The best inflation valves for an inflatable packboat aren’t the simple bungs you find on an airbed or an old Semperit. Nor the twist valves off a Feathercraft Java or an old Alpacka.
What you want are one-way valves like the high-pressure ones on white water rafts, pictured right and copied by many. Like a car-tyre valve, one-way operation as well as a secure seal are the key, so what pumps in doesn’t push back or escape when you remove the inflation hose.
With proper IKs valves, pushing the button down and turning clockwise locks the valve open to release air. For pumping up, push lightly and turn anticlockwise so it springs back up to seal. This closed ‘button up’ position is the best way to transport an IK as the valve mechanism is less vulnerable to damage. To lose a little pressure (say, the boat is getting hot in the sun) just jab the valve core button, same as on a car tyre.
Post-2010 Gumotex valves use ‘push-push’ valves (left). I always make sure I refit the cap seal straight away to keep grit or water out.
I’ve found these valves reliable on all my IKs, although this Gumotex 410C owner didn’t. Once in a while – or after the boat is new – you may want to check the valve is screwed tight against the fabric with the valve spanner, right. They’re useful too for removing the valve (or a PRV; see below) should it play up.
When it comes to inserting the inflation hose, one-way IK valves can take simple push-fit adaptors as shown below left; just shove the adaptor in and it sort of stays in place while pumping. It looks cheap but on a Gumotex at least, works fine. With higher-pressure boats like Grabners and Incepts and some Gumotii, you’re better off using a bayonet fitting (below right) so it won’t pop off as pressure builds.
Low-pressure valves for packrafts
Screw-cap Boston valves are used on cheaper IKs as well as slackrafts and packrafts. They have two caps: the main one unscrewed (below left) to dump the air, and a square cap to access the one-way valve to top off a boat (middle). These are low-pressure valves using a simple soft rubber ‘mushroom’ on a stem (below right) which is fine on a boat you top off by mouth, not a pump – ie: packrafts not proper IKs. With a packraft, the one-way valve eliminates the need for a separate top-up valve which means one less thing to leak or malfunction. Most packrafts use these now.
Pressure release valves (PRV) for IKs
I’ve learned to be careful not let an IK get too hot when out of the water. On a warm day you can feel the side tubes tighten like a drum. This of course happens to be good for paddling efficiency but isn’t good for the glued seams or an I-beam floor. Below warnings from the Grabner manuals.
The floor tube on my old Sunny had a pressure release valve – oddly it’s something never mentioned in the specs, even on current Gumboats. It’s there to protect the I-beam floor which could tear apart inside under pressure (I-beam floors explained here).
The valve is set at a certain pressure to purge when the air inside heats up and expands. It means an IK can feel a bit soft in the cool morning following a hot day; don’t worry, you don’t have a leak.
The handy thing with a PRV is that it makes a good guide to how hard you ought to pump up the rest of the boat without a pressure gauge. At whatever pump effort the valve starts hissing, that’s the same or a-bit-more pressure to put in the side tubes which may not have PRVs.
The air in an IK can also get cooled, for example when pumping up on a hot day and then putting in a cool river. Because you want the boat to be as rigid as possible, after inflation it’s worth topping up once the boat is in the water; splashing helps cool the sides. Topping up or tempering optimises rigidity and with long 2psi boats you need all the rigidity you can get. In the same way, pumping up your boat in way sub-freezing temps and then putting it on water which actually ‘heat’ it up, though this is a much less likely scenario.
My higher pressure Incept K40 had PRVs on all chambers which meant you could confidently leave it in the baking sun and it would safely purge then feel a bit soft once cooled down back in the water. Picture above: Incept PRV test with the protective cap removed and purging correctly through the centre.
Below: a PRV being resealed after leaking from the edges (left). This was because I failed to check their tightness after buying the boat, as recommended by the manufacturer. My Gumotii never needed such tightening or checking in years ownership.
I ended up also fitting side tube PRVs to my Gumotex Seawave to run higher pressures.
Oddly, my Grabner Amigo didn’t have any PRVs at all and neither do the latest Holiday models and a few others, even though all run higher than normal 0.3-bar pressures. One presumes Grabner are confident in their vulcanised construction to think they’re not needed, though see the warning above.
If your pump has no gauge Grabner do PRVs to fit on the hose (left) which purge at 0.3 bar, so dispensing with faffing about with a handheld pressure gauge.