Power is one of the most talked-about and most misunderstood characteristics on a blank technical data sheet.
Every blank we design and produce at Composite Forge ships with a TDS that lists three related values: Power, P100, and T15. In this second walkthrough of CF Engine, we’re breaking down what these numbers actually mean, how they’re calculated, and how they connect directly to the way a blank bends.
Watch the full CF Engine walkthrough on Power, P100, and T15.
Every Rod Forge blank lists its own TDS, including the Power, P100, and T15 values covered below.
What the TDS Power Values Actually Represent
Every Composite Forge TDS includes three related performance metrics: Power, P100, and T15. These three values are calculated using the same underlying method, but each one evaluates a different portion of the blank. Understanding why we use three separate metrics starts with understanding the graph they come from: flexural rigidity.
Flexural Rigidity: Stiffness Along the Length of the Blank
In CF Engine, a flexural rigidity graph shows how the stiffness of a blank changes along its entire length, plotted from the butt end on one side to the tip on the other.
As expected, flexural rigidity is highest at the butt, where the blank is stiffest, and drops off sharply toward the tip, where the blank is thinner and more flexible.
That taper is not incidental. If a blank held the same flexural rigidity value from butt to tip, it would perform essentially like a constant-diameter tube, and performance would suffer. A well-designed blank needs different stiffness values at different points along its length because the butt and the tip serve entirely different roles in how the rod loads and unloads.
From a Full Profile to a Single Power Number
Since flexural rigidity is profiled over the blank’s entire length, it is challenging to concisely describe the blank’s power performance from that profile alone. To describe a blank simply, in a way that can be compared across a full lineup, that profile needs to be consolidated into summary metrics. Power, P100, and T15 are essentially averages of the flexural rigidity profile evaluated over specific portions of the blank’s length.
Here’s how each one is evaluated:
Power, as its name suggests, is the primary metric for describing a blank’s power, or its resistance to bending under load, because the first third of the blank’s length is where it does the heavy lifting. P100, although it captures stiffness over the whole blank, begins to blend into performance characteristics associated with action because it also includes the mid and tip sections, where much of the blank’s action is shaped. Therefore, P100 serves as a secondary reference for power.
T15, on the other hand, is not a power metric at all. It is a performance metric focused entirely on the tip and is more useful for understanding tip behavior and action, a topic we’ll cover in a future video.
A full TDS report for the HTD-70MM blank, with Power calculated at 14,213.6 lbf-in² and rated Light for this blank.
Connecting Power Metrics to Deflection
CF Engine displays deflection profiles alongside flexural rigidity graphs, and the relationship between the two is direct.
Take a series of blanks with similar action, ranked by power and compared under the same load case: the highest-power blank shows the least deflection, while the lowest-power blank shows the most.
The relationship between deflection and power comes directly from the flexural rigidity profiles. Across a well-built series spanning different power levels but similar action, both the deflection and flexural rigidity profiles show consistent offsets, or step-ups, from one blank to the next. As flexural rigidity increases, deflection decreases in that same order.
The same trend carries through to the Power and P100 metrics, which provide an objective basis for defining the power level of a blank rather than relying on the subjective nature of how the blank feels to an individual.
From a Number to a Power Rating
Every blank’s Power value falls within a defined range that corresponds to a Power category, whether that’s Medium Light, Medium Heavy, Extra Heavy, or another rating along that scale.
For example, one of our recent TDS sheets showed a Power value of 35,883.4 lbf-in². Placed within our Power rating ranges, that value objectively classified the blank as Medium Heavy.
That objectivity is the real point of the exercise. Power ratings have historically been subjective, varying from one designer’s interpretation to the next. By evaluating Power directly from flexural rigidity data and comparing those results against measured blank deflection, CF Engine removes much of that ambiguity and allows us to define and compare Power consistently and with much greater granularity across every blank we produce.
What’s Next: Action
Power is only part of how we define blank performance. The next installment in this series moves into Action, a set of metrics that describe where and how a blank bends to provide a more detailed picture of its curvature and overall bending profile.
Look out for that walkthrough soon.
