Here's one to take you into the weekend. I've posted 3 in-depth pieces on fluorocarbon to the site, two of which I've written. In my two, I've largely showed the data I've researched, generated and/or gathered that suggests many of the fluorocarbon claims by manufacturers and anglers alike is largely a bunch of bull, in my opinion. Still love the stuff for certain applications, so I'm not knocking it, but instead saying the claims made to a largely unknowing public are crap.
The last post/article was entitled "Putting to bed another fluorocarbon myth", and I tackled the "stretches differently/less at lower pressure" theories you hear many espouse. In that piece, I basically said something to the effect that until someone can provide some test data using more sensitive/technical levels of equipment (Instron testing, etc.) to show otherwise, I was sticking with my opinion that individual lines are truly "individual" in their properties, and that to make an across the board declaration as relates to fluoros "stretching less" or "being more sensitive because they stretch less" in any capacity against monos or copolys is to put yourself at high risk of being wrong. Well, I've finally found more data that supports that stance, and it's courtesy of some high dollar testing instrumentation.
In this first graph is a series of tests ran against 4 different brands of monofilament fishing line, all of the same diameter. Notice the very similar stress-strain curves generated between the 4 samples. The differences between the line samples all fall within about a 10% variation level at any given point. They even all rupture at similar points, which you might expect with similar diameters and compositions.
If you take a representative sample from those similar curves, in this case they chose the sample marked 'Nylon 2', and compare it to a sample of fluorocarbon of the same diameter, you get the following chart on the right. Notice in the early stages of the test, the two lines overlap each other to the point of not being able to distinguish them from each other. They finally separate out about midway through the entire force range, but it's the fluorocarbon line staying slightly flatter, meaning it's stretching more for any given force. Eventually the curves almost touch near the end before rupture, and differences are similar to, and in line with, the nylon samples in the first chart.
The point here is that even using very highly sensitive equipment, there is absolutely nothing to suggest that fluorocarbon in any way stretches less, or resists stretching better (stretches differently), no matter how much (or how little) pressure you put on it. Keep in mind that this is just 5 samples of line, and certainly with enough testing and comparing of all brands of line out there, you could probably find some truly distinct differences, but it's looking more and more like the exception, not the rule. Bottom line is that it still looks like for every stretchy mono, there is an equally stretchy fluorocarbon - and for every low stretch fluorocarbon, there is also a low stretch mono that acts similarly. So, until someone generates actual data that tips the "stretch balance" in favor of fluorocarbon, as opposed to just claiming it or posting it as gospel in some message forum or advertisement, I'm not believing any of it, and you shouldn't either - call BS on 'em, and apologize later only if they can produce the data :) I'm guessing most probably can't.
The one area left that I'd like to find data on is impact resistance, which is another way of saying rate of stretch. Some might call it shock testing. How fast you apply a stress to a material can greatly affect differences between materials. Many otherwise strong fishing lines simply don't hold up well to a sudden impact force placed upon them. This might be the final and deciding piece of data needed to complete the mono-copoly-fluoro marketing puzzle.