I happened to learn something the other day and it’s applicable to fly fishing, well casting actually. Maybe some of you astute casters, scientists or just plain smart folks know the answer:
‘What speed does the tip of the leader reach and what causes the ‘crack’ sound on a backcast?’
H.[/i]
Mach 1
I would agree with Jerry. Since there is NO apparent other factor creating the “pop”, it has to be the tip breaking the sound barrier at approx 770 ft/sec
Sounds good to me.
Mark
Way to go Jerry, right on the money, Mach 1!
Yup. You got it.
H.
Same as snapping a bullwhip…
WELL, is it a good thing :roll: :roll: :roll:
WOW…I can do that :oops: :oops: :oops:
In that case judging by the sound of my back cast I Must be a crack fisherman. :lol:
Followed by “D*** I lost another fly!” :lol:
You broke your fly off 
A normal backcast does not exceed 100 ft/sec. and takes about one second to unroll. You can easily follow the fly with you eye. You can also create that crack at will by changing the timing of when you start your forward cast. The crack you hear is due to your changing the direction of the fly in a minute fraction of a second.
Since the speed required to produce a crack is greater than 700 ft/sec, the interesting question is, “For what distance is the fly traveling at a speed of more than 200 ft/sec.?”
‘What speed does the tip of the leader reach and what causes the ‘crack’ sound on a backcast?’
Not waiting long enough for the line to fully extend behind on the backcast, if I recall correctly.
Bingo! 
For the beginners here,“If” you hear that sad"cracking" sound it means.
A. You werent paying attention when your casting instructor gave you that “and what are you doing now”? look. :?
B. Have started your forward cast before you have allowed the line to load correctly. :shock:
C. Have complete disreguard for the price of a decent fly, as this practice tears them up in very short order. :twisted: