> I was reading Thomas Hill's "Ultralight Boatbuilding" and in it
> he recomends sheathing the outside of the hull with Dynel or Xynole,
> because they have better abrasion resistance than fiberglass. Does anyone
> know anything about these fabrics? Would they be better than glass on the
> outside of the hull? How much do they cost? Where do you get them? What
> doe the look like? What is their weight? Have I missed any questions?

> Mike, I read about Xynole-polyester in Reul Parkers book "Sharpies" His particular disgust with fiberglass leads him to recommend Xynole for sailboats. it is a regular weave like the 6oz glass we all use except that it drapes a little easier and wet's out like a T-shirt. I don't know if it is different than the polyester cloth I got from JR Sweet. You can get Xynole from Defender industries as well as Dynel. Dynel is a little different,it soaks up even more resin than polyester cloth. These synthetic cloths are good for bigger boat decks and possibly hulls because they give a fair amount,so not exactly for compressive strength but good tensile strength. Although not as much as glass and much less than Kevlar. WeNoNa canoes have a special layup that is some combination of polyester/glass cloth, I think some British boats have a "Diolene" layup that is also a polyester cloth in addition to the glass.

Guegeon Brothers (West Systems) have a great quarterly publication, in one of them they describe test panels for different layups for a very large restoration I think. In it you will get some sense of the weight and toughness of verious layups.

A couple years ago i was all excited about these materials as possible replacements or adjuncts to fiberglass. Talked to a sales rep at Defender about Xynole and Dynel, he relayed a story about a camp counselor that wanted to make some very tough canoes: so he built three small prototypes,one with glass on the bottom,one with Xynole , one with Dynel. Tied them to the back of his car and dragged them around the camp. The glass one was worn to the wood, the Xynole one was ok, the Dynel one kept getting dragged longer as it was holding up too well. I may be mangling the storyline a bit but essentially Dynel is very tough with regards to resistance.

Here's the downside, althought the stuff weighs in around 5oz it soaks up resin like 10oz glass cloth,especially Dynel. It is good stuff since it is less likely to fracture and let water intrude into the wood,but it has less comppressive strength so if you need panel rigidity you won't get as much as glass. It is very hard to sand cleanly, not as bad as Kevlar, but much worse than fiberglass.

My true confession, I used it on the hull of my clc 16 over 4oz S-glass, in retrospect I should have reversed the order, glass over polyester. The boat weighs about 50lbs. I could have made it lighter with the same stuff but a little more judiciously. It really isn't needed up the sides if abrasion is your concern. I suspect that 12 oz of glass would have weighed the same. I also have slid over oyster shells without going through the polyester.

Mostly I think this stuff has application in specific areas, the weight trade-off is pretty big for hull covering. I think someone at J.r. Sweet said if you did a hand layup with Dynel you could add another gallon of epoxy to your boat,not sure if that was hyperbole but after using Dynel in wear strips on the bow and stern I could imagine it, the stuff looks a little like t-shirt material and swells up with resin big time, if you try and squeegee it out , it looks fuzzy and dry, I plastic wrapped it down and that worked well. I'm guessing here but after looking at the wear on the stern strip of the boat I used the Dynel on and comparing that to another boat with a strip of glass tape and 6 oz glass it looks like the Dynel hasn't worn much, the glass is about 1/3 worn. In the test panels I broke up polyester didn't allow fractures and cracks to propogate half as far as they did in 6 oz cloth. One layup made from 4oz s-glass over 5oz polyester was so tough that the panel could be bent every which way but not come apart, another test panel with 5oz kevlar delaminated at the first layer of the plywood. So I'm thinking that the deformable characteristics of polyester make for less stress risers at the surface, kevlar just doesn't give at all.

So my take now on these fabrics is they are kind of a poor mans kevlar, good for vacuum bagging in all glass layups or for specific situations requiring toughness. But still too much of a sponge to replace glass.

One of the applications for Xynole , if you didn't mind the weight penalty, would be for a very big person ,,,but then again careful use of extra layer of 4oz s-glass might just be just as good (for twice the cost). If you beat the edge of the deck of your kayak with a sharp paddle Dynel might be good there, but mostly a 2"x24" strip on the ends id where it works for me.

I din't check your original question ,,,did Thomas Hill talk about this fabrics as skins or over wood?

I'm sure I've forgotten something,,,,,there's got to be big boat builders out there that could answer this more concisely than i have.