Fly Casting Terms

another real gem for us shared here with Mac Brown‘s kind permission.

casting terms

first published in 2009, this is most certainly the most comprehensive list there is. beyond the definitions themselves there’s a whole lot of food for thought borne from an enormous amount of experience both on the water and whilst studying how fly casting works leaving us with not only the obvious written but also a lot to read between the lines for the inquisitive and creative fly fisher/caster.

titled as fly casting terms, we’ll notice how Mac’s list delves deeply into the not-so-usually talked about world of 3-dimensinal casting and presentation line layouts. we’ll also find a whole host of fishing and equipment definitions as well; there’s a little something here for everyone and it’s all yummy. (even if it gets super-geek at times but that’s a necessity as Mac’s on a whole other plane compared to most !…)
i’d recommend taking your time, chewing slowly and let it all sink in one mouthful at a time. bon appétit !


” These terms are not set in stone. I have modified many of the terms I use when teaching over the years and am always looking for better ones. These terms below have served me well for my own personal learning curve and in teaching over the years. Most of them I came up with when organizing my text, Casting Angles in the early 90’s. These are ongoing and always subject to changes and amendments. I believe that the terms below can be used to teach all styles of casting and have enough tools for discussion of mechanics for specialty casts. When teaching, we often have revelations that seem like they move us through dimensional leaps of faith into new discoveries. When we can get a global recognition of terms commonly used in the sport, it will no doubt be much easier to get instructors on the same page.

I realize that most folks do not need to even witness these terms for their own casting. The casting geek lingo is helpful among instructors and educators of fly fishing. There has been so much offered over the years in dealing with the straight line casting stroke that in some ways I feel this has stagnated the general casting public. You can not use two dimensional terms and models and apply it for the real world of fishing casts (regardless of single or double handed rods). The trend here in the states is to call all of the 3D, constant tension casts, live line cast, etc.. and lump them all into the world of spey casting. This is a tragic mistake for the next generation of anglers throughout the globe if we continue on this path. It is essential that organizations globally break away from this two dimensional ideology for fly casting because it is very limiting on the water (as well as teaching). It is my sincere hope that something in these terms will cause curiosity to increase with your own casting and or teaching. “

Casting Terms

180 Degree Principle: The aerial back cast or D loop is made in a straight line exactly 180 degrees opposite from the target. Useful for straight line casts for distance and accuracy.

Acceleration– The rate of increase or decrease in velocity, magnitude, or direction.

Active Presentations– A presentation when the fly moves at a different rate from the current in which it travels so the angler may represent the food organism’s behavior. Active presentations impart an erratic change of direction, magnitude, and velocity to the selected imitation that closely mimics the natural organism’s state of being.

Anatomical Advantages– Diagnosing the weaknesses and strengths of the body parts and how they apply to the mechanics of the casting stroke. Many casting styles make use of various individual physiques.

Anatomical Position– The position of your body when standing upright with your arms at your side, while your palms face toward the same direction as your body.

Anchor– The anchor is typically the fly, leader, and a tip section of line that is positioned close to the caster (often a rod length away and in line with D loop and forward cast) prior to delivery. Shorter cast uses less anchor and a long cast uses more line for the anchor.

Angular Thrust-The casting stroke is a combination of the whole body involved for applying force to the rod. However, all casts involve using one or more combination of six different wrist positions (see directly below).

Angular Linear Thrust– A concept for describing the rod hand always remaining parallel with the forearm. The basic vertical foundation cast (most commonly taught) is an example of angular linear thrust. The motion includes usually either wrist abduction or adduction.

Angular Perpendicular Thrust– A concept for describing the rod hand’s perpendicular relationship to the forearm. It encompasses both wrist extension and flexion. This is often performed toward the completion of the casting stroke and line manipulation.

Angular Rotational Thrust– The circular motion applied from the forearm during the cast or mend. The motion is performed by varying the thrust force in which the forearm rotates (pronates or supinates) clockwise or counterclockwise.

Back Cast – A description that usually has the fly line cast opposite of the target area. It changes as well to other directions depending on obstacles, wind, or other change of direction fly line setups.

Bag of Tricks– The complete knowledge of understanding and ability to master several varieties of casts which aid the angler in challenging scenarios. It includes the full spectrum of control and force used for fishing casts.

Body Plane– The body plane refers to the positioning of where the rod and line is used while performing casts. The positioning around the caster will be a measurement of degrees always in a clockwise direction with 0° always directly in front of the caster (see also on–side and off–side).

Cast– The projectile loop motion of line created by varying the amount of force during the stroke that is applied to the rod by the caster. This dynamic motion propels the fly line, leader, and fly to a specific position on the water.

Casting Analyzer– A tool invented by Noel Perkins and Bruce Richards used for looking at the smoothness of applied force during the casting stroke. It also measures the symmetry for the back and forward casts for casts that are translatory. It also contains data of elite casters to compare your application of power with many of the greats. (the castanalysis.com site originally linked to this article is no longer accessible)

Casting Arc– (also Casting angle) The angle of rotational change of the rod when making the casting stroke. For many years arc was described as clock face positions.

Casting Cycle– The complete motion of implementing two casting strokes. Usually this is referred to as a back and forward cast. It could also mean two back or two forward cast. Casting cycle varies according to tempo for dealing with obstacles.

Casting Mechanics– A study of force and motion during and after the casting stroke. The force and motion are so completely interrelated (like braids of a rope) that neither can be defined independently from the other.

Casting Planes– Casting planes include all of the various airspace the rod and line are worked through a three–dimensional space around the caster’s body (see rod, loop, and line planes).

Casting Stroke– When the angler applies force to the rod to form a loop of line. This includes hand path and casting arc.

Closed Loop– Refers to a loop in which the fly leg crosses the rod leg during the cast (also called a tailing loop).

Complete System Forces– A concept for viewing all of the internal and external systems in unison (big picture), and the relationship of the interaction of forces present on the objects of the system.

Concave Rod Tip Path– A U-shaped rod tip path where the rod tip falls below, then rises above the effective straight line path (SLP) of the rod tip. May be problematic for causing higher chance for tailing loops (depending on application of power). Most common cause for this shape is applying force to the rod too abruptly or too early in the casting stroke.

Conservation of Energy– The sum of the potential and kinetic energy within the system remains constant for the complete system. The gain of kinetic energy must equal the loss of potential energy in any process of the system.

Control– The intended application or lack of force to achieve a desired line layout. A full range of control includes the concept of application of negative force, normal force, and positive force, as well as the usage of all rod and loop planes. A higher understanding of line tension.

Counterflex-When the rod springs down at the completion of casting stroke (after RSP) toward the direction of the unrolling loop.

Coupled Plane Pendula– A series of three or more hinges that perform motion. This concept is useful for understanding how body hinges of the caster may apply force to the casting stroke for either translatory or rotary motion. It can also be used to describe the fly line loop unrolling during the fly cast. The line is cast through a specific plane and is coupled together with a series of frictionless hinges.

Convex Rod Tip Path– A domed shape rod tip path (windshield-wiper like path in extreme cases) that may result in larger loops. Negative casts (also called underpowered casts) often use a convex rod tip path for controlling large fly loops for curves.

Creep– An ill-timed (too early) forward drift movement of little power to the rod in the direction of the next casting stroke that reduces available casting arc and/or casting stroke. Creep is often labeled as a fault and is usually (but not always) unintentional for many casters. Creep typically increases tension of the rod leg.

D Loop-The D loop is a loop of line that forms behind the rod tip and it can be either dynamic or static. Usually Spey casts make use of a dynamic D loop. A basic roll cast often uses a static D loop.

Damping – a). A term that refers to how quickly a rod recovers to a resting position at the end of rod motion. b). Also used to describe the relaxing on the grip of the rod butt after the stop to minimize rod tip oscillations.

Dangle– The line’s position prior to the cast that is usually downstream of the caster.

Delivery Cast– The final cast that delivers the fly, leader, and line to a specific location.

Direction Altered Cast– A casting stroke in which the forward or backward cast does not end up in the same plane from which it started.

