Tag Archives: leafield A6 prv

Fitting 4.8 psi PRVs on a Gumotex Seawave

Seawave main page
General article covering PRVs

Updated Summer 2020
yalding

My old Gumotex Seawave was a well spec’d IK for my sort of inshore paddling and occasional touring, especially as it was factory rated to run at a higher-than-usual 0.25bar or 3.6psi (normal is 0.2 on Helios, Palava, 410C, etc). That means greater rigidity which adds up to less longitudinal sag caused by paddler weight (who, me?!) and of course a better glide. My previous Amigo and Incept both ran an even higher 0.3 bar, and it’s said that this Gumotex can also be pushed to that sort of pressure on the side tubes without risking damage. Factory hull pressures are set on the conservative side, perhaps to limit warranty claims.
Like all the Gumboats I’ve owned, the more vulnerable I-beam floor chamber has a factory-fitted PRV, presumably set at 0.25bar/3.6psi (confirmed below). PRVs are important here as if an IK gets hot (typically out of the water on a sunny day) internal air pressure can increase to the point where seams can rupture or the boat can blow. If separation happens to an internal I-beam in the floor it will balloon up and becomes a very difficult repair. I would not meddle with the factory-set PRV on an i-beam floor.
As we all now know, the way round an I-beam floor’s limitations is drop-stitch technology – effectively zillions on ‘i-beams’ spreading the load over the entire area which enables much higher pressures.

PRV-PalaverIn a discussion with a French Gumtexer, he suggested that Gumotex use the same orange dot  0.243 PRVs in all their boats, irrespective of the stated official rating which is either ‘0.2’ like most or ‘0.25’ like the Seawave. He sent me a photo of his 2016 Palava floor PRV (right) – orangey-pink, same as my Seawave and classified by Ceredi as 0.243.
Officially the Palava is a ‘normal pressure’ 0.2 bar canoe. Upshot? Your Gumboat’s floor may be rated at higher pressure than you think or is officially stated – and you’d assume the tubed sides can handle at least as much pressure. Then again, in the table below, Ceredi state the orange PRV  will open between 0.21 and 0.243 so perhaps we all just need to calm down a bit.

Guatemala, Fuego volcano, Strombolian eruption

PRVs use springs set to purge air before it reaches structure-damaging levels. Then again, my Amigo had no PRVs at all so you assume Grabner were confident their floor construction was solid enough to handle occasional neglect. But I’ve been caught out before and always try to ensure a boat remains in the cooling water when moored up on hot days – even getting up to throw on a cooling splash as the sides tighten up like a drum.

cerediprv

Like most IKs with single side tubes, my Seawave had no PRVs in the side tubes as the tubular profile can handle higher pressures better than a flat, ‘lilo-like’ floor. However, if you’re planning to run them over-pressure as I am suggesting, that could be risky. The answer: fit PRVs in the two side chambers – just like my old Incept. That way you can safely leave you IK out of the water in the tropics, go and hike up a volcano (which might be described as ‘the planet’s PRVs’) knowing that all three chambers on your IK will harmlessly purge any excess pressure. Sure, when it all cools again in the water the boat may be saggy, but better a quick top up with your K-Pump than pulling bits of shredded Nitrilon out of the palm trees. Ideally I was looking for a PRV set at a reasonable 30% over the factory figure of 0.25 bar – i.e.: something around 0.33 bar or 4.8psi.

prvcolours
I admit that the colours look pretty close but it’s pinky-orange for the OE floor and red for my 0.33s

Well-known IK valve-makers Leafield and Halkey didn’t make anything matching my needs (or don’t sell to individuals). The Seawave’s valves are stamped ‘Ceredi Italy’ and once I managed to track them down online, I saw the same Ceredi 6600 PRV series came in options including Red 4.78 psi or 0.33 bar, (left and below). In the UK they were a special order via IBS and cost £35 a pair posted.


As you can read from Adam’s comment below, there is – or more probably was – a super valve which combines both inflation and pressure-release duties which means you simply replace the stock inflation-only valve. No need for extra holes to be cut. His link no longer works but I tracked it down to here; the Bravo Super Valve – that’s Bravo as in the cheap Italian branded pumps we all know and love. But there is no mention of a super valve on their valve page, nor is it in their catalog. Wet Works in the UK were selling 4.35psi super valves for £15. I ordered two; nothing happened soI take it they never actually had them.


