For me, the figures speak for themselves: films,and xfoil in particular—have for me an outstanding strength-to-weight ratio. If you look at the technical data (thickness, tensile strength, puncture resistance) and break it down to the weight per unit area, high-quality polyolefin films are in a different league to traditional tent fabrics in terms of performance per gram.
Specifically, this means for my setup : According to the technical data sheet, xfoil has a tensile strength of 132 N/mm2 in the machine direction and 141 N/mm2 crosswise, with a thickness of only 19 µm and a weight of around 18–20 g/m² (data sheet from the German UL forum).
For comparable silnylon/silpoly fabrics, there is a lot of information available on tear resistance (e.g., 30D nylon 6.6 with around 7.5–10 kg tear resistance depending on the source and weight), but almost never actual material tensile strength in N/mm². This allows Silnylon/ Silpoly to be roughly classified, but only approximately compared with films.
For 20D Silpoly, for example, tensile strength data according to ASTM ranges from roughly 45–55 lbf in the warp direction and 35–45 lbf in the weft direction (for 1.1 oz Silpoly, approximately 50/40 lbf). XFoil, on the other hand, has a tensile strength of 132–141 N/mm² at a thickness of only 19 µm. The units cannot be compared 1:1, but it shows quite well how extreme the strength-to-weight ratio of a cross-linked polyolefin film is – and that with Silnylon/Silpoly you usually only get such strip tensile strengths, but rarely real material characteristics in N/mm².
With Sil nylon and Silpoly, this is much more difficult to prove conclusively, because there are only a few genuine tensile strength values available and the data varies greatly depending on the manufacturer, denier, weave, and coating. It is only possible to estimate the strength, but in a direct, standardized comparison, xfoil has a clear advantage in terms of the “strength-to-weight” ratio.
Of course, film has the disadvantage that once a tear has formed, it tears more easily than fabric. That’s a trade-off I consciously accept. But if a sharp thorn or stone pierces the material, in practice it will also pierce pretty much any other lightweight material—whether it’s silnylon, silpoly, or Tyvek. The “invulnerability” of classic fabrics is often overestimated in this regard.
Nowadays, tarps are so good that I only use them when I’m out and about, and there’s a growing scene for them in Europe. They give me a complete panoramic view and, above all, an unobstructed view of the starry sky in all its glory. I feel much closer to nature than in any enclosed shelter – while at the same time it is very lightweight and absolutely robust enough for my use.
You’re probably right about the flimsy, but I also think that contributes to the fact that people don’t trust foil as much as fabric, because it feels like a breath of nothing and is more reminiscent of cling film. And working with it is really annoying too; sewing is much more relaxed.
I think it’s such a shame that so few manufacturers publish data sheets so that technical values can be compared (yes, I’m a nerd). It’s absurd that people have to exchange very subjective opinions about which mat or fabric etc. feels best.
(foil or film, I still don’t quite understand the difference between when to use which, please forgive me :))
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