Why do I get this sail shape?

aquaaddict

New Member
Hi,

Can anyone please suggest why I tend to end up with this stretched and crinkled luff?

2015-06-14%2011.50.00.jpg


I presume the sheet or vang are too tight, but when close hauled what else can you do.

Thanks,

Anthony
 
How easily does the upper section slide into the lower section? If it's a loose fit, you get a kink in the mast shape instead of a nice smooth bend. This may partially explain the poor sail shape. In fact, the mast kind of looks like a kink in your picture.

What you want to do is put a layer of tape around the collar of the upper mast where it slides into the lower mast. You can use packing tape in a pinch, but most people use something like this:

http://www.apsltd.com/one-design-parts/laser/laser-spar-tape-1-quot-x-10.html

Start off with a single layer. You want it snug enough that you have to apply a small amount of pressure to insert the upper mast into the lower, but not so much that it takes two people playing tug-of-war to separate them.

edit - To expand further, the sail is designed for a certain amount of mast bend. It expects the mast to bend in a smooth arc. With loose upper section you are getting two straight sections at an angle, not a smooth arc. Adding a layer of tape will change this behavior and allow the mast to bend as intended.
 
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How easily does the upper section slide into the lower section? If it's a loose fit, you get a kink in the mast shape instead of a nice smooth bend.

Ahhh I think you may have hit it, yes it is loose but it never occurred to me that it would make any notable difference. I actually have a new plastic collar to install as the current one has a crack so will install that and add tape if necessary and see how it goes.

Many thanks!

Anthony
 
A tight fit between the upper and lower masts never hurts, but as there's no crease coming from that point in the picture, I don't think tape in the joint will make much of a difference. Your sail looks just stretched out - how old is it, have you compared it with a new one, does it look the same in heavier air? Have you tried it on another mast, or tried another sail on your mast?

BTW, a few other things you might do differently than in the picture (assuming we're going upwind in very light air):
  • push the rudder down
  • pull the traveller tighter so it just touches the tiller
  • bend the mast with the vang instead of the sheet, so you can sheet the boom out
  • move your weight forward
  • keep the boat level or heel it a bit to leeward
Maybe you know all of the above and the photographer caught you at a bad moment, but anyway.

(I'd also like to have a closer look at your vang arrangement, as it looks kind of strange.)
 
Looks to me like your vang is completely loose. Or far too loose at least. So all the the mast bend is coming from the main sheet. But, the stern end of your boom is still quite high so there still isn't enough bend in the mast to match the curve of the luff tube on the sail. This means that you've still got too much tension (shown on your sail) between the tip of the mast... and even a distance down the mast from the tip... and the stern end of the boom.

So... the first thing to do would be to ease the main sheet all the way so that the mast is straight. Or an easy way is to crank down the main sheet like in the photo to bend the mast, then pull on the vang so it is tensioned, then ease the main sheet. Then gradually continue to crank the vang down while watching the shape of the sail. As you do this, the shape of the sail will look better and better. When it gets close to looking it's best, the end of the boom will be getting close to the deck. Less than a foot.

Now sail around and use the main sheet only to adjust the angle of the sail to the wind and see how the sail shape looks when the force of the wind has put a load on the sail. Keep playing with your vang tension and eventually you will find a setting where the sail "looks" the best.

When pointing to go upwind... in light to moderate winds... that is, not super light wind and not strong wind, using the main sheet you can pull the end of the boom down the rest of the way until you can't pull the blocks on the end of the boom and the traveler any closer because they are touching or almost touching. This is called, "block to block". This is how you keep the leach fully tensioned which allows you to sail upwind the most efficiently.

You then use the main sheet to change the angle of the sail to the wind to stay powered up and the water fully flowing over your daggerboard so you can still point well in light wind, or if you are starting to heel too much you also ease the main sheet some to keep the boat flat.

And what everyone else said!

- Andy
 
Thanks for all the tips, I was just coming in to shore in that pic hence the rudder up etc, but the sail looked similar in some of the further away shots with the vang on. From what you have all said it sounds like a combination of mast fit, bad sail shape (I have no idea how old it is), and more vang tension, at least I have a few things to go play with now and see how much better I can get it.

Many thanks for all your help, I am just coming to a laser from keelboats so your help is greatly appreciated!

Anthony
 

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