Fitting the PRVs

grabtool

Tools and time needed
• Gumotex inflation valve removing tool (fits Ceredi PRVs also). Right;  £12 on ebay

• Narrow-bladed knife or scalpel
• Water pump/lock channel pliers
• 30 mins

Short version
• Choose your spot, mark and then cut a 37mm hole in each side chamber. The Ceredi-suggested 35mm was not enough. Or fit a Bravo Super valve – see above
• Remove the side chamber’s inflation valve with the tool
• Squeeze the PRV’s threaded back collar through the bigger inflation valve hole, shuffle it over to the 37mm hole and screw on the external part of the PRV by hand
• Reassemble the inflation valve and tighten both valves with the tool
• Fit push-on caps to the PRVs
• Pump up and check for leaks. Maybe retighten some valves with the tool

prvvs.jpg
Hadron

Long version
I chose to fit the PRVs close to the inflation valves and at about the same level. There are mysterious markings on the inside of the Seawave to aid symmetrical positioning (Pic 2, below). I used a narrow-bladed knife and of course took care to gather up the hull skin so I wouldn’t inadvertently puncture the other side of the side tube. I assumed the 35mm hole would be big enough to take the back nut. When it wasn’t I was a bit flummoxed. Now I had a gaping hole in my boat, but no way of getting the back of the PRV inside the boat without performing a Caesarian on my Seawave. Luckily two brain cells dropped into my Hadron Collider and it occurred to me that once removed, the nearby main inflation valve’s hole might be bigger. And it was – just.
One stock valve was extremely hard to undo. I wondered if it had mistakenly been glued in or that the plastic valve removal tool would snap. When the other side undid with less effort I knew it had to be possible.

Another problem is that the internal collar or nut is only 10cm deep (pic 4, below) and so was hard to grab through the hull fabric. Until I realised this, I was grabbing the inside part of the outer valve body which screws through the collar from the outside. Trying to ‘unscrew’ the valve body from itself is like trying to pull you head off –  eventually  the valve tool would break. Another ‘Higgs boson’ moment came over me and I realised that by chance the two valve holes in the boat were close enough for me to get some water-pump pliers in there, grab the back collar and finish the job (pic 6, below). After that, no more problems.
One thing I noticed while doing all this was the unseen protective patch on the inside of the hull opposite the inflation valves to limit wear and rubbing between valve body and hull when the boat’s delated. Nice touch, Gumotex ;-)

I did all the valves up as hard as possible with tool and hand, and in four more years had no problems. On a hot day in the sun I can hear the high-pressure side PRVs hissing away. The gallery below shows the job in chronological order.

prvrv02
The bits you need
prvrv05
Incision, but the right-sized 37-mm hole is too small to pass through the ’35mm’ PRV back collar
prvrv06
37mm hole is better, but still not wide enough to pass through the inside ‘retaining nut’ of PRV assembly
prvrv04
You need to remove the main inflation valve  (it’s hard to grab the inside part by hand). Then the PRV back nut just squeezes through main valve hole and can be shuffled along towards the new hole
prvrv11
Holding the PRV back nut in place to tighten is hard by hand. So pass pliers through the main valve hole…
prvrv12
… to clamp onto the back of the PRV assembly. This is why it helps to cut the PRV hole close to the main valve
prvrv09
PRV done. Now replace main valve
prvrv07
Clamp them all up
prvrv14
PRVs as far as the eye can see

Now it’ll be good know that should I doze off as the tide ebbs away, I won’t be rudely woken by an exploding boat. Another side benefit of doing this is that you’ll never need to use a manometer (pressure gauge) again. You simply pump up all three chambers until they hiss and you know they are at full pressure.

smoko

Inflatable kayak valves and PRVs

Pumps are here
Installing high-pressure PRVs
Updated Summer 2020

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.

gumvalves

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.

grabtool

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.

lefielda6

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.

prvtest
A PRV purging
prv-leak
K40 PRV leaking from the sides not through the valve.
Needs tightening with special tool.

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.

grabnerprv

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.