Spey casting mechanics seems to be a mystery, but only apparently; it shouldn’t be that hard if you start your analysis based on sound Physics.
Of all the aspects involving a spey cast nothing as controversial as the function of the anchor. Just make a search on the net and you’ll find that anchor and rod load appear as if they were siamese brothers: impossible to pull them apart.
Without the intention of getting deep into this issue —for now— I want to share some video material I shot years ago. The following is one of the most viewed clips on my Vimeo channel, and judging by the comments it has prompted in different forums —some of them not very friendly, to be honest—, probably the least understood of them all.
The scenario is the following:
Echo Micro Practice Rod with its macrame and wool “line”; a —very slippery— tiled floor.
Now look how the rod gets bent without the anchor slipping bacward, even on that super slippery surface!
I am pretty sure that you have heard about action/reaction, right? For any action there is an equal and opposite reaction. That is the law responsible for the load on a fly rod.
We apply force to the rod and line in the direction of the cast; rod and line both react with an equal force in the opposite direction; the rod is flexible so that reaction force puts a bend on it.
In the case of an aerial cast we apply force to the whole line on each casting stroke —provided that there isn’t slack and that we pause at the end of each cast for the line to unroll completely.
But is that the case on a roll cast, or a spey cast for that matter? No! On these anchored casts we apply force only to a short portion of the line outside the rod tip, just the lengh of line we are accelerating during the casting stroke!
How do I know that is actually the case? Maybe the water grips the anchor and holds it in place when the rod tip is pulling, applying force on it! That is a good argument, and it is the reason for the video above as well: no grip on the anchor from a tiled floor, as drag is almost nothing, however the anchor holds without slipping backward.
So back to the law of action/reaction. If the rod exerts a force on the line in some direction, the line reacts with a force of the same magnitude and opposite direction. If the rod exerts that force on the whole line, the whole line will pull against it. On an anchored cast —as by the clip above— the rod is applying force only on a short piece of line, only that short piece reacts to that force and helps in bending the rod. The anchor is not pulled by the rod, so no action force is applied to the anchor, so no reaction force from the anchor against the rod, so no rod load due to the anchor.
Anchor and rod load aren’t siamese twins, in fact they aren’t even family.
The good thing about it? That you don’t need to think of rod loading to cast properly. Rod bend is just a by-product of a proper casting stroke.
The paradox in all this? That you get more bend in the rod when the anchor doesn’t hold than when it does! But this is stuff for some future articles. Meanwhile the following material might be of interest as well: