Spey Pages banner
1 - 11 of 11 Posts

·
Registered
Joined
·
344 Posts
Discussion Starter · #1 · (Edited)
This is not really a theory of spey casting, but of matching rods to lines. I originally wrote this on the rod thread where Steelie Addict was looking for the right Skagit line for his Skagit Specialist. That thread covered a lot of ground, and I was one of those that took it off-topic, so I thought I would start a new thread.

I theorize that all 3 of the following theories are correct!

(1) The total grain weight of the line is the parameter to determine whether a line matches a rod, and it is the entire D-loop that creates load. I'll call this the RA theory. (My interpretation; my apologies to RA if I have mis-stated any of this.)

(2) The "casting weight" of the line is the parameter to determine whether a line matches a rod, and it is the top leg of the D-loop that creates load. I'll call this the Peter S-C theory. (My interpretation; my apologies to PSC if I have mis-stated this.)

(3) A rod can handle more grains casting a longer line than it can casting a shorter line, and the grains per lineal foot of line is important. I'll call this the old speypages theory, since it is based on old threads here.

Here is this foolish engineer's perhaps unifying theory:

You move more than 1/2 the line to form the D. Obviously, the whole line is moved. However, it is not the whole line that loads the rod ON THE BACKCAST. It is mostly the top half of the D, although I doubt it is exactly the top half; I think there is some percentage depending upon the mass of line in the top half and bottom half of the D and the location of the anchor relative to the angler.

I have considered both total line weight and Peter S-C's casting weight when estimating whether a new, untried line will work on a particular rod. For me, I think the answer seems to be somewhere in the middle.

If you recall lengthy related discussions on this board in past years, when there was focus on longer lines, there seemed to be consensus among the more knowledgable casters (not me) that a rod could handle more grains if it was spread over a longer distance. I haven't really thought about that in conjunction with Peter's model, so I can't comment, but--at least for longer lines--that prior consensus is contrary to total line weight being the critical parameter.

If you think about it, it seems obvious that the lower leg of the D contributes much less, if any, to rod loading during D loop formation:
As the D loop forms, the line is stopped by 2 things: the rod tip and the water. The rod tip generally stops the upper leg, and the water generally stops the lower leg. To the extent the water stops the lower leg, it cannot be contributing to the rod load. It is the momentum of the top part of the leg that loads the rod. That is why it gets harder to make a good cast the farther the anchor is in front of the caster. Given an untapered line and an anchor in front of the angler, less than 50% of the line mass would go toward loading the rod, since the bottom leg of the D is longer than the top. A tapered line has relatively more mass in the top leg, so that would change things. That is part of what Peter considered in his model.

A related fact is that a rod will be well matched with lighter lines for overhead casting than for spey casting. This is because in overhead casting, the whole line does load the rod, but it doesn't for spey casting (but see below for how shorter lines contradicts this).

The concept of the water stopping the lower leg of the D leads to one of the very helpful things I learned on this board, which I think was communicated most clearly by RA. I can't recall the words, just the concept: put more energy into the back cast (D loop formation), and take it easy on the forward cast. Particularly with short lines, tips, and weighted flies, one can put a lot of energy into the D loop and not pull the anchor. The water stops the anchor from being yanked, but greatly increases the load on the rod, and the forward cast is easy. The few times I got out this winter, remembering this teaching saved my casting, and helped get rid of some rod tracking problems that had been bedeviling me for some time. I think the extra energy helped straighten the line (no bloody L's!), and the easier forward cast solved my tracking.

In contrast to loading of the rod during the D loop, note HOWEVER, that more of the line contributes to additional loading of the rod ON THE FORWARD CAST. As the rod moves forward, all of the line in the upper leg is accelerated, the D or V, is accelerated, and perhaps the rearward (most distant) part of the bottom leg of the D. When the rod is stopped, all of the line that has been accelerated up to that point has contributed to loading the rod.

I think this is the reason why the weight of the line that matches a rod is dependent upon both the casting weight model and the actual grain weight. I don't think the casting weight model included this accelerating of the line on the forward cast, and the full grain weight does load the rod with very short bellies. This also contributes to the relative ease of casting with shorter bellies--the rod can accelerate the whole belly before stopping. With a longer line, only part of the line is accelerated before the rod is stopped, and only the top leg loaded the rod during D-loop formation, so only part of the line loads the rod.

So, I think from a physics/engineering point of view, ALL OF THESE POINTS OF VIEW--RA, PSC, AND MORE GRAINS WITH LONGER LINES--ARE CORRECT! For very short bellies, i.e. Skagit lines, the rod does not stop on the forward cast until just about all of the line has been accelerated, so just about all of the line does contribute to loading the rod, and thus the total grain weight determines the match of the rod to the line. So RA is correct. In contrast, with a longer line, the rod stops well before all of the line has been accelerated, so only the upper leg plus a bit contributes to loading the rod. So Peter S-C is correct. And, with longer lines, since not all of the line loads the rod, a rod can handle more grain weight with a longer line. Therefore, the earlier speypages consensus is also correct.

