Selecting a Reel for a New Rod - Balancing

[Silver Creek]

Just picked up a St. Croix 9' Legend Elite 5 weight and I am trying to match a reel to it. This rod is quite light at 2.8 oz so I had assumed that it wouldmatch up with a very light reel. Not so fast.

I have read a number of articles on balancing rod and reel and it seems that the consensus is the rod should balance (be horizontal) at the fulcrum where your index (and some say middle) finger is placed on the grip during a casting stroke. An article suggests that a loaded reel should generally weigh 1.5X the swing weight of the rod. According to it, the swing weight equals the weight of the rod (2.8 oz.) plus maybe 0.2 oz for twice the rod length in line out of the tip. Therefore, according to this article, the loaded reel should weight about 3.0 oz X 1.5 = 4.5 oz.

http://www.flyfishohio.com/a_question_of_balance.htm


Yet I am puzzled by "swing weight." According to Yellowstone Anglers, and their 2013 5 weight shootout results, this rod (and many more) has a swing weight of nearly 9 oz.! Hmmm.
http://www.yellowstoneangler.com/gea...os-2-greys-xf2


So I tried each of three different loaded reels on it (6 oz, 7.0 oz and 7.7 oz) with about 18 feet of line extending for each out of the tip. Under these conditions, the reel that balanced the rod at my index finger was the heaviest one at 7.7 oz. loaded (Colton CRG II for 5,6,7 - very pleased with this reel BTW). The two lighter reels were too light as they caused the tip to dip. I was surprised by this result as I assumed I would be needing to pick up a Lamson Litespeed or some other feather weight reel. Am I doing this right?

My reply is in 3 parts: Part 1

You right in being confused. There is so much BS about ?rod balance? that it continues to this day.

But first let me address swing weight because it partially addresses what is actually being discussed in the article below that supposedly addressed rod balance:

http://www.flyfishohio.com/a_question_of_balance.htm

The Yellowstone Angler defines "swing weight" in the quote below:

Swing Weight 20 points available

You have heard this term if you are a golfer. Every pro shop has a simple scale that measures swing weight, the weight of the head of the club in relation to the shaft when you waggle the club. Since a scale like this won't work with a fly rod, we had to come up with a better way to measure swing weight, that weight you feel out ahead of your hand when you hold the rod in a horizontal position. The best way that we have found to measure this is by placing a foam fulcrum in the middle of our scale, position the handle of the rod so that the fulcrum sits slightly forward of the middle of the handle, then position the rod horizontally, put some finger pressure on the very butt of the rod to hold it level and read off the weight in ounces.

Rods with a low swing weight are a joy to use and fish all day. False casting while fishing dry flies all day becomes effortless. Rods with lower swing weights help protect light tippets too, as there is less inertia to overcome as the rod tip gets jerked around while you try to set the hook. Rods with a high swing weight are not nearly as pleasant to fish, and will extract their payment in arm pump and fatigue by the end of the day.

This year we gave swing weight 20 points rather than 10 as this is really a performance category and has a huge bearing on how well the rod feels in your hand and how it performs.

http://www.yellowstoneangler.com/gea...os-2-greys-xf2

Swing weight is actually a dynamic measurement. Swing Weight = moment of Inertia.

A larger moment of inertia around a given axis requires more torque to increase the rotation, or to stop the rotation, of a body about that axis. Moment of inertia depends on the amount and distribution of its mass, and can be found through the sum of moments of inertia of the masses making up the whole object, under the same condition. When a body is rotating around an axis, a torque must be applied to change its angular momentum. The amount of torque needed for any given change in angular momentum is proportional to the size of that change.

http://en.wikipedia.org/wiki/Moment_of_inertia

In very simple terms it is the momentum of the rod as it moves through the casting arc. When we cast a rod, we move it through a casting arc, and we apply torque which is the rotational force we use to move that fly rod through the casting arc. So swing weight is the simple way of expressing the amount of force or energy that we need to use to cast the fly rod. The greater the swing weight, the harder the rod is to cast. It is both the energy (torque) we use to both MOVE the rod and to STOP the rod for each back cast and forward cast.

The Yellowstone Angler uses a static measurement, the static mass distribution along the rod shaft - "that weight you feel out ahead of your hand when you hold the rod in a horizontal position" as a proxy for swing weight (moment of inertia). Realize that this is done WITHOUT the reel and is ONLY the contribution of the the ROD to the Moment of Inertia. However, moment of inertia during casting includes the reel and line. The greater the combined mass of the rod/reel//line that is being rotated through the casting stroke, the greater the Swing Weight = Moment of Inertia.

Although swing weight is Moment of Inertia , what the Yellowstone Angler described is a "Static" moment which is inertia, which is due to mass, which is felt as weight due to gravity. The rotational velocity component is missing in static momentum, but since the value of rotational momentum varies with the speed and axis of rotation; if two rods have the same rotational speed and axis of rotation, the rod with the higher static inertia distribution along the rod shaft will have the higher rotational momentum. So with an apples to apples comparison, we can compare the "that weight you feel out ahead of your hand when you hold the rod in a horizontal position? between two rods of the same length to get an idea of swing weight as we cast those rods.

There is a precedent for this type of comparison. Consider the Common Cents System that uses a static metric to estimate the line rating of a fly rod. The more "cents" it takes, the higher the line rating.

The Yellowstone Angler's definition is an attempt to use a static measurement to estimate what the comparative moments of inertia would be between two rods of the same length at the same rotation velocity.

Part 2 & 3 Address rod balance and fly casting