Category Archives: Gluing and repairs

Repairing a Gumotex Seawave

lm-pumperThe other day, while lashing the Gumotex drybag backpack to a chopped-down trolley I foolishly wore two holes in my Seawave ;-((
Pumping away like a donkey on Limehouse jetty (above), I assumed the non-standard PRV was playing up; probably a grain of Achnahaird sand stuck on the seal. I flipped the cap off, tried to clean it out by springing the valve from behind but no luck. So I gave up and was ready to dismantle or replace it later.
It was only when sw-holesfrustratedly rolling up the boat I noticed two small ragged holes in the hull and realised what had happened. With half a paddle shoved into the cinched-up bag to make a handle, and it all lashed in a to the trolley, I thought I was being rather clever and minimalistic. But strapped to the trolley, the pack soon sagged under its weight and rubbed on the sharp edge of the hard plastic wheels which wore through the pack and then the boat’s hull.
The cut-down trolley had worked fine with my UDB drybag in New Zealand (left), but that was partly because you can fully inflate a UDB via its unique one-way oral valve, transforming it  from saggy sack to firm sausage.
Ironically, just two days before this happened, I’d snagged a BNWT Orlieb RS140 (right) cheap on ebay. I’d been eyeing up this non-rigid wheeler duffle as a versatile Seawave transporter plus reliable on-water drybag/buoyancy aid (review shortly).
And what’s more, inventing the wheel was all very well but to be honest, for short 10-minute spells of urban pavement walking between trains and buses (as opposed to traversing Scottish glens), the 17-kilo Seawave is not so hard to carry as a backpack. Lesson quickly learned.

With enough practice with D-rings, let along bike punctures over the years, I was confident I could do a bomb-proof repair on the Seawave. In a way, I was even a little chuffed that my 5-year old kayak was earning its first battle scars. Plus, in my experience rubber-based IKs like Gumotex, NRS and Grabner glue more reliably than PVC boats. Shiny packraft TPU is even easier: you can just tape it, but packrafts are low-psi boats not normally inflated with mechanical pumps. My adapted Seawave side tubes run 4 or 5 psi.

ami-polyThings you will need

  • Patch
  • The right two-part glue (right)
  • Solvent and rag
  • Sandpaper or abrasive foam sanding block
  • Masking tape
  • Small brush
  • Tyre repair roller (right)
  • Space to do a good job


STEP 1 • Match up a patch from your collection, ideally identical fabric. For a small hole extend the patch at least an inch.

STEP 2 • Clean the punctured area and patch surface with solvent and wipe dry. This time all I had was brake cleaner spray, but ordered some toluene for next time.

STEP 3 • Sand down the two surfaces and then clean and wipe again with solvent. Avoid touching these cleaned surfaces with your fingers.

Some colour coming off is a good sign you’ve removed any sheen or patina.

STEP 4 • Position the unglued patch and mask the perimeter with tape to avoid excess residue and to help with positioning. If the patch is not perfectly symmetrical (like above) mark it – but make it bold – I still got it wrong!

STEP 5 • Mix up some two-part Hypalon (Nitrilon; EDPM) glue. It’s rare than one-part glue works as well, but Aquaseal has worked for me, gluing a skeg-patch to a Grabner.

I found some mini brushlettes in my repair kit box – they must have come free with some glue.

STEP 6 • Brush on the glue thinly to the two surfaces. With Polymarine you then to wait 30 mins for it to cure/dry, then apply another coat and wait till touch dry (5-10 mins). Here’s their full guide:

You can see I made typical errors: mixed up too much glue (but better too much than not enough)…

… and applied too much glue on the patch…

… but a just-right thin later on the hull.

STEP 7 • With the deflated boat repair positioned on a firm surface like a hard floor or better still, draped over a wooden stool, carefully lay the glued patch over the damaged area…

… then – STEP 8 • peel off the masking tape and ROLL DOWN HARD moving from one edge to the other and again at 90° and again diagonally with your Baltic pine-handled roller, making sure the edges have stuck down. It won’t hurt to roll again in 20 minutes and again after an hour to make sure the two parts have well and truly bonded till death do them part. And actually, only about 25% of the glue was wasted.

In 12 hours the repair is cured and ought to last the life of the boat. Never do that trolley thing again!


