Category Archives: Pumps, Valves & PRVs

Tested: Tyre pump adaptor for inflatable kayaks

You may have seen these bayonet/car tyre adapters on eBay in recent months (left). The bayonet end clamps into your IK’s raft valve (won’t work on Boston valves). The other end is a regular Schrader valve like on your car/bike wheel. Attach that to your 12-volt Halfords tyre compressor and you can inflate your IK from your car battery. No more of that effortful, back-breaking pumping!

Me, I’ve never seen the value of electric pumps for IKs. You can only use them near a power source and how hard is inflating an IK with a good barrel pump anyway? It seems some think it is

The difference between tyres and IKs:
• a car tyre is a low volume running high pressure (~30 litres @ ~30psi)
• an IK has high volume but runs low pressure (3 chambers of 50–160 litres @ ~3psi). Drop-stitch has less volume but runs much more.

That’s up to five times more volume in an IK but at a tenth of the pressure. I would guess the swept volume of my better-than-average car pump (left) is 3–5cc. My Bravo RED 4 barrel pump is 2 x 2000cc (it pumps on the up and the down stroke).
Even if my 12-volt compressor whizzes along at 1001rpm, it will still take a long, long time to fill a 160-litre IK floor. But for a fiver, I thought I’d prove myself right.

The easiest way was to pump my Seawave’s floor to the point the PRV purged at about 3psi. The actual psi is immaterial but it’s consistant.

No surprise: it took less than a minute to pump up the 160-litre floor with the barrel. With my car tyre pump it took over 7 minutes.
And if you want say 4psi in the sides, or a 10psi drop-stitch boat, the duration of the tyre pump (or effort with the barrel pump) rises exponentially. It will take forever with the car pump adapter and I think the tyre pump would auto shut-off or burn-out before it reached anywhere near 10psi.

I read about portable USB rechargable electric pumps like the Pumteck or Sunta (left) on amazon from just £15. These are great for pool toys, air beds and other low-pressure items which just need a shape, not rigidity.
The Pumteck claims an obscure pressure rating of 4.5 kPa which sounds impressive but translates to just 0.65 psi or 0.045 bar. That is slackraft presure; there is no worthwhile IK that runs such a low psi, so all it will do is save you the easy initial pumping. For a typical 3-psi IK you’ll still need some sort of manual pump to top off and on a D-S IK, forget it. If your back can’t handle a barrel pump, get a Bravo foot pump.

Tested: Anfibio Packrafting Nano RTC packraft review

In a line
Super-light but sturdy packraft with a low-maintenance solution to in-hull storage.

Simple but well-detailed design
210-D fabric feels durable
Optional mini-hand pump works very well and can be deployed on the water
Holes easily sealed from the inside with a stick-on patch
Compared to TiZips, RTC is a simpler, lower-maintenance way to achieve in-hull load carrying
Raised floor lifts paddler, limits wear and may help limit yawing
Like most short packrafts, it’s not a joy to paddle on flatwater for hours
RTC will need care and may need practice to achieve a good seal
Floor is same thickness as hull, not double-weight, as is usual.

What They Say
Extremely light packraft with roll closure (RTC), which enables luggage to be stowed in the tube and thus offers higher transport capacity. Minimal pack size, 1kg light and robust enough for calm and tame waters allow combined adventures with increased payload. Price: €389

Out of the box

This pre-used Anfibio Packrafting Nano RTC came with an optional backrest seat (€57), the airbag, an optional mini top-up hand pump (€10), a strap and 3 patches but no glue or instructions. The latter appear online.
On the IK&P scales the boat alone came in at 1002g. The full seat adds another 237g with the horseshoe seat base weighing 135g. All the other dimensions in the image above closely match Anfibio Packrafting’s own data.

This is not your usual shiny-exterior packraft; the Nano’s coating is instead on the inside like the plain Nano SL model. The woven texture of the 210D nylon fabric still gives a sense of sturdiness which I can’t say I felt with the 75D Supai Flatwater and Matkat we tried a few years ago. Such perceptions are important when bobbing about in the middle of a breezy loch or tackling some light whitewater. Maybe it’s the black colour, but the Nano also managed to look bigger and tougher than the virtually same sized Alpha XC (left) we tried a year or two back.

