celtic harp

Harp string Calculator

Calculate the length of your harp string or find the correct tension for your string given the note; string-length; and string parameters.

Harp string Calculator

Harp string Calculator

Here we provide a Harp string calculator compiled using formulae widely available. It is supplied as an Excel spreadsheet download. It is supplied "AS IS and although we have used it to calculate string lengths and diameters for our harps we cannot guarantee any results or be responsible for any errors or omissions.

 

STOP: Before you start to build your beautiful new harp, check that the string lengths you have designed for each note will make a working harp!


So you are designing a harp and then it occurs to you "What kind of strings do I put on it? "

  1. What length do I need for each note?
  2. How thick should the string be?
  3. What type of wrapping should the string
  4. have for a particular note?

Most people do not realize how important it is to design the harp so that each note has the optimum length and tension for each note. I have seen many beautiful harps built with out any knowledge of string design. Sometimes they work well sometimes they do not!

This formula will go a long way to helping you sort out the harp string dilemma, and save much frustration

You will need to have an "Excel" or "OPEN OFFICE" spreadsheet program installed in your computer for it to work. If you are not familiar with spreadsheets seek help from someone who does. This is a powerful tool to aid with harp design

General instructions are given. It is for nylon and nylon wrap strings only at this stage.

Download  Nylon
stringForm36paraNyl.xls

Appearance

NYLON STRING TENSION FORMULA  INCHES/POUNDS

Last Update"

F=FREQUENCY L= LENGTH in INCHES D- DIAMETER INCHES
T-TENSION IN POUNDS   %BS= percent breaking  strain for the string
%Bs of WR STR is for the string with wrapping

STRING NO   Frequency L mm L inch   D T BS %BS %Bsof WR STR
1 Bb 1864.655 80.000 3.150   0.025 6.661 22.092 30.2  
2 A 1760.000 100.000 3.937   0.025 9.272 22.092 42.0 n/a
3 G 1567.982 123.000 4.843   0.025 11.134 22.092 50.4 n/a
4 F 1396.913 145.000 5.709   0.025 12.281 22.092 55.6 n/a
5 E 1318.510 165.000 6.496   0.025 14.168 22.092 64.1 n/a
6 D 1174.659 175.000 6.890   0.025 12.649 22.092 57.3 n/a
7 C 1046.502 190.000 7.480   0.025 11.835 22.092 53.6 n/a
8 Bb 932.328 225.000 8.858   0.028 16.524 27.712 59.6 n/a
9 A 880.000 240.000 9.449   0.028 16.749 27.712 60.4 n/a
10 G 783.991 260.000 10.236   0.028 15.602 27.712 56.3 n/a
11 F 698.456 275.000 10.827   0.028 13.853 27.712 50.0 n/a
12 E 659.255 295.000 11.614   0.032 18.550 36.196 51.2 n/a
13 D 587.330 315.000 12.402   0.032 16.787 36.196 46.4 n/a
14 C 523.251 330.000 12.992   0.032 14.623 36.196 40.4 n/a
15 Bb 466.164 348.000 13.701   0.032 12.907 36.196 35.7 n/a
16 A 440.000 370.000 14.567   0.032 12.999 36.196 35.9 n/a
17 G 391.995 390.000 15.354   0.036 14.507 45.810 31.7 n/a
18 F 349.228 415.000 16.339   0.036 13.038 45.810 28.5 n/a
19 E 329.628 445.000 17.520   0.036 13.355 45.810 29.2 n/a
20 D 293.665 477.000 18.780   0.040 15.036 56.556 26.6  
21 C 261.626 510.000 20.079   0.052 23.057 95.580 24.1 50.3
22 Bb 233.082 545.000 21.457   0.052 20.898 95.580 21.9 45.6
23 A 220.000 585.000 23.031   0.052 21.451 95.580 22.4 46.8
24 G 195.998 628.000 24.724   0.052 19.621 95.580 20.5 42.8
25 F 174.614 675.000 26.575   0.052 17.991 95.580 18.8 39.3
26 E 164.814 728.000 28.661   0.052 18.644 95.580 19.5 40.7
27 D 146.832 785.000 30.906   0.056 19.955 110.850 18.0 43.6
28 C 130.813 850.000 33.465   0.060 21.317 127.251 16.8 37.7
29 Bb 116.541 900.000 35.433   0.065 22.262 149.343 14.9 31.1
30 A 110.000 950.000 37.402   0.076 30.210 204.167 14.8 34.2
31 G 97.999 1000.000 39.370   0.080 29.438 226.224 13.0 33.3
32 F 87.307 1045.000 41.142   0.085 28.804 255.386 11.3 26.9
33 E 82.407 1090.000 42.913   0.091 32.000 292.713 10.9 29.9
34 D 73.416 1130.000 44.488   0.096 30.378 325.763 9.3 23.9
35 C 65.406 1168.000 45.984   0.100 27.952 353.475 7.9 22.0
36 Bb 58.270 1205.000 47.441   0.100 23.613 353.475 6.7 18.6
37   0.000   0.000     0.000 0.000    
            total tension 660.118      
                     