Context is everything.

--Bill

P.S. I note that this can give me a brain cramp, and does little to help my actual casting.
 

·
Speyngineer
Joined
·
167 Posts
Words of wisdom, based on knowledge

Well written SparseHairHackl! I would agree on most of your points, having only problem with the Skagit part (your last paragraph "...Skagit lines, the rod does not stop on the forward cast until just about all of the line has been accelerated..." as with a line 3 times the rod, and anchor beside the caster, I cannot imagine this being possible. With a very short line, say 2 times the rod, and anchor well back, yes, that is the case.

Furthermore, in the other topic, where this spawned from, I asked if the tip is in these Total Mass-figures always constant weight and length, and what would happen, if a heavier tip would be used, it would still be nice to get an answer from someone who may actually have tried it.

The Casting Weight model (as the name states) has always been about determining the line mass we accelerate when forward cast is being made. The shape and dynamics of the D-loop in the backcast phase obviously effect the pre-loading of the rod, as the rod and anchor decelerate the backcast. The more preloading, the less needed in the forward cast. Just as you said.

We all have opinions here, and changing them is called discussion, which is what this board should be all about. Somehow it looks like there are some tabu-subjects, and whenever anything is being said that does not follow the general gospel, some people start to jump around. I find it very curious.:confused:
 

·
Registered
Joined
·
625 Posts
Theory of Spey casting

Hi Guy's,
Like the thread, just a word on the idea, Alexander Grant worked on much the same theory over 100 yrs ago, before designing his rod and line, before setting a world record cast and showing his rods at various demo's, it is something they still do with bamboo/ split cane rods to decide which line matches the rod best, like a curve test.
Gordon.
 

·
Registered
Joined
·
1,273 Posts
My take...

...Bill, not trying to be argumentive here, just presenting my perspective.

The further out in front that one places their anchor, the less line that can be "injected" back beyond the rod into the D-loop, which equals less "mass" traveling opposite the intended casting direction, meaning less "inertial energy" to "pull" against on the forward casting stroke, equals less rod load.

The way I see it, the weight of the line traveling "backwards" is the initial impetus, in "splash-n-go" type casting, for providing energy for a cast - I think that the term "inertia" would be correct to use for this. That energy is first formed when the line is first picked up from off of the water. That pretty much involves BOTH the upper and lower leg of the D-loop. The anchor then provides the means for redirecting that inertia from a back-traveling direction, to a forward direction. Now then, it is pretty apparent that just the energy formed from the pickup is not enough to fully empower a cast. There is an "increase" somewhere along the casting process. I believe that the major "enabler" is the apex of the D-loop. The sharper the D-loop the more inertial energy that is added to the cast. The best way I can illustrate this is by using a car going through a curve in the road as an example - the sharper the curve, the more speed that is developed and thus the more outward "pull" that the occupants will feel as they execute the curve - inertia. The sharper the D-loop, the more inertia that the rod has to pull against as it travels forward into the casting stroke. In this context, the apex of the D-loop acts somewhat as an aerial "pulley" through which the line must travel through as it goes forward into the casting stroke - the smaller the pulley (sharper apex on the D-loop) the faster that the line must travel to get "through" it and therefore the more inertia that is applied against the rod (load). The anchor is the "anchoring point" that allows the line to be "pulled" through the "pulley" of the D-loop's apex. Once again, BOTH legs of the D-loop are involved. Of course a bit more energy can be instituted by increasing the actual power applied by oneself into the casting stroke also. But I would contend that it is the energy provided by the initial pickup combined with that produced by the "pulley effect" of the D-loop that are the major players.

Of course my "take" could all be nothing but total [email protected]#$*, after all I am not an engineer.
 

·
JD
Joined
·
3,641 Posts
Validity

I think these are all valid points. Some may be more applicable to one or another line/casting style, but valid none the less.

The way I interpret what Ed is saying about inertia, the V-loop, and a pulley, is G forces. The more abrupt the change of direction, the more G's you're gonna' pull, at a given line/tip speed.

Anchor point, mass (weight) distribution, G-force, tip speed, they all count. As well does the timing of the application of power.

Are we waiting for another Einstein to come along with a magic formula? I think they have already been figured out, by a lot of you guys. And there is more than one formula. Just as there are cars and styles of driving, Nascar, sprint cars, dirt tracks, formula 1, etc, why should this be any different?

