Inflatable packboat valves and PRVs

Updated December 2018
Pumps are here

IKvalvesThe 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-presure ones off on white water rafts, pictured left and copied by many. Like a car-tyre valve, one-way operation as well as a secure fitting are the key, so what pumps in doesn’t push back at your or escape when you remove the inflation hose.
pump-barrelgrabvalveWith proper raft as found on good IKs valves, pushing the button down and turning clockwise locks the valve open to release air. Then, for pumping up, push lightly and turn anticlockwise so it springs gumvalvesback 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.
Old Gumotex valves were cruder versions of a Halkey Roberts; post-2010 Gumotex valves gumvalveuse superior ‘push-push’ valves (right) which lock open or close by simply pressing, like a click biro.
valvespannerI always make sure I refit the cap seal straight away to keep grit or water out.
I’ve found these types of valves to be reliable on all my IKs although this grabtoolGumotex 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.

pump-bayopush-fitadapterWhen it comes to inserting the inflation hose, one-way IK valves can take simple push-fit adaptors as shown 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 high-pressure boats like Grabners and Incepts and some Gumotex, you’re better off using a hose adaptor suited to bayonet fittings (right) so the hose won’t pop off as pressure builds.

Low-pressure valves for packrafts
anfi - 13Screw-cap Boston valves  are used on cheaper IKs as well as slackrafts and packrafts. They have two bosvalvcaps: the main one unscrewed (left) to dump the air, and a square cap to access the one-way valve to top off a boat (right).
valve-bostonThese are low-pressure valves using a simple soft rubber ‘mushroom’ on a stem (right) which is fine on a boat you top off by mouth, not a pump – ie: packrafts but not proper IKs. With a packraft, the one-way valve eliminates the need for a separate oral top-up valve which means one less thing to leak or malfunction.

Pressure release valves (PRV) for IKs
I’ve learned to be careful not let an IK get too hot 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 seams or an I-beam floor.
mod-esc valveThe floor tube on my Sunny had a pressure release valve (far left black disc, left); oddly it’s something never mentioned in the specs. It’s there to protect the I-beam floor which could separate under pressure (I-beam floor explained here). The valve is set at a certain pressure to purge when the air inside gets hot and expands. It means an IK can feel a bit soft in the cool morning following a hot day; don’t worry, it’s unlikely you have a leak. The handy thing with the 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 airing off, that’s the same or a-bit-more pressure to put in the side tubes which may not have PRVs.
lefielda6The 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 has got wet; splashing helps cool the sides. Topping up – or tempering – optimises rigidity and with something like a Sunny or Solar 410C you need all 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 less likely scenario.
prvk40prvtestThe 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 and then feel a bit soft once cooled down back in the water. Picture left – Incept PRV test with the protective cap removed and purging correctly through the centre. Right, a PRV being resealed after leaking from the edges – shown below. This was because I failed to check their tightness after buying the boat, as recommended by the manufacturer. My Gumotexes never needed such tightening in many years ownership. I ended up fitting side chamber PRVs to my Gumotex Seawave to run higher pressures but protect it fully.

prv-leak

K40 PRV leaking from the sides not through the valve. Needs tightening with special tool.

grabnerprvOddly, my Grabner didn’t feature PRVs at all, even though it runs potentially damaging high pressures. One presumes Grabner are confident enough in their vulcanised construction to think they’re not needed. I do notice that Grabner offer PRVs to fit on the end of an inflation hose (right) which purge at 0.3 bar and so dispense with the need for a pressure gauge to check how much you’ve put in.

This entry was posted in Cheap PVC 'slackrafts', Gear, Gumotex IKs, Gumotex Seawave, Inflatable Kayaks, Tech and tagged , , , , , , , , , , , , . Bookmark the permalink.

1 Response to Inflatable packboat valves and PRVs

  1. Simon Harvey says:

    great article – thanks

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