The RTC is a new idea to Anfibio Packrafting, though I see the scantily described Rapid Raft in the US uses a similar closure. The Nano differs by being a more sophisticated design, with a broadly symmetrical hull made from just three pieces of fabric: hull top; lower hull and floor; inner ring. This adds up to just two long seams which ought to mean fewer chances of errors during assembly as well as less weight. Symmetrical also means you can have the closure up-front (normal) or at the back where, with just four folds rather than five, it creates an elongated stern which adds more buoyancy where most of the weight is and acts as a fixed rudder to limit side-to-side yawing endemic to packrafts. Payload is 135kg.

The RTC has an extra TPU film bonded inside to ensure an airtight seal, as long as you roll it up tight with no wrinkles. Providing it works, as a way of enabling in-hull load-carrying, I’d sooner put my faith in this than a TiZip which must be kept lubed and clean and dried properly to work well.
At the RTC-end you have four mounting tabs on the tube top. On this you can mount Anfibio’s DeckPack, as pictured below. Bigger exterior loads may also be more convenient here if your route includes many awkward portages where carrying the otherwise heavily loaded and inflated boat may be tricky. Otherwise, there’s a tab inside the hull to secure loads and keep them towards the RTC end.
You get seat mount buckles at both ends too, though I found the fully inflated seats jammed in well by themselves. There will be the age-old annoyance of the backrest flopping forward as you get in, but used RTC-sternward you can hook it upright to one of the tabs. This backrest design hasn’t changed since I had my first Alpacka Denali over 10 years ago. What is actually wanted is lumber support which is best achieved from strap-braced backrests, as in my Nomad, but that gets complicated.

No you can’t inflate it by opening the RTC to the wind unless there’s a gale on, but it helps to fluff the boat out, and using the usual airbag, 5-7 scoops fills the boat, after which you top up the one-way Boston valve by mouth. If you find this a bit awkward, I find a section of half-inch garden hose works as a ‘blow-straw’. Or use the top-up hand pump (137g) to get maximum firmness. On the Nano it worked very well and for only €10 I’d say is a worthwhile addition for any Boston-valved packraft. More below.

The RTC cannot be compared to the usual roll closures of simple pack sacks [dry bags]!” proclaims the website, and I can believe them. We all know that Ortlieb-like roll-top dry bags don’t have a proper seal; water will seep through and air will leak out. But the multiple rolling of the film layer, as well as the fact they’ve dared use RTC on a packraft, gives a sense of confidence. Time to get paddling and see if that confidence is warranted.

On the Water

Mid-September and it’s nearly 30°C: too good to pass by so I head for a short run up and down the Medway. Airing up at Sluice Weir Lock, I had a good feeling about the Nano, even if at 95kg I expected to be on the limit, as I was on the Alpha XC. The extra 6 centimetres all round looked enough to make a difference, and one way to help the trim (level) would be to run the RTC at the stern and as long as possible (four folds) while perched forward on the backrest seat option. In the end I didn’t feel the need to do this.

Once inflated by bag and topped up by mouth, I knew the Nano would need a damn good tempering today. A boat firmly inflated by hot ambient air will go soft once cooled in the water. Sure enough, after some splashing the Nano went as limp as a stunned trout. While doing this I was reminded of the indispensability of a bow line to manage a boat at the water’s edge. I hooked the metre-long strap through the RTC (left); better than nothing.
Back on the jetty I tried the two-way hand pump: 20 pumps firmed it up. After over a decade of proven hull integrity, it’s become the norm to top-up packrafts with mini-pumps and not by lung, raising pressures up to 2psi or more. This added tautness is what differentiates packrafts from slackrafts and has a huge benefit on paddling efficiency and satisfaction.

They say don’t overdo the pumping but how are you to know? A well-made packraft may well handle a massive 0.5 bar or more before it blows a seam, but assuming the Boston one-way valve can handle it, I think the mini PRVs I tested the other day would be a useful addition to packrafts. They cost only 4 quid and you just keep pumping away until they hiss, knowing the boat’s reached the valve’s purge pressure which cannot be exceeded. It’s like an in-built pressure gauge. Fitting one to the open-ended Nano (or any TiZip packraft) would be especially easy

I decided to try RTC bow first (it made using the DeckPack easier). Once in the boat I felt fine, though from the pictures it’s clear the trim looks nearly as back-heavy as on the Alpha. Too many pies. But on these recommended ‘calm waters’ that didn’t seem a problem.

