Use this script to find the good strings for you instrument

#!/bin/bash
# copyright @lobzang 2021

[ $# -ne 3 ] && echo "Usage : $0 [Diapason(cm)] [Note] [String[P(plain)/W(wounded)]]
ex: $0 65 C3 10P" && exit 2

Diapason=$1
Note=$2
String=$3

case $String in
9P)  UnitWeight=0.00001794;;
10P) UnitWeight=0.00002215;;
11P) UnitWeight=0.00002680;;
12P) UnitWeight=0.00003190;;
13P) UnitWeight=0.00003744;;
14P) UnitWeight=0.00004342;;
15P) UnitWeight=0.00004984;;
16P) UnitWeight=0.00005671;;
17P) UnitWeight=0.00006402;;
18P) UnitWeight=0.00007177;;
19P) UnitWeight=0.00007997;;
20P) UnitWeight=0.00008861;;
21W) UnitWeight=0.00008293;;
22P) UnitWeight=0.00010722;;
24W) UnitWeight=0.00010857;;
26P) UnitWeight=0.00014975;;
26W) UnitWeight=0.00012671;;
28W) UnitWeight=0.00014666;;
30W) UnitWeight=0.00017236;;
32W) UnitWeight=0.00019347;;
34W) UnitWeight=0.00021590;;
42W) UnitWeight=0.00032279;;
54W) UnitWeight=0.00053838;;
*) echo "String $String not found"
esac

ScaleLength=$( echo "scale=10 ; $Diapason/2.54 " | bc )
Frequency=$(echo "$Note" | awk ' BEGIN{
position["A"]=0
position["A#"]=1
position["Bb"]=1
position["B"]=2
position["C"]=-9
position["C#"]=-8
position["D"]=-7
position["D#"]=-6
position["E"]=-5
position["F"]=-4
position["F#"]=-3
position["G"]=-2
position["G#"]=-1
}
{ 
  octave=substr($0,length($0))
  note=substr($0,1,length($0)-1)
  p=position[note]+(octave-4)*12
  print 440*(1.05946^p)
 } ')
Tension=$(echo "scale=10 ; $UnitWeight*(2*$ScaleLength*$Frequency)^2/386.4" | bc  )
echo "ScaleLength $ScaleLength ; Frequency $Frequency , Tension : $Tension"
echo $Tension | awk ' 
$1<10 { print "not enought tension !!!" ;exit } 
$1<15 { print "X-LIGHT" ;exit } 
$1<20 { print "LIGHT" ;exit } 
$1<25 { print "MEDIUM" ;exit } 
$1<30 { print "HEAVY" ;exit } 
$1>=30 { print "too much tension !!!" ;exit } '

]$ ./cordes.sh 59 E4 11P
ScaleLength 23.2283464566 ; Frequency 329.632 , Tension : 16.2649595905
LIGHT

]$ ./cordes.sh 59 E3 30W
ScaleLength 23.2283464566 ; Frequency 164.822 , Tension : 26.1532887319
HEAVY

]$ ./cordes.sh 59 E3 26W
ScaleLength 23.2283464566 ; Frequency 164.822 , Tension : 19.2265213229
LIGHT