One of the things that is commonly printed on spinning, surfcasting and boat fishing rods in Europe is the test (or working) curve. Yet in other countries, including here in New Zealand, it is rare to see it stated on a rod blank.

The test curve is a measure of the stiffness of the rod. It is the amount of weight that needs to be applied to the tip of your rod to bend it 90 degrees. In a nutshell, the higher the test curve the stiffer the rod. Stiffer rods have “fast” actions whereas less rigid rods which bend in parabolic curves easily have “slow” actions.

Why is it important to know this and why isn’t this information printed on all rods sold?

The test curve measures how much force has to be applied before line is pulled from the reel when the rod is held vertically. All of the spinning rods that I own have test curves between 0.8 – 1.10 kilograms. In my experience, when matched with lines in the 4 – 7 kilogram breaking strain range, a rough rule of thumb is that :-

• rods with test curves less than 0.90 kilograms are best suited to casting and retrieving hard baits

• rods with test curves more than 0.90 kilograms are best suited to working soft plastics

The test curve and drag are essentially cumulative. By that I mean that if the test curve of the rod is 1.0 kilogram and the drag is 1.0 kilogram then the cumulative force that can be applied on a hard charging fish is 2.0 kilograms. Many anglers fail take the test curve into account when setting the reel drag. They pull the line directly off the spool with a spring balance and set the drag at a pre-determined tension. The line is pulled through the guides but the rod is not bent in the drag setting process. The pre-determined tension is generally the rule of thumb that the drag setting should be no more than one third of the breaking strain of the line. This is a mistake.

Say for example that:-

• the breaking strain of the line is 6.0 kilograms
• the reel drag is set at 2.0 kilograms (one third of the breaking strain) and
• the test curve of the rod is 1.0 kilogram

This means that the force applied to the fish when the rod is working at its test curve and the fish is pulling line off the reel against the drag is actually 3.0 kilograms (2 + 1), or 50% of the breaking strain of the line. If the line does not have any stretch (i.e. braid) then the odds against the fish escaping are high. This generally happens either when the fish is a long way from the angler and the extra drag from water pressure on the line takes it past breaking point or when the fish is close and makes a sudden surge which either breaks the trace or pulls the hook free. The only reason that this does not happen more often is that breaking strain of braid is generally underestimated.

The reality is that the correct rule of thumb should be that the test curve of the rod plus the reel drag must not exceed one third of the breaking strain of the line.

In the example, above the reel drag must not exceed 1.00 kilogram as:-

• One third of the line breaking strain = 2.00 kilograms (6 x 0.33 = 2.00)
• One third of the breaking strain minus rod test curve of 1.0 kilogram = 1.00 kilogram

So set the reel drag setting at 1.00 kilograms and simply let the test curve of the rod wear down the fish. Apply extra finger pressure to the spool, if and when necessary, to help control the fish. My point is that if you know both the test curve of the rod and the breaking strain of the line it is a simple exercise to adjust the reel drag to ensure that the line does not break during the fight, especially when you can see your trophy almost flapping in the shallows. Nobody needs that kind of avoidable heartbreak.

To make it easier to understand the table below shows in italics what the drag  setting needs to be for various line breaking strains and rod working curves.

Working cruve graph

Note that one cell is highlighted in blue. This means that there is no need to set the drag on the reel at all with this working curve and line combination as there will be sufficient force applied by the rod alone when it is bent into a smooth curve to provide 33% of the line breaking strain.

So if you are fishing 4 kilogram breaking strain line with a rod this stiff then to avoid a break off when a fish is tiring and charging about in shallow water close to the shore it will be necessary drop the rod tip and point it at the fish when it runs. This eliminates the force from bending the rod (test curve) and effectively means that the fish pulls line off the reel at the set drag pressure which is well less than 33% of the breaking strain of the line.

Why is the test curve not routinely printed on rod blanks? Who knows, but I suspect it is because nobody is actively lobbying for it.

All is not lost however. It is easy to measure the test curve simply by doing up the reel drag, running the line through the rod and attaching a spring balance to the end of the line. Pull down the spring balance until the rod bends into a smooth tight curve and record the weight on the spring balance. Congratulations, you’ve just measured the test curve.


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