Double Haul– A line acceleration technique that increases rod load, tip speed, and line speed. It encompasses a haul on both the back and forward cast. Aids in keeping the rod tip straighter for a longer period.

Double Taper Line– A line that is tapered on each end and is uniform throughout the remaining length.

Downstream Wind– A wind that blows downstream.

Drag– a).The fly moving at a speed other than the current’s speed in which it is traveling.

b). Rod translation during early part of casting stroke that helps build momentum to the direction of the cast. It can be used to increase tension, take up unwanted slack, delay rotation, or assist casting stroke by starting to overcome fly line inertia. This has been called pull as well with some casting groups (see “Slide” also).

c). Casting geeks also refer to air/water friction on the coatings of fly lines.

Drift– a). Refers to the amount of drag implemented on the fly (sometimes called float).

b). A supplementary motion that takes place during the pause of the stroke for repositioning the rod. Drift also offers an advantageous position for shooting line at the completion of the casting stroke. Upward drift toward the unrolling line can also be an advantage for opening up the casting stroke and arc angle and makes it easier for shooting line due to rod position.

Effective Rod Length-Refers to the distance from tip of rod to the butt of the rod. Useful when looking at video analysis since the rod is bent when performing casts. The shorter the distance of (ERL) equates to maximum load.

Energy– A concept for the capacity of an object to perform work. Examples include potential and kinetic.

Enlightenment Casts– Creative and imaginative uses of various actions when performing the casting stroke. To gain an understanding on the full comprehension of the problems involved and their solutions on the stream.

External System Forces– A concept used for describing forces exerted to the objects of the internal system. Examples include gravity, surface friction of water, wind, diverse currents, obstacles surrounding the caster, and more.

False Casts– To implement multiple casting strokes without allowing the line to fall to the water or ground level.

Feed Lane– An area where food organisms are heavily concentrated in the water current.

Fly Leg-The part of the unrolling loop that contains the fly end to the center of axis of the unrolling loop (accelerating part of loop).

Follow-Through– To move the rod in the direction of the unrolling loop. It can accomplish easier line shoots as well as extending the overall distance of the haul. Follow-through may be either a form of drift or casting stroke.

Forearm Pronation– The rotation of the forearm in back from the anatomical position.

Forearm Supination– The rotation of the forearm in front when the palm faces opposite of the anatomical position.

Forward Cast– A cast that usually travels in front of the caster, but direction is often, but not limited to, a position in front of the caster.

Grip– a). The handle of the rod usually made of cork where the angler pilots the rod. b). Many various grips used to hold the rod depending on what you are attempting to accomplish.

Hand-Rod Path– A concept used for describing the path and distance that the rod hand follows when performing the cast. These paths include simple geometric patterns such as straight lines, circular, elliptical, triangular, and smooth curves.

Haul– A quick tug on the fly line with the line hand usually performed during the last half of casting stroke (used also with various timings for specialty casts).

Imitation– The fly pattern (also called the artificial or fly) attached to the end of the tippet. These typically include wets, nymphs, dries, and streamers.

Inertia– A property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force.

Initial Velocity– Refers to the velocity at which the rod begins the casting stroke.

Internal System Forces– The interaction of the mechanics on the objects within the system and the relationships they exert on one another. The internal system includes all components of the caster and the equipment used in performing the cast.

Kick– The abrupt, rapid or sudden turnover of a fly, leader, or fly line at the end of the loop becoming straight. Can be caused by overpowering a cast, having too much weight at end of leader, or by having no leader or a shortened leader. Positive casts make use of kick for driving a nymph down vertically into the water or when making curve casts.

Latent Rod Force– The slight potential energy (spring) of the rod when casting.

Layout– A concept used for measuring the displacement (initial positioning) of the imitation, the leader, and fly line following the casting stroke.

Level Line– A fly line that is a consistent diameter throughout its length (no taper).

Lift– A vertical form of sweep to lift line from the water prior to the the next line positioning move or casting stroke.

Line Hand– The hand that controls the fly line between the reel and the stripping eyelet. Example, if you cast holding the rod with your right hand, then your left hand is also called the line hand.

Line-Pull Cast– All casts that implement a haul after the stop of the rod has occurred for controlling the layout. This increases tension on the rod leg and causes the fly leg to turnover quicker.

Line Velocity (Average)– A measurement of the displacement of fly line divided by the time which it traveled.

Line Plane– The angle created of the fly line in relation to the surface of water or ground.

Load– To cause the rod to flex when moving the rod during the casting stroke. The resistance of the line weight and increasing momentum against the rod, usually when the line straightens or other similar tension is applied to the line.

Loading Move– The progressive buildup of forces applied to the rod that takes place after the initial velocity and before the stop of the stroke.

Loop– A moving length of line past the rod tip where there is a distinct rod/fly leg. Takes on a candy-cane appearance for the unrolling portion of the fly line. Loop formation always has two strands of line (rod and fly leg), that either may or may not run parallel to one another dependent on translation or rotary hand/rod paths.

Loop Morph–The loop is always changing shape and size during flight depending on overall velocity, tension, mass displacement of the line, and transverse waves put there by the caster.

Loop Plane– A measurement in angles from the perspective of the caster used for determining the relative position of the fly leg in relationship to the rod leg during loop travel. The loop plane is zero-degrees at vertical and is measured clockwise 360 degrees. Controlling loop planes often have hand-paths that deviate from straight (typically curved hand paths during the casting stroke). Learn to control loop planes on top, below, away, and toward the caster when using the same rod plane.

Major Drag– The fly dragging at a different speed from the currents, due to the whole leader tensioning the fly.

Maximum Rod Load– When the rod is bent (loaded) the deepest when performing the overall cast, sweep, mend, and other dynamic line positioning techniques. Usually maximum rod load is close to equaling maximum fly line acceleration.

Maximum Rod Flex (MRF)– The increased force that the rod possesses when it is flexed to near its elastic limit. Longer hand–rod paths, hauling techniques, increased rod arc, rod planes, body planes, equipment used, and optimal load placement (line planes) all influence the maximum rod flex.

Mend– A form of sweep used for manipulating the fly line in air or water that usually creates slack or removes slack in order to achieve a desired result with line layout. Used for placement of line position that typically takes place after RSP.

Micro Drag– The fly dragging at a minute different speed and direction from the currents because the tippet of the leader has increased tension (also called hidden drag).

Momentum– The measure of motion for a property of matter that relates the line’s mass and its velocity.

Narrow Loop– A loop typically with the distance between the fly/rod leg of less than two feet (since the loop is changing this is just a rough average).

Negative Force– A reduction of the net forces applied throughout the stroke by either releasing slack into the internal system or decreasing the amount of force from the rod hand toward the end of the casting stroke. The loop never turning over through infinite casting planes is characteristic of negative force casts.

Non-Parallel Loop– See “open loop”.

Normal Force– The minimal amount of net forces required for performing the cast which attains complete turnover of the loop through infinite casting planes (the fly line should be a straight layout).

Off-Side– The side of the body where the hand holds the line. Off–side includes everything from the ground to the caster’s center of the axis.

On-Side– The side of the body where the hand holds and pilots the rod. Example, a right handed caster’s on–side includes all casting planes from the caster’s center of the axis to ground level on the right (note: this angle is greater than ninety-degrees).

Open Loop– A concept used for describing the appearance of position and large displacement between the fly/rod legs of the loop (also called a curved line or non-parallel loop). This is a casting fault if the caster attempts a translatory hand-rod path. It is normal for rotary hand-rod paths to use an open loop (most negative force casts).

Optimal Line Length– A distance of flyline the caster has the ability and skill level to control when making the cast. To find your optimal line limit, perform several false casts and find the line distance that you can control with confidence. Measure this distance of line and divide the total by the length of the rod used. Beginners may find it practical to mark this point with a permanent marker or attach a nail knot for a reference when performing the cast.

Optimal Load Placement– The placement of flyline on the back cast which distributes the line’s weight most efficiently for bending the rod deep on the forward cast. This placement is critical for allowing the rod to perform more of the work during the cast.

