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Discussion Starter #1
I have heard that Mylar, Kevlar etc sails do not stretch. Does this mean that you cannot flatten the sails as you would a dacron one by sheeting on, tightening Cunningham, outhaul etc?

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They stretch a little, but not nearly as much as dacron. Thus, they need little or no re-adjustment in all but strong gusts. But stretchy sheets and halyards defeat the purpose of low stretch sails. That's why racers use both low stretch sails and low stretch sheets and halyards

Cunninghams, outhauls and similar sail trimming devices are as crucial with Mylar and Kevlar sails as with dacron.
 

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Discussion Starter #4
They stretch a little, but not nearly as much as dacron. Thus, they need little or no re-adjustment in all but strong gusts. But stretchy sheets and halyards defeat the purpose of low stretch sails. That's why racers use both low stretch sails and low stretch sheets and halyards

Cunninghams, outhauls and similar sail trimming devices are as crucial with Mylar and Kevlar sails as with dacron.
Thanks for the reply.
So would I be right in saying that you would just set everything tight and forget? With the possible exception of light winds where I can see you may be able to get a bit more draft. Does pulling on the Cunningham still move the draft forward or is all the shape just built into the sail by the sailmaker?
I have dacron sails so really don't know much about the exotic materials.

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It still moves it. All the controlls vang/ halyards, etc. do what they should (and are required for best performance).
 

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Discussion Starter #6
It still moves it. All the controlls vang/ halyards, etc. do what they should (and are required for best performance).
Thanks Loki, I figured they would but what I think I know and reality sometimes differ.
So my next query about these sails is from a cruising perspective, and by cruising I mean daysailing or heading up or down the coast for a few days, not sailing to Tonga, do you or others here think that a dacron or mylar/kevlar type sail would be more suited. My sails are about 10 years old and still seem fine but my mate has Kevlar ones about the same age and they have started to delaminate. Well they have been delaminating for years actually. He is considering Kevlar again but I can't see the point.

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Well, there's the best way to trim sails, and the way that's good 'nuff. It's your boat and you can do it either way.

I know lots of sailors, even some racers, who trim their sails to the same basic shape and tensions every time they sail, regardless of the wind speed, presence of gusts and lulls and point of sail. They usually get where they're going, but just a bit less efficiently than they could.

The best way to trim sails is to raise them and tension them each day appropriately to the wind speed at that time, and make minor re-adjustments each time there's a gust or lull, and every time you turn from a closehauled course to a point of sail off the wind.

Some people say they sail to relax and that's too much hassle. Others see sail trimming as a complex and never ending mystery to figure out how to maximize the boat's performance.

Personally, I do a bit of both. When I race, I am an extremely active sail trimmer, constantly looking for ways to find a wee bit better sail trim. When I'm cruising or daysailing, I'll do either. If I'm tired, I'll let it go. If I'm bored, I'll mess with sail trim to keep occupied.
 

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If you haven't bought sails before, the best way to buy them is to go to a good sailmaker and talk about where you intend to use them, how you intend to use them, and how many years of useful life you hope to get from them. A knowledgeable sailmaker can tell you which sail cloths will best serve your intended uses, and which will not, and also help you make choices that will fit best within your budget.

They don't charge to talk to you, so visit more than one, and compare their thinking, their products and their prices.
 

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Discussion Starter #9
Thanks guys, I guess my questions have been answered. Cunningham's, outhaul's etc are still important on exotic materials, but not as much adjustment available due to less stretch. That aligns with what I thought.
I have read a bit on sail trim so I understand the principles to an extent and what happens when you tighten this or loosen that. The difficult part is when. I imagine every boat is different and practice makes perfect. To illustrate, I have done a few races with my mate on his Elliot 7 and we have never really done well, always in the bottom half of the results sheet. We try and I have done some study via the interwebs re. Trimming etc. One race we had a new bloke on the boat for crew, he had done heaps of racing and new his **** so we all did what he said and finished the regatta 3rd. And that is with a few spinnaker gybe stuffups. Now I have pulled on all the lines and tweaked everything that he did but he just knew where everything needed to be to go fast. I guess practice makes perfect.
Unfortunately he was a bit of an ******* as well so we never invited him back and we reverted to the bottom of the fleet again.

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If you are investing in "exotic" materials, you likely are directly focused on maximum speed/efficiency of shape... so yeah, you'll be tweaking, consistently.

With the except of significantly off shore, winds aren't generally static, they vary in speed and direction sometimes significantly. The less flat (or more obstructions) the area is immediately around where you are sailing, the more dramatically these winds can shear.

The stretch of the material is more about the sails ability to be consistently shaped with similar settings.
 

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Invest $5.00 in "Sail Trim and Rig Tuning: A Captain's Quick Guide" Aug 5, 2005 by Bill Gladstone. This modest investment will provide the guidance you need to shape your sails.

