Winnebago siding. When did they become fiberglass?

[GOWINIGO]

So I realize now I should have started/title a thread with the question at hand. When did our bagos come sided with fiberglass? I have a 76 d21 brave that has flat(ish) fibergass sides. The rear looks like the normal bent aluminum. It looks almost like they applied a glass sheet over the original paneling due to the paneling having a ripple. Ill shoot a photo soon.

[Rickf1985]

I didn't think it was until the newer streamlined body style in the eighties.

[legomybago]

Aren't the 1978 Braves smooth sided? Not sure if that's fiberglass, or aluminum though?

[GOWINIGO]

This is a 76 and it is fiberglass