Spectra–Pros and Cons of Different Fabrics

Hi Dan: One of our friends has a ketch-rigged Deerfoot 72, and he is the process of getting new sails for her in New Zealand from the North loft. She has somewhat less than half the stability of Beowulf, and her rig is less aggressive in terms of potential for roach (she has standing backstays on both spars). I would like to get your comments on the pro's and cons of the different fabrics which have been offered. Regards–Steve

Hi Steve, There are 3 spectra fabric product lines at North Sails. They are basically tiers that range from highest performance to lower performance/price. High Performance in Spectra means more spectra and less dacron components, so more of the weight of the fabric package is made up of high modulus fiber. The tiers are:

1) Gatorback Spectra (what your current sails are made out of) 2) SR Gatorback Spectra (the SR 395TX fabric on Jim's quote) 3) SR Spectra (the 11.0 SR fabric on Jim's quote)

North cloth weaves 6 styles of spectra taffeta. The first 3 styles are very tightly woven. They have the highest spectra content of any taffeta in the industry. The other 3 styles are a little less tightly woven, the equivalent of what Dimension and Bainbridge use. Each group of 3 are comprised of light, med and heavy weights. The different weight spectra fabrics are made up of combinations of these styles and other components (mylar film, X pattern scrim layers, polyester taffetas in some cases). The Gatorback fabrics use only the very tightly woven components (first 3 styles) and the SR fabrics use combinations of the other 3 styles. The difference in construction is pretty subtle between the Gatorback and SR Gatorback tiers. In the weights required for Beowulf and Wakaroa both tiers of fabric are made from two layers of woven spectra taffeta(spectra warp and dacron fill) with film and an X pattern scrim sandwiched between them.

Comparing the 395TX and the 11.0SR fabrics in Jim's quote- both are the same weight (11 oz), but the 395TX has a higher spectra content (39,500 denier per inch compared to 33,000DPI). By comparison, your sails have a spectra content of 39,000dpi but the fabric weight is 9.6oz.

I know this is all very confusing and by attempting a simple explanation I think it might get even more confused. It is probably best to just reduce it to a cost/benefit argument. For the extra money of the 395TX Jim will get 20% more spectra at the same weight. The additional spectra translates into less creep so the sail shape will be marginally more satisfactory. On the other hand, either product is going to be orders of magnitude better than the sails he is replacing and the 7 batten construction and low aspect ratio are both in the plus column for shape retention. The SR 395TX also has the X scrim that gives the fabric a little off threadline support and an extra measure of rip stop strength. Both choices are on the very conservative side in terms of fabric weight and strength, especially considering the construction methods that NSNZ will use (assuming they are using the same spec as for the Sundeer 80 sails). If it were my money, I would have a hard time justifying the extra cost of the 395TX.

The dacron vs 11.0SR choice is a little easier. The 11.0SR is good for 4 years of sailing, the dacron more like 6 years. The 11.0SR sails will be flatter and more open leeched in breeze and better performing on all points of sail.

I hope that helps. Dan

Posted by admin  (November 30, 1999)

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