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AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
http://www.hobie.com/au/en/forums/viewtopic.php?f=71&t=58523		 Page 1 of 2
Author:  PeteCress [ Sat Jul 23, 2016 11:55 am ]
Post subject:  AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
When the wind gets into the mid-to-high teens, my AI2's sail takes on a pronounced "S" shape centered around the #2 batten where the white and blue colored material meet.

Probably should borrow somebody's GoPro for a visual.... but, until then, words will have to suffice.

The deformation persists when the sail is reefed.

Am I the only one?
Author:  tonystott [ Sat Jul 23, 2016 1:01 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
Hard to visualise without a photo Pete, but my guess would be batten tension. One thing you might try is to lay the sail out flat on the ground, and undo all the battens. Move the sail about a bit to enable the material and battens to find their normal "relaxed" position. Then tie the battens to the sail, using just enough tightness to have the battens firmly in their sockets.

Hopefully, this will remove any distortion in the sail.

Worth a try.
Author:  PeteCress [ Sat Jul 23, 2016 5:20 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
tonystott wrote:
....my guess would be batten tension......Then tie the battens to the sail, using just enough tightness to have the battens firmly in their sockets.
Sounds like you suspect too much batten tension.

If so, that rings true to me - having recently replaced Hobie's el-cheapo batten adjusters with Robichaud batten tensioners from an old Sailworks windsurfer sail - and probably having gone overboard on the tensions.

I will do as advised and report back next time there is enough wind for a test.
Author:  mikereddy [ Sun Jul 24, 2016 8:25 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
I have pictures of this happening with a slight reef in my AI2 sail. They are hosted on photobucket. But I cannot remember how to post them here. I've tried various combinations of the Img and URL tags above with the different snippets of HTML that photobucket gives me... but nothing works.

Can somebody remind me what the proper code looks like.
Author:  TI_Tom [ Sun Jul 24, 2016 2:27 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
It should look like '[' 'img' ']' 'the url of the picture' '[' '/' 'img' ']'. Sorry for all the ticks can't figure out how to display bbcode using Tapatalk.

Sent from my SPH-L720T using Tapatalk
Author:  Hogman [ Sun Jul 24, 2016 3:37 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
mikereddy wrote:
I have pictures of this happening with a slight reef in my AI2 sail. They are hosted on photobucket. But I cannot remember how to post them here. I've tried various combinations of the Img and URL tags above with the different snippets of HTML that photobucket gives me... but nothing works.

Can somebody remind me what the proper code looks like.



Open your library in photobucket. Move your cursor over a photo and click on the 3 horizontal lines. Then click share. Options will then come up and all you have to do is single click in the IMG section, and it will copy the image.
Then just paste into this forum.
Image
Author:  mikereddy [ Sun Jul 24, 2016 4:59 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
Thanks for the help with the coding.

OK, here's a slightly reefed AI2 main in about 15 knots. Don't the wrinkles suggest too little batten tension?? This is really not a nice sail shape, so any help would be appreciated. :-)

Image[/URL]

Image[/URL]
Author:  TI_Tom [ Sun Jul 24, 2016 5:06 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
At first glance it looks more like you're not sheeted in tight enough for the point of sail you're on and the front of the sail is stalling. But it also looks like when the first batten wraps around the mast that it might be introducing that 'S' curve on the second batten.

Sent from my SPH-L720T using Tapatalk
Author:  mikereddy [ Mon Jul 25, 2016 7:22 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
thanks Ti_Tom--it is definitely something to do with the first batten. Took these shots late last year, so maybe there's an issue of stalling. But what I remember is trying all sorts of mainsheet adjustments and not seeing this really poor sail shape disappear. Falling off didn't change anything except increasing the heel.

The mast is bending off a lot. It's supposed to do that, but is the sail capable of keeping its shape when this happens? I had a TI that I sold, and its sail didn't look that good reefed either. Maybe the roller-reefing does reduce your sail, but introduces problems with shape and flow as it does. Is this what should be expected??