Optimal Reach– A measurement of distance for the path in which the rod hand may travel. Mark a dot on an object to the rear and another far in front for finding your optimal reach distance.

Overhang– The amount of running or shooting line between the tip–top and the rear taper of the shooting head or weight–forward line.

Parallel Loop Legs-Refers to the displacement of the fly and rod legs of the loop remaining parallel. Useful for accuracy and distance casting (highly efficient for loop propagation).

Passive Presentation– Presentations where the fly moves at the same rate as the current in which it travels so the angler may represent the insect in a natural manner.

Pause-The time period between accents of applied force to the rod. Many claim casting strokes, but we have slight pauses for lift, sweep, circle casts, figure eight, etc… (see also rhythm, timing, tempo, and syncopation).

Perpendicular Rod– The rod’s position at the completion of the casting stroke which remains close to ninety-degrees in relationship to the target. This position enables the rod to become an action on altering the tension throughout the line due to rebound (common with positive casts).

Pickup– A form of drift to slowly lift the line from the water before starting the casting stroke.

Pop and Stop– A concept used to describe the amount of force applied to the rod and when it stops during the casting stroke (like paint being flicked from a brush). Has also been called the speed up and stop, power snap, speed move, power stroke, flicking motion, positive stop, and others through various casting circles.

Positive Force– An increase of the net forces applied throughout the stroke and the loop always travels back around to the opposite direction of loop plane in which it was created. Used for positioning angles in the relationship of fly, leader, and fly line (control). Use of greater force than needed for a normal force cast. Characteristics of positive force cast make use of a narrow loop that travels fast.

Presentation– How one presents himself, the cast, the imitation, stealth tactics, equipment chosen; your cumulative knowledge of the complete system for the deception of the fish.

Prime Lies– Areas in stream that offer fish food and shelter from predators.

Rebound– Refers to the rod bouncing back after counterflex (at completion of adding force to the rod with examples of casting stroke, sweep, mend, etc…).

Retrieve– Any method which pulls flyline in through the guides while fishing for controlling the amount of line outside and away from the tip–top.

Reverse Thrust– Any force which is straight away and in the opposite direction of flyline travel upon the completion of the stroke. Examples include pulling the line, backing the rod up, or perpendicular rod positioning (latent rod force) as soon as the abrupt stop occurs.

Rhythm– The movement or fluctuation marked by the regular recurrence or natural flow of related objects to the system. The pace of a singular movement during the cast (line positioning sweep or casting stroke). Used to describe applied force during rod motion. Syncopation, timing, and tempo are a few examples that are encompassed by rhythm. Very important concept for any fly casting model for dealing with teaching advanced casts or line manipulations.

River Left– Is the left bank of the river when facing downstream. This is actually a boating definition that is useful for painting word pictures.

River Right– Is the right bank of the river when facing downstream.

Rod Action–A concept used to describe the features of the rod pertaining to where and how the rod bends when put into motion under load. Characteristics of rod action include but are not limited to frequency, stiffness, sensitivity, distribution of mass, dampening, and mcuh more!

Rod Arc– The angle of change when making the casting stroke (also called casting arc).

Rod Fade–A movement of the rod at the completion of the casting stroke downward toward the water or ground. Used to relieve tension on the rod leg and typically gain greater control over negative force casts.

Rod Hand– The hand which pilots (grips) the fly rod while performing the cast.

Rod Leg– The portion of fly line that runs from the center of axis of the loop to the rod tip.

Rod Plane– A concept used for describing the rod position during the casting stroke. It is a measurement of angles with zero-degrees directly vertical and plus or minus ninety-degrees parallel with the ground or water.

Rod Pointing– On the final delivery cast, the rod is pointed directly toward the target. Pointing the rod is often used while casting in the horizontal casting plane or when applying angular thrust to the cast.

RSP (Rod Straight Position)-A concept of the rod being straight toward the completion of casting stroke. Useful for video diagnostic of overall stroke.

Rod Wavering– The tip-top path of the rod moves away from the parallel reference plane throughout the stroke. The rod hand does not remain consistent for applying force in a straight line during the casting stroke. Rod wavering is used for describing faults in casts when the caster attempts to attain straight line motion (see tracking).

Roll Cast Pickup– A method of beginning the casting stroke in which the fly line becomes aerial to load the line in front and to break the surface tension bond of water. The pickup enables the casting cycle to be more efficient (shooting line on the pickup). It usually proceeds as roll cast pickup, back cast, and finally the delivery cast.

Rotary Motion– Motion occurring in a revolving manner which can be around a fixed point, a point in translatory motion, or a point in rotary motion which may serve as the axis of rotation.

Running Line– The long thin section of fly line that extends from the rear taper of a weight-forward line to the back end of the line.

Shooting Head– A short heavy flyline which that may be tapered or level which is not attached to a conventional running line. The running section is usually made from braided monofilament as opposed to thin flyline.

Shooting Line– a).The thin running line attached to the rear of the shooting taper which is also called a running line. b). The release of additional line to be pulled through the guides by the unrolling loop when the rod has stopped. Shooting line relieves tension in the rod leg causing the fly leg to turnover slower. Late or early shoots are also common for various control casts (also called slip line techniques).

Single Haul– A method of accelerating the rod tip and line speed that uses a haul on either the forward cast or the backward cast, but not both. It is usually performed on the forward cast.

Six Step Method– A very simple diagnostics tool used for instructors that was originated by Bruce Richards. It works by observing the fault in this order line, rod, body, to slip in with the correction of body, rod, line. Once you get lots of teaching experience you can use this tactic to quickly make adjustments. The real art behind it in teaching is to solve a couple of things that solve many. Often times new instructors want to solve many things at once especially with new casters that have many faults. Often a few subtle suggestions leads to progress for the student much quicker.

Slide– Rod translation during early part of casting stroke that does not alter tension when done correctly. When timed correctly, the rod hand and the line hand move back together (without rotation) hence no change in tension. This is what separates slide from drag (drag increases tension on the line). Both enable the caster to setup in a more comfortable or powerful position for rod rotation. Most styles that use drag also use slide first.

SLP (straight line path)-A term used to describe the brief period of time that the rod tip is traveling in a straight line. Smooth acceleration during the casting stroke and hauling the line help to achieve longer SLP (useful for straight line casting).

Snap Casts– A type of cast that propels the loop creation opposite the direction of acceleration. It is the inverse acceleration of typical casting strokes.

Stop– The butt of the rod stops to transfer the energy from the bend of the rod to the line leading to loop formation.

Spey Cast-A form of fly casting that takes advantage of change of direction casts through roll-type casting that remains in constant tension (also called constant tension casting).

Spline– The spline refers to the stiffer section usually on the back of the rod (usually opposite the guides).

Stance– The orientation of the caster’s body during the cast determined by the placement of the caster’s feet.

Stream Awareness-A concept that describes the anglers knowledge and understanding of the behavior, intricacies, and relationships of the stream flow and aquatic organisms and how they relate to the ecosystem. This is best developed through empirical lessons learned on the stream.

Stripping Eyelet– The largest guide on the rod that is also the first one from the grip.

Stroke– The complete casting motion performed by the rod hand that includes only one backward or forward cast, depending on the perspective. The pause is characteristic of the completion of all strokes.

Style– Includes form (such as hand, elbow, stance, etc…), descriptive word pictures for application of force or hauling, and many other unique methods used to achieve various loop shapes. It also includes ones effectiveness to connect with others for communicating these topics in a fun non-boastful manner. Mel Krieger offered the concepts of substance and style. As the sport grows it is a bit easier for instructors and students to convey concepts if we keep these separate.

Substance– Includes the fundamentals of timing, mechanics, all of the specialty fishing casts nuances, and many other key concepts. Sometimes there will be gray areas that have both style and substance. These examples are best stated by Krieger when he said “if you are very fortunate you will understand that the profound path towards teaching mastery gets two miles farther away for every mile you travel”.

Surface Tension– The relationship of intermolecular forces that exist at the surface of a liquid whose properties resemble those of an elastic skin under tension. This force acts heavily on the relationship of line on the water and emergence or egg–laying stages of insects.