And as long as we keep an open mind, and dialog, it will continue to develope.
 

·
Registered
Joined
·
344 Posts
Discussion Starter · #6 ·
Thanks for the responses, guys. I've been out of town with little time to think about this and post back, until getting back last night.

Lohi, I agree with you regarding the issue with accelerating all of the line. To some extent I was talking about trends and the relative situation for different line lengths. So, it wouldn't really be until the line is really short that the cast accelerates all of the line before the rod stop.

speyghillie, is there a summary and/or explanation of Grant's theories available online, or could you summarize for us? I don't claim my "theory" to be original, I just thought the expression of it might be useful to others, as thinking about it has been useful to me in understanding casting a little bit more. When I started, embarrassingly long ago, I had no instructor and no understanding of spey casting at all, and the results showed it!

Riveraddict and JD, I unequivocally agree with RA's first paragraph and the first line of his second paragraph. I am less clear about the thoughts regarding the pulley or G-forces, as JD put it. There is some confusion with the car analogy, because the car travels at the same speed regardless of the tightness of the curve. The increased centrifugal force that is felt by car occupants, or by the line, is because of the more rapid change of direction in a tighter curve, but the speed of the car does not necessarily change. (I don't know about you, but I tend to drive slower in curves! <g>)

That said, in the case of casting, the line really is accelerating in "apex" of the D-loop, because the line in the lower leg of the D-loop is not moving, and the line in the upper leg is moving, and the acceleration occurs in the curve or apex of the D-loop. This acceleration does add to the load of the rod. However, the load factor is the product of the mass and the acceleration; the old F=ma equation. With a sharp apex (V-loop), there is little mass that is being accelerated in the apex, but the acceleration is great. With a wider D-loop, more mass is being accelerated, but the acceleration is slower. So I remain unconvinced that the shape of the D-loop affects energy in THAT way.

However, the shape of the D-loop seems to (certainly, in my mind) have a big impact on the energy in the backcast, since a narrower D or V means the line was traveling faster going back than if the D was wider, and there was less wind resistance, so the load when the line is stopped by the rod (and by the anchor) will be greater. Again, it is mostly the top half of the D loop that would contribute to rod load, since the lower leg was stopped by the water.

All of this is for a mostly 2-dimensional casting process. I have enough trouble thinking about that; trying to address a 3-dimensional, continuous load casting process is too much for me yet. As I've posted in the past, I do believe that the continuous load can increase power.

Anyway, I am happy to still think that there are reasons why the 3 "theories" I mentioned above could all be correct. Now to actually get out and do some casting. The summers are here!

Thanks for the discussion, everybody.

--Bill
 

·
JD
Joined
·
3,641 Posts
the formula

SparseHairHackl said:
the load factor is the product of the mass and the acceleration; the old F=ma equation.--Bill
You are off by a little bit. The formula is Energy=velocity squared multiplied by mass. So increasing speed a little bit goes a long way.
 

·
Registered
Joined
·
1,273 Posts
Me Too!

...I also slow down when driving into curves. Just using the situation to illustrate the workings of a cast. As I said, I'm no engineer (always hated math), and you are right, there isn't an increase in speed - the increase is in centrifugal forces (C-force).

I agree that a sharp D-loop, or V-loop as it then becomes, is more aerodynamically efficient and this definitely increases the performance of the cast. However, I will stand by the increased C-force as being the major factor for providing casting energy. There is no way I can prove my theory through correspondence, only through demonstration. Because I use a three dimensional, constant tension technique from sweep to casting stroke, I can form a V-loop using very minimal "backwards velocity" and yet on the forward casting stroke the amount of load produced onto the rod feels FAR out of proportion to the amount of energy that was initially applied. There is no way I can see that this marked "increase" in energy resulted from effects of less wind resistance.

I would be willing to bet that if one was to mount a large pulley and a small pulley onto sticks, the same distance off of the ground, then say stand 20' away with a strung flyrod, have someone string the flyline from the caster, around the pulley and then lay about 25' onto the ground towards the caster, then have the caster "yank" the line into a cast, that when the results from the two pulleys were compared, the smaller pulley would show a higher velocity cast than the big pulley.
 

·
Registered
Joined
·
344 Posts
Discussion Starter · #9 ·
RA,

Good example with the 2 pulleys. I'd like to try that! But I think that the difference would be because the pulley would have some friction. . (I'm not sure, and as an engineer I think I should be sure :roll: as this is basic stuff but school was too long ago.) Thanks for keeping me thinking! This is cool, but then I'm kind of a nerd. (And though you hated math in school, isn't it kind of cool when you get to ponder the physics behind stuff like a spey cast??) This is tough to do via correspondence, but if I have any thoughts that are more coherent, or if I decide I agree with you, I'll post again.

