Rod Weight and Power, Making Sense

“If you cannot measure it, if you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.” Lord Kelvin

I first saw the above quote when I read an article by Dr. William Hanneman called "The Common Cents System".  The article was about a method the he had developed to determine the proper line weight for a fly rod.  This article intrigued me because as I was building rods just for my personal use, I encountered a scenario that was frustrating.  

I had built myself an 8' , 5 weight rod on a name brand blank that I just loved, it cast better than any other rod I had bought or built, and instantly became my go to rod, and is still in use a lot today.  Next, I decided I needed a 4 weight rod.  So I acquired a nice 9', 4 piece blank and built my rod.  I loaded it with 4 weight line and off I went.  Imagine my disappointment that first day when casting this new rod, it felt terrible, I couldn't make a tight looped 30 foot cast.  The rod never felt like it loaded properly unless I was slinging 50 feet or more of line.  Which in the small stream I was fishing was not possible.  I decided that I just didn't like that rod and on the shelf it went, never to be used again.  

A while later, I built myself another 5 weight rod on another name brand blank, this one was 9 foot long.  I loaded it with 5 weight line and took it fishing.  I had the same experience with this rod, it never felt right, it didn't seem to load up and casting was difficult and frustrating.  So it too got resigned to being just a decoration. 

It was about this time that I first read Dr. Hanneman's article, and it really made sense to me.  His method uses bags of pennies, (thus the play on words, Common Cents), to deflect a rod to determine the amount of force required to fully load that rod.  So I followed his method and low and behold it explained a lot.  My favorite rod, the 8' 5 weight was according to his system truly a 5 weight, which explained why it cast well with 5 weight line.  However, the 4 weight not only measured as a 5 weight according to this method, it was a heavier 5 weight than my favorite rod.  This explained why it would not load up with 4 weight line.  Next on the rack was the 9' , 5 weight.   According to "The Common Cents System" it is actually a 6 weight rod, and explained why it would not load properly with 5 weight line.  

You see, according to Dr. Hanneman, "The current practice is for each manufacturer to label each rod with a recommended line weight. However, that recommendation is simply the subjective opinion of each rod’s designer."    

Although "The Common Cents System" does work well, the Engineer in me could not stop at stacking books on the handle of the rod, counting out pennies and using a tape measure to determine the correct line to put on a rod.  I had to have something better.  After a couple of prototypes and experiments, I now have developed a tool that uses Dr. Hanneman's basic premise and mathematical calculations to not only determine the best weight line, but to take it down to the recommended line weight in grains for a particular rod.

It consists of two stands, the one on the left holds the rod and has an adjustment system to get the rod level, and lined up with the stand on the right.  By definition a fully loaded rod has had its tip deflect by a distance equal to 1/3 of its length.  So, using a series of pulleys attached on one end to the tip top of the rod, and the other to a precision scale, the rod is deflected by 1/3 of its length.

7' 6" rod on the rack

The precision scale measures the exact amount of force needed to deflect the rod.  I have developed the correct formulas to convert that number to the correct line weight in grains to properly load the rod when casting.  Line manufactures list the weight of the first 30 feet in grains. 

So, lets go back to the three rods I discussed earlier.   According to my system, my favorite rod will load properly with a line weighing 140 grains, which is very typical for 5 weight line.  The second rod (originally labeled as a 4 weight), needs a line weighing about 150 grains to properly load.  A little research and I found Rio Trout LT WF 5 Weight Line having a head weight of exactly 150 grains.  The 3rd rod, (originally marked as a 5 weight) needs a line with a head weight of 170 grains to load properly, which is a typical weight for 6 weight line.  The two rods that I had previously written off as failures, now cast significantly better because they are matched with the appropriate weighted line, and see action in appropriate situations.

As of now, all rods leaving my shop will have a recommended line weight in grains, to allow the customer to select the best possible line to match up with their new rod.