[caldrail]

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Was the canvas cotton? I know the british used irish linen, perhaps some may have even tried silk, flimsey as those machines look today they're used the best they could for the time.

Irish linen where-ever possible. It was the most suitable material. Bear in mind that as antiquated as WW1 aeroplanes seem to us, they were cutting edge technology back then and not cheap. I've seen the cost of a Sopwith biplane quoted as £700 in an age when munitions workers, highly paid specialists doing dangerous work, earned between £6 and £10 per week.