Sweep-An action to position the line for the following casting stroke.

Syncopation– Syncopation is used when stressing a force in a normally unstressed location or a lack of force when it is normally accented during rod movements. It really comes into play for elliptical 8’s, snaps, and oval casting (but is very common for many things dealing with rod motion).

System Response Curve– A concept used for understanding the relationship of force and control for varying rod planes. It can be used to measure the system efficiency in explaining different casts.

Tailing Loop– Occurs when the fly leg crosses the rod leg and creates a closed loop (see also closed loops and wind knots). It should be observed past half way point in travel for the propagating loop (because many casts have crossover during setup of roll cast, distance cast, and others-these are not tails in the early setup stages). Since the legs can cross once, twice, and more is the reason for quantifying 50% of loop travel. I have yet to see one tail right at the rod tip that disappears before the 50% rule in flight (because the traveling transverse wave propagates down the line to the end). While it is true that many tailing loops are usually a fault, they can also be useful presentation casts for curve cast. There are many causes of tails but most of them stem from too early/abrupt application of force, line planes less than 180*, rod tip jumps above the oncoming lines path, improper haul timing, and many others. The fly leg wrinkle is the key for seeing the problem and you can easily go back to rod tip for the cause.

Tempo– The pace of the overall cast from start to finish. A beneficial concept to practice changes in tempo for dealing with fishing scenarios. As an example, a slow underpowered back cast static D loop followed by normal forward cast for missing obstacles right at your back. Practical for distance casting in taking tempo to the max for the amount of line carried.

Timing-The time period for each movement during the overall casting sequence.

Tension– Opposing forces that act on pulling the line apart. Make it a goal to really understand how your actions while making casts increase or decrease tension (very beneficial).

Three-Dimensional Casting Planes– A concept used for describing all of the air space around the casters body which the fly line and rod may be used in performing casts.

Tip-Top– The final guide at the tip of the rod.

Tip-Top Path– A concept used to describe the path that the tip–top of the rod scribes through the air when making casts.

Tip-Top Velocity– The velocity of the rod tip during the casting stroke.

Tip Travel– The total distance the rod tip moves when making a cast. This is the by product of casting stroke and casting arc.

Tracking-A term used to describe the rod tip traveling straight with out side to side wobble during the casting stroke (see also rod wavering).

Translatory Motion– A concept used to describe motion occurring in a straight line.

Transverse Wave– A transverse wave is a moving wave that consists of oscillations occurring perpendicular (or right angled) to the direction of energy transfer. One common example of a transverse wave occurs during rebound. Many specialty casts make use of transverse waves for presentations by initiating the wave pulse during the casting stroke which propagates down the fly leg for a desired result.

Upstream Wind– A wind that blows upstream.

V Loop– A V loop is a wedged shape back loop of line formed behind the rod tip that is more efficient than a D loop in flight. Offers greater load to pull against when timed with a proper anchor.

Vector Haul– A line haul method that manipulates two strands of fly line producing a two-to-one ratio for achieving deeper rod flex.

Vector Pull Retrieve– A line retrieval method that manipulates two strands of flyline at all times, as opposed to the traditional retrieval which pulls only one strand. One retrieval of line is equal to approximately twice your body height.

Vector Quantities– A concept used for describing a direction and magnitude that relies heavily on the logic of mathematical relationships for solving the resultant.

Video Capture-To use a camera for tweaking your own casting as well as diagnosing others.

Waltz– The transfer of the caster’s body weight from one foot to the other during the casting cycle. The shifting of the caster’s center of axis throughout the stroke.

Wave Speed of Line– The slight wave forms in the fly line during travel which is less efficient than straight line travel. These waves propagate quicker when tension remains high (see also Transverse waves).

Weight-Forward Line– A line that is tapered and consist of its casting weight distributed toward the front of the line, with the remaining line called running line.

Wind Knot– An overhand knot in the line or leader caused from a tailing loop during the casting stroke.

Wrist Abduction– To draw away from the body from an anatomical position.

Wrist Adduction– To draw toward the body from an anatomical position.

Wrist Extension– To draw away from the joint which increases the angle of the joint.

Wrist Flexion– To close the joint which decreases the angle of the joint.

Fly Casting Physics: Casting Mechanics, What Do We Need To Know ?

the world of fly casting, and it’s subsequent contemporary research has by necessity (and thankfully) gone past the ‘touchy-feely’ to further understand and explain how all this actually works.
for sure, an angler doesn’t need all this to go out and have fun but the inquisitive fly angler will greatly benefit from having a few notions of basic physics because simply put and to reduce things to the core, everything about fly casting is about physics.
if anything, the article below will be of great benefit to understand how casting is explained throughout the different medias, books, articles, at shows or with instructors but also goes a long way in understanding the equipment we use: fly lines, rods, leaders, etc. non-neglidgable as well is this knowledge will also help sift through all the BS that’s randomly but unfortunately spewed right and left in so many ways on how fly casting works.

Mark Surtees, IFFF Master Certified Casting Instructor from England has kindly offered to share his wisdom with us here with what i personally consider to be a monumental reference work to be bookmarked and shared.  thanks Mark !

Mark Surtees TLC 15-10-13


CASTING MECHANICS, WHAT DO WE NEED TO KNOW?

There are parts of angling instructor examinations that require a candidate to have a basic understanding of casting mechanics.
What does this actually mean ?, What, after all, is Casting Mechanics ?
There seem to be as many interpretations of what constitutes casting mechanics, what makes a cast work, as there are authors, bloggers, magazine journalists, TV presenters or DVD producers out there in the Anglerverse.
In the world of the professional and the published, where cruel commercial reality dictates that personality and self promotion matters, differentiation from the rest is critical in order to sell the product, this is what puts bread on the table. So, no terms are quite the same, the explanations often in conflict, one with another, and there is an underlying, but perfectly natural, predilection to promote neat and highly personalised instructing techniques or concepts.
I think this is great…… I freely admit to the regular breach of the intellectual rights of these authors. I mercilessly steal and adapt teaching techniques and simple field fixes because they are better than any I can think up on my own.
But, if you look closely, some of these quick rules of thumb work by being pithily memorable rather than having any bearing on what may turn out to be inconveniently complex physical facts.
No-one disputes the benefits that can arise when we use these things from an instructional point of view. They can be a fantastically effective means of communicating a difficult concept and, in the hands of a good instructor, they are invaluable. However, being effective doesn’t make them “true”. They often turn up, on closer examination, to be completely at odds with what really happens in the world beyond the pages of the book in which they are written. Some, if published in more academic circles, might merit a Nobel nomination for the uncovering of entirely new and, no doubt very exciting, principles, which would turn the world of physics on its head.
Does this matter? Well, that’s up to you to answer…but it’s always mattered to me.
So, if we do decide to look beyond the one liners, how far do we go ?
Is there a limit on the things that an instructor should know about Classical Mechanics? When is enough, enough?
At what point does the subject become so complex that it becomes terminologically impenetrable for anyone but a trained physicist to understand?
For me at least, the simple answers are, in order…”its up to you”,.. ”no, not really”,… “don’t know” and “pretty quickly”.
Obviously, we set our own limits on our pursuit of knowledge, no-one is going to tell us when we have had enough. For most of us, who are untrained but nevertheless interested in these things, we set our own pace and plough through the arguments with a supplementary dip into the internet for explanations which in themselves can introduce confusion as a by-product of their generality. It is too abstract, out of context, mathematically testing and the unfamiliar terminology will trip us up early if we do not know how it even applies to the world about us, let alone how we might apply it to simple casts.
Sometimes, it’s difficult to ask direct questions of our better informed peers without appearing irredeemably stupid….almost no-one wants to be seen this way and so we don’t ask…the prospect of a highly public, id savaging polemic from an advanced theoretician is too much for the vulnerable soul of a simple instructor to take and, so, unravelling the terminological mystery of mechanics continues to elude us.
In order to try and help avoid these embarrassments, this is a basic glossary of terms with a vastly oversimplified explanation of what they mean and how they might relate to basic casting mechanics.
Most of the things we are going to look at have a “value”, they are quantifiable, calculable, measurable and they are often inter-related. Some relationships between terms can be represented by simple equations. In the case of the key relationships there is nothing of any challenging complexity, however, the connection between each term is explained in words so as to avoid the possible onset of an algebraic crisis.
For each term, its value is measured using an international system of units called SI Units. These units represent the amount of stuff something might have, a quantity. Where relevant I have put the SI units in but, mainly, I have left them out. I’ve started with “quantities”, gone on to “stuff” and then moved into “motion”
There are no equations anywhere…there are, however, some elephants.. If you can….please..
Enjoy!

