Bicycle Cape can be Water Proof, because like an Umbrella there is ventilation under it..
As far as I know, ripstop nylon doesn't require any tech spray to keep it waterproof.
Then it would be urethane coated to be water proof
(mill costings peel off in time, an impregnated silicone-nylon will last longer)
They , capes/ponchos could be made of light weight material, they are for hiking,
but at much wind speed they start flag-like flapping..
JRA in Oregon Coastal rain Squalls I'm fine..
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