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I have bought about a dozen different types and weights of fishing line to try as strings.

I had originally intended to simply weigh a measured length of each line, and plug that weight into the formula for calculating string tension for a given pitch and scale length, and use that to work out which line would work for which note.

For those who want to make their own spreadsheets or otherwise play with the figures, that formula is:

Tension in Kg = 4 x Frequency in Hz squared x Length in cm x Mass of that length in grams / 980621

This works more or less OK for steel strings, but for nylon or other monofilaments it’s not that simple.

A nylon string stretches by anything up to 25% under tension, so the mass per unit length drops proportionately. The stretching is somewhat but not exactly proportional to the tension, and varies with time under strain in a complex interplay of short term elasticity and long term permanent stretch.

Bugger. My clever table of mass per unit length figures is only a starting point at best. Not to mention my Java string tension calculator which does not take stretching into account. I’m fairly sure D’addario’s published data doesn’t take stretching into account either, but I’ll check that later.

One of the first rolls of line I received after my shopping spree on evilbay was a roll of Ultima Red Ice 30lb 0.5mm line.

This stuff is a cool fluorescent red colour and I chose it as a likely candidate for a high A (440Hz) or B (494hz) string on classical guitar.

It is very flexible and ties easily.

I weighed a length of it and calculated a mass per meter of 0.245g – plugged into the formula that suggests a tension of 8.14Kg when tuned to 440hz on a standard guitar scale length of 648mm

That’s high tension for a classical guitar, but not much higher than published by D’addario for their higher tension E strings. Plus, I always knew it would stretch a bit so it was a good pick.

I put it on the guitar , and after a LOT of stretching, I finally got it up to an A, after a lot more stretching and a couple of days settling, it held the A pretty well. I had wound more than i needed to onto the peg, so the turns round the peg were also stretching, which made the process worse for settling in, although its irrelevant to the final tension. I am now testing by winding the absolute minimum onto the peg in the knowledge that the peg will still end up with plenty of turns on it as the string stretches.

Best of all it sounded pretty good. I could live with this as a high A string. First time WIN! (Call it beginners luck since my later experiments gave more mixed results)

After all that stretching I knew that the tension must have ended up much lower, and it certainly didn’t feel like 8kg. So I got another length of the line and tested it on a board with a machine head at one end, and a hanging scales at the other. I used two bits of wood to stop the string at the correct 648mm distance, and tuned it up to A 440hz. After some settling and stretching and retuning the tension measured 6.8kg. Quite a bit less than the 8.14Kg suggested by using the unstretched weight

The string had stretched by about 15%, but I didn’t get a very accurate measurement of that.

Once the string was at pitch I marked the ends of the 648mm with sharpie , and let the tension off, of course the string contracted again, by most but not all of the length it had stretched while tuning up. I then cut the string at the marks and weighed that piece, then plugged that weight into the formula. The result was 6.65kg. Close enough to the 6.8 measured directly, considering the many slightly inaccurate measurements involved.

So I can say that that particular type of line has a tension of around 6.7Kg when tuned to A440 on a 648mm scale. Unfortunately, because the amount of stretch is dependent on the tension, I can’t directly extrapolate to other pitch and scale length combinations.

My ambition of a universal string tension calculator for fishing lines is looking rather distant at this point. I would need accurate tension / stretch curves plotted carefully for each different sort of line. Stretching time would have to be left between each increment of tension for each line. I think this would be weeks or months of work and would benefit from better scales than I have.

All is not lost however. The table of weights of unstretched line serves as a maximum, the line will never be heavier per unit length than when it is new. The amount of stretch can be guessed to within a useful margin once you have some experience. I could perhaps even build this guesswork into an applet.

Heavier strings will stretch less, and strings made of harder materials such as fluorocarbon, will also stretch less. So this can be taken into account when choosing which line to use.

To complicate matters further, there is a wide variety of types of line available.

here’s what I’ve tried so far for classical guitar strings (I tune my guitar CGDAEA or CGDAEB, sorry about that, you’ll just have to extrapolate for standard tuning!)

Ultima Hard Core 70lb breaking strain 0.7mm diameter unstretched weight 0.536g/m

This stuff is very stiff, relatively hard to knot, a little heavier than the softer monofilaments and stretches noticeably less than most.

I tried it as a guitar E 329hz – I found it unsuitable for classical guitar as it just didn’t have the suppleness and the tone was not to my taste. The tension at E was a bit too high. (tension based on unstretched weight is 9.9kg, actual tension must be not much less than 9kg) A lighter gauge of the same stuff might work better, but I wasn’t inspired to experiment further with this for guitar.

Daiwa Sensor 50lB breaking strain 0.74mm diameter, unstretched weight 0.518g/m

This is a fairly normal supple nylon mono, in a nice dark brown colour. It knotted easily. There’s a fair bit of stretch, but i didn’t tune it all the way to E, so it didn’t stretch as much as it would have with more tension. I only took it up to D. I found the tone a bit dull, and the weight a bit heavy for an E string, but too light for an A string. It might work OK for a lowish tension B string on standard tuning guitar if you want a warm rounded tone.

Ultima Seastrike 50lb breaking strain 0.7mm diameter, unstretched weight 0.509g/m

This is the most normal standard nylon mono I have tried so far. It’s incredibly cheap. It is supple and bends easily, but is also very slick, so knots pull through unless you use lots of turns.

There’s a quite a lot of stretch, although of course none of these E strings stretch as much as the thin line I used for the high A.

I tuned this to E and it actually works pretty well. I could use this happily enough as an E string. It’s hard to say if the tone is as good as purpose made classical guitar strings, but it’s reasonably close at first listen.

Ultima Seastrike 25lb breaking strain 0.45mm diameter, unstretched weight 0.182g/m

This line was bought for an attempt at a high B. It is the lightest line I have. Like the 50lB version it is very slick, and knots pull through easily, but worse because the line is so thin and flexible. The first attempt the knot unravelled. The second attempt I broke the string with a bad knot. The third attempt the string held, and after much stretching made it up to high B 494hz.

It doesn’t sound too bad. Given that this is pushing the absolute limit of pitch that is possible on a guitar I’m fairly pleased. I think this line might be a tiny bit too light for the best tone. Unstretched weight implies tension of 7.6kg at high B, but of course it will be much lower with all the stretch of this thin line. It feels more like 5.5kg. I have a couple of other lines using different materials to try for high B and I’ll report on those when I’ve tested them.

Supacast 100lB breaking strain 1mm diameter unstretched weight 0.936g/m

I bought this to use for my mid A string 220hz. Tension implied by the unstretched weight is 7.76kg, and since the string is so thick and doesn’t stretch too much actual tension is probably around 7kg. This line is similar to the seastrike, but the tone is duller. I think the 1mm is too heavy, it feels a bit heavy and the tone is rather dull and round, reminiscent of the daiwa sensor. The tone is brightening a little as the string plays in and stretches a little more. This line might work OK for G in standard tuning, but I will look for something a bit lighter around 0.9mm for my A.

That’s all I’ve tried for classical guitar so far. I have also tried several lines as E strings on cello and viola, and learned that the criteria for that are very different from classical guitar! I will leave that report until a future post as this one is quite long enough already.