QUANTITY, BUT NO “STUFF”
Some quantities can stand alone, a “Kilogram” or a “Meter” or a “Second” for example. Others require a combination to produce a more complex value such as “Meters per Second” or “Miles per Hour”. These sorts of quantities have a simple magnitude and are called “Scalar” values, basically they have scale.

Scalar
Quantities with magnitude only.

Some quantities have an added element of direction. This implies that whatever scalar value this quantity has, its size… it’s going somewhere or it’s pointed somewhere. These are called “Vectors”.

Vectors
Quantities with magnitude and direction.

Vectors give us a means of placing, or describing the movement of, an object in a three dimensional world and explain its direction of motion. They can also be used to indicate the direction of a force and thus the direction something will move under the influence of that force.
To demonstrate the difference between scalars and vectors we can use two other common, inter- related terms.

Speed
The distance travelled by an object over time.

For our purposes speed can be measured in Meters per Second, or Miles per Hour…or Meters per Hour or Miles per Second, whatever we want. We measure the Speed of Light, Speed of Sound, Cars, Rabbits etc. in terms of distance and time. Speed is Scalar, that is, it is just a quantity with magnitude, but, rightly or wrongly, it is often used interchangeably with…

Velocity
The speed of an object and the direction in which it is travelling.

Velocity adds a direction to the scalar quantity Speed and so represents Meters per Second or Miles per Hour perhaps, but in an easterly direction or south or up or down or left or right or a combination of these sorts of things.
Velocity is a vector. Velocity is a term that will re-occur as we move on. It is used to describe rod tip velocities, line velocities, angular velocities, linear velocities, loop velocities.
When talking about velocities, or any other vectors, force vectors for example, you will often hear the term “Component”.
In most casting contexts components are simply used to represent the amount of “upness” or “forwardness” of something, by displaying it graphically and using the X or Y axes of the graph to measure it. Usually, the X axis is the horizontal axis and the Y axis is the vertical axis, so when you hear someone talking about the X component of a vector they mean how much it is travelling forwards or backwards and the Y component is how much it is travelling upwards or downwards. Combined, these two “components” form a “resultant” which is the actual direction of the object in motion or the direction of the force being applied.
Imagine you’re on an ice rink, one person is pushing on an elephant in the X direction, in Fig 1 this would be to to the right, while another person pushes on the same elephant in the Y, upward, direction. The resulting motion, if any, is exactly the same as single person pushing the elephant in the direction that is upward and to the right,… none probably but you get the idea I’m sure.
Figure 1 shows how the X and Y components of a vector can be added to generate a resultant vector.

surtees

“STUFF” BUT NO QUANTITIES

What about the inherent properties of the things we are trying to describe? The rod, the line and the fly attached to the end.
First and foremost …all these things have Mass

Mass
The amount of stuff in an object, how much “matter” it contains.

For all practical purposes this value is most commonly equated with, and, even though strictly speaking it shouldn’t be, it is used interchangeably with Weight.
Mass is measured in SI Units of Kilograms and its sub divisions, it is Scalar.

Weight
Is a measurement of the mass of an object under the influence of gravity
Weight is the mass of a thing multiplied by the force of gravity.

It is very important to understand that when we are standing on the earth, or any other planet you can stand on, things fall down. No matter what other forces are influencing an object there is always a force pulling down on it, and we will look more on this later.
Because it has a direction, Weight, Mass times Gravity downwards, is a Vector Quantity. What of this terminological confusion between Mass and Weight?
Well, just as with Speed and Velocity, most of us make no real distinction between the two terms. Weight is properly measured in SI units of Newtons. Because most of us don’t leave the surface of the planet, the force of gravity is treated as constant and we don’t weigh ourselves, or beans, or rice or anything else in Newtons….we save these units for something else and we blur the distinction further by using the SI units for Mass, Kilograms etc, when we weigh something.
No non physicists use Newtons for weight, in fact no one I know, physicist or not, knows their weight in Newtons, though I dare say they could work it out….however, these units are not wasted and become more relevant later in this discussion.

Just as a matter of interest, more massive things like the earth have more gravity than less massive things like the moon but less gravity than even more massive things like the sun….in a non fishing context this explains why exceptionally large tie knots attract more fluff and airborne detritus than small ones… .
Anyway… This leads us to…

Density
The mass of an object by volume.

For a given mass, the more space the mass occupies the lower its density, the less space for the same mass the higher the density.
It is differences in density that explain why a floating line floats and a sinking line sinks when they both have the same mass or weight. A #5 floater floats because it has less density than water, and a #5 sinker sinks because it is denser than water, even though the two lines weigh exactly the same.
As our lines get denser, for any given weight, the volume decreases and so too does the surface area. The less the surface area, the less water resistance the line will have and the quicker it will sink. Fly fishers call this the sink rate of the line.
(A physicist would call this the lines “terminal velocity in water”, but, if you speak to a physicist who fishes they will know what you mean when you say “sink rate”… in fact, anyone who uses “terminal velocity in water” instead, should, in all probability, be repeatedly hit with a heavy skillet until they agree to stop.)
Rods are tapered, this usually means that there is a regular reduction in mass towards the tip. Uneven or irregular mass through the taper may result in an odd action or tip wobble. This is usually referred to as Mass Distribution and is most commonly met with when discussing lines and line profiles.
We can see just by looking, that, for rods and lines, the mass and or density is not evenly distributed. A weight forward line has more mass towards the tip while a double taper has its mass evenly distributed for most of its length. A 5# floating line has less mass than a 7#.
We will see later that it is changes in mass and density, along with a few other simple concepts, that explain why a sink tip can kick like a mule, or a shooting head turns in to spaghetti, or a roll cast sometimes just won’t roll. The relationship between the mass in the line, the air or the water and the motion of the rod is often crucial to understanding how these things occur and how basic casts actually work.
Any object with mass has a ….

Centre of Mass
This is just like the centre of gravity.

In a sphere or a cube where mass is evenly distributed, the centre of mass is slap in the middle. Because we know that rods and line don’t have an even distribution of mass, the centre of mass isn’t necessarily going to be anywhere near the centre of the object. This is going to affect its balance, how it moves and how easily or difficult it is to actually move it.
In addition CoM is commonly used as a reference point for measuring purposes. When discussing forces and motions we can think of objects as being imaginary points, i.e. they have no size, so no matter where we push on the point object we are always pushing on its centre of mass.
Obviously, in real life, rods and lines are not imaginary points and we don’t always apply force directly against the centre of mass. In fact, we most commonly don’t, and, as a result, the rod may turn or twist in addition to moving away from the force we are applying.
If you know the relationship between an object’s centre of mass and any forces applied to the object you can determine if that thing will simply move away from the force in a straight line, turn, twist, or any combination of these things. We will talk about straight line motion as, “translation”, and turning through an angle as, “rotation”, later.
You can locate the centre of gravity of an object like a rod by finding the point that it balances on your finger. This is not so easy for a length of fly line…but it still has one..

MAKING THINGS MOVE
Of course, things are never quite as simple as we would like, just describing the properties of an object isn’t enough.
Because we want to move these objects around, we have to take in to account certain rules that relate to getting an object to move from A to B. We have to get our rods and lines and flies moving and we may want to change the direction, or speed, that they are moving in once we have managed to get them in motion. If we are completely nuts, we also might want to be able to record or measure how we have made this movement happen so that we can repeat the process.
Three basic rules were outlined by Sir Isaac Newton approximately 325 years ago.
Just in case you’ve missed them, here they are… they are sometimes referred to as N1, N2, and N3. I have paraphrased Sir Isaac, he won’t mind I’m sure…

Newton’s Laws 1/2/3
1- An object will remain in motion, or not, at the same speed and in the same direction until acted upon by an external force.
2- Force equals mass times acceleration.
3- For every action there is an equal and opposite reaction.

