I'm one of the restoration staff at the Smithsonian Institution's National Air and Space Museum, and I took a look at our Bleriot XI this week to see what I could find out for you. First, I recommend you find a copy of our book on the subject: "Bleriot XI: The Story of a Classic Aircraft" by Tom D. Crouch, 1982, Smithsonian Institution Press, ISBN 0-87474-345-1. There's a fairly detailed description of our restoration in the book. It's out of print, but the usual sources of used books should be able to help.
Original factory fabric on the Bleriot XI was "rubberized Continental fabric." Our aircraft is covered in Grade A cotton applied on the bias on the wings, as is necessary for wing-warping aircraft, and the fabric has French felled seams. The fabric is on the straight-of-grain on the tail surfaces and fuselage. It's held on the flying surfaces with what appear to be reed or narrow wood strips: 3/16" wd. on tail and outboard wing, 3/8" wd. on inboard wings. The strips wrap around the leading edges and are tacked at irregular intervals of 1-1/2 to 2" spacing. There are NO tapes on the ribs, but there are straight edged, straight-of-grain tapes around the edges. Factory finish was varnish, but we used clear dope to avoid yellowing and potential fabric damage. I personally would be very concerned about the use of any finish on a flying wing-warping aircraft -- I suggest you get your local FAA office or equivalent to advise you on that subject.
I'm told there is more than one Bleriot replica in the works. Which one is yours?
I hope this information is useful to you. If you need further information, please contact me here or directly.
Cheers, Anne McCombs