I'm wondering if anybody out there has experience (or pictures) of an AI2 reefed about like this and setting up well. This sail has seen only light use for one season. Thanks for any help. :-)
Author:  Bazinga [ Mon Jul 25, 2016 7:34 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
Have you tried a lot of Downhaul? This can give more pre-bend to the mast and may take some of the looseness out. My mast seems to have a lot more curvature than what I see in your photos.
Author:  PeteCress [ Mon Jul 25, 2016 8:02 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
mikereddy wrote:
Thanks for the help with the coding.

OK, here's a slightly reefed AI2 main in about 15 knots. Don't the wrinkles suggest too little batten tension?? This is really not a nice sail shape, so any help would be appreciated. :-)

Image[/URL]
That is pretty close to what I am seeing - except I see it both reefed and not reefed and my sail lacks the nice new crisp look that yours has.

And I guess that amount of reef pretty much eliminates the #1 batten as a player.


Also, if this is common across many sails, I would not discount the possibility that it is part of the sail's design.

Modern windsurfing sails - like the Ezzy line - are designed with floppy leaches. They rig kind of ugly, but the floppy leach somehow improves the aerodynamics of the sail.

Increasing the downhaul increases the amount of flop/slop and makes the sail usable in more wind.

Costs about a half meter in terms of lifting area, so a newer 7.5 has horsepower closer to an older 7.3 or 7.2.
Author:  mikereddy [ Mon Jul 25, 2016 9:15 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
I'll play with the downhaul first chance I get. Thanks for that tip.

Can't fully agree that the first batten is not causing this. We are not seeing a flat luff up at the top like a windsurfer sail tuned with a ton of downhaul. We are seen reverse curves. If the first batten is too stiff and is bulging forward where it wraps around the mast, it seems like that could pull the sail into something like this shape.

I've shaved battens before on an H16, but they were flat--reducing the stiffness of a round batten progressively near the top seems like it would be harder.
Author:  PeteCress [ Mon Jul 25, 2016 10:42 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
Bazinga wrote:
Have you tried a lot of Downhaul? This can give more pre-bend to the mast and may take some of the looseness out. My mast seems to have a lot more curvature than what I see in your photos.
I claim no knowledge of sailmaking.

Having said that....

The downhaul on this sail does not look to me like something intended for high downhaul forces - as in mast-bending, or even less.

I would expect more mechanical advantage and a far more robust cleat if high downhaul force were part of the design.
Author:  mikereddy [ Mon Jul 25, 2016 11:51 am ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
Peter... I believe you are correct here. Plus which, imagine if the downhaul did impart noticeable mast bend. When you roller reefed, that mast bend could end up in any direction, or else you would have to reef in terms of one full turn at a time.

Still, a little downhaul might stretch the sailcloth and maybe affect the wrinkles.
Author:  PeteCress [ Tue Aug 02, 2016 7:22 pm ]
Post subject:  Re: AI-2 Sail: "S"- Shaped Deformation Around #2 Batten?
PeteCress wrote:
tonystott wrote:
....my guess would be batten tension......Then tie the battens to the sail, using just enough tightness to have the battens firmly in their sockets.
Sounds like you suspect too much batten tension.

If so, that rings true to me - having recently replaced Hobie's el-cheapo batten adjusters with Robichaud batten tensioners from an old Sailworks windsurfer sail - and probably having gone overboard on the tensions.

I will do as advised and report back next time there is enough wind for a test.
Well, today was the day.

Varying batten tension does not seem to help.

OTOH, after I replaced the #2 and #3 battens with Robischaud tubular battens harvested from a windsurfing sail that has gone to the Great Sailing Spot In The Sky, the problem (?) went away.

I can see that the sail material wants to take the "S" shape, but the new battens prevent that from happening.

Dunno if it works any better, but it certainly looks a lot nicer.

Only anomaly (?) I see now is fluttering on about 2" of entire leech between mast and #1 batten.
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