modern equivalent to doped canvas?

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Dav3xor

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I've built a few SOF kayaks, I used 8oz polyester from the kudzu craft guy -- it shrinks better than nylon and is lighter than canvas. Aircraft fabric works but its pretty thin, might be a little fragile if you drag it across rocks.
 

Riggerrob

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Caution:
Most of the fabric currently sold as "ballistic cloth" has diverged from the original Military Specification for the ballistic nylon that was used in flack vest.
MIL SPEC C-12369, Ballistic nylon cloth weights 13.5 to 15 ounces per square yard. It is woven 2 by 2 of 1000 denier thread. Modern bullet-proof vests are made of Kevlar or Spectra (polyethaline) supplemented by ceramic plates.
15 ounces is way too heavy for kayaks.

I would use a 400 denier Dacron. Why Dacron? Because it is easier to heat-shrink and lasts far longer in sun-light.

Orotex 600 fabric weighs 3 ounces per square yard and Orotex 6000 weighs 4 ounces per square yard. That roughly equals 300 denier and 400 denier fabric.
 
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Aesquire

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Second the nomination for Dacron ( polyester ) and suggest the newer less hazardous solvents/coatings.

Polyester has replaced cotton etc canvas in aviation for a reason. Lighter stronger and less dead from poisoning builders.

I haven't used the New coatings, so don't have a brand name suggestion, but uncertified Dacron in the "ultralight" versions from aircraft supply houses is the cheaper, Functional recommendation. Fabric store polyester has generally been pre-shrunk at the factory and won't work as well. If it all.
 

Pilot-34

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Most of me is in IL but my hearts in Alaska
Oh I do like the idea of a glass bottom boat!
I built an Aerolite single paddle canoe from Platt Monfort's plans nearly 30 years ago, and used the lightest un-certified Dacron from Aircraft Spruce to cover it, glued on with Stitts products, and heat shrunk it per the PolyFiber instructions. I filled the weave with marine spar varnish. In the water, it was transparent enough to see the bottom whizz by.
 

Michael Silvius

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FWIW. The earliest pioneer of skin-on-frame kayaks to use synthetic fabrics for his kayaks was Geroge Dyson.
https://images-na.ssl-images-amazon.com/images/I/71hPuRppnXL.jpg

All the fabrics he sourced were "greige" state fabrics nylon and polyester used in paper mills as giant filters. Greige means that that they are pulled off the production line before the finish process that shrinks them. He bought them in bulk and price was very reasonable. In the kayak building community he became the retail source for the products. His lightest fabric were on the order of 8 oz/yd and went as high as 30 oz/yd. All too heavy for aircraft use. More details on the materials and the distinction between polyester and nylon handling here:
 
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Victor Bravo

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I don't know anything at all about boats, but I am a world class Ph.D expert on the cause and effect accidental puncture of fabric. It's annoying enough when the vehicle is airborne, but I can imagine it being a lot more annoying if waterborne.

This sounds like a 'poster child' case for thin Kevlar fabric and whatever kind of resin, varnish, wax, etc. to waterproof the weave. Might have to stretch the fabric taut with clamps and glue instead of heat, but it would be worth the effort and cost if you prefer being above the water level..
 

Michael Silvius

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This sounds like a 'poster child' case for thin Kevlar fabric and whatever kind of resin, varnish, wax, etc. to waterproof the weave. Might have to stretch the fabric taut with clamps and glue instead of heat, but it would be worth the effort and cost if you prefer being above the water level..
Interestingly enough VB, the polyurethane coated synthetic fabrics in the kayak application stand up extraordinarily well to abuse. You really have to try to puncture them. And I speak from personal experience. There are videos on YT where someone tries punching a hole in it with a screwdriver and fails. Failure points tend to be abrasion on the keel from repeated scraping on rocks and ice, so patches are possible when you note the first traces of wear. That said, because weight is not as much a concern as on aircraft, the fabrics used are an order of thickess about four or five times heavier than aircraft grade fabrics. The major advantage being their heatshrink capability to conform to the compound shape of a kayak hull. Again in the use of modern polyurethane coated synthetic fabrics are a substitute for marine mammal skins used in the original SOF kayaks as the local Clam Warden would have something to say if we tried to harvest those today. a (36).JPG
 
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Bigshu

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Ceconite, Plastidip waterproofing then spar varnish for UV
I'm not a ceconite fan, but I like the idea of the plastidip. I wonder if the flex seal stuff you see everywhere is easier to apply ( comes in spray, or brush/roll on, or dip).
 
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Riggerrob

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I don't know anything at all about boats, but I am a world class Ph.D expert on the cause and effect accidental puncture of fabric. It's annoying enough when the vehicle is airborne, but I can imagine it being a lot more annoying if waterborne.

This sounds like a 'poster child' case for thin Kevlar fabric and whatever kind of resin, varnish, wax, etc. to waterproof the weave. Might have to stretch the fabric taut with clamps and glue instead of heat, but it would be worth the effort and cost if you prefer being above the water level..
Kevlar does not last vey long when exposed to Ultra-Violet sunlight. It requires UV-blocking dope or paint, etc. for longevity.
A disadvantage with Kevlar is that it cannot be heat-shrunk to fit the complex curves of a kayak hull.
I would go for a newer material like Spectra (aka. Microline, Dyneema, cuban fiber) because it is as strong as Kevlar, but can be heat-shrunk. Cuban fiber is based upon the same polyethelene as plastic shopping bags. It was fashionable for parachutes lines starting in 1990, but faded after we learned that it shrinks with heat. Cuban fiber is favoured for ultra-light back-packs. The challenge is sourcing greige-state cuban fabric before it has experienced the later stages of heat-shrinking and coating.

Forget about the latest parachute materials like Vectran or High Modulus Aramid because they do not heat-shrink.
 
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