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.
Note: New zippers are very tight and difficult to open the first time. Don’t worry – this is normal and your zipper will loosen with use. They’re especially difficult to open before they are mounted, because you have very little to grab on to. If you want to try it out before it’s installed in the packraft, you can clamp one end of the mounting fabric in a padded vice or vice grips and pull on the T-zipper handle. Thread something through the webbing loop to make a larger handle, if necessary. That first opening will require a lot of force, but the zippers are very strong, so you shouldn’t break it if you pull steadily. After it’s open, adding the silicone lubrication to the zipper will help it slide, and after it’s been opened and closed several times it will start to loosen up. My recommendation is to open and close the zipper a few times before installing it, but to wait and lubricate it after it’s installed so you don’t risk getting silicone on the fabric, which could interfere with the heat sealing.
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 (note: this was a V2 DIY Packraft):
- 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.
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.