Confident I wouldn’t wet myself, I set off 2km up river for Oak Weir Lock, passing some happy Itwiters on the way (left). Those things are everywhere now! Good on Decathlon for satisfying the huge demand this summer.
Within a few minutes it became clear the Nano had cooled further and needed another 50 pumps off a handy concrete slab below the steep riverbank. I also remembered that, unlike my IKs, low-floored/high-sided packrafts want the seat base pumped right up to give height so as to get the paddle over the fat sides.

Back on the move, speed and response increased dramatically, but not having paddled a normal-sized packraft for a while, I’ve forgotten how slow they are, topping out at maybe 2.5mph/4kph. Riverside walkers were outpacing me; normally it’s the other way round on the Medway, albeit heading downstream. Where noticeable, the current here is about half a mile an hour.
I took off to explore some mysterious side creeks which I’d normally shoot past on my downstream burn-ups, careful to avoid the many brambles which line the river here. There’s a perception that the Nano’s textured woven surface could snag a bramble more easily than a smooth one, but should that happen it would be easy to open the RTC and slap a stick-on patch on the inside: the best place for such a repair. The heat and dense, overhanging vegetation reminded me of a boat trip I took years ago up the remote Roper River in Australia’s Top End.

Back out on the main channel and heading upstream, after a while it took some effort to move the Nano along, with the tell-tale bobbing of a soggy slackraft. A squidge of the sides showed they were soft again. More tempering needed or a slow leak, probably from the inexpertly sealed RTC. I hacked on and at Oak Weir jetty and got my weight over the bow to push the RT closure underwater. A couple of tiny bubbles popped up occasionally, but they may have been just trapped air escaping the folds.

The picture above makes it appear worse than it was, and being a hot day on cold water, I felt one more tempering may do the trick. I often have to do this with my bigger Nomad; which takes a good few minutes on the water to fully cool on a hot day. I did my best to check for tell-tale bubbles elsewhere, but anything easily spotted would have seen the boat droop in minutes.

I realised the seemingly redundant hand pump hose was actually ideal for topping up on the water. I reached behind and carefully undid the upper cap of the Boston valve (you don’t want to undo the main valve…), pushed on the pump hose nozzle and gave it another 50 jabs + 10 for luck (about 8-9 litres). With the Nano taught again, I couldn’t resist hopping out and sliding back down the shallow Oak Weir canoe chute which the Nano took in its stride. This boat could easily manage river riffles; the caveat would be too much scraping in the shallows. The exposed fibres can probably take some rubbing but it’s the coating inside that counts. I wonder if spraying a slippery coating (303 Protectorant springs to mind) on the undersides may help reduce possible wear.

I’d asked for the backrest seat option to push my bulk forward off the overloaded stern, but comfort, or a relaxed all-day paddling posture, will take some experimenting. With the unusual raised floor and seat base pumped right up, the now higher backrest had less to lean against so I tipped backwards. I should have tried deflating the seat base a bit.
Even at my height (1.82m) I can still stretch my barefoot legs flat out, when in fact a bent leg is better for paddling. So you might want to fit Antibio’s footrest (as I use on my Nomad), shove a bag or shoes up there, or better still (for trim), put something behind you to act as a thicker backrest and centralise your weight (as we did on the Alpha). However you achieve it, a solid back–to-foot brace improves paddling efficiency which means it takes longer to get tired.

Running back downstream to Sluice Weir felt like it took half the time, and I got there with the boat still firm. I do wonder if wetting the inner film surface provides a better seal, just as licking a suction cup before sticking it to glass. One to try next time.
I also noticed that for a short, wide raft, the Nano barely yaws left to right. Besides my fine technique honed over the years, the profile of the raised floor may help the side tubes ‘bite’, like ice skate blades. Or it may be the subtle protrusions (below) under each end of the boat which my 2.9-m Nomad also has and which are said to have a skeg/keel effect.

