How long does a dry fly need to float?

[EdD]

... if you do the math, given a 3 mph* current speed, 10 seconds would result in an approximate 44 foot drift and given a 4 mph** current speed, 10 seconds would result in an approximate 58 foot drift.

That would suggest that your guess above is a good one, at least for the vast majority of fly anglers in the vast majority of situations.

John

*3 mph = 5280' x 3 = 15840' / ( 60 seconds x 60 minutes = 3600 ) = 4.4 fps x 10 seconds = 44'

**4 mph = 5280' x 4 = 21120' / ( 60 seconds x 60 minutes = 3600 ) = 5.8 fps x 10 seconds = 58'

John, you show your work beautifully and get full marks.
For those of us who want to cut to the chase, 1 mph = 1.46666666 ft/sec. or a little under 1 and a half fps.

Next math problem: If the fish ignoring Ed's fly is 21 inches long and the stream is flowing 1.3 mph, how long will the fly take to pass down the length of the offending fish?




Ed