You need to test your cloth to see how it reacts to water. Cotton gets tighter when wet. Nylon gets a lot looser.
You need to test your coating to make sure it will stick to your cloth and not be wrecked by water.
If your cloth gets loose when wet, your coating needs to fully encapsulate the cloth fibers.
A bad cloth/coating combination can wreck a boat skin.
A wrinkly skin is slow and makes a bendy weak boat.
Nylon requires particular attention. It elongates ~10% when it gets wet. That's why your tent is so saggy in the rain and so tight when the sun comes out. If you use nylon for a boat skin your coating has to fully encapsulate the fibers and keep moisture off them. Most random coatings don't do that.
I think my cloth is polyester and I think it won't elongate when wet. I test it anyway.
I cut a strip of cloth a yard long. I wet it and measure it again. It's okay. I paint a dry piece of cloth with the varnish I intend to seal it with. I put it under a lamp to dry because I'm in a hurry. The coating seems to soak in and bond fine. It's not brittle, but that usually develops later. Wolfgang
tells me it's good stuff. He's tried and seen almost everything.
Some combinations that I've seen:THIS IS A TABLE - I WISH IBLES LET ME USE SPACE ' ' CHARACTERSCloth Coating
Cotton Anything- It works great and needs to be replaced in 5 years.
Cotton Rubber latex roof paint (Cozy Boat, Wolfgang)
Cotton Catalyzed Polyester resin mixed with Rustoleum (Boston Currach Club)
Cotton Thompson's WaterSeal, then Oilbased paint. (Wolfgang's book "Aleutian Kayak")
Nylon Neoprene thinned very much, followed by Hypalon (George Dyson's book "Baidarka")
Acrylic Artist medium is a disaster (me)
Just Anything. Most things don't stick or don't seal.
Nylon Varathane #93 Clear Satin Spar Urethane (Wolfgang, Follow his directions
Polyester Varathane #93 Clear Satin Spar Urethane (Wolfgang, this boat)
Polyester Anything is survivable. Even if it flakes off the skin will stay tight and you can re-coat.
Epoxy. Most epoxies are too rigid and the skin will crack. The coating needs to be more elastic than the cloth fibers.
Polyester resin. It's also too brittle, and It doesn't adhere or encapsulate as well as epoxy.
Exceptions to the last two rules are where the cloth is fully supported by planks or foam. Then you can use hard resins to "fiberglass" it on there. In the good old days they called fiberglass FRP(fiber reinforced plastic) because they used all kinds of cloth, not just fiberglass cloth.