The windows are hinged at the top and have a gasket that seals against the outside aluminium of the trailer, so the trailer is mostly water-tight. But the cross-section of the wall is exposed where the window openings were cut. There is nothing sealing/holding the aluminium, wooden sill and interior sheeting together around any of the openings. Total wall thickness is ~1-5/16" at the front, maybe a bit thinner on the sides. The corners are have a radius, so I need something flexible. Ideally I'd like to be able to buy the materials in Canada.
I was trying to find a rubber U-channel gasket, but had difficulty finding one with a gap that wide. Next thought was a 4" butyl flashing tape to wrap around the exposed edge. But the edge isn't entirely smooth, so I thought the tape might get punctured. Current thought is a maybe mould my own U-channel trim with oogoo, but I'm worried about final appearance and longevity.
This is my first travel trailer, so I'm hoping I'm missing a super easy fix/product that is the actual correct material to use. If not, I'm hoping you creative builders can offer some "why didn't I think of that" ideas. Thanks for your time!
Thanks for posting though. 
