Welp, sailing season is over up here and I was going through all of me rigging. I am thinking about buying new sails for my Nacra.

More than likely I am going to go with a square top. The big question is 5oz. Dacron or a laminent sail (dyneem, mylar, kevlar...). Anyone have both? Got some upsides and down sides for me?

For all around sails I have had the best luck with Pentex (a mylar) and the dacron Tornado cloth. The Pentex is a little faster and the dacron a little more forgiving (it works well over a wider range of settings (or screwups)).

Carl,
I agree Pentex is a very good option. Kelvar does not have enough give and Dacron has too much.
Did you know pentex is actually a by product of the automobile tyre industry. Makes a mightly good sail.
Regards,
Phill

Carl,

All agreed.

I've been discussing the alternatives for my sails with the (reputedly) best multihull sailmkers in Brazil, Cognac/Elvstrom and they sent me one of their published articles where they (basically) say that:

a) "Rigid" sails (3DL, reinforced film, etc.) have one important shortcoming - since they are not flexible, they can only be relatively more efficient in the tight wind speed range they were designed for.

b) "Flexible" sails (Dacron and others), if properly designed and cut, have a wider speed range where they are efficient, making better all-around sails. They can be more efficient then rigid sails, depending on the frequency and amplitude of the pressure changes in the specific day.

c) Sailmakers prefer rigid sails because more sails are needed in a complete inventory, with obvious $$$ consequences.

d) As a consequence, sailmakers generaly downplay the merits of flexible sails - which, by the way, are more difficult to design and cut.

Also, they claim that rigid sails do not maintain the design shape they are supposed to. Their practical metaphor was: when you cut an avocado in two and eat the pulp of both sides, the remaining half-shells do not match anymore only because the pulp (mold) was removed. A similar thing happens with rigid sales, although obviously in a lower scale. After they leave the mold, they do not hold their shape for long.

Cognac-Elvstrom has access to cheaper labour costs in Brazil, so their flexible sails are relatively inexpensive (and reputedly excelent to all but grand-prix racing). Since they also do rigid sails, it is easier for them not to have the same bias.

However, although all this seems logic and reasonable, I am just summarizing their opinion and am far from being an expert.

Cheers,

Hmm, it was a bit of a surprise to me that Elvstrom was advocating Dacron..

Anyway, at this years IDM (international german championship) I think I counted three dacron jibs. The rest of the jibs and mainsails was Pentex. Some of the top ranked teams was there (Bundock, Gaebler, Polgar, Sachs..) and they all used Pentex jibs/mains. Cost is not a big issue to these guys, so if Dacron was better they would have used it. Especially since you only are allowed to measure in one set of sails for any event.


I have a Pentex mainsail on my Tornado, and are very pleased with it. I like it, especially when it really blows. In contrast, my Dacron jib is awful when it starts to blow. Also, I find Pentex sails to have better durability than Dacron sails. Going for a Pentex jib next season (and Pentex main + siliconised spi if my sponsor (wife) agrees )!

I would stop worrying about the material (Pentex of course) and rather start evaluating sailmakers.

Did I mention that I like Pentex sails ??

Thanks for the info - it will certainly help me choose the sailcloth. Will check Pentex prices now.


They are not. Cognac is Elvstrom's representative/connection in Brazil, but the article is not signed by Elvstrom, only by Cognac. (also, the sails they make are different and use different sailcloth).

Very probably their article targets cruisers wondering what sailcloth to choose. Racers will take the last 0.1% extra speed and pay the price.

Cheers,

Hello Luiz-

Is that you in the pic??

thom

Yes, I liked sailboats even before K3. That's my very first photo on a sailboat, taken in the same club in Ipanema where I learned to sail later on.

The mono is a "Sharpie" class (plywood, hard chined, with a steel plate centerboard and steel plate pivoting rudder). They were relatively popular in Rio at that time, but not as much as other plywood boats, like Snipes and Penguins.