Either way I was confident I’d survive the sporty Sluice Weir chute, catching only a cupful of water as I hit the frothing base. With that ticked off, I paddled over to the portage jetty crawled out and aired down. Being a black boat on a hot day, the Nano dried itself off in no time.

Packing the boat up, I checked for seepage into the RTC when it had been submerged for a minute or two. As expected, water crept along the textured outer nylon surface but the inner film was dry, though as Gore Tex will tell you, air can pass where water can’t. If that was the issue, not just heat, I’m sure getting a good seal is a knack that can be acquired.

Conclusion

Providing they can handle the added pressure of a hand-pump, I wouldn’t be surprised to see RTC-type closures becoming more common on packrafts. Using zippers for such a critical seal always seemed a bit dodgy to me, though I’ve only read of them playing up.
Besides that novelty, the sturdy 210-D Nano makes a great crossraft at a price that’s competitive with the thinner Supai boats. It’s very light, compact (3 litres rolled up), comes fitted with enough useful tabs and can be paddled RTC-stern to level off the trim, if needed. Seats are quite a lot extra, but you can sit on your gear, and for a tenner, the little pump is a no-brainer to get the most from your boat. And if the Nano’s RTC arrangement is not for you, choose the conventional Nano SL costing about 15% less. Either could make a great entry-level packraft or an ultra-light crossraft.

Testing unbranded mini PRVs

See also:

IK valves and PRVs
Fitting 4.8psi PRVs to a Seawave

I fitted over-rated 4.8psi Ceredi PRVs to my Seawave’s side tubes a few years back. I like the idea of not having to worry about the boat getting hot in the sun (and exploding), just as much as gaining some extra rigidity by fitting PRVs rated a little higher than recommended side tube pressures.

I bought a pair of unbranded Chinese PRVs off eBay (<£9 posted – about 30% of Ceredi/Leafield prices) to consider for my next IK. Some sold on eBay don’t even mention the purge pressure! These ones did: 4psi or 0.27bar, just a bit over the 0.25 of the boat I have in mind.

Out of the bag, the quality of the molding looked no worse than a Ceredi. I was a bit surprised they’re smaller than usual PRVs, (the listing gave these dimensions), but what does it matter as long as they work.
I worked out a way of testing them by removing the backing ‘nut’ and screwing the ‘male’ PRV housing onto a rubber motorcycle throttle grip. The other end of the grip I jubileed to the barrel pump nozzle.
Pumping the pump, the pressure built up and PRV ‘burped’ suddenly at an indicated 0.4 bar. But as my manometer needle zeros at 0.1 bar and not zero, we can probably subtract that 0.1 and call that 0.3 bar which is 4.34psi. Close enough to 4psi. Now I can fit these PRVs with confidence.

The hole which must be cut in the boat to fit this valve is 24mm ø, but to get the back nut inside the hull you’ll need to go in via the larger inflation valve aperture. So cut the PRV hole close to the inflation valve. Once loosely screwed together, the knurled outer housing can be tightened with some wrench or another.

MRS Nomad S1 – a few mods

MRS Nomad Index Page

After paddling around in the S1 I can see some ways of improving it. So I did.

Replace the inflatable backrest with a plain foam backrest. The backrest which came with the boat had already been repaired twice and, unless it’s at the back of a packraft, who needs an inflatable backrest anyway? It’s more about support than weight-bearing comfort, like a seat base. As on my Seawave, a foam backrest (£12 on eBay; 200g) does the job and is one less thing to blow up. The press-pivot clips from the old backrest fitted on easily, and even though it only has 4 straps, not 6, it works fine. I trimmed about a foot of excess from each strap.

nomanewseat

I bought some mesh zip pockets about 6” x 10” off eBay costing next to nothing from China. I zip-tied one to the back of the backrest. A handy way to ensure the airbag, K-Pump adapter and a couple of zip ties are always in the packraft.

mrsfootrest

I fitted an Anfibio footrest cushion. You lose some inflating time there, you gain it here but the Nomad’s seat is too far from the bow for efficient bracing, even for me, and moving the seat has its limits.  I’ve since found the broad flat resting edge makes a more comfortable footrest than having them jammed in the bow. For flatwater I may not even need the thigh braces.

