Once more: TC vs casting weight

There have been many debates about the validity of the relation between test curve and casting weight. I know many people have concluded the concept of the TC, casting weight and eventually line strength is flawed. The thing that struck me however was that all discussions seem to be fueled by theory much more than empirical data. Finally I think that modern blank design and materials are of no influence to the idea, opposed to what many people have written.

So I decided to do a simple experiment. I took six of my rods and loosely took their TC by hanging a bottle with water at the end of the line, approach the 90 degree angle by adding water and then tried the derived casting weight to see if there is fixed relation between the two. The rods in question vary from a 1 1/4 lb 12 ft carp rod (yes, very old, soft and light), a Vendetta spin, a telescopic spining rod, a light glass spining rod, a micro spinning rod (just under 4 ft) and an ultralight spinning rod with a test curve of barely over 3 oz (that's 90grams ).

I found on these six rods the rule of using 1/16th of the test curve as casting weight is usable, to say the least. A bit on the heavy side to my liking but that could very well be subjective.

When optimizing the casting weight by trial and error I found a varying ratio to the measured TC of 17 to 20. As I said, I feel the rule of 1/16th results in casting weights a bit on the heavy side. My way of 'measuring' TC might also have to do with that.

Apart from the above (which is kind of interesting) I very much liked the idea of knowing the TC of my rods. There where a few surprises, f.i. the 90gr UL. I knew it is a very light rod but I could never describe it until now.

Are there people here who tried the same or would be interested in testing their rods just out of curiosity? Would be nice to collect data and see how valid a rule can be found

I did something similar with my Fox Avon and Specialist Duo rods. The Specialist felt like it had more oomph than the 0.5lb TC suggested (closer to the 1.0lb TC Avon,) so I popped a reel on each and hung lead weights on a rod held parallel to the floor until the rod started to lock up (I stood on a chair!) Both rods were bang on their stated test curve, which seems to suggest that despite the method's crudity it works well.

As for relation to casting weight, using your formula the Avons would have a suggested maximum casting weight of an ounce. This holds true for a full-blooded throw, yet it'll happily cast a two ounce combination of feeder and bait a goodly distance with a controlled lob. Similarly, my 1.75tc barbel rods are happiest throwing a couple of ounces, but with care will cast a 4 or 5oz, Jaffa-sized method ball up to 40yds.

I found something similar: The heavier rods seem more tolerant for -relatively speking- heavy casting weights. The carp rod f.i. was often used with weights up to 2 oz with some consideration from the caster. The lighter rods seem to tolerate less (also in a relative sense).
However, the carp rod I tested was casting most effective when using about 1 oz. which again is spot on. The problem with this matter is that many factors are subjective and none of the variables are exact. A bit like fishing, one could say .

The old rule of thumb of 1oz casting weight to 1lb of test curve dates back to when rods were made of cane and various other materials.
The early glass rods of the 60s and 70s maintained a similar ratio but modern materials are far more versatile especially when different tapers are brought into play.
A good example today is the fashionably long Continental type beach rods that are often rated to 8 oz casting weights but have a test curve more like 2lb.