Fabrics

Introduction

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 polyurethane (PU) coated nylon fabric. This combination of materials is strong, airtight, waterproof, UV resistant, doesn’t stretch much, 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 (see the Fabric Comparison video to see why). To see how I activate the heat sealable coating to bond the seams, check out the videos on the How-To pages and read Proper Heat-Sealing Technique.

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.

Fabric Weaves

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.

Ripstop
Ripstop weave creates a square or diamond pattern.
Oxford weave produces a small "checkered" pattern.
Oxford weave produces a tiny “checkered” pattern.
Taffeta Weave
Taffeta weave produces no visible pattern.

I also did some research into the new non-woven, ultra lightweight, high-tech polymers such as Cuben Fiber, (now called 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 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).

32 thoughts on “Fabrics

  1. Hello there, nice report very interesting ,I am in the position as you ; I want a packraft but don’t like the idea of to much $$ .
    as i am looking for a more whitewater (III-IV)and rocky river
    did you a have a suggestion for the fabric ..just to give me an idea of the mat’l that i have to buy
    Your site is very nice and helpful
    thank you

  2. Hi, the German online store “Extremtextil” sells TPU coated nylon directly to customers and will ship it across the world if you want to.

        1. Hi, I have not ordered from them, myself. I can’t get that link to work, but it looks like that particular fabric has heat sealable coatings on both sides, so it wouldn’t be suitable for constructing a packraft using my methods (the iron would stick to the fabric). It’s fine to have a TPU coating on one side and a PU coating on the other, but not TPU on both sides.

          Cheers!

            1. Others have tried this material with mixed results… see the topic in the forum about alternative sources for materials. If you can get it to work it will have a similar strength and weight to the big packraft manufacturer’s tube material.

  3. Hello,

    I am really interested in making my own packraft. I would like to try bicycle pack rafting so I think I would want a stronger material than you used for your white prototype as I would be lashing my bicycle to the raft.

    Would the material from Seattle Fabrics listed below work? Also, when do you think you may be selling fabrics?

    Thanks, Craig

    Heat Sealable Oxford
    200 Denier (aprox. 6.5 oz./sq. yard). Lighter and more flexible than the 430 D. Packcloth, 200 D Heat sealable Oxford has a special coating that makes it possible to be heat-sealed, coated side to coated side, using a household iron.

    1. Hi Craig,

      Yep, I’ve played around with samples of that fabric and it should work and be tough enough for bike rafting. I will be offering a similar fabric, probably in August, but mine will have a TPU coating on one side and PU on the other, instead of just TPU on one side.

      Cheers,

      Matt

    1. For the regular size packraft, each side will require just over 2.5 m (2.75 yds), and 6 m (~6.5 yds) will be enough for the tubes and the floor, even allowing for a double layer on the floor (regardless of whether you make it TPU coating in or out). You may want an extra metre (or yard) of fabric if you plan to make a seat or any other accessories.

  4. Matt,

    Regarding the inflation bag, is there an additional fitting needed to attach the inflation bag to the inflation valve?

    Would having the TPU coating on the outside be better for in the field puncture repairs and also for added tie down attachments?

    Thanks

    1. I recommend gluing a short length of rubber or plastic tubing into the inflation bag that will pressure-fit snugly into the valve – I will post a more detailed explanation.

      I would recommend having the TPU coating on the outside of the tubes for the fabric that you were considering – mainly because it has no coating on the other side so it would soak up water if the TPU was on the inside, but also for attaching tie-downs and making field repairs.

      Cheers

  5. I would like to make inflatable pontoons for a small raft suitable for leisurely bobbing down a river. I am thinking of sewing the pontoons out of a tough fabric and inserting inflatable bladders constructed out of TPU+PU fabric with the PU side facing out. Do you see any immediate flaws with this plan? One thing that comes to mind is that the PU side of the fabric will be rubbing against the pontoon shell which might test it’s resistance to abrasion.

    1. Hi Harry,

      I think for leisurely bobbing down a river a double layer of fabric might be overkill unless you’re expecting to encounter very sharp rocks and sticks, but I don’t see any obvious flaws with that configuration. Bakraft packrafts are made in a similar way. Movement between the inner and outer layers would be minimal, so I doubt internal abrasion would be an issue. Let me know how it goes!

      ~Matt

  6. Thank you for all this great information.
    I know that many of the best commercial pack rafts that are capable of doing white water have floors that are 800d nylon floors. Have you been able to find any fabric this heavy to use with your plans?
    I see you recommend a double floor using two layers of 210d fabric, do you bond all of the two layers together or just around the edges? How does this compare to 800d fabric? Thank you.