nomafootrest
nomappump
kpumpmini

Top-up pump. The Nomad’s large volume takes a lot of tempering (topping up) to get it firm, but I can only do so much by lung. With a bit of hose on the end, the £3 pump (left) should have enabled a higher pressure, it’s the same one Alpacka were selling with some boats at one stage. But it didn’t work – or would take forever. I think it just hasn’t got what it takes. By comparison, my bulkier K-Pump Mini also with a hose nose (below), effortlessly packed in enough air to firm up the Nomad like a drum. So if it’s that important, the K-Pump it will have to be.

nomazips

Quicker detach seat base. I replaced the knotted-in laces with long, thin unzipped zip-ties threaded through the holes to make the seat easier to remove for land use or for drying and cleaning the boat. Any similar plastic wire-like thing will do, as long as there is no puncture risk. But it’s still not clip-off easy. I have a better idea.

2bags

I replaced the blue MRS airbag with a brightly coloured Anfibio one. Visibility is the rationale: because packrafts lack somewhere to stash this important item (but see below), with a neon green bag I’m much less likely to forget it when packing up (done that before). It could also be handy to wave as a rescue aid if stuck on a stormy skerry in the North Atlantic (not done that yet).

For the same reason I stuck some hazard tape on the skeg. I also threaded a reusable zip tie through a hole in the back so it can be securely attached to the boat when packing up, but in fact, unlike my IKs, on the Nomad a skeg is not essential to make it track well.

mrsskeg

I added some sidelines; handy handles when manhandling the boat, and also useful to tuck in the paddle securely across your lap while controlling a sail. Or course having the mounting points pre-fitted makes all this much easier.

Pumps for inflatable kayaks and packrafts

Inflation valves and PRVs are here
My PoV on electric pump here

ikpumps.jpg

Your inflatable packboat needs a pump to get going and to top-up once on the water. These functions may be best performed by two different pumps. It seems the era of the bellows footpump (left) is over and even low-pressure IKs now come with some sort of barrel pump.
A plastic-bodied barrel or stirrup pump is light but bulky so not something you’d want to tour with. They’re usually used for pumping up high volume/low pressure things like rafts, lots of IKs or kite wings. Some pump air on both up and down strokes to fill your boat more quickly, but automatically or manually switch to downstroke-only to reach higher pressures. They work best on flat, firm ground where you can stand on the stirrup plates and get stuck in. The Bravo 4 RED pump above is still only about £20 and will pump up an IK in 5 minutes.

sw05

I got a Bravo 6 with my Seawave once but found it hard work – who knows why. The cheaper Bravo 4 does claim to be an ‘R.E.D’ (‘reduced effort device’) and I can confirm this isn’t some gimmicky acronym.
Like a Bravo foot pump, the other port on the Bravo’s handle can be used to deflate or suck air from an IK so it rolls up good and flat; you can see creases forming in the hull as you suck it down.

I left my Bravo 4 RED at home one time so bought a Sevylor RB2500G barrel pump (below left) for a tenner off ebay. Same size as the Bravo barrels, it did well for the awkward topping-up of my Semperit’s lilo plugs. It came with push-fit, lilo-plug and bayonet adaptors and sucks as well as pumps. But pumping up my Seawave from flat was exhausting towards the end: I actually got out of breath and had to rest. Morale of this fascinating story: get a Bravo 4 RED and the right adaptor for your boat.

Not all barrels have a built-in pressure gauge which is obviously dead handy in getting the right pressure without needing to faff about using a separate manometer (see below). It’s worth an extra tenner to get a built-in gauge, especially with D-S boats/
Or fit your own manometre: see bottom of the page.

kpump200

The K-Pump Mini (above right) is a handy top-up pump or compact 600-g travel pump. It took 15 minutes to fully inflate up my Seawave; the push-fit nozzle works on any IK with one-way spring valves. You have to press the body of the pump against the valve. Using it a lot one time, I got the feeling it might break something or wear out the seal (which needs regreasing once in a while). I also now use the K-Pump to top up my Nomad S1 packraft which is too big and long to inflate firmly with just its airbag. Fuller review of the K-Pump Mini here. Hard to find in the UK, the long, and slim US-made K-Pump 200 (right) may also be suited to DS applications.