Alternative to D-rings for IKs

IKavityMichael S from BC came up with a good idea for securing stuff, seats or thigh straps to the floor of your IK without resorting to gluing on expensive D-rings – something that takes application and the right glue to do well.
He suggests the cavity formed between the floor and the sides when you pump an IK up can be used to jam in short tubes attached to tape loops. Example left is a Sea Eagle tieseawavDS, but I know the Gumotei and other IKs I’ve owned form a similar space along the sides.
Pictured below are some Sherpak Quick Loop tie-downs which go from less than $10 a pair on amazon US. You can buy Thule ones too for six times as much. tielidThe idea is tidownyou shut them in under your car’s bonnet, tailgate or doors (right) to help lash on stuff including boats.
But they could also be lodged in an IK’s floor/side cavities as you pump up, and of course can be positioned anywhere and slid forward or back.
tiddownIt’s possible the 1-inch diametre tubes shown may be too big, so make your own using smaller conduit from a hardware store, or just a shore-side stick and washed up rope. Neato mosquito as my Kiwi mate used to say.

IK autopsy

Performing my cutting-a-kayak-in-half trick gave me a long overdue chance to see exactly how they’re put together, as well as other stuff, like why it was failing and how well certain glues stuck.

The neoprene inside
I used to assume it was the same coloured coating inside the boat as out; it’s just simpler. But of course the diagram right is clear: what’s hypalon fabricoutside and what’s inside an IK hull is not the same stuff. There’s no need to waste UV-resistant hypalon sempauto - 16coating (or colouring or that matter) inside the boat’s benighted chambers. All it needs to be is the same durable and airtight coating, and neoprene – the brown rubber-like coating left – does that fine.
I bet I’m not the only one to mistake ‘neoprene‘ as simply that closed-cell sponge used in wet-suits or laptop sleeves. In its solid form it’s a durable synthetic rubber, but I presume lacks the full-on UV resistance of hypalon which DuPont invented shortly after.

I-beam floor
As mentioned here, an inflated vessel will seek equilibrium by attaining a rotund form, be it tube or sphere. A flat inflated plane such as an airbed or an IK floor needs to be a series of parallel tubes – or just a non-inflated sheet, like packraft and white-water raft floors. It also works the other way with bed mattresses. The springs and foam must be constrained by straps or whatever to keep the spring mattress flat.
sempauto - 17So this is an IK I-beam floor (left): probably the same tough core of nylon or polyester scrim, but without the impermeable hypalon and neoprene coatings of the exterior panels.
Note the pre-folds or creases to help the Semperit pack flat. I imagine modern IKs do the same, but it all explains the necessary attention to detail which makes ‘tubeless’ IKs like this so labour intensive, compared to ‘bladder’ designs like Aire.

sempauto - 2Twin side-tube IKs like this Forelle, the Incept and Grabner Holidays, have two smaller tubes one on top of the other, rather than one fat side tube like my Seawave (left, red) or Amigo. It gives the same buoyancy, more freeboard (above water height), a slimmer profile (more speed) or make more volume inside (easier packing). The red Seawave on the left is 82cm wide; the Semperit is 72. It makes the boat look a whole lot better too and overall because it’s also no less stable, I’d say it’s the best design for an IK, but it also needs I-beam sections to constrain the two side tubes.
I can’t say I could suck air through the scrim easily, but I’m pretty sure it’s porous – I didn’t find any transfer holes to allow air to flow between adjacent tubes – they might be a weak point.
sempauto - 14When an IK like this is over-inflated (or left in the sun) and is unable to purge through PRVs (none on the Semperit), you imagine it’s this scrim which either tears apart, most probably at the T-join where it’s glued to the neoprene (left). I tried tearing sections of scrim by hand;  impossible where it was uncut, but as soon as you nick it with a knife it would tear quite easily. This fabric was at least 40-years-old and had one or two patches of mildew, but was still tough and the whole assembly of the boat has held together amazingly well over the years.

sempauto - 4Where mine failed
sempauto - 10Inspecting the fatal second leak alongside the earlier repair, it seemed air was pushing through where two sections of I-beam scrim butted against each other. Perhaps the old coatings stretched differentially here or were just worn out.  It did look like the hypalon was simply flaking away – as you’d expect after four decades.
I could have fixed that leak but, as mentioned, another would probably pop up somewhere else, quite possible while at sea in either my- or a new owner’s hands.

