This page is an introduction to inflatable packraft fabrics for the general reader. It’s a good place to start if you have never worked with fabrics before.
Fabric and Coating Types
Most (if not all) decent packraft manufacturers make their boats out of thermoplastic polyurethane (TPU) coated nylon fabric. This combination of materials is strong, airtight, waterproof, UV resistant, doesn’t stretch much but has a bit of “give”, and retains its strength even at very low temperatures. Cheaper pool toy-type boats are often made of polyvinyl chloride (PVC), or PVC-coated fabric. PVC is heavier, weaker, brittle when cold, and gives off noxious fumes when heated to high temperatures.
Thermoplastic polyurethane (TPU) is a variant of PU that bonds to itself when heated with an iron or hot air gun. It forms a very strong, permanent bond, eliminating the need for sewing or gluing – perfect for those of us who have no sewing experience and don’t want to breathe glue fumes. The resulting seam is actually stronger than the fabric itself, so sewing the seam as well would be redundant. To see how I activate the heat-sealable coating to bond the seams, check out the Proper Heat-Sealing Technique page.
Fabric Strength & Weight
One way to classify fabric is by “denier” (D), which is a measure of the thread weight, with 1 denier equaling the weight of a single strand of silk, and higher denier numbers indicating heavier (and therefore thicker and stronger) thread. The relationship between denier number and fabric weight and strength is not linear, however, because the thread count (T) must also be taken into account. Thread count indicates the number of threads per square inch in the fabric, and a higher thread count at a given denier will be heavier and stronger. As the denier increases, thread count generally decreases, because the number of threads that can be packed into a square inch decreases as the threads become thicker. For fabrics of a given denier, you are unlikely to have options of different thread counts (indeed, T is not even listed in many fabric descriptions), so don’t worry about it too much – just be aware that a 400D fabric is not twice as strong as a 200D fabric (not even close), an 840D fabric is not twice as strong as a 400D fabric, and so on. In fact, in my comparison of a double layer of 210D fabric with an 840D fabric, the 840D loses out. Also, not all fabrics of a given denier are created equal (thread count, polymer type, and fabric quality matter just as much).
Typical name-brand packraft tubes are made of ~210D fabric with a polyurethane coating on one side, while the floors are ~840D and coated on both sides. This makes for an average packraft weight of about 2.5 kg, or 6 pounds. The lightest commercially available packraft I know of is made of 15D fabric and weighs about 680 grams, or 1.5 pounds (it’s also significantly smaller than a normal packraft and not recommended for any sort of whitewater). Note: this packraft appears to have been discontinued.
The thickness of PU or TPU coatings is usually expressed in decimal millimetres, though it is rarely advertised in product descriptions.
In America, fabric and coating weights are often described in ounces (oz), which indicates the weight of one square yard of the fabric (1 oz per square yard = 33.9 grams per square metre). The weights of fabrics with coatings are sometimes notated something like “1/3.9 oz”, which would be a 3.9 oz fabric with a 1 oz coating. It gives you a sense of the total weight per square yard (4.9 oz, in this example), and how thick the coating is relative to the fabric itself.
There are several types of weave you might come across when reading fabric descriptions, such as ripstop (a square or diamond pattern made by weaving thicker strands into the fabric to help stop rips from propagating – common in tents, backpacks and other lightweight outdoor gear), oxford (a tiny checkered pattern made by bundles of threads criss-crossing each other – common in fabrics heavier than about 200D), taffeta (each strand is woven separately, producing no pattern other than an extremely fine criss-cross – like silk and waterproof-breathable jackets). Cordura is a brand name pack cloth, and pack cloth is a generic term for tough fabrics, which generally have an oxford weave. Ballistic nylon is also a term used to describe tough, heavy nylon fabric with an oxford weave. Cordura, pack cloth, and ballistic nylon are commonly used in high-wear, high-stress applications such as luggage straps.
I also did some research into the new non-woven, ultra lightweight, high-tech polymers such as Cuben Fiber, (now re-branded as Dyneema). Unfortunately, they are not very puncture-resistant, despite being very strong under tension, so while they are great for tents, sails, and lighter-than-air craft, they aren’t really suitable for packrafts. They are also extremely expensive.
How Fabric is Measured and Sold
Fabric is generally sold by length, cut from a roll (measured by the yard or the metre, depending on the country). There is no standard width for fabric rolls, but all of the fabrics you are likely to find will probably be approximately 145 cm (57″) wide, give or take a few cm/inches. If purchasing online, look for the width in the product description. The usable width is often slightly less (usually ~3-5 cm or 1-2″) than the advertised width because of the “selvage” (rough, unfinished edges), so take that into account if you are laying out your own patterns. When comparing prices between suppliers from the US and elsewhere, don’t forget to convert yards to metres or vice versa, depending on what units you’re working with – the difference is almost 10% (1 metre = 1.09361 yards).
Shipping costs can be quite high relative to the cost of the fabric, so don’t just look at the advertised price – get a quote including shipping before deciding where to buy. You may also have to pay taxes or import duties, depending on where you live and where you are ordering from. I have written more about this here.
Calculating the amount of fabric needed for a packraft (or any project) is more complicated than simply calculating the area of the fabric used in the packraft itself, because some amount of fabric will be wasted as you cut out the irregular shapes that will join up to make a packraft. Check out the How Much Fabric Do I Need? page for more on this topic.
Choosing Your Fabric
When choosing your fabric, it’s important to think about what kind of paddling you want to do, and also how you tend to treat your outdoors gear. Are you a whitewater paddler who wants to scrape down shallow rivers full of sharp rocks and sticks, or are you an ultralight through-hiker who is careful with your gear and most concerned about weight? The trade-off between strength and weight, combined with your willingness to make field repairs, will determine what fabric or fabrics will work best for you.
For example, I’m pretty careful with my gear, but I also wanted to be able to run some mild whitewater in my first packraft. I purchased many samples and then settled on a very lightweight TPU-coated ripstop for my first boat. For my purposes, it was a good compromise between strength and weight, and the full-size packraft I made from it weighs 813 grams, or 1.79 pounds with a double layer of fabric on the floor. It performs very well on flat water, but is not durable in shallow moving water with sharp sticks (as I soon found out). It’s easy to repair though, and I’m comfortable making field repairs, so this is not a problem for me.
Sourcing Fabric Elsewhere
The fabrics in the DIY Packraft shop are custom made to my specifications, and all of my instructions and iron recommendations are based on the assumption that you are using these fabrics. You are more than welcome to purchase fabric elsewhere – just be aware that the only reason I started the DIY Packraft shop in the first place was that there weren’t any fabrics this good available online. Also be aware that the recommended tools and techniques may not work well with other fabrics. Always test a sample before purchasing a large quantity.
TPU Coating In or Out?
You may wonder whether it’s better to put the TPU-coated side of the fabric on the inside or outside of a packraft, and I have posted a separate page about that here (short version: I have tried both, and either way works, but I prefer the TPU-out configuration).