Left, the Bestway Air Hammer is an upside-down barrel pump which comes in three sizes and costs from just £6 on eBay. If you don’t want to paddle with your full-size barrel pump, the smallest Air Hammer could work as a compact top-up pump, like the K-Pump below but a tenth of the price. The one of the left came with my RIBfin and is rated at 4psi

High-pressure pumps

More and more IKs now feature super-rigid, high-pressure drop-stitch hulls – either just floors or the entire hull which runs 2–5 times higher pressures than regular IKs. Your old Bravo footpump will blow its brains out trying to reach the typical 7-10psi.
Barrel pumps with slim and long bodies (as opposed to some of the shorter, stockier examples above) will put out less volume (D/S IKs have less volume anyway) but can attain higher pressures. You don’t need a super high-pressure iSup board pump. Some of these pumps may be double action, but at a certain psi will become single action to help gain higher pressures. I beleive the Bravo Alu 4 R.E.D (0.8 bar) works like that.
Whatever you get for your D/S IK, make sure it is rated to comfortably exceed your D/S boat’s pressure rating by say 50%.

Left: Bravo Alu RED <£20 • Middle: Bravo 110 >£40 • Right Itiwit (Decathlon) £20
bravohose

Suited to low-pressure (non-dropstitch) IKs the once-popular Bravo bellows foot pump looks a bit crap, but lasted well, was fairly travel-compact and was easy to use without doing your back in. Occasionally the yellow tube split near either end if packed too tightly, so needed taping up (left) or cutting down and got shorter and shorter over the years. as mention, the bellows era seems to have passed.

Left: Kokopelli Nano pump: fold-out feet, screw-off handles, switch for one-way pumping as pressures increase, manometer in the handle.
Right: twice the volume Bravo Alu 4 with auto one-way switching (so it says). Bayonet valve fitting on the Nano keeps the valve open and so is for static manometer readings. With the push-fit adapter on the blue pump DIY manometer only reads as you pump and open the valve.
Both are better than soggy footpumps.


After many years a crease in the back of the bellows wore through, though that’s also easily fixed with duct tape. It’s a shame the Bravo pump is a tight squeeze into the Gumotex drybag’s outer pocket. If you use a Bravo footpump very frequently it just plain wears out, so if you’re using the car to get to the water get a barrel pump.

Bayonet nozzles
Who would have thought there’s something to be said about bayonet nozzles? Well there is. There are two types: plain (below right, Gumotex) and crossbar-peg (left, Bravo). Both need spacer washers to fit snugly against your boat’s valve but the small peg inside the green one will press open your valve stem as you connect it. You will notice a similar peg on car tyre inflation hoses and also on a hand manometer (below). It could not get a reading without this peg partially opening the valve.
A nozzle with a peg means that
a: you’re not pushing the valve spring open each time you pump (easier pumping) and
b: if your pump has a manometer you will get a live reading as the pressure climbs which is the point of having a built-in manometer. The Bravo one goes from 3 quid; search: ‘Bravo Adjustable HP Valve adapter”.
The only drawback might be that you need to remove a pegged nozzle carefully with Push-Push (Gumotex) valves. Normally a little air escapes as you do this but if the valve gets locked open air will rush out. Remove slowly.

Pressure gauge (manometer)
Until I got a Grabner which has no PRVs but ran a relatively high, 0.3 bar (4.3 psi), I never bothered with a pressure gauge (manometer, left) and just pumped up by feel.
Since then I got a Gumotex Seawave and fitted PRVs to all chambers. That means I didn’t need a pressure gauge to get the right pressure, I simply kept pumping until each PRV hissed: the boat was then at operating pressure.
With high-pressure D/S IKs you probably do want a pressure gauge as the boat will perform best at the right pressure which may be higher than you’re used to.

Add a manometer dial to a plain barrel pump

I got myself a new Brave 4 Alu R.E.D barrel pump (left) rated to 0.8 bar (typical D/S pressure). It was under £20 without a gauge. The next similarly rated barrel with a gauge worked out at nearly fifty quid. That’s inflation for you.

