Fabric Choices for Ultralight gear

 Considered use of ultralight fabrics in this Wrath Outdoor sub 600g shelter system which utilises a ripstop silnylon fly and a PU coated nylon tub floor

Ultralight backpacking gear has to work in the real world, it has to have an adequate safety margin, it has to look after the user in unexpected situations. By the same token it has to offer weight savings over main stream alternatives.

The ultralight backpacking shelter designer is looking at combining a design which cuts away redundant or over engineered features to save weight, adjusts panel shape to cut away wasted cloth and so on. Even using the same materials as the mainstream shelter designer the ultralight design will still be lighter. 

The real game changer however is the fabric and other materials used to make the shelter. These fabrics are the best and most fit for purpose fabrics on planet earth at this time. These fabrics can be quite expensive and utilize everything that modern fabric manufacturing can bring to the table. Yes, the design can make a difference, in the end though there are only so many ways to make a tent or shelter. The utilization of cutting edge fabric is what cuts the weight. Think about the steel body shell of a modern car, its strong fairly light and works well as an outer skin for the average vehicle. Then think Carbon Fibre and Kevlar, if well designed the same shapes can be derived but the parts can be stronger AND lighter. 

Ultralight backpacking gear designers and manufacturers are using the fabric equivalents of Kevlar and Carbon Fibre. Most ultralight tent designs come from cottage manufacturers running low overheads, selling their offering online or direct. So even though the fabric costs are perhaps 10 times more expensive than the usual mainstream tent fabrics the final product finishes up similarly priced or even cheaper than a mainstream relatively heavy counterpart. In this sense ultralight gear is a bargain. If a mainstream manufacturer were to build their products from the same fabric they would price themselves out of the market, which is perhaps why ultralight gear remains the preserve of the cottage gear manufacturer. Mainstream gear has to pay the brand owner, the factory, the distributor and the retailer and in fact for a whole marketing infrastructure to bring the product to market. The actual fabric cost was probably less than 10% of its final value. 

The cottage industry is by definition a low key, low overhead operation with a minimal marketing outlay, perhaps even a single website. Custom builds through word of mouth amongst like minded individuals. The value is added into the fabric and design which is passed on to the final user of the product - the customer. 

So which ultralight fabrics are most popularly used by the cottage gear industry. 

There are four  mainstay fabrics in reducing weight order:  PU coated nylon, Silicone impregnated nylon, Silicone impregnated spinnaker fabric and finally Cuben Fibre. There is little to no loss of shear strength as the weight goes down, but the cost increases quite a bit. Cuben fibre costs around 4 times the cost of silnylon. 

Here's the lowdown on each fabric:

PU Coated Ripstop Nylon: 

Very water resistant. Easy to work with, glues will stick to it, and it has at least one face which is not slippy. Its a good choice for making your own gear. The fabric usually has a nylon base fabric which is then coated with a PU coating which then makes one face of the fabric water resistant or waterproof depending upon specification.  The mainstream manufacturers that are looking to offer a lightweight choice would probably choose this fabric as its fit for purpose, fairly light and as mentioned easy to work with. It is relatively inexpensive so a margin can still be achieved in a supply chain scenario.  The main disadvantage is that PU coatings at the lower end of the quality spectrum can be heavy and when subjected to abrasion will begin to peel or rub off rapidly. 

Ripstop Silnylon

Is very difficult to work with, it is super slippy, glue will not stick to it and you cannot put pins through what will become a waterproof membrane, in essence a manufacturers nightmare. On the other hand, there is no coating to rub off, the fabric is totally impregnated with the silicone. Not even mildew can get a foothold. The fabric still has some stretch and both sides of the fabric are waterproof. The strength is around 4 times that of canvas for the equivalent weight and is much more abrasion resistant. Even small pin holes will mend themselves in time. It is more expensive than PU coated nylon, but it is around 25% lighter. 

In many ways this fabric offers the perfect balance of weight and strength for an ultralight product. You can really feel the weight advantage straight away.  It can be used for either a ground sheet or a flysheet. The fabric poses no real compromise for the end user, all of the negatives fall to the cottage manufacturer that has learned how to work with the cloth.

Some mainstream manufacturers have offered what they describe as silnylon.  Quite often it is a hybrid of silicone one side and a thin coating of PU or other coating on the other to make it easier to glue and work with. Always ensure what you are getting really is 'Silnylon' .You can tell straight away by feel. Silnylon is slippy on both sides. PU coatings have a tacky rubbery sort of feel.

Silnylon is flammable. Consider safety if using a silnylon shelter near an open flame. Having run a burn test or two myself I can report that silnylon is not as flammable as some say but do bear this mind.

Silicone impregnated Spinnaker Fabric:

About half the weight of  standard silnylon and just as slippy, at around .98oz or 25g per square metre this is very light, but twice the cost of standard silnylon. Spinn fabric as its known can either have a polyester or nylon base fabric which is then impregnated with the silicone, personally I prefer the nylon. It has the same advantages of the standard ripstop silnylon, is very strong, has a bit of stretch but is not quite as waterproof.as standard silnylon. Still more than fine though for a flysheet, perhaps not so great for a groundsheet as the pressure of knees or elbows over a small area can force water through the membrane.

The main disadvantage is often the colour choice. The fabric is mainly manufactured for sailmakers, who specify bright colours for spinnakers. Natural white or cream is probably the best choice, or pale grey if you don't mind it.

A 3m x 3m  shelter in such a fabric will weigh less than 300g, incredible really and it  is really strong. Look for sewn on ties with bar tack stitching, as grommets will pull out of the thin fabric unless heavily reinforced and hand-stitched as in the clew of  a sail. Personally I love the look of this fabric but if you are planning to stealth camp the color may be a consideration.

Cuben Fibre

Two drawbacks, cost at this time, the fabric cost is four times that of silnylon, and the fabric is very slightly transparent. Oh and did I mention not so abrasion resistant, so that's three drawbacks. On the other hand its the lightest fabric in this list at a quarter the weight of silnylon. It can also be noisy in the wind so pitch technique needs to be practiced. There is less stretch in this fabric so designs that work well in silnylon do not always translate into Cuben Fibre without modification.

I would say that the huge price hike to gain a few grams over say a spinn fabric shelter is hard really to justify, so I am not going to try, but if you have just got to have the lightest this is the way to go. So, would I choose a Cuben Fibre shelter for myself, erm, yes absolutely! :).