Get a ride on a boat with good sails and carefully heed the shape and what the crew is doing to shape the sails.

It's not rocket science but it's hard to get better without a structure approach on a boat with bagged out sails.
 

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Hey,

The sail adjustments are NOT to compensate for stretchy or worn out sails. The sail adjustments are to make sure the sail is working as efficiently as possible for the wind and point of sail at that exact moment. If the wind changes by 5 kts, adjustments should be made to halyard, outhaul, travelor, etc.

If you are racing this is extremely important. If you are not constantly adjusting the sails you will not win. Besides, most boats racing have a full crew and the guys need something to do besides sitting on the rail. So making small change to backstay, jib cars, outhaul, can be fun.

If you are cruising this is probably not so important - does it matter if you arrive at your destination one minute faster? However, knowing how to trim and adjust sails for windy conditions will make the boat more comfortable and safer for everyone aboard.

Good luck,
Barry
 

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Thanks guys, I guess my questions have been answered. Cunningham's, outhaul's etc are still important on exotic materials, but not as much adjustment available due to less stretch. That aligns with what I thought.

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You have it a bit backwards, the sail with less stretch is going to respond better to the adjustments of the rig. there is more adjustment available. when you set an adjustment the sail responds and resists the forces of the wind. with a stretchy sail cloth you will have to make a larger adjustment to get the same result because the wind is forcing the sail out of shape easier . the sail is made to a designed shape, you do not make adjustments to stretch the sail, you make adjustments to compensate for the sail stretch to keep the sail with in the designed shape. as the wind builds and you want to flatten the sail a bit the high tech materials will respond better than the stretchy material to an adjustment. if dacron sails worked as good as the new materials then there would be no reason for the new materials. if we consider sail shape as the most important aspect of a sail, a dacron sail is good for about 20 days of sailing and a high tech sail is good for 100 days of sailing before the sail starts to loose the designed shape.

you can not compare the high tech sail materials of today to the high tech sails of ten years ago. there has been a lot of good development in the last ten years. all the delam stories no longer apply to many of the new materials used today.
there are many of the new materials that will wear better then dacron and hold the shape better for longer. the draw back is the initial cost is higher but not in the long run.
 

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On your friend’s sail, the resin surrounding the kevlar yarns is beginning to break down. This is ultimately how Arimids die. This happens before the sail is all bagged out. Good old Dacron starts stretching the first time you use it and goes down from there. They are bagged out way before the fabric breaks down. So, you can potentially use them much longer than an Aramid or composite albeit with a greater degradation in performance. The Arimids and composites also have a benefit if being much lighter and weight aloft is important if you sail in windy conditions like San Francisco Bay. Being stiffer and “flatter”, main sails can be constricted with full battens on top and partials on the bottom allowing you to have a loose foot which greatly enhances the outhaul adjustments. On the race boat we run carbon all the way. On the family cruiser our main is a UK Spectra Tape Drive and our jibs are Quantum Pentax. If I was looking into something with more performance than Dacron, I’d look at Quantum’s Fuson or Doyle’s Stratus sail cloth.
 

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Discussion Starter #15
You have it a bit backwards, the sail with less stretch is going to respond better to the adjustments of the rig. there is more adjustment available. when you set an adjustment the sail responds and resists the forces of the wind. with a stretchy sail cloth you will have to make a larger adjustment to get the same result because the wind is forcing the sail out of shape easier . the sail is made to a designed shape, you do not make adjustments to stretch the sail, you make adjustments to compensate for the sail stretch to keep the sail with in the designed shape. as the wind builds and you want to flatten the sail a bit the high tech materials will respond better than the stretchy material to an adjustment. if dacron sails worked as good as the new materials then there would be no reason for the new materials. if we consider sail shape as the most important aspect of a sail, a dacron sail is good for about 20 days of sailing and a high tech sail is good for 100 days of sailing before the sail starts to loose the designed shape.

you can not compare the high tech sail materials of today to the high tech sails of ten years ago. there has been a lot of good development in the last ten years. all the delam stories no longer apply to many of the new materials used today.
there are many of the new materials that will wear better then dacron and hold the shape better for longer. the draw back is the initial cost is higher but not in the long run.
Ok. So the sail that stretches less will be able to be shaped better to suit the wind speed. That does make more sense. I only really get out for at max 1 day a week, more likely one day a fortnight. I do like to try and get the sail angle right by using the telltales but usually just pull things tight enough to get the wrinkles out as far as the shape goes. I only have a little 20ft Trimaran and a set of flash sails would probably be cost prohibitive. I bought a jib when I got the boat and it was 1/5th the price of the boat so Kevlar or whatever would be like putting lipstick on a pig.

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