Cuben of DCF (Dyneema Composite Fabrics) in it’s simplest form is two sheets of plastic, pressed and bonded(usually just by pressure) over a “loose” woven Dyneema/Spectra material. There are a lot of variations possible, of course, carbon fiber, mylar, kevlar, different weights, multiple layers, type of weave used for coring…well, a lot more research and experimentation is needed. Anyway, the fibers will form a grid of “stand out” areas that will abraid quite easily, and like any plastic will shred. But, being well bonded to the core and other layer of plastic, it just forms little fibers that will “hold” water…not really soaking it, nor penetrating through it. Rather than having a plain sheet of plastic, only those areas that stick out get worn quickly. That usually means that some large percentage of any wear will be concentrated on a tiny portion of section of fabric. Ripstop does this also, but nylon is more elastic, it bends away from abrasive stuff rather than developing small shreds.
So, as a plastic, I assume that it just picks up a lot of surface water that becomes nearly impossible to wipe off unless it is fairly new. Yes, it will likely also stick with other things that we do not normally associate with sticking to plastic: silicone, “stains” & discoloration, epoxy, etc.But just like water, it is not really “bonded”, it is just surface bound.
Plastics are by nature, heavy. Most plastics are about the density of water maybe slightly less. Look in the sink with a plastic bowl. The bowels barely float. Polystyrene will actually sink. Anyway, only the size makes them light. Or, injecting them with “air” (styrofoam for example.) Spectra is one of the few fibers I know of that floats.
Given the same coverage tarp, say 9×9, silnylon will generally pack 10-15% smaller because it is a softer more elastic material. I can fold it paper thin and there is no damage. DCF will whiten showing that some (the outside molecular layers) is extended beyond what it was capable of tolerating. Like my cedar strip canoes, with two layers of fiberglass over a center core of cedar, the two plastic layers over a web of Dyneema/Spectra fibers makes it much stiffer than simply adding up all three layers. That means there is more air in every fold because it will not flatten as much. When repeated in the same area, DCF weakens. You really should not fold cuben tightly (as in a “too small stuff sack”,) nor, repeatedly in the same spot, it is really too stiff for tight folding, rolling is best. But, then you worry about the edges. Generally this comes through to most people as abrasion resistance, but it is really a property of the DCF and the materials they use.
Similar to winding a 1/32″ steel cable as opposed to using a 1/32″ steel wire, silnylon is a twisted batch of “small” diameter “wires.” Much more flexible and stronger, except in stiffness. The silicone treatment is highly elastic, and doesn’t really count as a separate item, but it flows into the “wire” like threads, not really bonding, but again a very strong bite. You can fold it repeatedly in the same area and have it simply bounce back. Fold a wire repeatedly in the same area and it breaks. It also has a strange property which is self affinity. If the coating is damaged, it will actually stick back together, or “self healing,” much like a modern tire.
However, UV damage done to either material is likely not good. Fortunately, mostly I camp in the ADK’s and in heavily forested areas. So, I can get 10-15 years out of a tarp. I worry more about punctures and abrasion. (As was mentioned, elastic bands (hair ties) will keep things fairly tight in the rain.) But, it is usually heavier at 1.3-1.5oz/yd as opposed to .6 or .8oz/yd like DCF. The trade off is what keeps this list interesting. I have settled on a 20oz maximum devoted to my shelter for solo use. I usually do not bring a net, nor, ground cloth. Depends on your area and what you will tolerate.
