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sail problem or pilot error?
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frederick23



Joined: 24 Dec 2013
Posts: 409

PostPosted: Mon Jun 16, 2014 4:16 pm    Post subject: sail problem or pilot error? Reply with quote

Having about 1 1/2 hours of TOW yesterday morning before having to hit the road, I rigged my Gaastra GTX 7.5 (circa 2002, 2 cam). Knowing the winds were going to increase all day, I rigged it flatter than usual in expectation of gusty winds within an hour. Normally I rig it with a little pocket in the sail for expansion where the battens are slightly under the mast. This time it was pretty flat with battens out from the middle of the mast.

The first half hour I spent 80% underpowered, mostly non planing, looking for gusts. 20% of the time (in the gusts), I was powered just right.

The 2nd half hour I was rigged just fine given the normal gusty conditions we have in the midwest (when itís windy). No problems getting the board going and having a great time, blasting back in the straps.

The last half hour I was 80% overpowered and the last ten minutes, WAY overpowered.

Here is my question. After waterstarting or uphauling in the overpowered conditions, the board, a 2013 JP Funride 130, would be very difficult to get going and push off the wind. I would have to use as much foot pressure as possible and all my skill to get any forward momentum and begin to push the board off the wind. It really didnít want to go. Way overpowered. Once I got the board off the wind and moving, back in the straps, the overpowered conditions were very manageable. Even the way overpowered conditions. The problem was getting the board moving and falling off.

I dont recall this ever happening when overpowered on my Retro 6.5. Could this be a result of an older race sail design or are most cam sails difficult to get going when overpowered? Maybe I need an excuse to buy a new 7.5 Retro and have no cams in my quiver?

I also wonder if it could be due to rigging it flatter than usual? If rigged normal, possibly it would have worked better?

Mast track was slightly forward of center. 460 w/ mcs of 25

Thanks for your help!
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zirtaeb



Joined: 03 Jul 2009
Posts: 2388

PostPosted: Mon Jun 16, 2014 6:18 pm    Post subject: Reply with quote

Overpowered, the draft moves slightly back, but more important in overpowering winds, the leech of the sail takes the load, forcing the board to want to head upwind initially, before you start to move.
You have to sheet in hard to force the nose off the wind, then sheet out a bit to maintain correct trim position. You can lean the sail slightly forward to drive the nose off the wind, but that is launch city, so I'd not recommend that. Better to plant your weight back, step your front foot a bit forwards to drive the board off the wind, while sheeting in carefully and maintaining a body position well back on the board, with the front foot well forwards, weight balanced and LOW.
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johnl



Joined: 05 Jun 1994
Posts: 1170
Location: Hood River OR

PostPosted: Mon Jun 16, 2014 9:15 pm    Post subject: Reply with quote

I worry when somebody says they rigged a sail flat. The FIRST thing you should be doing is increasing downhaul to make sure the leach has plenty of twist. If you are really overpowered having a floppy leach down to the boom isn't terrible (but a tad more extreme). But the leach between the main upper batons (usually the 2nd and 3rd on most sails) should be loose.

This allows the sail to still have a good "pocket" (i.e. power) yet allows it to twist off when hit by strong gusts. I always go with SLIGHTLY positive outhaul. In other words about 1" of outhaul AFTER the downhaul is set correctly. Then I can "flatten it out more" i.e. 2 or maybe 3" of outhaul if needed even while floating in the water.

Now some sails have called for negative outhaul, but they are rare. The normal is neutral or slightly positive.
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cgoudie1



Joined: 10 Apr 2006
Posts: 1250
Location: Killer Sturgeon Cove

PostPosted: Tue Jun 17, 2014 12:04 am    Post subject: Reply with quote

I'm with John here. You've pulled the draft back in the sail, with too
much outhaul. Make that sucker floppy down to the boom and leave a
little pocket in it. That pocket will be forward and will drive the nose of the board downwind somewhat, but you're probably going to have to drive
the nose off with your front foot Like Lee says also.

-Craig
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frederick23



Joined: 24 Dec 2013
Posts: 409

PostPosted: Tue Jun 17, 2014 7:58 am    Post subject: Reply with quote

I thought I might have over cooked the outhaul. Makes sense. So in anticipation of being overpowered, maybe a little more outhaul to increase twist? Or rig it always to spec? Is this circa 2002 GTX a modern (enough) sail? In perfect world I would love to replace it with a no cam Retro.

Thanks Guys.
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spennie



Joined: 13 Oct 1995
Posts: 823
Location: Thousand Oaks, CA

PostPosted: Tue Jun 17, 2014 8:28 am    Post subject: Reply with quote

Switching to a Retro is ALWAYS a good move, but I used to have Gaastras, and the GTX is a good sail. Funny nobody mentioned your waterstart technique much, although I agree that without any pocket in the front your sail is going to feel like a sheet of plywood, and won't generate much forward momentum. But you said it felt fine part of the time, so maybe it's something else? My rule is always downhaul to spec or beyond, then tune with outhaul, making sure you don't get too flat.

Without really knowing, of course, I'd guess you use a fairly large fin, and are trying to sail across the wind right away. Try maneuvering your gear in the water so you're going downwind slightly when waterstarting, and when you get up keep heading downwind a bit, then turn across the wind once you get moving.

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frederick23



Joined: 24 Dec 2013
Posts: 409

PostPosted: Tue Jun 17, 2014 8:43 am    Post subject: Reply with quote

Got it. I meant to say increase downhaul to increase twist, not outhaul.
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PeconicPuffin



Joined: 07 Jun 2004
Posts: 1211

PostPosted: Tue Jun 17, 2014 10:09 am    Post subject: Reply with quote

frederick23 wrote:
Got it. I meant to say increase downhaul to increase twist, not outhaul.


Yes. What John said. The more downhaul, the more power your sail can spill in the gusts. Outhaul is used to control the pocket and tune the overall power, but you must have pocket. If you're floppy most of the way to the clew, and have a shallow draft, and you're still overpowered, it's time to rig down. (If you have no smaller sail with you then try a smaller fin.)

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Michael
http://www.peconicpuffin.com
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johnl



Joined: 05 Jun 1994
Posts: 1170
Location: Hood River OR

PostPosted: Tue Jun 17, 2014 10:41 am    Post subject: Reply with quote

frederick23 wrote:
I thought I might have over cooked the outhaul. Makes sense. So in anticipation of being overpowered, maybe a little more outhaul to increase twist? Or rig it always to spec? Is this circa 2002 GTX a modern (enough) sail? In perfect world I would love to replace it with a no cam Retro.

Thanks Guys.


Welcome to the world of rigging (i.e. guessing). Experience will help here. You need time using the sail to figure out how to rig the sail Smile

I always start with the leach floppy down between the main top batons. This should match most manufacturers specs. If I feel I will be underpowered then I might back off the downhaul, if I think I will be powered up strong, then I downhaul a bit more.

If it helps, most people who are working on rigging don't downhaul enough.
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swchandler



Joined: 08 Nov 1993
Posts: 5816

PostPosted: Tue Jun 17, 2014 12:50 pm    Post subject: Reply with quote

If you're having difficulty bearing off when getting moving, I would suggest raising the boom a bit.
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