Indeed. I believe that Grendel's suggestion does it. Well done, gang ! And thanks a lot. Your help is much appreciated.

Jean-Paul

Andy - That makes sense..you would want some sort of waterproofing to prevent the wings from retaining water and some way of pulling it taut over the frame.

Grendel - that dope or, taughtning dope, as they called it did all that. Some celluloses based compound.
Awfully smelling stuff. That why the name.
Andy