Recent posts on how a Catskill dry floats on the water reminded me of a picture I have had for many years. A RW is not a Catskill pattern but the proportions of the dly in the picture is that of my understanding of a Catskill pattern, Tail is shank length. Hackle is 11/4 to 11/2 hook gape.
Art Flick in his Master fly tying Guide describes how the dry should float. "When the fly hits the water the point of the hook acts as a keel and the fly will ride on the tail and hackle with the keel
just on the water.If the tail is too short, the fly will sink tail first. If the wing is too far forward the fly will land on its eye. If its wing is too long, the fly will lie on its side.
The picture of the Royal Wullf in this Scientific Angler Ad is floating as described by Flick. In my experience, the fly, if properly tied will float in this manner. How long it will float in this manner is dependant on the roughness of the water and how much water is soaked up by the fly.