Jib trimmed but main luffing? - SailNet Community
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post #1 of 13 Old 06-18-2012 Thread Starter
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Jib trimmed but main luffing?

I was out for a great sail yesterday, winds around 13 knots. It was also my first sail with "company" (other than the admiral) on board, so I was a little nervous and didn't want to look incompetent to my non-sailing guests. O

n my first few tacks I sheeted in the jib tight, but when the jib telltales were flying perfectly the main (sheeted tight over centerline, traveller in the middle) would luff. What would cause this? I'm thinking that the jib was sheeted in too tight and the main couldn't go any tighter, or that the jib can be set closer to the wind than the main, but I'm really not sure if this is the correct or logical explanation.

On subsequent tacks, I just let the jib out a little and the main would fly fine. We were pointing fine and had good speed, but I'd still like to know if there was something I could have done differently.

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post #2 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

Do you have a leach line on the luff of the sail? if so try tighting it up some.
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Re: Jib trimmed but main luffing?

When you say that the main was sheeted over the center line...traveler to the center.

Does that mean that the boom was centered? If not, you could try moving the traveler to windward a bit.

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Re: Jib trimmed but main luffing?

Sorry- the boom was as close to center as I could get it with the traveler in the middle.

There is no leach line on my main and my topping lift was fully eased.

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post #5 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

As Tempest commented earlier- move your traveler to windward. You don't need to stop it at the centerline.

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post #6 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

If you are sailing with an overlapping jib, as the breeze comes on you will experience some backwinding on the main...all the air volume trying to squeeze through the slot between the jib leech and the main luff can't fit, so some of it flattens the luff of the main.

This is OK, you cannot trim backwinding away, and definitely dont take the traveller up in a breeze! when sailing closehauled like this, the jib is powering the boat, the main is just helping your balance and pointing, dont worry about the backwinding.

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post #7 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

What sailingfool said. You've got the backwind bubble going on.

Last edited by puddinlegs; 06-18-2012 at 08:32 AM.
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post #8 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

I'd be careful about trying to point to high. There is a point of diminishing returns, just because you can point a few degrees higher doesn't mean that's the best way to move upwind. At some point you'll lose speed at which point you'll start making more leeway in the water. If you've got the boom pulled all the way in (inboard of the rails) and it's still luffing I would think you'd want to let the jib out.
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post #9 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

My P30 sails much better when the "luff bubble" is present while pointing (150% genoa). The helm is very well balanced and leeway is minimized. It took me a whole season to figure that one out.
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post #10 of 13 Old 06-18-2012
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Re: Jib trimmed but main luffing?

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Originally Posted by nickmerc View Post
My P30 sails much better when the "luff bubble" is present while pointing (150% genoa). The helm is very well balanced and leeway is minimized. It took me a whole season to figure that one out.
Many boats are like that. When trimming I use the mainsheet to get the right twist, then adjust the traveler until there is a slight amount a luffing. That usually means moving the car windward. A good guideline is that when close hauled, the boom should be on the centre line. Your knotmeter will let you know if your trimming is effective.

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