Glue test
sempauto - 3semp- - 6I repaired the big original ‘L’ tear with a 5″ round patch of hypalon and two-part glue (left). I then patched a down-to-the-scrim scratch under the hull with one-part Bostik 1782 (right). I used the same glue to repair the first new leak inside (bubbling above left).

sempauto - 11Although I’m pretty sure they’d have lasted, I could easily pull off the Bostik patches by hand. Pulling off the big round Polymarined patch was another matter. It just so happened I’d sawn through the round patch but, only once I got some pliers under a lip (left) was I able to separate it from the hull. As you can see in the big image below, either the ancient orange hypalon coating of the IK, or the newer red hypalon of the patch separated from their respective nylon cores – the glue’s bond was stronger than the actual hypalon coatings.
sempauto - 13I get a bit lazy about having to faff about with two-part glue, and I also wonder if I ever guestimating the 25:1 ratio (or whatever it is) correctly. But as you can see, this stuff sticks. If you absolutely, positively want it to stay stuck, use two-part ami-polyadhesives. I still don’t know if the second part curing agent merely speeds up the drying process, or is actually chemically integral to creating the very strong bond. I’d think it’s the latter, otherwise why bother.

There’s more about glues and repairs here.


semp-bowwowOther stuff
sempauto - 15Well, the distinctive marine plywood bow has lasted fine – no warping at all and the rivets still intact.
It may have been an early design solution to easily joining the three sections of the hull in a nice sharp point, though they managed that join easily enough at the back. Maybe it was as much for protection and a frontal tracking aid.
I now have enough hypalon patches and D-rings to see me out. Other images from the autopsy below.




Semperit Mori

sempp3A couple of days after trying out the Semperit I noticed a scratch on the hull bottom (left) so decided to pre-emptively patch that with Bostik sevy4-71782 (less faff than 2-part). It looked like an old scratch which had opened up by reusing the boat.
I reinflated a day or two later, but a few days on noticed the floor was flat. I pumped it up again – air was hissing from a crack in the hypalon coating inside the boat, more or less under the seat (below left; colours enhanced for clarity).
sempoThis seemed a bit odd. The boat hadn’t been over-inflated or left in the baking sun, and there wasn’t any obvious rubbing in the two hours I’d used it, though I suppose this is a high-wear area and an old boat.
I suspected general, age-related delamination or entropic porosity. The outer orange hypalon coat can be rubbed or cut down to the fabric core, as with the hull scratch I’d just repaired. But inside should be an airtight layer of neoprene. No way of checking that without open boat surgery.
To be honest it’s what I half-expected from a 40-year-old IK, which is why I’d kept the refurb to a minimum. I suspect sudden use after many years possible neglect had accelerated its decay. I see the keel-strake is coming away too, as are some other black patches holding the rusting D-rings.
merkelI’ve experienced similar deterioration when buying old vehicles for long trips. They seem like a bargain and had a solid ‘they-don’t-make-’em-like-they-used-to’ reputation in their day. But sempoereviving them, or just asking them to perform as they once did, can lead to a string of failures until it’s just not worth it (left). Much depends how they’ve been maintained over the years. I recall writing in one of my books (or maybe here): “you can’t give your old gran a pair of trainers and expect here to run a marathon without having a heart attack“.
I patched the wear-hole with more 1782, reluctant to waste good two-part Polymarine. Pumped up and filled it with water: all good, but an anomalous perforation somewhere else can’t be ruled out.
That’s another thing I’ve learned with old cars and bikes: you replace the clapped out engine then the clutch goes; you replace the clutch and the gearbox goes; you replace the gearbox and so on… The strain of refurbishment gets passed to the weakest point. An IK will get you to shore on two chambers, especially if its just the floor that’s gone. I had that once with the Incept. Out with your pals on a warm summertime river, that’s no drama. Elsewhere, alone with the wind picking up; not so trivial.

There’s a such a thing as hypalon paint (right) to revive old boats, but that goes for at least £100 a litre – possibly worthwhile on your cherished RIB; not on this old IK. If the hypalon is delaminating from the woven nylon core, paint won’t save it. You’ve got to know when to call it a day, and that day may have come for the old trout.

sempsawnA few hours later the floor was soggy – this time it had let go a few inches up from the recent patching – the ‘clutch going after the engine’. Up to then I’d been considering putting it back on ebay with a clear semperit caveat emptor. But then I decided sawing it in half would be more fun. I always wondered what an I-beam floor looks like.
Read the IK autopsy.

