Originally Published in NZ Hunter Magazine, Issue 100
Author: Luke Care, Editor
The humble fly, or tarp, has been around since the first shelters. Would a woolly mammoth skin qualify? Probably
Given there’s been a few thousand years of development, it’s a pretty difficult recipe to improve on. The concept is simple – a sheet of fabric to stretch over yourself and shelter from the elements. So where to from there? There’s the basics, like tie-out points – fairly easy to get right. There’s the extras, like the guy ropes – again, not that hard. But you can’t talk about tarps without addressing the fabric.
With tents so light these days the simple tarp has to work even harder to maintain it’s weight advantage. Tarps are mostly commonly made from nylon, or silicone-coated nylon (SilNylon) to be more accurate, but fortunately the fabrics industry is always developing something new, and this time a product from Challenge Sailcloth has come served on a golden platter for hunters and hikers. Kiwi Ultralight were quick to realise its potential, and have brought a tarp to market made out of the ground-breaking new fabric, and from what I can see they’re the only ones doing it.
UltraTNT
No, it's not an explosive. Lighter than nylon, heavier (but tougher) than DCF/Cuben Fibre, UltraTNT is part of the ULTRA collection at Challenge Sailcloth, and they've really pushed to create a material that's not just lightweight but tough too.
UltraTNT is 15 times stronger than steel by weight. It has huge tear strength, around 30-40kg, and an abrasion resistance of 3,600 cycles, it's designed to handle pretty much anything the great outdoors throws at it. Imagine both Ultra TNT and DCF as grids of super tough strings, with a softer fabric in between. Your typical nylon is a more uniform fabric. The fibres of the weave mean any punctures shouldn’t tear and compromise the whole fly as it would with nylon, and you can easily fix them with patch tape.
It is thoroughly waterproof, rated to an astronomical 140,000mm. It absorbs zero water, so simply shake any rain beading off the outside and package it away knowing you’re not carrying any extra weight. I will say though, do air it out when you get home, as any moisture trapped inside won’t find its own way out!
So, we know it’s awesome, but how does it stack up to the competition? Cuben Fibre (now called Dyneema Composite Fibre/DCF) had dominated this space until now. Both materials are known for their incredible strength-to-weight ratios. DCF is a similar structure, consisting of a grid of Dyneema fibres laminated between layers of polyester, offering superb tensile strength. This makes DCF a top choice for applications requiring ultra-lightweight yet strong materials. However, the biggest performance advantage of UltraTNT is that the fabric has a diagonal weave as well, meaning it’s stabilized in three directions instead of DCF’s two. This means that while UltraTNT has bigger gaps between the grids, it is more dimensionally stable than DCF, which really reduces the deformation of the fabric under load. This deformation isn’t like nylon stretch that springs back, once DCF is deformed it stays that way. This superior stability increases durability along with making the fabric extremely rigid when pitched well. Ultra TNT is also available in more opaque colours than DCF, meaning more privacy inside and better shelter from the sun.
DCF's proven track record in ultralight backpacking gear makes it particularly suitable for those absolutely prioritizing weight savings, though it comes at a much higher cost than any alternative and with some maintenance considerations. At roughly half the price of DCF, Ultra TNT is not only better performing in many ways but also leads to much more affordable shelters.
UltraTNT isn’t a lot lighter than the lightest SilNylons, about 0.94oz per square yard vs 1oz per square yard, but that’s comparing it to the very lightest of fabrics. A nylon that light would be incredibly delicate, and ignores the fact that nylon absorbs water and will get heavier through a trip. Comparing a more common nylon tarp weight you’d expect 30-40% weight savings.
Interestingly, both the puncture resistance and abrasion resistance of Ultra TNT are lowest when it is brand new. I noted it when I pushed my pack down under my feet one night and the frame caught the stiff fabric, it deformed the gaps of polyester but was caught by the strong fibres before it could puncture the fabric. Ripstop design in action.
As the material softens abrasion and puncture resistance go up, essentially it has more give after a bit of use. You’ll notice this too as the fabric is quite crinkly and noisy to begin with, but softens with use. The tarp is a little more bulky when packed compared to a nylon fly, and you must loosely roll it, not stuff it, so that you don’t form hard creases in the material. It pushed down into a bag a bit smaller than a 2l bottle of milk.
Yes the Ultra TNT tarp is more expensive than nylon counterparts, and yes it requires a little more management, but you don’t get something for nothing in this world. This fabric nearly halves the weight, is for all intents and purposes completely waterproof, doesn’t stretch or sag and is outrageously strong. It’s cheaper and more durable than DCF and has better abrasion resistance. It provides a much more palatable price point for people like me who are looking to save some weight in their sleep systems and sits pretty much right in the middle between nylon and DCF.
The result of this is that Kiwi Ultralight are offering a 3x3m fly that weighs only 350gm, 420gm including the guy ropes and bag. With sleeping mat (380gm), quilt (670gm), fly and guy ropes (420gm) but no ground sheet (watch out for speargrass) my whole sleep system weighs a staggering total of 1.46kg. I’ve got sleeping bags heavier than that.
Bug bivvy
The partner addition to the tarp is the bug bivvy. Something I’ve yet to come across in NZ, but wish I had.
Fly camping is fun, lightweight and easy. I do it a lot, I did it all April. But I’ve never regretted the decision more than a hot and humid night in December 2022. I’d just worked my way up the bottom end of Mt Adams on the West Coast to watch some slips for chamois. The sandflies are just part of the landscape and I’ve learnt to live with them mostly, but the mosquitos … years later I’m haunted by what a terrible night that was. Swarms of bloodthirsty mosquitos descended on my exposed body as soon as the sun went down. I was caught between roasting alive by tightly sealing my sleeping bag, or being eaten alive whenever I had to expose some skin to breathe again. I got zero sleep and arose drenched in sweat and so painfully swollen on my face and around my eyes that I had to walk out!
I needed the bug bivvy - a lightweight inner to use alone, or pair with the 3x3 tarp, or any fly really. It is essentially a mesh bivvy bag, weighing 250gm and stretching 215 by 85cm to easily accommodate a large sleeping bag and the inevitable bits and bobs you want close.
It has a 4000mm 20D Silpoly floor and comes with guy ropes so you can utilise the same tie out points as the tarp if you want, or use Kiwi Ultralight’s titanium pegs. They’re another super lightweight addition at just 11.2gm each. It doesn’t use poles for shape, just attaches to the fly above you. Very easy to use, the bivvy reduces a bit of draft under the fly as well as keeping you away from the creepy crawlies. I’m looking forward to the double model though, Sam thought it was a bit rough asking me to sleep outside ….
Note from Kiwi Ultralight: We greatly appreciate this independent 3rd party review from Luke at NZ Hunter Magazine! This article was republished unchanged with permission from the author.
Check out the Tarp and Bivy over on their product pages by clicking below.
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