Why add a Top-Up Valve?
A top-up valve can be added to your packraft so you can regulate the air pressure in the tubes by adding or releasing air without going ashore. It’s possible to do the same thing with a Boston valve, but a top-up valve makes it more convenient, so you are more likely to actually do it.
Top-up valves are also good alternatives to Small Valves or Boston Valves as the primary inflation/deflation valve in smaller inflatables, such as packraft seats, as they are smaller and lighter than Boston valves, but easier to operate than Small valves.
Top-Up Valve Placement:
One nice thing about making your own packraft is that you can customize it to fit your body. The ideal location for a top-up valve will depend on your body size and flexibility, but in general, a good place to start is in tube piece #5 (either Left or Right) near the seam with piece #4 and on the down-slope on the outside of the packraft. If you’re measuring during construction, that’s about 38 cm (15″) from the corner between pieces 4 and 5 on the outside of the tube, and about 7 cm (2.75″) away from the seam.
I recommend waiting to install the top-up valve after your packraft is otherwise finished, however, because then you’ll be able to paddle it first and practice twisting your body around to find the perfect location for your valve. If you find it too awkward to twist your body around while sitting in the boat, an alternative placement would be on the inside of the cockpit near where your face ends up when you bend forward (i.e. close to your knee, but not so close the valve will poke your leg as you paddle). If you like, you can use field repair tape or something similar to hold the valve in place while you experiment with different locations on the water.
Wherever you decide to install your top-up valve, make sure your arm/elbow won’t hit it during your paddle stroke!
Top-Up Valve Installation:
The installation method is similar to that shown in the Boston valve video, except that the new (black) top-up valves are heat-sealable, so instead of using glue you can just heat seal the pieces together so the valve flange is sandwiched between two layers of fabric. First, seal a patch of fabric to the valve with the valve stem poking through a hole in the patch, and then seal the valve and the patch over a small hole cut in the packraft’s tube.
Here’s a picture sent by Jeb T. showing his top-up valves mounted in fabric rings, ready to seal to the packraft tube fabric:
If you haven’t installed an airtight zipper in your packraft, you will not be able to heat seal the top-up valve in place from the inside of the tube after the boat is complete, so you will either have to install the valve before the rear-center seam is closed, or use some Aquaseal on the underside of the valve’s flange after heat-sealing the fabric ring to the top side of the flange.
Eventually I’ll make a video showing how to do this, but for now, if you have questions, please post a comment below!