Semperit Forelle 2; afternoon refurb’

semperHere in the Summer Isles the reliable May  sunny spell  is about to end – great for solar panels, but strong afternoon easterlies not so good for day-long IK-ing. Suilven mountain even caught fire. Yesterday, before it picked up we nipped out in the Seawave to Eilean Fada Beag and listened to the birds. By the afternoon it was blowing hard.


semp- - 3High time to patch up my latest IK: an old Semperit Forelle 2 I picked up in Cornwall. The boat was sold with some classic paddles which went straight in the bin, as well as a big tear in the side (right). Plan is to patch that hole, then see if it still holds air.

semp- - 1Semperit is an Austrian tyre manufacturer who’s still in business. Afaik, their IKs were a bit of a short-lived rubbery diversion in the 1960s. If my 40-year-old boat has no other more awkward leaks, I’ll rig it up and take it for a semp- - 2spin. But first, I scrubbed off a couple of decades of crud and let it dry.

semp- - 6I wondered about sewing up that L-tear before patching it – the Forelle’s hypalon seems pretty thin, but decided to just slap on a 5-incher. I’ve glued on loads of accessory patches but have never actually had to repair a hole in a hypalon IK in all these years. So I took note of the NRS repair video here: rough up hole and patch: wipe clean with solvent; apply two coats of glue and when knuckle dry apply the patch and roller the living daylights out of it.
semp- - 5semp- - 8Watching that vid, I saw they used a much better tool for pressing down patches; an ash-handled  Sealey TST15 tyre patch roller, unless I’m very much mistaken. The knurled metal wheel embedded in the wooden handle can lay down much more pressure than the wide plastic lino roller I’ve been using.
Just before I did that, it occurred to me stray semp- - 7glue may squeeze through the tear and glue the insides together. Don’t want that nein danke so, with no better ideas, I stuck a bit of paper in there. Seems to have worked.

semp- - 13With glue left over, I thought I may as well stick on couple of floor patches for a seat base and a footrest tube. As these are non-critical fittings I used any old D-rings I had: a woven nylon one and probably a PVC. I’ve glued PVC to hypalon before for other fittings.

semp- - 20With them in place I couldn’t resist rigging up the old Trout with a rope-and-pipe-lagging backrest, an old Alpacka packraft seatbase; a drainpipe footrest tube and a lead. All stuff I happened to have in my IK box of bits or found in the barn among the rat droppings. I jury rigged the K-Pump for nozzeling but haven’t pumped it right up to 2psi as I’m letting that big patch cure for a bit.

semp- - 15Looking round the repaired boat I see it has rudder mounts; not sure I’ll need one on a 3.56m boat. There are six D-rings on top of the double side tubes but they don’t look like they’ll take the backwards strain of a fabric backrest semp- - 18 Forelles came with wooden backrest bars, (like Grabners who took over Semperit) and which I’ve found prone to bending when used with a firm footrest tube. There’s also a squished up full-length keel strip along the bottom. If it works for tracking it will be nice not to have the usual skeg-grounding aggro in shallows or on land.semp- - 4 But maybe that keel will slow down turning which is why they have the rudder attachment? We shall see. With twin side tubes the Forelle is just 70cm wide – that’s <28″. But with a thin floor and me sat low in the high sides I’m sure it will be stable enough.
Gumotex still use them for their seats, but the ‘lilo plugs‘ on the three chambers are a bit of a faff for getting a good charge of air.

If the Semp proves viable, I may replace them with proper IK valves. Or I may just leave them as they are. Three £15 Gumotex valves + a £20 PRV will cost the same as the boat, and the lilo plugs can be regarded as their own ‘total loss’ PRVs – when the boat gets too hot they pop! And anyway, there’s no room to fit a big IK valve in the floor as the tubes are too close together. Knock-off Halkey valves go for 7 quid; I might stick a couple in the sides and leave the lilo plug in the floor.

sepmelI put it back in the barn with my other restoration project for a couple of days. When I came back it was limp but not draped over that cabinet like a wet pizza. I pumped up and it stayed firm enough, semptestthough I’ve forgotten how mushy an 0.2 bar IK feels. It reminds me why I seriously took the idea of trying to increase the rigidity of my old Sunny before getting other IKs. A the beach I filled it with water and stones – no obvious leaks, afaict. A testament to 40-year-old hypalon and glue.