Application of these very simple rules enables us to describe the processes involved in moving our rod and line.
Sir Isaac Newton should not be confused with Isaak Walton.
Isaak Walton was author of “The Complete Angler” and never mentioned Newtons rules mainly because he knew nothing about physics and he died before the other Isaac published his “Principia Mathematica” and this also probably why he never became an SI unit like Newton. (I would however like to recommend that forces used in angling contexts are from now on measured in SI units of “Waltons”.)
This disconnect between the great angling literature and basic mechanics has existed down the ages and whereas Isaak W..had a pretty good excuse on the basis of his prior demise…no-one else since can honestly play the same card…
Anyway, we can see from Rule One that nothing is going anywhere until we apply a force to it…

Force
A pressure, a push or a pull, something which causes an object to move or deform.

A force, in a casting sense, is just something needed to make an object move. We apply a force to the rod, the rod applies a force to the line, and the line pulls the fly.
With objects that are elastic, a rod for example, a force is also necessary to make only part of that object move i.e. to deform it, like bending, and it is force that causes the line to stretch as we cast.
Forces are vectors, they have magnitude and direction and, like weight, are measured in Newtons too.
We know from experience that it’s not just any old force that is going to make an object move. Anyone who has tried to pull an elephant around an ice rink or push one out of the bathroom will know that it takes a lot of force to get it to move at all. How much force is dependent on the mass of the elephant, small elephants are easier to shift than large ones.
Based on the first rule, if an object is already in motion we need to apply a force to change its current speed or direction otherwise it will just carry on and that the more mass the object has, the more force we will need to apply to it to make it change its speed or direction.
This resistance to moving, or having a change in motion, is a property called…

Inertia
The propensity of an object to resist a change in motion.

We already know from our experience of elephants in the ice rink that, when something is stationary we won’t be able to move it until we have applied a force big enough to overcome its inertia. This is not the same as overcoming friction or Gravity. Inertia is closely linked with mass, lots of mass, lots of inertia. We think of inertia usually in terms of things that are stationary and subject to other frictional and gravitational forces, but objects in motion also continue to have inertia. A rod or a line have the same inertia when they are moving as they did before you made them move and to change their speed or direction the force you apply must still be big enough to overcome that inertia. Of course the mass of a rod or line isn’t very big so you don’t need much force to overcome their inertia when they are moving…an elephant on the other hand is a different kettle of fish.
What we also know from Newton’s second rule is that, once we have overcome that inertia, if we continue to apply the same force then the object will accelerate.

Acceleration
The rate of change in velocity of an object.

We have to be a bit careful here because we are dealing with velocity and velocity has two elements, speed and direction. So, the force we apply can do one, or both, of two things. It can either change the object’s speed or it can change the object’s direction of motion. Either of these things would change the object’s velocity and so acceleration isn’t just about making something go faster, in physics an object undergoing a change of direction is also accelerating.
This is sometimes a bit difficult to grasp and it is further complicated by physicists referring to decelerations as negative accelerations. For the most part however, non physicists use acceleration when we are talking about increasing speed and deceleration when decreasing speed. It’s not right, technically speaking but it is what we mean.
If an object has mass and a velocity then it is said to have

Momentum
The mass of an object times its velocity.

Momentum is about mass moving…a 5000kilo elephant in the bathroom has mass but no motion, so it has zero momentum. Because it is linked to velocity, momentum is a vector quantity, it has direction. Momentum is often confused with inertia but they are not at all the same thing.
A 5000kilo elephant shoved out of the bathroom at 10 miles per hour has a momentum of 5000kg x 10mph and is quite likely to be pretty hard to stop. Of course, if you get in the way of the elephant as it comes out of the bathroom it will, in turn, thanks to Newtons third rule, apply a force to you. Quite a big one probably, which will cause you too to either move, move and deform a bit, or, if you’re up against the opposite wall waiting your turn in the bathroom, deform quite a lot.
The more momentum an object has, the harder it is to slow it down. So, in the case of a fly line for example, the greater its momentum, the harder it is to stop and the farther it will go.
When discussing fly line trajectories, the fact that mass is commonly not distributed uniformly throughout the fly line means that the momentum of the fly line is not uniform either. For a given velocity, the parts of the fly line that have the most mass have more momentum than those with less mass and it takes more force to change their speed or direction.
This explains why the line doesn’t really follow the path of the rod tip, why a weight forward is easier to shoot than a Double Taper, the hinging effects of overhang, hooked line layouts, dangling leaders and the kick of heavy flies and sink tips as mentioned above and many other phenomena.
So, we have applied force to our line, overcome its inertia, accelerated it and it now has momentum…what stops the fly line carrying on indefinitely once we have stopped applying force to it?
If Newton’s first law is true then some sort of force or forces must be slowing it down and causing it to fall to the ground. The most obvious candidate is gravity. Gravity operates uniformly over the line and, irrespective of the magnitude of the line’s mass or forward velocity, left to its own devices, (which it isn’t, bear in mind we are holding one end up with the rod) it will all fall to the ground at the same rate. Obviously, the more velocity it has, the further it will go before it hits the deck. In this respect, if distance is your goal, velocity is king.
Also working on the line is air resistance, this is called…

Drag
The force exerted on an object in motion as a result of friction in air or water.

The greater the surface area of the thing in motion, the higher the drag will be as a result of friction. As velocity doubles the effect of drag quadruples – the higher the speed the greater the drag will be.
Also, the more line is in the air the greater the surface area and so the greater the drag.
However, remembering density, if we can squeeze the mass into less volume then we can reduce the surface area and thus reduce the drag. This is why a #5 sinking line will cast further than a #5 floating line… less drag.
Sometimes drag is referred to as “lift”. This is because drag opposes the force of gravity as an object falls to the ground. Since “drag” or “lift” increases with speed, something in freefall will continue to accelerate until its lift is equal in size to the force of gravity acting on it. At that point the object will have reached its “terminal velocity”. (It’s OK to use terminal velocity in this context so don’t reach for the skillet.)
Since there is more drag when an object falls through water than when it falls through air a sinking line will have a much higher terminal velocity in air than in water. This, if you are casting for distance for example, may have an effect on the trajectory you choose for your particular cast. A sinking line will go forwards faster than a floater because it is denser and has less drag but it will fall quicker because it has less lift and thus a higher terminal velocity in air than a floater.
You may have heard of Galileo’s experiment dropping cannon balls of different sizes from the Leaning Tower of Pisa. In Galileo’s experiment the two cannon balls fell to the ground in exactly the same time. If he had replaced one of the balls with a feather he would have had an entirely different result.
Since drag is a result of friction with the medium the object is travelling through, would a feather fall at exactly the same rate as a hammer if dropped in a vacuum?
In fact, this experiment was demonstrated during the Apollo 15 moon mission and the hammer and feather did fall at exactly same rate. So, even if you are one of those who believe the Apollo missions were faked, you can take comfort in the fact that “they” must have built a massive vacuum chamber in order to also fake the hammer –feather drop experiment and so the money wrenched from the pay packets of hard working US taxpayers was spent in a way that genuinely represented real value for money….for people reading this in the US this must be a huge relief. (Sorry about the weight in Kilograms thing earlier too)
In this context, Drag is about the amount of surface in contact with the air or water, it is not the same as…

Form Drag
The force exerted on an object in motion in air as a result of its shape.

A ball with a given surface area will have less form drag than a cube with the same surface area simply because of its more aerodynamic shape. If Galileo had flattened one of his cannon balls out before dropping it he would have found that the differences in form drag would have changed the outcome of his experiment.
The line only has Momentum with which to work against the effect of drag….for a given mass, more velocity means more momentum, velocity is king…but sadly for the tournament casters, drag always wins in the end.
A fly line in motion is under…..

