|
Hi Gordy,et.al.
Interesting thread to me - I read from start to finish and what follows is embellishments, corrections, and scientific remarks.
1) Crise says sometime about how a line falls - "Although a stationary loop dropped from normal height might
hit the ground in .375 sec., a good loop will drop very little until it straightens. Watch any good caster carrying 80 ft. of line. If gravity was the only force acting on the line the loop would hit the ground before it went very far." and Miller says 2) "I agree that we have favorable lift dynamics
helping reduce the effect of gravity to SOME extent, but they don't compensate 100% IMHO. The work done " The line will fall about 2 ft in .375 seconds - a trivial distance. A good thing to do is just simply to memorize the simple equations for free fall from rest (since readers here aren't aspiring engineers its OK to us rote memorization). They are ==> 1/2gt*2 and sqrt(2gh). Just a few factoids. There is a 2 ft fall in the first .375, 7 ft fall in the next .375 seconds and for a realistic time of about 1. second for one side of a cycling series of false casts the fall from rest is 16 ft. Only on the last figure is drop height much of an issue and you don't have to generate much lift through the rod tip to counteract a 16 ft fall if your're just casting on grass (5 ft up to your hand, another 6 ft above that to the rod tip under heavy rod flex, a couple of ft to the top of the loop and it is necessary to counteract 3 ft or drop - not hard to accomplish with only a very modest lift from the rod tip. No magic required here.
I sense some misapplication of information that is in the fly casting channels. I am aware of a nice little paper Noel Perkins wrote about skin friction drag and the lift derived from that effect. Some interpretation of that information is necessary to put that information into context. The context and interpretation is that the effect is very insignificant and you can completely ignore it. When I first saw the analysis I had an inner feeling that something more need to be explained but did not reexamine the analysis. Several months ago it crossed my mind and I thought there was something to follow-up on but on reexamination the concern I had was answered. However I have just recently realized the impact of this analysis. To his credit Noel accurately describes the impact of his analysis right in the title to the paper but I guess it's signficance is illusive (otherwise it would have been apparent to me on the first reading) - the title includes words like "drag induced lift on the front loop". These minor forces (fraction of a "g") act on only about 3 ft of flyline and the remaining 57 ft are acted on by gravity in the normal way. This is maybe a 1% effect and you might just as well simply forget about it. There are dominant aerodynamic effects that can be called into play - for kicks I recently did a hand calculation deriving 160% of gravity over almost the entire flyline. This effect squares very well with I observe in actual casting but when seeing these effects in casting I hadn't given it any thought in the past. If this hasn't been discussed here I'd like to know and I can try to develop a sound layman's explanation. There is, in my opinion one other dominant effect that I have run into in my own experiences which I have given a careful examination using physics and time permitting I can describe that as well.
I must run to appointments but hope to share thoughts on the remainder of thread as time permits.
Regards - Server Sadik
|