Backpacking tents are often made from (ripstop) polyester or (ripstop) nylon. Ripstop nylon is generally stronger and more durable than polyester. The tear strength of the materials depend on the chosen thread thickness. The scale of measure is ”D” for denier which is an indication of the yarn weight. The thicker the thread, the stronger the tear strength. But also the thicker the thread, the heavier the fabric becomes. In example, a 10D flysheet can be very light and therefore attractive to the superlight hiker. But the tear strength will be weaker and material less durable than say a 30D. We apply 30D flysheet to our tents as we think it gives the required tear strength without compromising the lightness of weight.
The quality of the fabric also depends on the coating that is applied. Coating is required to make the material waterproof. The fabric normally used for low end tents, is polyester covered with a layer of polyurethane coating. It is a more economical way to achieve a waterproof flysheet. Unfortunately a flysheet coated with PU (polyurethane) is often prone to chemical degradation which leads to the coating dissolving over time and becoming anything but waterproof.
With silicone coated flysheet the case is very different. At NorTent our choice of fabric is ripstop nylon coated with silicone on both sides. Also called silnylon. It is highly water repellent, elastic and durable. The waterproof qualities do not weaken over time. Silnylon is significantly stronger and lighter than PU coated fabric. It also has a smoother surface which lets the snow slide off the flysheet more easily. Too much snow piling up on the surface will cause unnecessary stress to the flysheet and poles. You want to keep wet and heavy snow off the tent
The smoothness of the silnylon flysheet also means that it is impossible to attach anything to it. If you get a tear it is not possible to tape it together. The tear has to be sewn together and applied with seam sealer to make it waterproof.
We have chosen silicone coating on both sides of the fabric as opposed to a silicone/PU combination. Double sided silicone makes the flysheet lighter, stronger and more durable. It is a little more cost expensive than silicone/PU. But for the upgrade in quality, we’d say it’s worth it.
The seams on our tents are sewn with the purpose to achieve optimal waterproofness. However, the seams must be sealed with a lubricant by end user prior to first outing. (Tents are not seam sealed with lubricant at factory). With the seam sealing completed you have a fully waterproof tent. The quality and durability of lubricant sealing is far better than taped seams which the PU coated tents and silicone/PU coated tents are equipped with
Mix your own seam sealer
We advise to make your own mix of seam sealer. Something we do ourselves with our personal tents. You take one half of transparent silicone and one half of weak scented paint thinner (white spirit) and mix 2-3 centiliters in a cup. Seal and leave to dry preferably for 24 hours to make sure it is not sticky. You can do either side of the seams. We prefer to seal the interior so that the outside is left unblemished.
Worth mentioning is also that silnylon is somewhat elastic. This means you are able to stretch the tent a few percent . That's a good thing because you “stretch” the tent into place when the surface is uneven or where you have uneven sides. Silnylon also stretches a little when it gets wet. This means that the flysheet often gets a little slack when it gets wet, where you have to adjust the tent pegs to get the smooth /straight flysheet back. All our tents therefore have the ability to easily tighten the flysheet without having to adjust the actual tent pegs.