Tension
For our purposes tension is a force that attempts to stretch the fly line.

For tension to exist there has to be a force at one end and a resistance, or an opposing force, at the other end.
If you pull your finger it will go into tension. The tension in your finger will be uniform all the way from the end that you are pulling on, to the joint. This is because both ends of your finger are to all intents and purposes, fixed…this is not true of a fly line because only the rod end of the line is fixed (unless you’ve hooked a 5000 kilo elephant in your bathroom that is).
Discounting the effects of drag for the moment…, because only one end is fixed, we rely on the inertia of the line to oppose the force applied to the line at the rod tip, but, the mass and inertia become less and less as you approach the leader end…why is this we wonder ?
Imagine the line as a series of, let’s say, a thousand tiny interconnected balls and give each ball an equal mass. During a casting stroke the ball at the tip has to pull 999 balls along behind it, the next ball 998, the next 997 and so on until the last ball which is pulling on nothing but the fly and leader, so the tension on the last ball is 999 times less than the tension on the first. Basically, tension in the line is greater at the rod tip end than it is at the fly end and this fact will help us when we look at “waves” later.
For the moment let’s leave lines and look at the rod.
An ordinary single handed fly rod is both a spring and a lever. It is what is known as a “third class” lever which is, in this case, a device that goes faster at one end than the other and we use it to increase speed.
To make this happen we rotate the rod, as we do this the tip will travel a much greater distance than the butt in the same amount of time i.e., it has travelled faster.
We describe the motion of the rod in terms of…

Rotation
The angular change in position of the rod.
Translation
The linear change in position of the rod.

To make the rod move we apply force to it at the butt end. To make the most of the lever effect, that is the magnification of velocity at the tip, this force needs to make the rod rotate. This is not a force which acts in a straight line, a linear force like the one needed to push the elephant out of the bathroom, or the tension in a straight fly line, this is a force which needs to act through an angle. This sort of angular force is called a torque.

Torque
An angular force, the force required to rotate an object.

A linear force, one which makes the rod translate and, an angular force, torque, one which makes the rod rotate can, and do, act on the rod at the same time. By combining these forces we are able to move the rod through a vast range of positions at various rates and it is the combination of these two simple processes that enable us to cast at all.
The use of our springy lever has the effect of converting the angular force, torque, applied by us at the butt into a linear one applied by the rod tip on the line.
Up to now we have used terms that are largely linear, the directions in vectors are unchanging. When rotations are involved, the directions in vectors change, the relationship between the x and y components changes constantly but the terms we use are very similar to those described above. If we are able to understand the terms as they apply to linear forces then it helps enormously when we try to deal with their rotational, or angular counterparts.
So from Velocity we can generate the term Angular Velocity.

Angular Velocity
The speed and direction of an object as it rotates.

In rotation, direction is measured relative to the axis or point about which the object rotates, e.g. clockwise, counter clockwise, positive or negative degrees per second. Speed is measured by the amount of arc travelled in a given time, e.g., degrees per second or revolutions per minute.
Changes in Angular Velocity are Angular Accelerations.

Angular Acceleration
The rate of change of angular velocity.

Because we are using a flexible lever, it gets lively with this one. If the rod were to be completely stiff then the rate of acceleration at the butt of the rod would be the same as the rate of acceleration at the tip. Even though the tip is travelling faster than the butt, the rate of change is the same, as the speed at the butt doubles, the speed of the tip doubles.
The rod isn’t completely stiff though, it bends when we apply force at the butt as we try to overcome the inertia of the line and the inertia of the rod itself. This means that even if the acceleration at the butt is constant the acceleration at the tip won’t be. If the rod has inertia which is its resistance to changes in linear motion then it also has a resistance to angular motion. If we were being consistent, this should be called Angular Inertia but it isn’t.. it’s called…

Moment of Inertia
The propensity of an object to resist a change in angular motion.

The mass distribution in the rod will determine how hard or how difficult it is to rotate it.
A rod doesn’t just act as a lever, it also operates as a kind of spring.
There are a huge number of reasons why a springy rod is easier to use than a rigid one which we won’t go into here, but, springy things have unique properties too and act in a regular and predictable way.
Springiness, that is, the way that the rod bends and unbends is a function of the properties of the material that it is made from and how that material is distributed through the rod.
The relevant material properties are described by using…

Modulus
A quantity that numerically expresses the degree to which a substance possesses a property, such as…

Modulus of Elasticity
Modulus of elasticity is commonly used to refer to stiffness in fishing rods, it is the property of a material that describes how much it deforms and how it recovers from a deformation to its original state, its “elasticity”, so, the higher the modulus, the stiffer the material.
Elastic or springy things have been studied for centuries and one of the basic relationships is described by…

Hookes Law
In a spring, or elastic material, the extension of the spring, is proportional to the load.

So, for a rod, when it behaves as a spring, the bigger the load the more it will bend. This seems very obvious, but what, in physics terms, is a load…?

Load
The forces that are working on the rod.

Load is commonly associated with the bend in the rod due to the weight of the line that we are trying to move and there is nothing inherently wrong in looking at things in this way. But it is also related to the other forces at work on the rod. The amount of torque and how we apply it at the butt will also influence how the rod bends.
The weight of the rod itself and the mass profile of its taper, its moment of inertia, its surface area and the effects of drag all influence the way the rod behaves when it is in motion.
Where there are multiple forces at work like this we can add them all together using the term…

Net Force
The sum of all the forces acting on an object.

This is like the resultant force we described earlier. Since force is a vector quantity we can sum all the forces acting on an object to determine the net force. In turn, this tells us which direction all of the individual forces acting on an object will tend to move the object. For example, if we look at the line the net force acting on it will be a combination of forces applied by the rod tip, gravity, and those caused by air resistance.
By the nature of springs they have a propensity to boing, that is, the load forces the spring to extend and then the spring boings back to its original shape and so on, there’s a whole lot of boinging going on here. And, if it needs a force to make it extend then it must also need a force to make it go back to its original state, this force is called a…
Restoring Force
In a spring or elastic material it is the force that works to return the spring or material to a state of equilibrium.
Since we have introduced the topics of tension and restoring forces it might be a good time to talk about waves

Wave
A wave is a disturbance that travels through a medium and transports energy from one place to another without moving the medium itself.

As the wave travels through the medium there is some displacement of the medium but the medium returns to its original position after the wave passes by.
If we drop a pebble in to the centre of a pool we create waves on the surface of the pool. The waves transfer the energy from the falling pebble to the edge of the pool. Obviously, the water from the centre of the pool does not end up piled along the sides of the pool so we know that, although we can see the
waves moving the water up and down, the water itself does not move laterally with the waves. As the wave moves the water is initially displaced upwards and then restored downwards to its original state.
When a wave travels through a medium in one direction and causes the medium to be displaced sideways or upwards or downwards the wave is called a transverse wave. Examples of transverse waves can be seen when we cast, in tailing loops, some types of mend and the irritating wobbles we occasionally get in the rod leg of the line.
If the medium is displaced in same direction that the wave is travelling then the wave is called a longitudinal or compression wave. For an example of a compression wave simply listen for that bead or fluff whipping past your head…sound is made of compression waves.
At this point you are no doubt wondering what tension or restoring forces have to do with waves.
If you have a guitar handy, pluck a string. You will hear a certain note. It doesn’t matter how hard or soft you pluck the string you will always hear the same note.
What do we have to do to get it to make a different note? The answer is to adjust the tension. By turning the tuning peg for the string we change the amount of force being applied to the string and this changes the tension on the string. Add more force and the tension increases and the note becomes higher because the wave moves faster. Reduce the tension and we get a lower note because the wave moves slower. Remove all tension and we hear nothing. Waves simply won’t travel along the string any more. Pluck the string and it just stays plucked. The wave just stays where it is. We have removed the tension and this removes the restoring force.
Why does this matter ?
Well, if you remember the discussion on tension in the fly line, there is more tension at the tip end than the fly end. We know that the greater the tension we have on a line the faster a wave will travel along the line. And without tension there is no restoring force to bring the material the wave is travelling through back to its original position.
So, a wave in a fly line will travel fast at the beginning and slow down as it approaches the fly end. Here it is now going so slowly, or the restoring force is so weak, that it can appear to get stuck. This is a wave that can collide with the rod leg during a casting stroke and produce the classic tailing loop.
That’s enough about waves for now. Let’s get back to our discussion on forces…
So, what do we want all these forces to do? Essentially we want them to do work to the line and the fly to get these things from one place to another. In physics work has a particular meaning…

Work
Work is force applied to an object, times the distance over which the force is applied.

