Epoxy coating?

[Traveler]

Anyone have experience with epoxy as a coating for 9 ounce polyester? Have read posts elsewhere (from 5 or 10 years ago) where people have apparently used it successfully over very lightweight Dacron polyester cloth, including with a layer of fiberglass cloth, but it doesn’t seem like a very common practice which makes me hesitate. But I have done some small samples and it seems very promising - has anyone here given this a try in the past? If so, how did it work out? 

Thanks

Tony

[Kudzu]

Not trying to be insulting but  Why?

 

The cloth with a waterproof coating works just fine.  If you are going to be using it in a place where you need fiberglass you should be looking at something other than Skin on Frame.

 

It will ad a lot of weight which defeats one of the biggest advantages of the these boats. It will add a lot of cost and a lot weight and then you really get no advantage in return.

 

I have paddled hundreds of miles in many skin boats and never damage but one and I was using it is mild white water which I tell everyone not to do because it will ruin the skin.  And it did.

[Traveler]

Thanks Jeff - I guess the “why” is mainly because I have a lot of epoxy on hand and I am familiar with how to apply it. It is more expensive than paint, but not that bad and quite a bit cheaper than something like Corey’s Goop (which after my last kayak I have decided I won’t use anymore - just too hard for me at least to get a decent-looking application and you can’t go back and touch things up once it dries). 
 

As to weight, it probably would be a bit heavier, but not that much if you just do the hull and paint the deck - probably one quart would cover the bottom of the boat below the gunnels with 3 coats, so around 2 pounds or so for my 15 footer - that plus a light coat of paint or varnish for UV protection can’t be much more than the weight of 4-6 coats of paint.  And likely not more than a full application of Corey’s Goop, which I have measured at 3 pounds total for a kayak my size.

 

Anyway, I agree with your points, but willing to live with a small weight penalty (and since I already have the epoxy on hand there really isn’t a cost issue). My main concern with trying it is whether it would stick well to the cloth over time. 

 

 

[Traveler]

I  should also say that I am talking about just epoxy as a coating, not fiberglass cloth as well. 

[Hirilonde]

The characteristics of a SOF boat are related to the design and materials used. The strength comes from the fact that the frame can twist or bend and absorb impacts.  The skin is pliable, so it doesn't crack when impacted. Cured epoxy is brittle and will make the skin brittle. Now when you bump something the skin cracks because it can't give. The same could happen if the frame twists or bends as well. To top it off, epoxy has no UV protection.  It breaks down when exposed to the sun.  You would have to paint it after epoxy any way.

 

In total quality management quality is defined as "conforms to requirements" Paint conforms to the requirments, epoxy does not. 

 

If you want a bomb proof kayak, you want ABS plastic, or Kevlar composite.

[Traveler]

Yup - agree that flexibility is critical to SOF performance and durability, but a couple of thin coats of epoxy over the skin doesn’t seem like it will change that very much. Have you ever taken a single piece of cloth - polyester or nylon or even fiberglass - and wet it out with epoxy on its own (ie not bonded to anything)? Once dry It is stiffer than uncoated cloth, but still waterproof and very flexible - you can bend it, fold it over on itself, even tie a strip of it into a knot.  
 

So with a couple of thin coats I am not worried about brittle in the sense of shattering on impact. Epoxy is less flexible than the cloth though (as is paint or polyurethane), so a question I have is whether the bond might work loose over time since it probably won’t penetrate the fabric as well as some coatings.
 

I have looked high and low for any information on use of epoxy coatings on SOF, and can’t really find anything here or elsewhere on long-term, “real life” experience, aside from some older posts on other forums from a few people who have done it and claimed it works fine, and others who warn that the world will end if you try it. But it’s pretty clear that there are very few hard and fast “rules” for SOF builds (life would be so much easier if there were), as is evidenced by the wide variety of coatings that people swear by, all for very good reasons.  So I’ll probably invest $50-$75 worth of epoxy and cloth in an experiment on this.  I’ll at least satisfy my own curiosity, but I suspect it will actually work out ok. If it does work I’ll post my impressions here if there is any interest -  if it is a miserable failure you will probably never hear from me again . 

[Hirilonde]

I think Jeff asked the key question:  why? What do you figure it will do better than paint? Besides add weight.