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? "
- What length do I need for each note?
- How thick should the string be?
- What type of wrapping should the string
- 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:
-
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.
- 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.
- 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.
- The chart you download is for a 36 string Paraguayan harp. Change
the string lengths and diameters to your hearts content.
- 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.
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 |
