#2 Genny Trim Issues - SailNet Community
 
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post #1 of 9 Old 09-13-2010 Thread Starter
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#2 Genny Trim Issues

Hi all, wondering if sailnet can shed come light on this.. It has my crew and our combined 40 odd years of experience a little confused

I race a tanzer 22 (run of the mill over-keeled mastop marconi rig sloop) in the local beer league, last year Skip' purchased a brand new number 2 genoa.. It seems to perform well, but something is wrong about the trim

Last time we had it out, and probably the first time we raced with it in optimal conditions.. Wind was variable from about 10-17 kts

When sheeted for any point of sail between close hauled and a close reach near the beam, and the sail trimmed properly to the bottom telltale, the top half of the sail is almost always backwinded about a foot back from the luff.. .. even sheeted in as tight as she will go closehauled the full top half of the sail is backwinded several inches back of the luff, .. if we sheet in enough on a close reach to eliminate the backwind, the sail is very obviously overtrimmed and the boat slows down dramatically.

It doesn't seem that bad, we've won two races with it despite the backwinding issue, but we still are curious what's wrong with it.. we've experimented w/ fairlead position to no avail.. we are fairly sure we have them set right -- up about maybe 6 inches from where they would normally be for the number one..

We're starting to wonder if maybe the sail is just cut wrong for the boat..

What do the experts have to say?
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post #2 of 9 Old 09-13-2010
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post #3 of 9 Old 09-13-2010
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Where is the genoa fairlead block being positioned?? Do you have photos??? Was the sail made for your boat new, or is it a new sail for a different boat bought new to you? What loft made the sail?

Without photos, it is hard to say if your fairlead position is wrong or if the sail is cut wrong.

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post #4 of 9 Old 09-13-2010 Thread Starter
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next time we run it, i will snap some photos and post them here .. i've read a couple places that it could be that the leads are positioned too far aft.. skip and helm say they are fine, but i'll explain to them my sources and that should convince them to slide them up a little further and give that a try.

they may just be underestimating how far forward they have to go

to answer the other questions:

- yes, the sail was cut for our class of boat, it is a T22 .. errrrmm.. not sure if it is a 160% or a 140%
- the maker was either North, or Doyle.. I'll have to check tomorrow when i am aboard.
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post #5 of 9 Old 09-13-2010
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Quote:
Originally Posted by CaseyJones View Post
When sheeted for any point of sail between close hauled and a close reach near the beam, and the sail trimmed properly to the bottom telltale, the top half of the sail is almost always backwinded about a foot back from the luff.. .. even sheeted in as tight as she will go closehauled the full top half of the sail is backwinded several inches back of the luff,
...
What do the experts have to say?
I don't know as I'd call myself an "expert," by any stretch of the imagination, but it sounds to me like too much twist in the top. Move the fairlead forward until it stops. If you cannot find that happy place where all the telltales are streaming happily (the inside ones, particularly near the top, may be allowed to flutter up--as a rule), then it tells me the sail is cut wrong for the rig. (See below for more.)

Quote:
Originally Posted by CaseyJones View Post
i've read a couple places that it could be that the leads are positioned too far aft.. skip and helm say they are fine, ...
Waitaminute... Do you mean to tell us y'all haven't tried running the jib fairleads forward? They're where the skipper and helm think they need to be, so no need to mess with 'em? On a new sail? Really?

Expanding on my initial comments: Here's how you set the foresail fairlead position:
  • Assuming the optimum isn't already known: Draw an imaginary line from the middle of the sail's luff, thru the clew, extending to the fairlead car track. That's the best starting point.
  • On a close reach or above: All the telltales should flow back--possibly with the middle-thru-top inside ones allowed to flutter up "some." (More on that below.)
  • If, when trimming or easing the foresail, the top telltales start fluttering before the bottom ones: There's too much twist in the top. Move the fairlead forward.
  • If, when trimming or easing the foresail, the bottom telltales start fluttering before the top ones: There's too much depth in the bottom. Move the fairlead back.
As for the top, and perhaps middle, inside telltales being allowed to flutter up "some": That's dependent on the sail, the boat and the conditions. But, often, some upward fluttering in the top, inside telltales is desirable. Your knotmeter, VMG, tiller, what-have-you, will tell you that.

Jim
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post #6 of 9 Old 09-13-2010
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Sounds like the leads are too far aft,
or the clew is cut too low for the boat.

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post #7 of 9 Old 09-13-2010
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I addition to the fairleads being too far back ...... is your forestay (backstay) tight enough? A too loose forestay plus an 'oversheeted' (too tight jibsheet) can radically change the luff and upper panel shapes. A t22 with a 28ft. luff length typically will only have about 3.5" of max. sag in the forestay .... more than that the sail shape 'goes all to hell'.
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post #8 of 9 Old 09-13-2010
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Watching the break difference between the top and bottom telltales is the scientific means of adjusting your lead position, anything else is guesstimating.

SEMIJim covers the concept well, although when closehauled I've always done a gentle luff up to check for upper breaking versus lower breaking as opposed to trimming sheets.

As the wind goes aft of closehauled, the sheet lead should go forward and out..to the extent you have beam and rail..in pursuit of the same even breaking of the luff.

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post #9 of 9 Old 01-28-2011
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Hey CaseyJones,
Did you get to the bottom of this one? Whilst i agree with all the points rasied with regards to optimum trim, car positions etc, I am not convinced that any of this would casue the a genny to backwind as you have described. I'm thinking backstay tension.......
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