S-Shape in Main going upwind. Why?

[Franziska]

Hi,

my boat has a double mainsheet system.
Usually it works wonderfully to control sailtwist on the main.

Still, yesterday I was puzzled by a strange S-Shape in the battens aft.
Happens upwind.
Rig is toprig without spreaders.

Do not think it's a result of the genoa blowing into the main.
Anyone got an idea why this happens and what remedies might work?

Will try with more luff tension and more batten compression tomorrow.

Thanks for your thoughts,

Franziska

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[Sailmonkey]

That sure looks like the leech is loose to me. How is your main attached to the boom?


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[Franziska]

Fully inside a groove on the top of the boom. Has an outhaul too.
Outhaul was tight, both sheets where pretty tight, and the boom was slightly off to leeward.


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[barnakiel]

I believe the leech may be blown out.

Show to your sailmaker, discuss. I think this is easy to re-cut given your sail design.

b.

[Sailmonkey]

How large of a genoa I behind that? And if it's around 140-150% how cupped is it?


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[Seaslug Caravan]

Goody, I love these games

My guess is either to much mast bend or insufficient luff curve cut into the mainsail.

Lack of batten stiffness can also contribute but to a lesser degree.

[StuM]

How old is that sail? I tend to go with Barnakiel.

[zeehag]

looks like luffing to me... ha ha ha but i could be wrong.
possible batten fail. happens when ye try to emulate an airplane and sail nose dead into wind. 747s can do it. how to remedy you ask? by putting the wind into your sails.
could be an overstretched leechline, as someone else mentioned.. but i am partial to battenfail.

[Oliver L.]

Hi Franziska,

you've had the topping lift tightened too much. Happens to us when we tack and forget to loosen the topping lift, but then we only tack every 6 weeks...

Oliver

[Franziska]

Actually we did not sail nose into the wind and she was not oversheeted either.
Will check battens today and tighten the rigging more.
That might have contributed, I already wanted to retighten few days ago.

Many thanks,

Franziska

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[Snowpetrel]

Unfortunately I think barnakiel has it right and the sail needs the leech recut slightly. You might be able to improve it by pulling a bit more prebend into the mast to flatten the sail and maybe firmer battens, esp in the middle and leech. The topping lift idea is a good one as well, make sure its eased and prehaps playing with easing the halyard tension and outhaul slightly?

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[sartorst]

That would happen on my main when I had my batten pockets too tight in light air

[Barra]

I agree with last post - loosen the batten adjustments on lower battens

[Seighlor]

Wind direction near sea level was somewhat different than the wind aloft. I've experienced this a few times. It's not a matter of recutting your sails. Just trim for the wind that you're experiencing at the lower level... not at your masthead fly.

[Cavalier MK2]

Just for the heck of it I'll suggest less leach tension for the wind strength but think the batten tension shouldn't be over looked either as mentioned above.