Wanted - something like epoxy/fibreglass resin but easier to use, needn't be as strong

Diluted PVA? Not waterproof, though. Or check what they used on fabric car bodies, etc.

How rigid and how much flex does it need to support when dry?

It isn't the two part that causes trouble it is the heat generated by the curing and the relatively low viscosity at the early stages.

The latex resin sold for dipping mould making at craft shops might do what you want provided that the fabric is not subject to too much stress and strain. Might be easier to use the right sort of fabric instead.

Does the final product need to be waterproof?

PVA (dries transparent)

Semi waterproof

Roseal wet rot resin - one part with the consistency of water - solvent based so possibly not suitable with some fabrics.

This will dry hard so bending the cloth afterwards will crack it (the same will happen with fibre glass resin and perhaps anything else.

Not wishing to be obtuse, but exactly what properties are you after. Nothing is really rigid, even glass bends a bit before it breaks. How strong does it have to be? Like postcard material? Like metal shim? How thick can you make it? Does the final appearance matter?

Sounds to me like you may be on the right lines with "varnish". After all, even the skins of some WW2 military planes were covered with cloth and stiffened with "dope". Does anyone still make balsa aeroplanes covered with tissue paper and stiffened with "dope"?

Traditional shellac type varnish will be stiff, but brittle. Polyurethane is more flexible, but tougher and stronger. Are you looking at large areas?

A clue to the exact application might help!

I believe that dope covered fabric isn't UV stable.

Dope , No not you the stuff they used to use on fabric covered aeroplanes.

There are a few vintage planes around so perhaps a perusal of that hobby may yield something or NP may know of source via his hobby.

G.Harman

Whatever happened to banana oil?

Yes, though it might not be stiff enough. I've toyed with trying that for some other ideas so it would be worth a go anyway.

Quite. Household alkyd gloss paint waterproofs, but doesn't add much strength. Dope shrinks the cloth, which makes it seem rigid if on a frame. Non-shrinking dope aka banana oil doesn't.

NT

Yes

Presumably that's *not* waterproof.

That would probably do, it's not going to be in water.

I want it to dry hard.

No problem, this isn't going to be exposed to sunlight, at least not for any significant amount of time.

Well the $64000 question is 'how stiff do you want it?' as the actress said to the bishop, stirring her tea with the other hand...

Aircraft dope works to shrink but its not that stiff. Same for any other vbarnishes. If you actually THOUGHT about the problem you would realised that what gives stiffness is a relativiely inelastic material and some depth to it.

fibregflass is not glass cloth with a coat of resin, its a thick layer of resin given tensile strength by glass fibres

Stiff means thick, and thick means expensive. Yoiu coiuld gor example glue foam boiard to te cloth to make it stoiff.

I think you probably need to explain what you want to achieve, because thsi sounds like one of these 'if I wanted to go there, I wouldnt start from here' situations.

Plaster of paris would be far stiffer

Shrunk and airproofed with dope yes.

Aircaft lifetimes are not that long either in war...I beleive the average life expectancy of a spitfire was 6 weeks, representing perhaps

Not even long enough to need a plug change

Pointless for the purpose required here. It doesnt stiffen. Mereley airproofs and tightens

The technically correct but silly answer is plaster of paris.

How to make cardboard stiff - put plaster of paris between two sheets of it and call it 'plasterboard'

Can still be got, but very few people use it

But not very waterproof. If he said what he wanted it to use it for it would be a lot easier to suggest a sensible choice of material(s).

If I wanted something really strong and tough I would probably use a two part epoxy paint and several layers with glass fibre mat in between. For a small job a couple of tubes of long working time standard epoxy. It is OK so long as it is a thin coat when it is curing. Bulk it gets mad hot.

WW1 pilots life expectancy around two weeks. As they didn't carry parachutes every life lost was an aircraft lost.

Spitfire metal skinned - Hurricane fabric skinned