Impact of Blank Cutting on IP and AA

cover blank cutting

Intro and operating mode

The aim of this experiment is to measure the effect of cutting a blank at the tip and then at the butt to see the effect on the power and the action of the blank.

For this purpose, we used two strictly identical blanks. The first one was cut at the tip to 1, 2, 3, 4, 5 cm, then 7.5, 10 and 15 cm. The second one was cut at the butt at 5, 10, 15, 20 and 30 cm.

We took the IP and AA measurements each time. To sum up, the IP measurement indicates how many grams will be needed to deflect the tip of a blank by 1/3 of its length. It is therefore a unit for measuring power: the more weight it takes to bend a blank, the more powerful it is.

The AA value is a measure of the angle formed by the last few centimetres of the tip, once it has been bent by one third of its length. The higher the AA is, the more the blank has a fast action, in other words with a high measured angle. 

If you would like to go into more details, we invite you to find out more about the CCS (Common Cent System).

decoupe blank

Tip cutting

The results of the measurement of the cut-outs at the tip are as follows:

gif blank coupe scion
tableau decoupe blank au scion pointe
graphique coupe blank scion pointe AA degré

Trend curve calculation model: Logarithmic

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that 96.5% reflects the data).

graphique coupe blank scion pointe IP

Trend curve calculation model: Polynomial

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that is 99.6% reflective of the data).

Data indicates that cutting a blank at the tip makes the blank more progressive, some would say rounder, and that the impact is very strong from the first few centimetres. On our test blank, a 3 cm cut increases the AA from 78° to 75°, then 12 cm must be added in order to lose 2 degrees of AA again.

Cutting a blank to the tip also increases the IP, thus the weight needed to lower the tip by a third of the length of the blank. To give an estimate, please note that the measurements and impacts may vary from one blank to another, our blank estimated at 2-12 grs of lifting power tends to reach the IP characteristics of a 7/17 grs after 5 cm cut, the IP characteristics of a 10/25 grs after 10 cm cut, and the characteristics of a 10/30 grs after 15 cm cut. 

Where the curve of the impact on the AA (the angle) starts strongly at the beginning and then stabilizes, the impact on the IP (the power) seems, at least on the first 15 cm, more linear.

mesure angle blank decoupe

Cut at the butt of the blank

The results of the measurement of the butt cut-outs are as follows:

gif blank coupe talon
tableau découpe blank au talon butt
graphique coupe blank au talon butt AA degré

Trend curve calculation model: Polynomial

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that reflects 98.1% of the data).

graphiquecoupe blank talon butt IP

Trend curve calculation model: Polynomial

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that is 99.4% reflective of the data).

Cutting a blank at its butt makes it more progressive again, we can see that the AA (angle) decreases very clearly as we cut the blank. Basically, the effect on the action seems to take twice as long as when cutting the tip. It takes 30 cm to lose 5 degrees of AA, it would take 15 cm of cutting at the tip of the blade to achieve 5 less degrees of AA. Here again, the first few centimetres are the most impactful, you lose 4 degrees of AA on the first 15 cm of cut at the butt, where the next 15 cm will only lose one degree.

The IP measurement indicates that cutting at the butt clearly takes away the lifting power at the blank: the more you cut at the butt, the less weight is needed to lower the tip by a third of the length of the blank. This effect seems to be quite linear this time, the first 15 cm make us lose 42 grs of IP, the next 15 make us lose 40 grs of IP.

mesure tableau decoupe blank

Conclusion

Cutting a blank, either at the tip or at the butt, will make its action more progressive, with a lower angle measured at the tip. However, the action (the curve of the blank under charge) should not be confused with power (its rigidity): by cutting a blank at the tip, you make it more progressive but you increase the feeling of power.

Cutting a blank at the butt makes the blank more progressive as well (more moderate), while at the same time increasing the lifting power. While the impact is less important when cutting off the tip, it is still clear and perfectly measurable.

We recommend when cutting off the tip, to go cm by cm, whereas a cut at the butt can be done 5 cm by 5 cm

graphique variation IP decoupe blank scion

Trend curve calculation model: Polynomial

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that reflects 99.8% of the data).

variation AA decoupe blank au scion

Trend curve calculation model: Exponential

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that reflects 96.3% of the data).

variation IP decoupe blank au but

Trend curve calculation model: Polynomial

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that reflects 99.5% of the data).

variation AA decoupe blank au butt

Trend curve calculation model: Exponential

R representing the degree of correlation between the trend curve and the data collected (i.e. a curve that reflects 90.3% of the data).

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