Cheers,

Is there any reason why you wouldnt consider Cuben, or CarbonX? I have been running a CarbonX Smyth Main on my F31R and It has been great, The jib however has shown more wear after 3 years of racing the mylar has proven to be the weak link, mostly because the jib is a 110 Blade jib, and rubs the spreaders when tacking. However the Main has no signs of wear!

I thought it was pretty simple and I'm getting confused about how a stretchy sail can be an advantage. Dacron is less expensive than the laminates and as things go...you get what you pay for. Dacron will not maintain it's shape as long. The laminates utilize the stiffer and stronger scrim materials (pentex, kevlar, carbon fiber, etc.) so that they will maintain shape better and longer.

On our cats, why do you want a stretchy sail? If it's blowing hard and I'm trying to flatten/depower my sails I would think the last thing I want is for the sail to stretch and become fuller (and/or loose shape).

Jibs, however, go through a lot of flexing and bending crossing the mast and all the hardware up top during tacks and gybes. Laminate sails are not good at this constant flexing but Dacron is. Because of that we see a lot of Dacron jibs.

Stretchy sailcloth can be used to make sails that flatten when the pressure increases. For this reason, they are useful in a wider range of wind speeds and replace more then one rigid sails, which are more wind-speed specific.

A stretchy sail is slower then the two or three rigid sails it replaces - if you can always have the proper rigid sail up. However, the wind speed may be very variable and eventually you'll be caught with the wrong sail up. Also, in these conditions you'll have to change sails more frequently, making the stretchy sail a better choice.

Summary: a properly designed stretchy sail (one that flattens with higher pressure) is an advantage in highly variable conditions.

Durability is a separate issue.

How does a stretchy sail flatten as it reaches higher pressure? The stretching that you refer to - is it due to pressure generated by additional downhaul (cunningham) and main sheet?

Perhaps to a lesser degree but the lack of stretch in composite sail cloth is easily offset by the amount of bend induced in the mast is it not? Mine looks like a bananna when we're at full depower mode. My question is, with the adjustment range that we (cats) have isn't a stretchy sail is less necessary?

About the sail that flatens authomatically when the wind increases, all I know is that it is a tri-radial design that was developed by Lars Grael (former Tornado Olympic Medalist) and Arnaldo Andrade (Cognac Sailmakers) many years ago.

If you want more information, I suggest you write directly to Arnaldo Andrade ([email protected]). You can mention this forum and my name if you want, but I don't think it's necessary - he will probably reply anyway.

Cheers,

First stretchy is relative.

Dacron and mylar both stretch. Mylar does not stretch as much.

Dacron has the same strength and stretch in all directions mylar does not. That is why layout on mylar sails is important. The material has to be turned so that the load is in a direction where it is strong.

Forgiving on cat sails. If you don't have everything set just right on a Dacron sail, the load will stretch it out a little. With a Mylar it will wrinkle and look like you have too much of something and not enough something else. Also if, the Sailmaker slipped up a little or the fabric gives in a local area Dacron will stretch. If a small section of a mylar main yields, it can look very ugly.

All this being said, the best sail I have ever seen is an Ullman pentex 18 sq, a scaled version of the new rig Tornado main

Actually...

A panel of dacron will have its strength in only one direction (both ways), because of the way the fabric is weaved from fibers. One a square piece, the strength will either be up and down or left and right. Generally, on a long roll of cloth the strongest direction will be from side to side, not along the length. But it also comes with the strength lengthwise.

On our normally panelled Dacron main and jib sails, the seams for the panels are on the battens, meaning the cloth is rolled out side to side on the sail and sewed together panel-wise going up, giving the strongest part of the cloth to take the biggest loads, mainly up the leech and luff. Anytime the force goes out of alignment with the direction of strength in the cloth, it will stretch and ultimately deform. This way of making sails obviously can't account for the fact that almost no load on the sail will line directly with the strength of the cloth.

Radial cut jibs and mains are an attempt to line up the strength of the cloth with the loads on the sail. This is a case where the strength in the cloth is lengthwise. But again, for all the effort, the load paths will not always line up with the strength of the cloth, leading to stretching and deformation.

