Originally Posted by tlcrep
I dont suppose you can find a cite for this? Because i am fairly certain that
rods used to be labeled 5/6, 5 wf 6 double tapper. The front of the weight forward weighs less, so the wf weighs. Now since almost everyone uses a a WF rod makers have taken off the second double taper designation.
You have it backwards.
brands of WF and DT fly lines have the identical front taper and body for the first 30 feet for the same line wt. For example a WF and DT Orvis Wonder line 4 wt lines will be identical in line mass and profile for the first 30 feet.
"DT and WF lines are generally the same in the front taper and belly"
Why Fish Double-Taper Fly Lines? | MidCurrent
AFTER the first 30 feet, the WF has less mass for equal lengths of line because it has running line and the DT has the thicker and heavier line belly.
See line chart and profile below:
Now consider the fly line profiles of the Cortland WF and DT 333 fly lines below.
When casting beyond 30 feet of fly line, you can see that the DT version of the fly line will gradually have greater mass for the distance of the cast BECAUSE the WF will be into the lighter running line. THEREFORE, when the cast is over 30 feet, the rod has to cast more mass with the DT version of the fly line than with the WF version. THEREFORE, the dual rating of a 5/6 fly rod is size 5 DT and size 6 WF fly line. Eventually for the identical longer cast, the mass of the DT 5 line will = the mass of the WF 6 fly line.
The reason that manufactures have removed the dual line designation is that it causes confusion (as it has in this case) AND because modern graphite fly rods can cast 3 line wts.