Then I decided a gauge probably was a good idea in case my next IK doesn’t have full PRVs (quite likely; most don’t). I couldn’t find a way to fit my handheld manometer (as pictured far above) neatly, but on ebay saw manometer dials at various displays and with rear (behind) rather than bottom inlets for a fiver (right)
I chose one which displayed up to 1 bar / 14.5psi. Whatever boat I get next, D/S or otherwise, it won’t be higher than that, and anyway the Alu 4 is only rated to 11.6psi (0.8 bar).
The easiest place to drill the hole is into the hard plastic end of the hose by the handle (below). The brass thread will screw into the plastic hole easily enough, but a dab of glue does no harm. Now, finally I can measure as I pump.

Fitting 4.8psi (0.33bar) PRVs to Seawave IK sidetubes

Seawave main page
General article covering PRVs
Unexplained Seawave failures ;-/
Testing unbranded PRVs

My Gumotex Seawave was a well spec’d IK for my sort of coast-hopping and occasional touring, especially as it was factory rated to run at a higher-than-usual 0.25bar or 3.6psi (Gumo normal is 0.2). That means greater rigidity which adds up to less longitudinal sag caused by paddler weight (who, me?!) and of course a better g l i d e. 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 to limit warranty claims.

Like all the Gumboats I’ve owned, the more vulnerable I-beam floor chamber has a factory-fitted PRV 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 might rupture. 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 answer to I-beam floor limitations is drop-stitch technology – effectively zillions on ‘i-beams’ spreading the load over the entire area which enables much higher pressures.

In 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’ on the Seawave. He sent me a photo of his 2016 Palava floor PRV (left) – 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. You’d assume then that 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 0.21 it is and we all just need to calm down a bit.

Guatemala, Fuego volcano, Strombolian eruption

PRVs use springs set to purge air before pressures reach 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 splash the sides as they tighten up like a drum.

cerediprv

Like most IKs with single side tubes, my Seawave had no PRVs as the tubular profile can handle higher pressures better than the 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 side tubes – just like my old twin side tube 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 will harmlessly purge any excess pressure. Sure, when it all cools again back 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 33.33% 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, (above right). In the UK they were a special order via IBS and cost £35 a pair posted.

Ceredi prices too steep for you? On eBay I bought unbranded ‘4psi‘ PRVs from China for about £4 a shot and delivered in less than 2 weeks.
Note these are smaller than your Ceredi and require only a 25mm hole. The back nut will easily fit through the inflation valve hole, once you remove that.
I pressure-tested the valves I received and they stood up to the claim: more here.
Search eBay: ‘Air Safety Release Valve Kayak’.

As you can read from Adam’s comment below, there is – or more probably was – a super valve which combined 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 Italian branded Chinese-made pumps we all know and love. But there is no mention of a super valve on their valve page anymore, nor in their catalog.


Fitting the Ceredi red dot PRVs

grabtool

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

• Narrow-bladed knife or scalpel
• Water pump/lock channel pliers
• 30-60 mins

Short version
• First, remove the side chamber’s inflation valve with the tool. They can be extremely stiff. If you can’t undo it, maybe think twice before going ahead.
• Choose your spot, mark and then cut a 37mm hole in each side chamber. The Ceredi-suggested 35mm was not enough. Or fit the smaller, unbranded mini PRV (~25mm hole); see above.
• Squeeze the PRV’s threaded back collar through the bigger inflation-valve hole, shuffle it over to the new PRV hole and loosely 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 push-push valve was extremely hard to undo. I wondered if it had been glued in or that the plastic valve removal tool would snap (you can buy a metal one for loads more). 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 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.

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 operating pressure.

smoko

Inflatable Kayak and Packraft Valves & PRVs

Pumps are here
Installing high-pressure PRVs
Testing unbranded mini PRVs

The best inflation valves for an inflatable packboat aren’t the bungs you find on an airbed or an old Semperit. Nor the thin, twist cap stems off a Feathercraft Java or an old Alpacka.
What you want are one-way valves as fitted to white water rafts and pictured left. 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. Brands include Halkey Roberts, Leafield or whoever makes your boat. In America they’re also called ‘military’ valves.

gumvalves

You either push and twist the button clockwise to lock open (deflating). 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 too. 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 are ‘push-push’ valves (graphic left) which are even easier to use. 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 also useful 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 Gumotex (as well as drop-stitch boats) , you’re better off using a bayonet fitting (below right) so it won’t pop off as pressure builds.