This term is closely linked with another….

Impulse
Impulse is force applied to an object, times the time over which the force is applied.

Between them, these two concepts are crucial for understanding how we manage the variables, force, time and distance, to make the most basic of casts function in our favour.
Interestingly, work is measured in SI units of Joules. Joules are also used to measure energy and so work can also be used to describe the change of energy in an object. So, notwithstanding the effects of drag, we can work out the velocity of an object if we know what its initial energy level was and how much work we have done to it.
Managing the three variables using the concepts of work and impulse, we can say that a high force applied over a short distance, i.e., in a short time, will have the same final result as a low force applied over a long distance, i.e., a long time. In a casting situation we choose how we will mix this up to achieve the desired line velocity that we believe we need for the circumstances we find ourselves in or just to fit our own biomechanical preferences.
We briefly touched on energy as we looked at the concept of work. In this context we can look at energy as the ability of a thing, in quantitative terms, to do work on another thing. Energy is most commonly described in two forms…

Potential Energy
Energy stored in an object.

A rod that is bent has potential energy or PE, stored energy, and has a capacity to do work on the line. When that energy is released it is converted into….

Kinetic Energy
The energy of an object in motion.

Also called KE by people who have a hard time spelling, or saying, kinetic. The energy of the line when it is in motion for example. This is the stored energy being used.
We often talk about the combination of Potential Energy and Kinetic Energy as Total Energy.

Total Energy
The combined kinetic energy and potential energy of an object.

Most people can spell total so total energy is never referred to as TE. Usually totally energy is just referred to by physicists and clubbers alike as E.
Energy is said to be “conserved”, that is..

Conservation of Energy
In a closed system energy in = energy out.

A closed system is a construct used for analyzing interactions between objects and forces. In a closed system the amount of stuff or matter within it does not change. And, similarly, in a closed system, energy is neither created nor destroyed ie it is conserved.
If we are juggling elephants, as we throw our elephant in to the air we give it a certain kinetic energy. As is rises it goes slower and loses kinetic energy. The amount of kinetic energy lost is identical to the amount of potential energy it gains as its height increases. As the elephant peaks and begins to fall the potential energy is again converted to kinetic energy and by the time it reaches our hand again, it is going the same speed at which it left.
Whilst we are elephant juggling away in our closed system there is another property that we met earlier also being conserved…

Conservation of Momentum
In a closed system momentum is conserved.

A familiar example of this is Newton’s cradle. When two objects collide and bounce off each other, the momentum lost by one of the objects will be precisely equal in magnitude, but opposite in direction, to the momentum gained by the other object.
This has, historically, been used to explain the phenomena of a fly leg appearing to speed up toward the end of the cast but the jury is definitely out on that one. So, as a lay person, I think it’s best to watch the argument unfold slightly away from the bathroom door…just in case I get involved in conserving the momentum of a rapidly moving, entirely metaphorical, elephant.

 

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As I re-read these things, garbled as it all seems, I wonder if it is particularly useful, from an instructional point of view, to be anything other than dimly aware that these concepts even exist.
After all, no-one is going to be explaining to a complete novice the concept of conservation of momentum or the value of KE in a line with a non uniform, mass distribution. In fact it is massively unlikely that they would be discussed with anyone other than like minded instructors.
However, for an examination candidate to express themselves properly and correctly to questions that might arise on these matters, they must have a clear grip on the basic terms and how they fit together to explain how a cast actually works without resort to those pithy one liners that we mentioned in the intro. Having said this, I still frequently use these teaching tools myself but, where necessary, I amend them in order to better fit the facts.
To do this properly I have tried myself to understand the relationships between Force and Work, Levers and Springs, Speed and Velocity, Momentum and Inertia and the choices made by us, the casters, in how we manipulate and manage them to our advantage because, without us, nothing happens at all.
Just for the record, I am no physicist and it has never crossed my mind to actually work out the values associated with these things on a cast by cast basis. From a teaching perspective I can see no useful purpose in trying.
There are others out there, however, for whom this quantitative analysis is a source of constant fascination…sadly, perhaps, it is not for me.
Thanks, Mark

© Mark Surtees


NOTE- originally published Oct. 15 2013, this article has since been revised by Mark Surtees: curent version Nov. 11 2016

Tension Glasses

i remember Lee Cummings bringing this up several years ago and i’m pretty sure it’s still in the back of his mind.
the idea being, through high-tech chemistry and ingenuity, someone could devise a fly line that would change colors as it goes through various degrees of tension throughout the cast. the tension glasses would allow the caster or viewer to see these colors while the line is dancing in the air and as a bonus, look extremely cool and cause large amounts of envy by having shades no-one else has !

it’s easy to see how a visual back-up confirmation of explanations such as this would greatly benefit casters of all levels.
“With a beginner, one way I like to describe fly casting is to get them to imagine that the head of the fly line out beyond the rod tip is like a piece of bath plug chain of the same length and the typical objective of a normal overhead cast is to get every ball and link of this chain moving in the direction toward intended target area prior to ceasing to apply force with the rod.
If we don’t do this then there is the risk that the last few links/balls at the very far end of the chain were not fully utilized as available weight during the casting process and as one result, the leader and fly of which is attached may not be directed accurately at the target.”

tension glasses lee cummings

as per Lee’s ‘vision’ demonstrated by the photo-shopped image above, bright red would designate highest tension and i guess, bright blue when completely slack. (blue being at the opposite end of the visible spectrum for humans)

anyhow, somewhere right in the middle of downright absolutely f’n brilliant and something pulled from an old pipe-dream sci-fi flick, i fully applaud this kind of thinking and imagination because, even if it never really comes through, (but i hope it does ! this already exists so changing a few things here and there and transposing the idea to a fly line doesn’t seem so exotic) the idea might lead on to another way of achieving the same result, furthering the knowledge of fly casting without resorting to horrendous and boring charts, graphs and equations that have become the norm when discussing casting physics.

“I think if I ever get these glasses it would open up a whole new dimension to fly casting pleasure, actually seeing tension change with the eye would probably stand right by what we have actually come to learn what it is that we feel when we cast.”

for the complete Fly Casting seen through Line Tension Glasses article click this link or the pic. put on your shades and enjoy !

related articles

Boring Poetry

a brilliant article  from Aitor Coteron addressing a rather big issue contemporary casting instructors are experiencing. needless to say, i couldn’t agree more.

” The late Mel Krieger classified casters in two broad groups: “engineers” and “poets”. The first group needs to know how things work in order to learn them; the other one relies more on feeling and doing those things than in any analytical approach.

Mel didn’t make any qualitative distinction between the two groups; although he himself was a “poet” instructor I think that he never dismissed those more inclined to the engineering way of seeing things. In fact he saw both views as equally valuable and complementary.
When in the recent history of flycasting instruction this has changed I don’t know for sure, but currently those who claim themselves as “poets” like to dismiss on a regular basis those of the “engineer” class.

To be honest I am able to differentiate very easily those instructors of the “engineer” kind: they just can explain, when necessary, casting issues by means of applied physics.
I have a hardest time, however, when it comes to distinguish those who consider themselves “poets”. Of course you find them using examples and similes to explain casting mechanics, but I don’t see why being an “engineer” prevents you from doing the same. There is, however, one key trait that makes “poets” as noticeable as a priest on top of a mound of lime: they proudly declare that concepts like “inertia” or “acceleration” are utterly unintelligible, whereas you can find tongue twisters like “kinaesthetic” appearing frequently in their conversation. “

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