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Re: Skin-on-Frame: Material - Fabric

Dyson, Baidarka & Company
435 West Holly St., Bellingham WA 98225
telephone: 360-734-9226 — fax: 360-671-9736

Kayak Skin Materials, September 2002
Over the past 22 years, we have sold 38,189 feet of kayak skin material—now covering some two thousand boats. This sheet makes no attempt to ex­plain how (or why) to cover kayaks with these mate­rials; it is just to help you select which of the avail­able materials you may want to use. Before discuss­ing specific fabrics, there are three general ques­tions—closely related and without definite answers—to be discussed first:
1) Nylon vs. Polyester. About 3/4 of the material used so far has been nylon (polyamide); but use of polyester (Dacron) has been growing in the past few years. There are two reasons for this: a) we are selling more material to builders of traditional wood-skeleton kayaks, and dimensionally-stable polyester is less likely to distort lightly-constructed wooden frame­works by shrinking up too tight, and b) more builders are using one-part or water-based polyurethane coat­ings, whose lesser elasticity and adhesion is better matched to polyester than to nylon. (The coating should be more elastic than the fabric to which it is expected to adhere). If you use an elastomeric, solvent-based coating like Hypalon (chlorosulfonated polyethylene), Neoprene, or one of the elastic but very expensive 2-part polyurethanes, however, nylon will produce a tougher, more damage-resistant skin. Nylon’s greater elasticity makes it easier to cover complex curves, but the looser-weave polyester fabrics drape pretty well too—especially in twill. Bottom line: polyester is better for the perfectionist; nylon is better for those who paddle loaded kayaks into rocks. Most kayak builders fall somewhere in between.
2) Shrinkage. An essential characteristic of all the fabrics we sell is that they will shrink. The question is how much! Shrinkage usually ranges somewhere between 1% and 5%. Getting the tension right re­quires careful tuning—see what happens if you loosen or tighten a guitar string by a quarter of an inch. Nylon’s behavior is especially complicated be­cause it tends to loosen (even when coated) by ab­sorbing ambient moisture and then tightens as it dries out. So you are aiming for middle ground: the skin (before coating) should fit snugly, but not drum-tight. As one builder describes it, “If you drop a quarter on it, it shouldn’t bounce.” From the point of view of the boat’s structure and performance, it is better for the skin to be too loose than too tight, but from the point of view of the builder, too loose (suggesting sloppy workmanship) is worse. You shrink nylon by apply­ing moist heat (wetting it and going over it with an iron so that you are steaming it without drying it out). The moisture relaxes the skin while the heat shrinks it, so that when it dries out it will be taut--hopefully not too tight. If you attempt to shrink nylon with dry heat—either with an iron or a heat gun--the combined drying and heat will tighten it up so much that the fibers are permanently stretched, and when it returns to room temperature and absorbs ambient moisture, it will be looser than when you started out. Polyester, however, which does not absorb moisture, can be shrunk with a dry iron (safer than a heat gun) and the resulting tension remains stable: “what-you-see-is-what-you-get.” Some people view nylon’s idiosyn­crasies in response to moisture as a disadvantage; some people view it as an acceptable part of a craft whose relationship to water should be that of a living thing.
3) Coatings. No coating (so far) is ideal. In general, more poisonous solvent-based coatings perform bet­ter—especially in sticking to nylon—but water-based coatings can be toxic too. The main reason to favor polyurethane over Hypalon is that it is more widely available (as floor coatings, concrete coatings, etc.) and results in a translucent skin. In general—and there are numerous successful exceptions—if you want to use a translucent polyurethane coating that is a good reason to choose a polyester skin. If you choose to use Hypalon—best, in our opinion, for long-term du­rability, both because of UV resistance and because the surface can be easily replenished over the years—that is a good reason to favor nylon skin. As for which coating to use on the lighter fabrics: Hypalon is definitely more robust. But if you use translucent urethane, the kayak is slightly lighter, looks a lot lighter, and tends to get treated much more carefully, and so may last as long or longer in the end.
Now the specific fabrics (weights in ounces per square yard, and prices in US Dollars per lineal foot):
8N67: 8-ounce Nylon, Oxford weave, 67-inch width. One of our most popular fabrics, easy to work with and very low cost. The supply is reliable and it is usually in stock. The low cost is because it is “sec­ond” quality which means there may be very occa­sional minor cosmetic flaws. If we find a serious flaw in rolling out your order we stop and go on to the next acceptable length. The weave (Oxford is your stan­dard over-and-under symmetrical weave) is just about right—loose enough to drape acceptably and tight enough to hold a seam. Shrinkage is moderate, and well suited to lightly-framed wooden boats. $2.00