Low-pressure valves for packrafts

Alpackas and even Feathercraft used to use crappy, soft plastic twist-lock oral stem valves (below left) which you could never be sure were done up just right and which didn’t take well to pump nozzles. I suppose they were a step up from blow-up toy valves and airbed plugs (below) which are still found on cheap IKs.

Now best used on inflatable seats and the like, they’ve been superseded by similar one-way stem valves (below right) with a light spring closure easily openable by lung pressure. They’re a bit trickier to deflate: you have to depress the ‘X’ with a finger while squeezing out the air. The one below right is actually on a buoyancy vest.

Boston-type valves are a one-way valve long used on cheap IKs as well as slackrafts and have now become common on packraft hulls. Note they’re widely copied and not all may be identical, like well-known branded IK valves.
The square top cap screws onto the round valve body which itself has a knurled edge to easily unscrew from the hull port (below right). Here you attach your air inflation bag or open to quickly dump the air when rolling up.

Ideally suited to low-pressure boats like packrafts, they use a simple rubber ‘mushroom’ valve on a stem (above middle). Once the main valve body has been screwed back into the hull, unscrew the square cap to finish the inflation process by either topping off by mouth or with a hand pump.

A one-way Boston-type valve eliminates the need for the old separate stem valve and the whole assembly has swivelling plastic lanyards so nothing drops away when unscrewed.

Pressure release valves (PRV) for IKs

I’ve learned the hard way to be careful and not let an IK get too hot when out of the water. On a hot day you can feel the more exposed sidetubes tighten like a drum. This of course happens to be good for rigidity and paddling efficiency but isn’t good for the seams or an I-beam floor or the sewn seams of a cheap shell&bladder IK.

lefielda6

The floor tube on my old Sunny had a pressure release valve – oddly it’s something rarely mentioned in the specs, even on current Gumboats. It’s there to protect the I-beam floor which could rupture inside under pressure (I-beam floors explained here).
The valve is set to purge (open) at a certain pressure when the air inside heats up, expands and pressures rise. It means an IK can feel a bit soft on a cool morning following a hot day; don’t worry, you don’t have a leak, it just purged some air when hot yesterday and in the cool air is a bit soggy. A quick top up is all you need to so.
The handy thing with a PRV is that it makes a good guide to how hard you ought to pump up the other chambers of the boat without PRVs and when you don’t have a pressure gauge. At whatever pump effort the floor PRV starts hissing, that’s the same or a bit more pressure to put in the side tubes which usually don’t have PRVs.

As mentioned, the air in an IK can also get cooled, for example when pumping up on a hot day and then putting the boat in a cool river: a normal scenario. Because you want the boat to be as rigid as possible, after initial inflation it’s worth topping up again once the boat is in the water; splashing helps cool the sides.
Topping up, or tempering as it’s called, optimises rigidity and with long, 2psi boats you need all the rigidity you can get. Conversely, pumping up your boat in sub-freezing temperatures then putting it on water which actually ‘heat’ it up, though this is a much less likely scenario.

prv-leak
PRV leaking from the sides not through the valve.
Needs tightening with a special tool; a common necessity
with hastily assembled new IKs.

My higher pressure Incept K40 had PRVs on all chambers which meant you could confidently leave it in the Sahara 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 tightness after buying the new boat, as recommended by the manufacturer. (My Gumotes IKs never needed such tightening or checking in years ownership.)
I ended up also fitting sidetube PRVs to my Gumotex Seawave to run higher pressures and the be able to leave it pumped up and out of the water for months at a time.

Oddly, my Grabner Amigo had no PRVs at all and neither do the latest Holiday models and a few other Grabners, even though all run higher than normal 0.3-bar pressures. One presumes Grabner are so confident in their construction they’re not needed, despite the warnings above.
It should be included with the boats, but if your pump has no gauge, Grabner do pressure relief adaptors to fit on the hose (left) which purge at 0.3 bar, so dispensing with faffing about with a handheld pressure gauge. It’s a good idea.