The lightest weight ultralight backpacking shelters are tarps, including flat tarps and catenary curve tarps, sometimes called “flat cut” or “cat cut” tarps for short. They both have their pros and cons as we discuss below, but if your goal is wilderness immersion and carrying minimal gear weight, they are the ticket.
What is a Flat Tarp?
A flat tarp is square or rectangular in shape, has flat edges, and 90-degree angles in the corners when laid open on the ground. Some good examples include the:
Flat tarps are wonderfully versatile and can be set up in all sorts of configurations depending on weather conditions and terrain. While you can set them up in a standard A-frame pitch between two trees or trekking poles, you can fold one end down for more wind protection, set one up as a pyramid, or incorporate boulders, embankments, or tree trunks for even more weather protection. Setting flat tarps up in different ways is a real art form and a lot of fun to master.
When comparing flat tarps it’s important to pay attention to their guylines, if they have them. Some flat tarps come with permanently attached line locs tensioners in the corners, on the ridgeline, and on the sides with guylines in pre-cut lengths.
Other tarps come with webbing loops instead, so you can add guylines where you need them and in different lengths when you set the tarp up. The use of webbing loops makes it easier to set up a flat tarp in different ways and is something to consider when purchasing a flat tarp. But it means carrying an assortment of guylines and learning how to tie different knots. Alternatively, you can use special guyline hardware sold by companies like Dutchware that removes the need to tie any knots, which is a popular option.
Where can you find a list of all the possible setups you can use with a flat tarp? There is an infinite number, actually, which is what makes using one so much fun. There are plenty of tarp pitching videos on Youtube you can watch and if you want you can beat your head against the wall trying to pitch the ones in Macpherson’s classic Tarp Shelters (free) which lists every mathematical folding and pitching possibility…many of which are impractical.
But the reason there are an infinite number of flat tarp pitches is that you can create organic pitches that use natural features which are not, by nature, derivable by mathematical permutations. While geeky, there is an art to pitching a flat tarp that must be learned by doing and experimenting. It’s very satisfying when you get good at it, but most people don’t bother and opt to use a catenary cut tarp instead. That’s not bad, it’s just a very different experience and skill set.
When purchasing a flat tarp, you’ll be faced with a decision about which fabric or material you want the tarp to be made of. Some flat tarps are made with ultralight Dyneema Composite Fabrics (DCF) in order to save weight, while others are made using polyester or silnylon to save cost. I’ve found that DCF tarps tend to have no stretch in them which makes them more difficult to use when creating ad hoc tarp pitches that incorporate natural elements, while a fabric like silnylon is ideal. It’s just something to consider when purchasing a flat tarp.
What is a Catenary Cut Tarp?
A catenary cut tarp or “cat cut” tarp, as they’re often called, is a type of shaped tarp, where the edges of the tarp or the ridgeline are curved and the corners do not form 90-degree angles. Pyramids or “mids” are another type of shaped tarp but out of the scope of this discussion. Catenary curves are shaped like the gently curved cables on a suspension bridge and are designed to be more aerodynamic in the wind so that the edges of the tarp flap less in the wind which can be an issue with a flat tarp. Catenary curves also reduce the amount of fabric needed to create the tarp, providing a weight reduction.
Some good examples of cat cut tarps include:
The downside of a cat cut tarp is that it is designed to be set up in one or two different variations, but doesn’t offer the same degree of flexibility as a flat tarp. The missing element is often symmetry, as many cat cut tarps are tapered and not rectangular or square. Some cat cut tarps also have doors or overhangs called beaks at the end which can further reduce their flexibility.
Most cat cut tarps have line loc tensioners at the ends instead of webbing loops which further limits their flexibility, with the exception of tarps made by hammock companies for hammocking and ground camping, where you can often choose between line locks, webbing loops, or other plastic hardware. Some cat cut tarps also have doors at the end or overhangs called beaks for added weather protection which also reduces the ways they can be pitched, although this can further reduce the number of ways they can be configured.
One advantage of cat cut tarps is that they are much easier for tarp beginners to set up because there are so few ways to do it. Most people set them up in A-frame pitch with the ends tied to a tree or trekking poles and the sides staked to the ground, or one side elevated for views and ventilation. There’s nothing wrong with that and it is a fast way to get out of the weather.
As you can see, there is a big difference in the flexibility of flat tarps over cat cut tarps, although substantial skill development is required to fully exploit it. When choosing a tarp for the first time, one thing you want to consider carefully is the size you want, not just for weather coverage, but also because it’s the main factor that determines gear weight. It’s also important to make sure that the tarp you want has hooks along the underside of the ridgeline, so you can hang a bivy sack or bug shelter underneath for insect protection if that will be needed.
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