Other types of cloths used in panel type construction attempt to have strength in more than one direction, but ultimately will still not be able to exactly match load paths. Still, an improvement. Most of our mylar sails are radial cut fabric laminated with the mylar. Same issues apply ultimately, depending on the directional strength of the cloth used.

The modern laminate sails, place fibers in the sail to directly correspond to the load paths, then laminate it all together.

Sorry, couldn't resist, from a lecture on sail materials from our local North shop...

What is being said here flies in the face of everything that has been learned within the windsurfing community for the last 30 years.
When Dacron was used, the rig was easy to overpower and had a very narrow wind range…the Dacron/Mylar laminate was better…then battens were added which helped increase the range, then camber inducers to force more shape into the sail. All these things helped, but when the sail manufactures started to use Mylar film and scrim/Mylar sandwich things really started to happen…all the sudden one sail could cover the wind range of 2-4 Dacron old school sails.
The designer could then design the shape into the sail and be sure it would keep its shape in a wide wind range, if set on the correct mast and used with low flex carbon booms…
The sails became much more responsive to tuning…if you set the down haul or out haul a certain place, it stayed there until you changed it…the wild fluctuation of center of effort in the sail was now gone…as the wind picked up by proper adjustment of the down haul and out haul the center of effort could now be brought down lower and moved forward on the sail making it more controllable, with the head bleeding off excess power that would slam a sailor with similar size old school sail under equal conditions.

You can’t keep the design foil in as wide of wind conditions if you have a fabric that is constantly changing shape. Dacron is generally cheaper, and more resilient to rough handling, although I have had just as many Dacron/Mylar windsurfing sails delaminate as I have Mylar, mylar/scrim/mylar sails.

Bob

that's what I'm talkin' about!

You are right. The said article agrees that it claims the opposite of what all of us believe.

I'll try to have the quoted sailmaker read this thread and explain his point.

My best guess is that the rigidity of the sailcloth is not THE reason behind the improvements in windsurfer sails.
Those are probably linked to better masts (mostly) and to the other features you cited.

Cheers,

I wish we could get Dave Calvert to comment on this, he is the only well known sail designer I know of that has been deeply involved with both Windsurfing racing sails and Catamaran racing sails…he is uniquely qualified to explain what may or may not work when translating sail design from one discipline to the other…

You are right to point out improvements in carbon mast design and construction, and also low flex carbon booms as having a major impact, but having a more stretch resistant sail material to work with was touted by all the major sail makers (Pride, North, Gastra, Izzy, Sailworks) as the vehicle that allowed them to build in more shape to the sail, and to lighten the sail by not using so many mechanical features (battens, camber inducers). Many of the sail makers have developed camber free designs that have a more stable shape then the camber induced sails just a few years ago. When you have a whole industry that is tech driven, and very competitive aligning so strongly towards one design feature (stable sail material) it makes some rouge statement (even by a known designer) a bit hard to swallow.

Bob

While we wait to see if Arnaldo (writer of the article) answers my request to step in or send me his reply, I'd say that what sailmakers tell customers is naturally biased by their specific business needs (as anyone's, for that sake - no recriminations). More resistant materials mean less stretchy materials. But it also means less weight, less work (aligning panels' stronger direction with stress lines is time consuming) and more profit (higher cost materials + less work time + same profit % = more $$).

Add the fact that rigid sails ARE superior in racing conditions - when everyone is supposed to wear the sails that best suit the conditions most of the time - and the rigid sails sells themselves. And what would anyone atribute the performance to? The sailcloth, naturally.

But what he said in the article is that the story is not necessarily the same when you are cruising, when the pressure is very volatile, when the cost of aligning those panels is less important in the total cost of the sail and/or your rig is less high-tech then windsurfers (or some beach cats). Jibs, for example, are a lot more dependent on sailcloth flexibility and design exactly because they are not attached to a flexible/adjustable mast. Even more, if they have no battens.

Hopefully, both Dave Calvert and Arnaldo (author of the article) will go on with this thread. I can see that I'm just repeating the same reasoning... Sorry, this is already beyond the limits of my knowlege!