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post #1 of 15 Old 02-01-2018 Thread Starter
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A question about sail shape and non dacron sails

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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Re: A question about sail shape and non dacron sails

Face on should read Dacron in title. Could not edit on phone[emoji4]

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Re: A question about sail shape and non dacron sails

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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Re: A question about sail shape and non dacron sails

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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.
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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Re: A question about sail shape and non dacron sails

It still moves it. All the controlls vang/ halyards, etc. do what they should (and are required for best performance).
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Re: A question about sail shape and non dacron sails

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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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Re: A question about sail shape and non dacron sails

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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Re: A question about sail shape and non dacron sails

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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Re: A question about sail shape and non dacron sails

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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post #10 of 15 Old 02-01-2018
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Re: A question about sail shape and non dacron sails

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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