Allow me add one other proposition as more food for discussion.
I am of the opinion
that it is easier to learn to cast a tight loop over a range of distances with a faster action fly rod than a slower action fly rod. I arrive at this conclusion because casting over at wide range of conditions, requires that the fly rod flex over the range of energy that is required to cast over those distances.
A faster fly rod bends less and shortens less over that range of casts than a slower rod. That means it requires a greater range of adjustments of the stroke path to cast a slow rod than a fast rod. It would seem to me to be more difficult to perform a greater range of adjustments than a smaller range.
Said another way, the same degree of convexity of stroke will cast a tight loop over a greater range of distances with a fast rod than a slow rod.
I understand that an accomplished caster can cast tight loops with slow or fast rods, and I also understand that there is a limit to the validity this proposition. A stiff rod that does not bend at all cannot provide the feel of a rod that does bend. But within the parameters of commercially fly rods, I think moderately fast fly rods are best as teaching tools for beginners.
What say you all? What rod action is the sweet spot for learning to cast.
---------- Post added at 02:45 PM ---------- Previous post was at 02:34 PM ----------
Lest we have a physicist that notes in my post about rod bending and load that KE refers to the energy of the moving fly line and PE (potential energy) is the energy stored in the flexed fly rod, I do realize that. I used KE to illustrate that the energy of a cast relies more on velocity than mass.
Master the Cast: Fly Casting in ... - George V. Roberts - Google Books