HI Spey Casters
I don't have the answer, but please allow me to give you some thoughts on this.
Loading the rod is bending the rod, its that simple !
The wieght of the line or resistance that it creates is what bends the rod. You don't need an anchor to bend the rod.
And over head cast has no anchor, nor does a Belgian cast.
Does a roll cast use only the line to load the rod, or is it a combination of anchor and line? As you make a roll cast you literally roll the loop down the line, as it's laying on the water. So yes, the line is anchored on the water therefore it plays a roll in loading the rod, but in a roll cast the loop behind the rod (in most cases) is not significant enough to load the rod. Or is it?
That being said, does the anchor play a roll in loading the rod in a spey cast , or is it's roll to stop the lines direction? Which Allows the line an opportunity to do its job (load the rod)
One would think that the point of the arrow loop or "D", is where the resistance comes from, at that point the line is being forced to change directions, the resistance as well as the weight of the line would bend the rod. The sharper the "D" loop the more resistance.
You might concider this, its not the amount of line you have on the water (to much anchor) that screws up a spey cast, but rather the rod is not loaded deep enough to carry this amount of line, or put another way, you've not used a proper application of power, but rather shocked (or over powered) the rod tip at a point during the forward stroke.
In single hand casting if you over power the rod at any point in the forward or backward cast, you'll get a tailing loop, In spey casting as in single hand casts the rod needs to be loaded smoothly (not abrupt). Then you need a sudden stop, and pause, to execute a proper cast. Derek Browns, mentions this on his tape ( the catipult comment)
One last question, is the forward stroke (in a spey cast) started before the anchor touchs the water or after?