Install an Airtight Zipper


In the DIY Packraft Shop, I offer waterproof and airtight TIZIP SuperSeal zippers, which, when installed in your packraft, allow you to store your gear inside the tubes.

These zippers come from the factory already mounted in very tough, heat-sealable fabric. The heat-sealable side faces the outside of the zipper, so if your packraft has the heat-sealable TPU coating on the outside of the tubes (as is the case with the DIY Packraft kits), then you’ll need to add a rectangle of TPU-coated fabric around the zipper to bond it to the packraft.

Cut a rectangle of fabric 60 cm (24″) long and 11 cm (4.5″) wide. If you like, you can leave a strip of fabric extending from the center of one end of the rectangle 2.5 cm (1″) wide and 10 cm (4″) long to make a grab loop so you’ll have a convenient handle to pull against when you want to open the zipper. Then cut a slot centered in the middle of the rectangle, 2.5 cm (1″) wide and 50 cm (19.75″) long, for the zipper to fit through. Round off the corners of the rectangle for a nicer finish.

Use your heat-sealing iron to bond the rectangle to the zipper fabric, making sure to center the zipper in the slot so the fabric won’t interfere with the zipper’s slider.

Note that the TPU on the zipper fabric is activated at a slightly higher temperature than the TPU on the packraft fabric, so you may need to boost the temperature of your sealing iron a bit higher than normal to get a strong bond. With a Clover Mini Iron II this can be done by wrapping the shaft in aluminum foil. You could also use a clothes iron for this step, or a larger hobby iron like the one pictured below. Also note that the zipper fabric does not conduct heat as well as the packraft fabric, so you will have better luck sealing it from the packraft fabric side. 

This heat-sealed bond feels quite strong; however, because I don’t want to destroy the zipper by tearing it apart to see how strong the bond it is, I add a bead of glue around the inside edge of the bond to reinforce it. Over the next few years, we’ll see how well the heat-sealed bond holds up, and hopefully we’ll find that the glue isn’t necessary. If you choose to add glue here, I recommend that you cover the zipper with a piece of tape first to mitigate the risk of accidentally gumming it up with glue.

Now it’s time to cut a slot in the packraft’s tube fabric. If you haven’t already assembled your packraft, this will be easy, but if you are retrofitting a completed boat, you’ll find it easiest to inflate the packraft first and then figure out and mark where you want to locate the zipper.

When choosing where to locate your zipper, make sure you have satisfactory answers to the following questions:

  • Will installing the zipper here allow me to store gear in both sides of the boat?
  • Will the zipper be exposed to abrasion from obstacles I paddle over or past?
  • Will the zipper interfere with spray deck installation or anything else I want to attach to my packraft?
  • Will my hand catch on the zipper’s ridge while I’m paddling?
  • Will I be able to roll the packraft into a tight bundle without folding the zipper? (The SuperSeal can be rolled lengthwise, but not folded.)

After considering the above points, you’ll probably decide to locate the zipper as close to the tip of the stern as possible, in either tube piece #5-Right or #5-Left. I located the demo zipper in tube piece #5-Right according to these measurements:

  • The “bottom stop” (the raised black rectangular zipper stopper) is 9 cm (3.5″) from the small-radius corner that forms the packraft’s pointed stern.
  • The horseshoe-shaped dock at the other end of the zipper (where the zipper slider sits when the zipper is closed) is 10 cm (4″) in from the longer curved side of the fabric, and about 14 cm (5.5″) from the shorter curved side.

Be sure you have at least 1 cm of overlap between the tube fabric and the rectangle of fabric that you bonded to the zipper for a good seal, and if your packraft isn’t assembled yet, leave at least 1.5 cm clearance between the rectangle’s edge and the edge of the tube piece so the rectangle won’t interfere with the seam fabric you’ll add later.

 

Mark the location of the zipper and then cut a slot in the tube fabric a few cm wide and slightly longer than the zipper.

Position the zipper over the slot with the TPU side of the rectangle facing down against the TPU side of the tube fabric, and then heat-seal the rectangle to the tube.

Now the zipper is installed in the boat.

If you want to add a grab loop, as I did, see the two different methods shown in the cross-section diagrams below.

A quick sketch showing two alternative methods of making a grab loop: first, from a single strip bent into an “omega” shape and then reinforced with a loop of fabric on its inside; second, two shorter strips spliced together to form the omega shape, with the inner reinforcing loop attaching them together. (The second method is shown in the video above and pictures below.) In either case, the inner reinforcing loop should be positioned so that it bridges between the “feet” of the omega so that pulling on the loop does not apply a peeling force between the feet where the omega attaches to the boat.

 

After your packraft is complete, don’t forget to lubricate the zipper with the included silicone gel (but don’t do that until you’re finished, otherwise you might get silicone on the fabric and this could interfere with your heat-sealing).

Questions? Please leave a comment below.

14 thoughts on “Install an Airtight Zipper

  1. Hi Matt, After watching the video a million times, I cannot figure out how to make the loop. It looks like your strip is initially a single layer about 15cm long. But then later it appears to be a double layer strip, perhaps folded in half (???). At one point there seems to be a strip coming out from inside the loop, which you then cut shorter. I don’t understand where that came from.
    If I seal a single strip to the tab, the tpu side of the strip ends up facing out. That means I’m sealing non-tpu side of the strip to tpu side of the tube. That’s not going to work. And then, since I have non-tpu side of the strip on the inside of the loop, I can’t seal an extra layer of fabric to the inside of the loop to bridge the joint.
    There’s something I’m missing. Help!

