Hello and Opinions Needed

What kind of boat? Isotope? (Just assuming because of your user name.) If so, have you asked the manufacturer, or other isotope owners, what they recommend?

Hi Mary,
Yes I do own an Isotope and I have asked the manufacturer as well as other Isotope owners and was told that it was whatever my preference is but I dont have a preference at this time as I am new to sailing.
I currently have dacron sails and would like to know what advantages-if any mylar would offer me.
Walter

walter
some advantages of mylar does not strech (well not as bad as dacron)mylar sail have a better shape and holds it for there whole life, stornger, they are very easy to repare looks beter
cheers..kurt

Maybe I don't know what I'm talking about, but I think your question would apply primarily to the mainsail, because regardless of what the main is made of, most people want dacron for their jib. I may be going out on a limb here, but as a crew, I need to be able to "read" the jib, and it needs to be a "soft" material.
And what I have heard about mylar mains is that they are the best IF they are cut right in the first place, but if they are not, it is a little harder to change the shape and the draft by altering battens, than with a dacron sail.

i sail on a monohull with mylar sails. i was told by the owner that the sails actually shrink a bit over time and become flatter.

Mylar is good for a main sail and Dacron is good for a jib.

Mylar will hold it's shape longer but is more suseptable to damage from ragging the sail or improper rolling of the sail. Once you put a crease in Mylar it is there to stay so you can never fold a Mylar sail.

Dacron is a great material for Jibs because it withstands abuse very well. Dacron is also a pretty good material for mains but because it stretches easier than Mylar most racing sailors like Mylar better.

And I forgot to say welcome to the forum and to catamaran sailing.

Keep One Hull Flying,
Mike Hill
H20 #791

The used boat I bought had a dacron jib and a mylar main sail. When the class began allowing mylar jibs, I was one of the first to get one - I like it very much better than the dacron version. It seems to keep it's shape better in the puffs. I may have had a too-well-used dacron jib and a more modern shape was used for the mylar one, but I have been very happy with the mylar.

I should note that I own a Mystere 4.3, on which the jib is very small (an 85 or 90% jib that doesn't overlap the main sail).

Best of luck - those Isotopes look like fun boats.

Thanks to everyone for all the great responses. I think I understand the differences a little better now.
I didn't realize mylar and dacron could be used together; I thought it was either one or the other.

Which cut would be better for racing: a square top or a pin top? and can this be done on a dacron and a mylar sail?
Some of the Isotopes I race with have pin tops and others have square tops.

Mike H- Thanks for the welcome. I was very glad to find this forum.
John W- Yes-the Isotope is a great boat and it definitely is a fun boat!

Hi Iso,
and welcome to the forum!
The numerous "personal opinions" is what makes the forum so interesting and informative. Like anything else, sift through the replies (mine included) and learn to apply the information as it applies to "you".
My opinion on sails concerns budget and use. "Generally" speaking....If you "don't race all that much" and "are concerned about expense", you may find that you are in the Dacron/Dacron end of the spectrum. If you "race a lot" and "expense is of no concern", you would probably be in the Mylar/Mylar end of the spectrum. If you "don't race a lot" and "expense is of no concern", you too can play at the Mylar/Mylar end of that curve. To make things even more interesting.....there are upper and lower ends; both in the Dacron and in the Mylar materials. Some Dacron cloth is "very nice" and some Mylar is "not so nice".

If you can afford the Mylars, then as another poster mentioned, have the sail built by someone that knows what they are doing.

I sail an awful lot, race in local distance races in the Gulf, and have been very satisfied with the Mylar (Pentex) Main & Jib designed and built by Randy Smyth.

In addition to the information you gather on the forum, talk to sailors that have your type of boat, sail in your particular area,
and maybe get to get on different boats set ups.

Hope this hasn't been confusing..I didn't intend it, id it was.

My input.
Dave

Iso,

Calling Laminate sails "Mylar" is a bit of a misnomer. The Mylar that compromises either side of a laminate sail does carry some load but most of the stretch resistance is carried by the scrim material that is inbetween the two Mylar outsides. The most common laminate ('mylar') sail material that folks are buying these days is Pentex and it will likely be what a sail maker like Calvert or Smyth would recommend for your mainsail. In the Pentex, there is an open crosshatch of Pentex fibers inbeded between two clear (usually) layers of Mylar. This kind of sail is usually opaque in color but can be tinted. Pentex is not much more than a stronger dirivitive of Dacron that is more suitable to be made into individual fibers. You can also get other kinds of mylar laminate sails that have Kevlar, Carbon Fiber, or other exotic fibers woven or in combination in place of Pentex. Pentex is largely affordable and very widely used for beach cats. Most all laminate sails are more expensive, but stronger and longer lasting than Dacron sails.

However, the Pentex and other Mylar laminate sails do have a weakness; they don't like to flex and are brittle (as someone mentioned before). The reason you see most jibs made from Dacron is that the constant abuse the jibs make as they tack and gybe past the mast and diamond wires would quickly break the stronger, but more britle scrim material. In John's case on his Mystere, his jib does not overlap the mast and mainsail and therefore does not go through the same kind of abuse. A laminate jib is more applicable in this case and the same is true for the likes of the Inter 20 or any other boat with a smaller, non-overlapping, jib. Dacron material, while not quite as strong or long lasting as a Mylar laminate, will handle bending and flexing better and last longer in a typical jib application.

Also of note: most laminate sails are built using a tri-radial construction so that the fibers can be better oriented along the stress lines. A laminate material is not strong when stretched at 45 degrees to the scrim pattern. As to the contrary, because Dacron material is stronger on the bias, these sails don't suffer much from being cut from large rectangular panels and a large cost savings can be had by using this construction method. See Murray's catalog for sails to see the different kinds of cuts.

I see that you also asked about getting a square head or a pin head. Hands down, the square head has more performance potential than the pin head. However, the tradeoff is that it might not be class legal for your Isotope or that you will, at least, take a portsmouth 'hit' (modification factor) for having a square head - if the OEM sail for your Isotope was a pin head. The square head acts like a taller sail in light air but when the wind pipes up, the square part will blow off and loose power at the top...exactly where you need it to. But if you do have a square top you will loose rating points, or potentially be dis-allowed in class racing.

You probably should check your class rules if you think you may want to race along side other Isotopes. Usually class rules specify that sails should be of a certain cut, material, and from a specific manufacurer. Anything else and you will not qualify for class racing. The other option is to plan for the boat to race in 'open class' under Portsmouth handicap ratings and the choice between square top, pin head, or material will not be quite as critical...just some thoughts.

Hey Jake I really appreciate the good detailed information.

I do have Dacron sails now and after reading all the posts here, the Mylar main, Dacron jib combo is what I'm leaning toward.

I will take your advice and talk to some more Isotope sailors on the class rules/legalities for square head vs. pin head but as far as I know, there isn't any modification factor for having a square head sail.

Some of the Isotopes have square heads and others have pin heads-I believe the Isotope fleet is not as strict on that point as other fleets may be.