Notching: The Bane of Tension Holding

Notching is the groove created in the string due to wear and tear. Usually, it is the string that moves that notches. Not the one that stays still (link).

Often overlooked, the impact of notching on string tension is huge. To understand that, we must first understand how strings stretch. 

Depending on the type of strings, an additional 20 lbs of tension, from 40 to 60, stretches the string only a mere extra 4 to 7 mm.

When a string notches, it weakens. The "U" shaped notch leaves the string with about half its original diameter, or less, to hold tension. As a result, the "U" is always stretched apart, looking more like a wide-mouthed "V". The string lengthens.

Since the cause is wear and tear, notching always occurs around the sweetspot. That would be the centre 8 to 10 mains, and between the middle 8 to 10 crosses. 

Translated, that means about a total of 20 strings (10 mains + 10 crosses) could have about 10 notches each. Assuming all notches are equally deep, and each notch lengthens the string by 0.5 mm, that's a total of 5 mm (0.5mm x 10 notches each) relaxation PER STRING!

Based on the string stretch above, almost 20 lbs of tension is lost. It could be more!

The other implication of notching is string deflection. The rules require the mains and crosses to be alternately interweaved. So each string's path is like a sine curve, with peaks and troughs.

Since notching occurs at the intersection between mains and crosses, the peak-to-trough amplitude reduces after notching. With this lower amplitude, the total "distance" each string has to travel from grommet to grommet is reduced. So tension drops some more! 

Notching is an inevitable double whammy! It cannot be prevented. We just have to manage it through regular restrings or mitigate its effect with stringsavers. 

Or bear with the floppy trampoline stringbed!