Have to say too, once pumped up, for an IK the old trout is not bad looking. I think the discreet upsweep of the bow, that plywood ice breaker and slender twin tubes make it look a lot less of a bloat than some. Sea trials to follow.

semp- - 22

Adding latex socks to Kokatat Dry Pants

kokoswiftA few years ago I wrote:

… I deliberately chose [these Kokatat Swift] dry trousers with no sewn-in socks as my drysuit has those. With the Swifts … I’ll just wear short Seal Skins and have no worries about the sewn-in socks getting holed by gravel. Time will tell how they wear and perform. 

Well, I’ve changed my mind. I’ve never been convinced by the Goretex/membrane magic; at least not for hillwalking – I get too hot and sweaty. But making less heat paddling an open kayak on a cool Scottish day, the stuff seemed to work. It keeps out the splash and light rain, but because the leg muscles are inactive, sweatiness is barely apparent. Using a regular eVent hiking cag on top produced more mugginess, but nothing as bad as on the hill and easier to control with the front zip and adjustable cuff cinches. Unlike a hardshell, for an IK there’s no great benefit to buying a regular kayak cag with a waist seal as there’s no cockpit spray skirt to seal it against. If you really want to keep dry all over, just use a dry suit.
omnioOn one trip I found that the Swifts with knackered SealSkinz didn’t really work. ‘Waterproof’ SealSkinz only work for a while after which the clingfilm-like membrane goes and they become saggy sock-bags with insulation qualities no better than woollen socks. In fact, they may well chill damp feet. Wearing my slowly dilapidating Teva Omnium water shoes (left), I now think it’s better to seal dry trousers feet properly with latex socks. IMO latex is easier to repair than socks laboriously made from off-cuts of membrane fabric which, like all that kind of stuff, has a limited life span, especially under the grinding weight of a foot. Bizarrely, Kokatat don’t make pants with integrated latex socks, only membrane, but many others do, like Palm or Anfibio.

Gluing in latex boots
latexerFirst I trimmed the latex on the trousers and the boots to similar lengths. Getting a circumference match is important if there’s to be no leak-prone creasing once they’re joined.
You’d think gluing latex boots to latex trouser cuffs would be simple. Not so it seems. My first go using regular rubber glue didn’t take to the shiny outer surface of the pants’ latex.

I read of using two-part adhesive, even though ami-polythat refers to the tricky latex-to-dry suit fabric seal, not similar latex. So with the leg and the sock remounted on a piece of 5-inch plastic drain pipe (below), I tried again mixing up some PolyMarine Hypalon adhesive. This stuff sticks like a velcro electro-magnet
, but curing times are lengthy and there’s the whole faff of hoping you guess the 25:1 mix correctly.

latiiI folded back the sock about 3cm on the pipe end and nudged it against the exposed trouser leg cuff (top pic). When the adhesive had cured after 30 mins, it’s another coat (middle pic), wait 3 mins then just roll the sock over onto the leg and lay in with the roller then strap it up for a couple of hours.
There was one small leak, easily fixed.

When cooler weather requires them but you don’t want a full-on drysuit, the sealed pants have been great; you can wade right in without getting wet feet, and with socks underneath the feet are warm and comfy. A few years later one sock started leaking; a tiny hole, easily fixed with a dab of Aquaseal. They say latex is prone to UV so is best kept out of sunlight (which is why cuffs are often covered) and given the odd squirt of 303 UV protectorant.