JD,

I wasn't off at all. You changed my formula from referring to Force to referring to Energy. They are not the same thing. And your energy equation was wrong. The equation for energy is ONE HALF times mass times velocity squared.

I referred to force, because the velocity in all of the D loop approaches zero just before the forward spey begins, at least for longer bellies with non-continous load. RA's situation with continuous load is a bit different, and I have trouble with that third dimension. Perhaps I would have been more correct to use POTENTIAL energy rather than kinetic energy (1/2 mv^2); I'll have to think some more.

--Bill
 

·
Speyngineer
Joined
·
167 Posts
Not sure if this helps,

But this is the way it goes, energywise that is. The phases may overlap in some cases, but the basic mechanics should not vary much.

In the beginning of any cast, line on the dangle, and rod too, all energy is zero in the system.

Caster starts to move the rod, in order to position the line for the forward cast with a move called the back cast. The type of moves depend on the cast, is it a single spey, double, or what ever. The moves will be different, but the basic mechanics and energies will be pretty much the same.

In any case, the line mass is accelerated with a force, applied to the line by the rod, and to the rod by the caster. As soon as line moves, it has kinetic energy, the greater the velocity, the more energy. Again, whatever the back cast moves were, if a speycast is to be performed, in the end a D-loop is formed, which should be 180 degrees from the target forward cast direction. Just before the anchor lands, all energy in the system is in the line kinetic energy. I stress that it does not matter, how we ended up into this situation, the energy does not care, whether the initial moves were in plane (switch cast) or in 3d (Single spey).

The next phase is the deceleration of the line, which sucks the kinetic energy from the line. The line deceleration occurs by two forces, applied by the anchor and the rod. In the end of this phase, all kinetic energy has been taken from the line, and it has a zero velocity. Thus there is no energy whatsoever stored in the line at this moment. However, there may be some potential energy in the rod, if the cast has been completed such, that the rod is in a bent shape (that is not always the case). At this point the caster starts to move the rod forwards, again accelerating the line mass, but now into completely opposite direction. The line on the lower leg of the D-loop is immobile, and has no energy, the upper leg accelerates as the forward cast progresses, and in the end of this forward cast stroke, the rod is straight. At this point, all energy from the rod preload in the earlier phase, plus the added energy by the caster applying the rod butt translation and rotation has gone to the line. The shape of the D-loop at this point reveals the line mass that can be accelerated, and the mass of this part is the Casting Weight. All the energy in the cast has now been applied, and is stored in the line kinetic energy (the part of the line that is moving can only have kinetic energy).

The moving line draws the nonmoving part from the water, and this eats the kinetic energy. So this part of the line has to be moved to the final position in the cast by the kinetic energy stored in the upper leg of the line.

The way I see it, centrifugal forces play a role e.g. in the Double Spey, when the rod is being swept into the final position. Also in Snake Roll, we create a centrifugal force by rotating the rod. However, this energy has been spent by the end of the sweep, and only energy left is potential one in the preload of the rod. The D-loop shape in the beginning of the forward cast has importance, as the shallower it is, the more the line mass in the upper leg can be accelerated, as there is no slack, and the accelerations starts as soon as the rod tip starts to move forwards.

The amount of potential energy, that can be stored in the rod preload (and which is the only energy left from the back cast phase) can vary, but one can easily test its importance by two people, one pulling from the end of the line (weight similar to the upper leg part) so that the rod bends to its maximum at the normal cast situation. The other guy just keeps the rod butt still, when the other releases the line. I would bet that it does not fly very far.

It is rather difficult to explain without these mechanics terms, but these have a physical background.:D
 

·
Registered
Joined
·
273 Posts
Tension and the D-loop

I'm late to this thread AND I have no background in the sciences of energy. The closes I got to science in college was musical acoustics.
The question I have concerning loading a rod from the D-loop is: What does tension have to do with loading the rod. Many say that the bottom of the d-loop has no energy but why does the anchor skip if not properly set? Second question is more complicated to ask but here it goes: A switch cast is made and no anchor happens then the rod does not load efficiently, the line whips and a poor forward loop is produced. There was no tension between the rod tip and the water anchor. Do we need Tension for the cast to work? It seems to me in my non-scientific mind that "Tension" is needed to add load to the rod and to keep the line aerolized. The "PULL" against the tension point is critical to add "Load".

Lee Wulff said, “Line speed, line speed, line speed” and I believe that is our goal. Develop line speed in the most efficient way possible. Inertia in the opposite direction of the forward cast, line weight and tension points all contribute to the total rod-loading package.


Klem,.........................................::::::::::::::::::::::::>
 
1 - 11 of 11 Posts
Top