Warning: word from some casting geeks
Some guys I know just went through the related math and physics on this question. We tried come up with something akin to "swingweight", to put a number on it. There's so much hype and advertising about weight and ease of casting lately that we wanted to look at what really makes a difference. Rotating a rod is mostly akin to the technical term Moment of Inertia (MOI, roughly the torque/force needed to rotate it). It's very dependent on how long a rod is and where the weight is distributed.
It turns out that a weight change at the grip (a lighter reel, a lighter reel seat) has very little effect on the overall MOI of a rod because it's so close to the point of rotation. Conversely, even a slight weight reduction in the upper half of the rod (lighter rings, finer wraps, a lighter blank) has a major effect on the feel because this weight is magnified by the distance away from the point of rotation (think choking up on a bat).
We went through this very technically from a physics point of view (some great work by Grunde Lovoll PhD) and then justified it with samples in the hands of a very experienced tackle reviewer (Magnus Angus of Fly Fishing and Fly Tying Magazine). Grunde's model very closely matched Magnus's impressions of feel.
Keep in mind that the model is most accurate for a casting style that rotates the rod close to the reel seat. For styles with a stiffer wrist using rotation at the elbow, the reel weight will have a greater effect, but even so a weight change at the tip will have roughly a 16 times greater effect on swing weight than an equivalent change at the butt (4 times further from the point of rotation with this length squared in the equations).
I scripted an
online calculator for the MOI equations and using the
Sage Z-axis 590-4 data as a sample, here are some numbers for comparison...
Rod with no reel: 63.5 gram-meter2 moment of inertia
Rod with reel: 70.3 (with 4.5 oz reel such as the Galvan T4)
Rod with heavy reel: 75.5 (with 8.0 oz reel, couldn't find any 5wt reels this heavy)
So for a typical modern trout rod, the reel contributes about 10% to the overall swingweight, and 1 oz of weight in the reel has about a 2% affect. Whether this is significant is up to you to decide (try it before you buy it??).
Here a link to the full article...
Measuring Fly Rod "SwingWeight"
Shawn,
That's very interesting. I haven't heard that before. I'll bounce it off the guys.
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