Modifications to my Gumotex Seawave

Seawave main page

yaldingGrappling to get the boat out of the muddy Medway river at Yalding the other day put a light scrape on the hull. It reminded me that, along with the PRVs, another winter job was to fit a protective strake under the bow where most scraping occurs. Better to get the protection in early while the boat is newish.
Upstream the Medway had been high and even had a noticeable current. Two-up we were flying along at a good 5mph+ at times. Some of the chutes I was looking forward to were closed even though they look merely ‘sporty’, but then weir by weir, lock by lock the level started dropping so that never before seen eddies, whorls and rocks appeared. The super-sporty chute at Sluice Weir Lock was high and dry (clambering out onto the nearby jetty was a real effort) and by the time we got to Yalding near the end there was a 6-foot drop with muddy banks to either side on which you sank up to your knees.
medclosedSoon covered in muck, we managed to clamber out over the mossy weir wall and haul the boat up. Had I been less cavalier about my preparations I’d have read what was going on right here. Looks like the Medway chutes will be out of action till March (right). Knowing that would have saved half the next morning hosing myself and all the gear down.
strakerBack to the strake. A 70 x 15cm Hypalon off-cut (close enough to Nitrilon) was 14 quid on ebay and once trimmed left enough for another strake or two. I had some Polymarine two-part adhesive (below) and glued the strip to the boat’s curved form with the floor inflated, ami-polyeven if that meant working the roller to press it all together was less effective. I then slathered some Seam Seal around the nose of the strake to protect it from unpeeling (less runny Aquaseal would have been better but a Seam Seal tube was open. More on glues here).
footerWhile the boat was filling the hallway and causing a hazard to domestic navigation I also bodged up a better system for the all-important footrest. A bit of inner tube now counter-tensions the footrest from the bow to keep it in position. It means the thing is now fully adjustable across a wide range ofsw-cantilastic positions, can easily be fine tuned from the water, removes in seconds for boat cleaning/drying and needed no extra fittings glued to the boat. Once great thing about the Seawave is the multitude of attachment points on the floor and sides.
While on the river my aged Mk1 Alpacka U-seat base went flat, split right in the U. This seat is part of a lighter and comfier system I brought over from my Amigo – an improvement on the one-piece Seawave seats. It’s currently unfixed to the boat and the thin nylon must have ripped while yanking it into position on the river after getting back in. Again, I’m trying to avoid gluing extra D-rings to the hull – they’d limit seat base adjustment options anyway.
sw12Better then to attach the seat base to the base of the backrest (right) with a couple of zip ties. The whole backrest/seat base can then slide forward and back off the backrest side straps and it all unclips from the boat in less than 3.7 seconds. alpacka-seatI glued up the punctured U-seat but it won’t last, so I’ve ordered MkII Alpacka seats (left) from Packrafting Store: €70 delivered for a pair. From Alpacka US the seats cost $25 but their auto-calculated international postage is nuts, let alone tax and VAT issues. These seats have the U filled in like a webbed foot: stronger and less floppy for just ~12g extra weight.
Since then I decided not to fit the seat base to the backrest, but simply attach it to the floor between a similar the same adjustable strap and elastic tension system used on the footrest. So far so good. Will add a photo next time the boat’s out.
SOTstrapI’ve also ditched my old my SoT thigh straps (right). Nanfistrapsicely padded and effective though they were, the brass spring connectors and padding made them feel heavy and bulky at ~720g.
Instead I got some non-padded Anfibio packrafting straps from the Packrafting Store (without their biners or D-ring patches). With my biners they come in at 270g. The delta-straps dangling off the sides are a clever idea, designed to give a fpy165more direct pull when rolling a packraft for example. Can’t see myself doing that in any of my boats, but if there happens to be a handy attachment point on the Seawave’s hull I may give them a go (normally you’d have to glue on the D-ring patches supplied). Whether you’re rolling or just paddling, in rough water the more direct connection with the boat the better. I’m a big fan of these light but effective straps now. No need for paddling

Fitting 4.8 psi PRVs on a Gumotex Seawave

Seawave main page
General article covering PRVs
Updated February 2018 – see Adam’s comment below

yaldingMy current Gumotex Seawave is a well spec’d IK for my sort of inshore paddling and occasional touring, especially as it’s 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 also 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 damaging the structure. 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 separate or the boat can blow. If separation happens to an internal I-beam in the floor it will balloon up and make for a very difficult repair. I would not meddle with the factory-set PRV in the Seawave’s floor.

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.

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.
Guatemala, Fuego volcano, Strombolian eruptionLike most IKs with single side tubes, my Seawave had no PRVs in the side tubes as the rounded 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 could be called ‘the planet’s ‘PRVs’) knowing that all three chambers on your IK will harmlessly purge any excess pressure. Sure, when it all cools again 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.

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.


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

Fitting the valves

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

• Narrow-bladed knife
• 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
• Remove the side chamber’s main 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 tool


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). HadronI 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 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 a year or three have has 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.


The bits you need


Incision, but the right-sized 37-mm hole is too small to pass through the ’35mm’ PRV back collar


37mm hole is better, but still not wide enough to pass through the inside ‘retaining nut’ of PRV assembly


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


Holding the PRV back nut in place to tighten is hard by hand. So pass pliers through the main valve hole…


… to clamp onto the back of the PRV assembly. This is why it helps to cut the PRV hole close to the main valve


PRV done. Now replace main valve


Clamp them all up


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.