9PE66: 9-ounce Polyester, twill weave, 66-inch width. This is our lightest polyester—and still more than twice the weight of the 3.7-ounce Dacron com­monly used for covering aircraft. Since the fabric has not been shrunk at all at the mill, the weave is very loose and it can be difficult to work with (in general, the heavier fabrics are easier to work with than the lighter ones). And since it shrinks considerably, seams have to be sewn (or stapled) carefully to avoid pulling the weave apart. A few people are very happy with this material--especially Harvey Golden, who has used it in covering his growing series of replicas of the kayaks he has been surveying at museums around the world. The twill weave (same as denim) holds coatings well, and because of the light weight, even with minimal coating the surface remains quite smooth. $2.00
12NB65: 12-ounce Nylon, 2x2 basket weave, 65-inch width. This is classic “ballistic nylon”—now popularized in sporting goods and luggage, if no longer used in bulletproof vests. Basket weave (sym­metrical over-and-under, but with two bundles of fi­bers at a time) makes for a less-smooth but pleasantly textured surface. Weave is a bit loose, and shrinkage is moderate. Cost is low. We do not have a reliable supply, but presently have lots in stock. $3.50
12N75: 12-ounce Nylon, twill weave, 75-inch width. Our most popular fabric, middle-of-the-road all around and reliably supplied. Very user-friendly weave, moderate shrinkage, drapes well, holds seams. Twill weave is tough and good at holding coatings, resulting diagonally-ridged surface looks good on deck where less coating conceals the weave. Well suited to wood-framed baidarkas that will be actively used. Near-identical sibling to the slightly heavier 15N72. $5.00
13PE79: 13-ounce Polyester, Oxford weave, 79-inch width. This was the first polyester fabric we distributed, and it has developed a small but loyal following over the years, led by custom kayak-builder Bill Low. This material has been almost fully pre-shrunk, so the weave is exceptionally tight—making it somewhat stiff and difficult to use. Because of the dense structure, it takes very little coating to saturate, but there is very little porosity to encourage the coat­ing to mechanically adhere. Due to UPS length re­strictions, it is much more economical to ship small quantities of fabric folded than rolled, but if you re­ceive this material folded, unfold it and roll it up smoothly as quickly as possible, since like permanent press polyester trousers, it tends to hold a crease. $6.00
14N88: 14-ounce Nylon, Oxford weave, 88-inch width. This material will probably be discontinued when the current supply runs out. It’s a tough, dense cloth that has been used (predominantly in 65-inch width) on many kayaks over the years, but we have not found enough demand to purchase it regularly in large quantities and have been focusing our attention on products from other mills. The main reason to use this material (over the 12 or 15-ounce twills) is if you have a need for the extra width. $7.50
15N72: 15-ounce Nylon, twill weave, 72-inch width. We have been supplying this material to builders since 1982, and it has proved its worth on many hundreds of boats—ranging from short retrieval kayaks and surf boats to 25-foot aluminum-framed triples whose builders want to keep the boat light enough to be easily lifted on top of a car. It is slightly heavier, but otherwise identical, to 12N75. Almost always in stock. $6.00
16PE82: 16-ounce Polyester, 2x2 basket weave, 82-inch width. We acquired a large run of this material about a year ago, and it has been receiving good re­views so far. Weave is a bit loose, but it will still hold a seam and of the three polyester fabrics available it is the easiest to use. Shrinkage is moderate and easily controlled. The price is excellent, especially given the extra width. $5.00
26N68: 26-ounce Nylon, double weave, 68-inch width. An amazing fabric, which we discovered in 1980 and which has withstood decades of severe abuse on many large, heavy boats. It is the heaviest material we sell, but it is also one of the easiest to use. The thick, interlocking structure makes it behave more like real sea-mammal skin than any­thing else we have seen. Coatings penetrate and bond well, and because of the layered structure the surface can suffer serious abrasion and the skin will still not leak. Unfortunately its manufacture has been discon­tinued, but we bought up the last production run of this material and should have it on hand for many years. Also unfortunately, it is available only in 68-inch width, so wider doubles and triples require a small patch on deck where the two sides of the fabric don’t quite meet. Otherwise perfect for covering large, hard-working baidarkas—and umiaks, too. $10.00
George Dyson 9/14/02

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Skin-on-Frame: Material - Fabric
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Re: Skin-on-Frame: Material - Fabric
Re: Skin-on-Frame: Material - Fabric