by dahlberg » Thu Mar 24, 2011 3:18 pm
Sorry, but I have to respectfully tell you that you are laboring under a false assumption. The physicist and advanced fiber composite guy who brought graphite technology from england to the usa back in the sixties helped me research this same question when I was in my late teens. The explanation I gave you is the one he and I figured out.
Quick fly line history.
First lines were level lines. No taper. If you were a really good, high speed caster, they kicked horribly when they turned over due to the amount of energy generated when they change direction. In order to mitigate this, the mass at the end was reduced, or tapered. Most manufacturers tapered both ends and thus the double tapered line came into being. It made them slow down. It also made a line that was better for roll casting.
But, because these lines stayed "fat" beyond the 30 feet of "head" needed for creating enough weight to load the rod the line was designated for, they did not shoot very well. They simply generated too much friction. (It's the friction in the line that makes the loop turn over--it turns over because the lower section of the loop is traveling slower than the top part. In fact, if you had zero friction on the line as it passes through the guides, and there was no gravitational effect on the line being shot, the loop would never turn over!)(unless of course you stopped the line with your hand)
Fly line makers began making weight forward lines to reduce friction on the running line.
If you want to prove the taper thing to your self, just take a tapered fly leader in your hand and try to cast it with out a rod. Now turn it around and do it backwards. You will see what I mean.
Actually, if you discount the short forward taper, which is included for reasons explained above, weight forward lines are tapered backward! The bug tapers, etc are designed with a shorter forward taper based on the exact same principles.
best,
L
Larry Dahlberg
The Hunt For Big Fish