    1. Hi Thor,

      Sorry it wasn’t clear – I will update the page with a diagram! The way I did the one in the pictures and video is a bit more complicated than it needs to be because I didn’t leave a long enough strip for the loop, so I had to splice two pieces together using a third piece on the inside of the loop. If your fabric is long enough, I recommend making the loop from a single strip bent in the shape of a capital Greek letter omega, and then reinforcing that with a loop of fabric inside the loop of the omega… diagram to follow!

      Matt

      1. Thanks Matt.
        I am having a lot of trouble getting the fabric to bond to the T-zip. No matter how long or hard I press the mini iron, it does not bond. The only way I’ve managed to get any sort of bond (only patchy and not very strong) is to use my household iron, get it really hot, remove the iron (the fabric curls up and away from the t-zip) and then press down really hard on the hot fabric for a minute. The problem is that I might be wrecking the tpu where I need to bond the fabric strip to the kayak tube, and if I try and go over a section again, re-heating just un-bonds what was previously bonded. This is really just a comment. From your videos, it looks like you are not having any trouble. I will do the best I can to bond, use a lot of glue, and hope for the best.

        1. Hi Thor,

          It sounds like your mini iron might not be hot enough… what sort of mini iron are you using? Feel free to send me pictures if you think that might help diagnose the problem.

          In some situations it is necessary to press down on the fabric after removing the heat source in order to keep it in place while it cools – usually this happens if the iron is very hot (the TPU loses its stickiness if it liquefies) or if there is tension on the fabric so it won’t stay in place. As you mentioned, reheating the bond will un-seal it, so try to avoid reheating areas that have already been sealed unless you need to re-position the fabric.

          If you are going to apply glue around the zipper, I recommend covering the zipper with tape first (inside and outside) so you don’t accidentally get glue on it!

  2. Hi Matt,

    Do you think a 620mm zipper would be too long to fit on a packraft sensibly?

    Rob

    1. Hi Rob,

      I chose the 50 cm TIZIP because it was the longest zipper I could sensibly fit. In this picture you can see where a 50 cm zipper fits when located as close as possible to the tip of the stern. A 620 mm zipper will extend 12 cm farther down the back rest area towards the floor of the boat, which would preclude the installation of a spray deck and might interfere with a back rest (or a back rest might interfere with it), and if you didn’t use a back rest, you would have the zipper slider and pull digging into your back. You might be able to wrap the zipper down around the underside of the tube on the outside, but that would expose it to abrasion from below, add drag to your packraft, and make it difficult to roll up your boat without folding the zipper (a definite no-no, as the zipper will be damaged!). Placing the zipper across a seam would add a higher level of complexity because it could not be heat sealed in place, and again, it would be difficult to pack the boat into a tight roll without folding the zipper. Placing a zipper on a side tube would solve all these problems, but of course you’d only have access to one side of your boat!

      Cheers,

      Matt

  3. Matt- I bought a tizip from you and I was trying to unzip it (haven’t gotten to the step of installing it) to test it out and I cannot get the darn thing unzipped! Why is it stuck? Have you ever run into a stuck zipper? I mean, it won’t even budge….

    1. Hi Steven, the zippers are very tight when new – so tight you may need to hold the end in a (padded) vice or pliers to open it for the first few times. After opening it the first time, apply some of the included lubricant, and that will help it slide, but it will still be quite stiff. Over time, it will loosen up a bit, but the tightness is what makes it airtight, so it will always require some effort. That’s why I like to add a grab loop on the packraft at the end of the zipper so I have something to pull against. Cheers!

  4. If I were to add a zipper to a prebuilt pack raft are a there different sequence of steps to install the zipper?

    1. The procedure is basically the same, but start by inflating your packraft and holding the zipper against it to figure out exactly where you want it, and then mark the location before deflating it and cutting out the slot. Most of the major brands have TPU on the outside of the tube fabric, so the same heat sealing procedure will work; I believe Supai is one exception, with TPU film on the inside of their tubes. TPU on the inside makes installing a zipper even easier because you can seal the zipper directly to the tube fabric without adding a second piece of fabric. Cheers!

  5. Hi Matt, thanks for a great writeup. I’m about to install a TiZip on a Yak, and wonder if you recommend or have had an experience with just gluing it, rather than welding? I’m considering gluing it from the inside of the tube, using something like Bostik 999, which I’ve used for tiedowns, and it seems to be bulletproof.

    Not sure though, there might be something I haven’t thought of, or the pressure too high for the glue to hold in shear like that.

    I’m all set up for welding, but just thought it may be simpler just to glue.

    Thanks for any advice!

    1. Hi Chris, TIZIP cautions against using glue to mount their zippers, but I don’t know how much stronger a welded bond is (if at all). I do remember seeing somewhere online a DIY installation of a zipper in a packraft using glue, and over time the glue failed, but I can’t remember the type of glue or packraft that was used. I haven’t tried gluing anything to the inside of an Alpacka, so I would start by testing your glue on that side of the fabric, as adhesives will react differently with the nylon on the inside of the tubes compared to the TPU on the outside. Assuming the test goes well, I don’t see any reason not to use glue if you want to avoid ironing, as the glue will be strongest in shear. If you go ahead with it, just be sure to cover both sides of the zipper mechanism with tape before gluing, as accidentally getting glue in the zipper could ruin it’s ability to form an airtight seal. Cheers!

  6. Hi
    Looks like 55cm long strip will be just short, since the zipperfabric is 55cm itself.

    Wouldn’t it bee nice with a grab loop in both ends? Or is the zipper much easier to close than to open?

    1. Hi Nils – thank you for the correction! I have changed the “55 cm” to “60 cm”.

      The zipper is much easier to close than to open, and will loosen over time, but you could add a second grab loop if you like – just make sure it won’t drag in the water (it wouldn’t slow you down much, but it could catch on something).

      Thanks again!

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