A Belly in New Main !

[STATUE]

I had a new main made on 2012.

With little use last year, I have this year noticed a vertical curved belly in the luff - this extends aft about 30 cm at its widest point at half way down the luff.

Sailmaker advises too much halyard tension and to slacken that tension.

Is it me or the sailmaker ?

I look forward to your good guidance.

 

[Seajet]

Photo's would be helpful as ever, but maybe difficult.

I think I get the idea of what he was aiming at though, a more powerful, fuller sail until reefs are required then it flattens out - have you got a flattening reef or cunningham cringle ( cringle eyelet a few inches above the gooseneck for a purchase to attach and tension the luff, flattening the sail ) ?

 

[sailorman]

I had a new main made on 2012.

With little use last year, I have this year noticed a vertical curved belly in the luff - this extends aft about 30 cm at its widest point at half way down the luff.

Sailmaker advises too much halyard tension and to slacken that tension.

Is it me or the sailmaker ?

I look forward to your good guidance.

most folk over tension outhaul & halliard.
I helped a chap a few weeks ago hoist his furley whorley he hauled it bar taught, saying that will do for the season. i said i always leave mine slack & adjust tension as req for wind conditions, he took no notice & made it off.

 

[DJE]

I tension the main halyard until there is a vertical crease just behind the mast with no kicker or sheet tension. The crease disappears once the sail is properly set. But NB this only applies if we are going to be going upwind in a blow. At other times there won't be enough leach tension to balance out all that luff tension so ease the halyard to get rid of the crease. If you can induce a bit of mast bend it might help too.

 

[sailorman]

I tension the main halyard until there is a vertical crease just behind the mast with no kicker or sheet tension. The crease disappears once the sail is properly set. But NB this only applies if we are going to be going upwind in a blow. At other times there won't be enough leach tension to balance out all that luff tension so ease the halyard to get rid of the crease. If you can induce a bit of mast bend it might help too.

http://www.scribd.com/doc/13395369/How-To-Tune-Your-Rigging-And-Mainsail-For-Optimum-Performance

 

[Redshank Evo26]

I tension the main halyard until there is a vertical crease just behind the mast with no kicker or sheet tension. The crease disappears once the sail is properly set. But NB this only applies if we are going to be going upwind in a blow. At other times there won't be enough leach tension to balance out all that luff tension so ease the halyard to get rid of the crease. If you can induce a bit of mast bend it might help too.

^I agree with this^

It also depends on the rig, if you have a swept back spreader fractional rig you may need quite a bit of mast bend. My Evolution has about 4" of static bend and a lot more than that with the back stay on full. As DJE says you only want to flatten that belly out (assuming it not a crease) in a blow up wind, it gives power in light wind, or off the wind.

Pictures would help!

 

[[3889]]

I tension the main halyard until there is a vertical crease just behind the mast with no kicker or sheet tension. The crease disappears once the sail is properly set. But NB this only applies if we are going to be going upwind in a blow. At other times there won't be enough leach tension to balance out all that luff tension so ease the halyard to get rid of the crease. If you can induce a bit of mast bend it might help too.

I have to put quite a bit more tension on this, or the luff sags when kicker is applied. Oldish sail so is this a sign it is done for?

 

[dom]

Is it me or the sailmaker ?

I look forward to your good guidance.

You say 30cm "vertical curved belly" which I am assuming refers to a plane perpendicular to the chord of the sail. By definition this "belly" must equal the draft in terms of its length dimension (not camber because the luff is longer than the foot). To get a better feel for your concern it would be useful if you could provide the approx measurements of the sail, batten type, and the details of your rig (i.e. fractional, masthead, etc.)

Some photos would also be helpful. The two sails should be considered as a single airfoil, but it's easier to consider them separately here. The most useful shots can be taken in a low/moderate wind, with only the main up. Start by setting the sail up with moderate halyard tension. Then stand at the pulpit (always wear a harness doing this as it can make one dizzy!). Take a couple of steps forward and another photo until you are standing at the mast (sit/lie down at the mast when doing this so as to get the tack into the photo). Then take a couple of shots you walk along the windward rail to the stern. Finally get down underneath the boom to locate, note down and photograph the sail's draft (point of maximum depth).
This might all sound like a bit of a pain, and it is because 3-D airfoils are difficult things to describe. But I can guarantee you that the extra info will help both your sail-maker and the good folk here to give you some really hard and practical advice.

One more thing, whilst you are doing all this have a play around with your kicker, cunningham, outhaul and backstay (on a fractional rig) to get a feel for what happens the sail. If you see anything interesting photograph it and note the settings!

 

[STATUE]

Wow, excellent guidance everyone, thank you very much indeed.

Regards.

 

[Javelin]

Noooo,
Halyard tension is the same as cunningham ONLY do this to depower.
If your luff sags when you apply kicker or mainsheet tension its because you're using a stretchy braid on braid halyard, either upgrade to a bigger dia or pref change to dyneema or even consider going to a 2:1 main halyard which we've done a few of recently especially for the older cruising folk as it makes getting the sail up a whole lot easier.

The halyard is there solely to pull the sail up and NOT the tension the luff.

If you tension the halyard too much you pull fullness from the designed 40% aft to more like 25 or 30% reducing power.
It also releases the upper leech which you then try and fight by adding kicker and /or sheet tension, flattening the sail more and again de-powering the sail.

Exactly the same for the jib on a roller spar except this time pulling the fullness forward will also make it harder to point.

If you don't listen to me then listen to Sailorman as he's spot on.