sailing world on its collective ear in the early 70s.
... (also includes the aerodynamically correct explanation of 'how sails really work' - VERY/deeply 'technical'), and sets as total HOGWASH most of the 'so called sail theories' that you find in 'sailing books' and (still) out the mouths of USA highschool science teachers ---- ALL ENTIRELY WRONG.

Hope this is clear and hope this helps.
:-)