Dear all,
The PUL parameter of Savarez strings is the mass of 100m string length,
so NFA 230 is a nylon multifilament string wound with silver plated
copper that has a mass per length of 230 g/100 m.
Given the PUL in g/100m, you can calculate for wound strings (following
from the Taylor equation):
- Tension: T (N) = 0,4 PUL [L(cm) f (Hz)/10000]^2 L= string
length, 1 kg (force) = 9,807 Newton (N) approx. 10 N
- Frequency f (Hz): f (Hz) = 15180 Sqrt [T (N)/PUL (g/100m)] / L
(cm)
- needed PUL for given f, T, L : PUL (g/100m) = 2,5 T (N) / [L (cm)
f (Hz)/10000] ^2
The relation between PUL and the equivalent gut diameter deqiv is (gut
density of 1330 kg/m3 assumed):
PUL (g/100m) = 104,5 d eqiv^ (mm) ^2
deqiv (mm) = 0,09784 Sqrt [PUL (g/m)]
Savarez Alliance KF strings
KF presumably means the Japanese Kureha Fluorocarbons corp. , who has
invented PVDF (Polyvinylidenfluorid) in the past. So Alliance KF would
be the product of an alliance of Savarez with Kureha.
The strings with diameter up to 0,91 mm are plain strings made of
clear PVDF.
The thicker strings (0,95 mm +) are plain strings, opaque and of a
yellowish colour. In the center some plastic fibers are embedded.
Savarez somewhere wrote that these strings are produced by
multicoating. I assume, that these strings are made from PVDF too. What
fibres are used - I don't know, presumably PVDF too, for a stable
composition of the materials.
I have calculated the density of a KF 125 string (1,25 mm) from weight
and volume and got 1775 kg/m3 (+/- 18). This is fairly near to the
usual density of PVDF, 1770-1780 kg/m3. Arto Wikla found a density of
1791 kg/m3.
Savarez wrote on their web site: "... and the density is very close to
gut." !!! ([1]http://www.savarez.fr/anglais/instanci-pince.html#1)
If you believe this, you will get string tension 34% higher than
assumed.
Dear Martin, I have recalculated the tensions for baroque lute string
set (Paul Beier's Calc); I hope the chart of results will come over
correctly.
D-minor Lute_M Shepherd_11crs_sl69.bsc
Beier String and Fret Calculator File
Name: D-minor Lute
Maker: M Shepherd
String Chart
Pitch: A 392hz.
Bridge tension: 517,97 N.
String
Note
Length (cm.)
Tension (N.)
Gut Diameter
Alternative string
Alternative Diameter / Catalogue number
1
f
69
37,84
0,44
2
d
69
31,84
0,48
3
A
69
27,93
0,6
4
F
69
26,76
0,74
5
D
69
23,23
0,82
6
A'
69
23,02
Carbon PVF
0,95
octave 6
A
"
27,93
0,6
7
G'
69
22,32
Carbon PVF
1,05
octave 7
G
"
25,22
0,64
8
F'
69
21,63
Carbon PVF
1,16
octave 8
F
"
28,23
0,76
9
E'
69
22,37
Carbon PVF
1,25
octave 9
E
"
27,86
0,8
10
D'
69
21,02
Carbon PVF
1,36
octave 10
D
"
26,76
0,88
11
C'
69
20,29
Carbon PVF
1,50
octave 11
C
"
25,8
0,97
You can see, that the tensions of the KF basses are somewhat lower than
you had them. I would have expected them to become higher, for the
density used in the calculator is 1776 kg/m3, while you used ca. 1300
(?) x 1,1608 kg/m3, alright? Is it possible, that you used a higher
density?
I agree with you that in the case of unwound (dull) bass fundamentals
their tensions should be lower than those of their octaves. Some
octave tensions are a bit high now, for my opinion.
All the best
Karl
Am 25.04.2016 um 15:53 schrieb Matthew Daillie:
Hi again Herbert, Martin, Arto et al.,
I have just spoken with the technician at Savarez. They are redoing
their website and hope to update their string calculator at some time
in the future.
In the meanwhile I managed to get some explanations regarding their
reference numbers for over-wound strings. They offer silver wound
strings (NFA), copper wound strings (NFC) and plastic wound strings
(NFP). I have never tried the latter but Savarez recommend them for
transitional strings on theorbo-necked instruments. I would be
interested if anybody has any feedback on them.
The numbers correspond to the PUL (linear density). For example, NFA
230 is a silver wound string with a PUL of 2.3 g/metre. The silver and
copper strings have different reference numbers because copper is
slightly less dense than silver and to compensate the inner core is
thicker so as to give the same tension.
One can calculate the tension with the following formula, making sure
to use the same units for SL and PUL (I hope I've got it right, I'm not
a mathematician by any stretch of the imagination!):
4 x the frequency^2 x string length^2 x PUL
This gives tension in kilos, for Newtons divide by 9.8
The technician gave me specific tensions for your baroque lute 9th
course fundamental (E at a'415):
NFA 230 gives 2.7 kgs
NFA 250 gives 3 kgs
NFA 275 gives 3.1 kgs
Strangely, when I do the calculations with his formula I don't get
quite the same results so maybe he was using a more complex formula (or
winding down for his afternoon nap).
I think Paul Beier's calculator is definitely the way to go for
simplicity's sake. Otherwise, why not use Kuerschner or Aquila, their
references use gut equivalent diameters and so are very straight
forward for tension calculations?
Anyway, one string down, 23 to go!
Best,
Matthew
On 25/04/2016 05:00, Herbert Ward wrote:
As an experiment, I put extremely light strings on my baroque lute.
This made the tone very difficult to control. This is pretty good
practice, but in a month or two I need to venture out of the house
with the lute.
So it's string buying time.
Can someone give me a Savarez PUL number for the fundamental of the
9th course (E) at AA5 with a 68.5 cm string length? Also helpful
would be an indication of whether the PUL corresponds to heavy, medium,
or light stringing.
Google searches gave nothing useful.
To get on or off this list see list information at
[1][2]http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
.
--
References
1. [3]http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
kg/m assumed
--
References
1. http://www.savarez.fr/anglais/instanci-pince.html#1
2. http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
3. http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