    1. Hi Quincy,

      The double-layer 210D floor is comparable in strength to 800D. I bond the entire floor surface together, but I have been thinking of ways to create an inflatable floor, so that might be something I tackle in 2017. I will also be adding new fabrics to the Shop 🙂

      Cheers!

      1. Hi Matt,
        I’m super keen to make a packraft after spending hours reading through info on your website. I share Quincy’s concern about the floor especially since I live in Australia and our rivers are very rocky and if the water levels are low (most of the summer) there can be a lot of scraping over rocks. I’m willing to give the 2 layers of 210D a try, but wondering if you might be adding new floor fabric to the options any time soon, in which case I would be better to hold off for a bit. Thanks, and thanks for doing such a great job.

        1. Hi Thor, I am working with the factories to develop new fabrics, but I have learned not to estimate when new products will be available because these things always take much longer than I anticipate!

          Rather than building a heavier, bulkier boat out of stronger fabric, I recommend building a lighter boat and accepting the fact that you will probably have to patch it occasionally (for more on this, read my Punctures, Leaks & Repairs page). Aside from avoiding sharp objects, the best way to prevent tears in the fabric is to use an inflatable seat, padding under your heels, and store hard gear on the deck instead of on the floor. This allows the fabric to bounce, stretch, fold, and flow around obstacles instead of being pinched between a rock and a hard place.

          Cheers!

          1. I ha e also been thinking more about this. I think another way to strengthen the floor would be if you cut one of the floor pieces rotated 45degrees so that the weave between the two layers don’t line up. The fabric rips easier along the weave so if the two different layers have two different weave directions any hole will be harder to tear. Unfortunately this will take more fabric as there wasn’t a way to fit two floor patterns in such a configuration on the 2 yards that I had…

            1. Hi Quincy, I think you’re right, but as long as the threads are not exactly parallel it should have a similar effect, and they are unlikely to be exactly parallel. Cheers!

  7. Excellent website, very inspiring!

    Why do you recommend an 800D floor for a dedicated whitewater raft when your tests are showing that double 210D is stronger?

    Also, do you happen to know why Alpacka stiches and tapes their whitewater rafts instead of sealing them, like you?

    Do you think that your rafts with double 210D floors would be theoretically solid on Class 4? I just want to get a sense of how much these rafts may be able to handle.

    Looking forward to picking up a kit when your new fabric arrives!

  8. Excellent website, very inspiring!

    Why do you recommend an 800D floor for a dedicated whitewater raft when your tests are showing that double 210D is stronger?

    Also, do you happen to know why Alpacka stiches and tapes their whitewater rafts instead of sealing them, like you?

    Do you think that your rafts with double 210D floors would be theoretically solid on Class 4? I just want to get a sense of how much these rafts may be able to handle.

    Looking forward to picking up a kit when your new fabric arrives!

    1. Thanks, Jonathan – I’m glad you’re finding the site useful! The pages are constantly evolving and I probably wrote that before testing a double-layer floor. I’ve written so much it’s hard to remember what I need to go back and change when I learn something new – if you can point me to where I said that I’ll update it.

      Alpacka’s founder came from a sewing background and they’ve always made their packrafts that way – it works for them, so why change?

      No packraft will ever be as solid as a kayak – even the toughest $2000 packrafts at four times the weight of a DIY Packraft can’t compete with a kayak for durability. In moving water there are too many factors to consider (paddling skill, water level, wood, care taken during construction, weight of paddler and gear, risk-taking, bad luck, etc.) to answer that question with a “yes”. The best way to get a sense of the strength of the fabric is to purchase a fabric sample pack and test it for yourself.

      Thanks!

  9. Great site and thank you for the tons of information! I earlier sent you an email regarding the floor but my questions was answered here on this page already.

    I’m also wondering where we are with the spray skirt as I would like to add that to my purchase. I will look around some more and see if that has already been answered somewhere!

  10. I am looking for a fabric that would be good for class 4 rapids with a inflatable floor kinda like a alpaca packraft

  11. Very informative. Thanks! I am looking for a lightweight fabric to go inside a float tube shell. In the army we had yellow water flotation wings. Do you know what kind of material that is? What kind of lightweight fabric would you suggest? Also, are welded seams better than glued? Thank you.

    1. Most inflatable life jackets I have seen are made from TPU coated fabric, similar to the 210D fabric in the DIY Packraft shop, and most inflatables are welded. 40D fabric could work for your float shell if you want it to be lighter and more packable, but it’s not as resilient. Cheers!

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