    WRAPPED  STRING DETAILS            
  CORE WRAP Total Diam RADIUS core A totalArea TAr/Carea %BS %BS for wrap str  
21 0.036 0.008 0.052 0.026 0.001 0.0021 2.1 24.122 50.3  
22 0.036 0.008 0.052 0.026 0.001 0.00212 2.1 21.864 45.6  
23 0.036 0.008 0.052 0.026 0.001 0.00212 2.1 22.443 46.8  
24 0.036 0.008 0.052 0.026 0.001 0.00212 2.1 20.528 42.8  
25 0.036 0.008 0.052 0.026 0.001 0.00212 2.1 18.823 39.3  
26 0.036 0.008 0.052 0.026 0.001 0.00212 2.1 19.506 40.7  
27 0.036 0.01 0.056 0.028 0.001 0.00246 2.4 18.001 43.6  
28 0.04 0.01 0.06 0.03 0.0012 0.0028 2.3 16.751 37.7  
29 0.045 0.01 0.065 0.0325 0.0015 0.00331 2.1 14.906 31.1  
30 0.05 0.013 0.076 0.038 0.0019 0.00453 2.3 14.796 34.2  
31 0.05 0.015 0.08 0.04 0.0019 0.00502 2.6 13.012 33.3  
32 0.055 0.015 0.085 0.0425 0.0023 0.00567 2.4 11.278 26.9  
33 0.055 0.018 0.091 0.0455 0.0023 0.00650 2.7 10.932 29.9  
34 0.06 0.018 0.096 0.048 0.0028 0.00723 2.6 9.325 23.9  
35 0.06 0.02 0.1 0.05 0.0028 0.007855 2.8 7.907 22.0  
36 0.06 0.02 0.1 0.05 0.0028 0.007855 2.8 6.680 18.6  

 

Notes:

  1. There is a small inaccuracy in the calculation for wrapped strings, The calculation did not allow for the circular shape of the wrap and is based on a square cross section. This causes the percentage breaking strain to show approximately 15 - 20% higher than calculated.
     
  2. Due to the variation in parameters for nylon strings the calculations are not exact. Do not exceed 70per cent breaking strain unless you are prepared to risk frequent string breakages.
     
  3. Best results for monofilament strings occur between 45% to 60% breaking strain. Less than 45% gives a sloppy sound ,50 60% is good for medium tension harps, 70% is for high tension harps.
     
  4. The chart you download is for a 36 string Paraguayan harp. Change the string lengths and diameters to your hearts content.
     
  5. MAKE A BACKUP COPY OF THE ORIGINAL BEFORE YOU MODIFY IT. It is very easy to make a mistake and mess up the formulae in the spreadsheet.

  6. The formulas show the tension in each string and the total tension on the whole harp. The harp needs to be designed to withstand the total tension and at the same time be responsive enough to make a good sound.

 We supply this spreadsheet in good faith
It is supplied "AS IS and although we have used it to calculate string lengths and diameters for our harps we cannot guarantee any results or be responsible for any errors or omissions. If you can offer any improvements we are happy to hear from you

 

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