Tag Archives: hypalon

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

Semperit Forelle – the original IK

forelleIn 2017 I bought an old Forelle 2. Read more about the…
…afternoon refurb
Semperit at Sea
Semperit at Sea 2
Semperit Mori
Semperit autopsy

sempNot for the first time I will boldly speculate that the Austrian-made Semperit Forelle (‘trout’, left) was the first serious modern IK, designed in the 1960s from tough hypalon ‘rafting’ fabric. According to my measurements a Forelle 2 is 3.56m long, 70cm wide and weighs 10.5kg + seat. This guy says Semperit were last made in 1983 at which point (or soon after) Grabner (also Austrian) bought the rights.

funfunGrabner then got Gumotex, in Braclav just over the border (and maybe the Iron Curtain, back then) to produce a cloned Forelle called the Grabner Fun (right), but made from Gumotex’s hypalon-like fabric called Nitrilon. Back in the 1980s I’m sure Commie Nitrilon would have been cheaper and probably as good as DuPont hypalon made in western Europe. The Fun was discontinued (or stock ran out) a few years ago.

Grabner Fun: length and width 365 x 75 cm; weight 12 kg; payload 170 kg; pressure 0.2 bar; fabric 1100 dtex Nitrilon

grabcomp2011funnyNot being one of their boats, the Fun was undersold by Grabner (notice the table, right). Instead, the similar but longer Holiday range got the fanfare and is still made today with few changes. Grabner boats were made from another hypalon-like fabric called EPDM which, combined with Grabner’s hot vulcanising method, explains how their boats managed to run 50% more pressure (0.3 bar) than the Fun and other Gumotex IKs at the time. Gael A. paddled an aged Grabner H2 along the Scottish Sea Kayak Trail a couple of years ago. Among others, Incept also used the twin-side beam design to produce a 70-cm wide K40 which is also 70cm longer than the Forelle II, and one of the fastest IKs around.
You can occasionally find aged Forelle IIs for around €300 in Germany; a new H2 goes for €1600, while Funs were being discounted for as little as €400 new, but seem much rarer now. I was curious about tracking down a Forelle recently (I succeeded) and below are a few shots I picked up off the web and from some sellers. Apart from the odd repair, the indestructible hypalon fabric stands up well and the seats may well have been improved (Grabner’s still use the crude ‘backrest bar’ design).

gumvalveSome boats come semperit forellewith a huge wooden rudder which might be replaced by a skeg, but one off-putting aspect are the basic inflation ‘lilo plugs’ (left); no better than an old Gumotex seat. These could easily be cut out and replaced with proper Gumotex valves (right), maybe in a more accessible position, too. It seems older versions (grey and orange, below) have a half-inch deep keep strip right along the bottom (as well as a rudder fitting) while later ones like the yellow below, do not. A long keel is a bad idea, I suspect. Some modern Sevys or Sea Eagles have them; good for tracking but makes the boat harder to turn.
One thing that can’t get avoided is that a Forelle (and a Fun) still run only 0.2 bar pressure. Same as most Gumoteii, though helped by the stiffer twin side beam hull. Modern Grabners run .03 bar which I feel makes a big difference. Some newer Gumotex IKs now run 0.25, though that can be pushed to 0.3 bar with care.

Thanks to Gael and OP for extra details. Pics not mine lifted from ebay sellers.

Overhauling a Grabner H2

by Gael Auffret

Gael’s H2 review here, compared with other kayaks here, and solo paddle up the Scottish Sea Kayak Trail: Part 1 Part 2

After more than 12 years my tandem Grabner H2 IK was showing signs of wear all over. The most visible sign appeared behind the fore half deck where two grommets fed the grab lines (right). Around those grommets the rubber coating had worn off, showing the bare woven core material of the Hypalon fabric.
Another major concern was a crack that developed under the aft backrest bracket (left). This ill-designed bracket has a sharp edge that gets pushed into the skin under the weight of the paddler. After some years of chafing it had worn a small hole that proved difficult to patch reliably.
I must to admit the H2 is not as perfect and tough as I’d claimed so loudly. Encounters with various submerged obstacles and a number of uncontrolled landings had resulted in many scars and scratches all over the hull. I now also own a similar Incept K40 for solo paddles, but as I intended to keep the H2 as a tandem boat, I thought it was time to give it a serious makeover.
I knew Grabner could provide an MRO service as stated on their web site and the French Grabner reseller confirmed he could send my boat to the factory in Austria for a quotation. That came the week later in German, but what didn’t need translatimg was the substantial figure at the bottom of the quote which added up to something like “you’re better off buying a new boat”.
Grabner’s attitude to those requiring a more seaworthy kayak than an H2 was get an Explorer or the framed but now discontinued Discovery, but those IKs are way too bulky and heavy (26kg and 29kg respectively) for transportation when shuttling about – my H2 weighs just 16kg. Plus they are just about the most expensive IKs in the inflatable world (right). I discussed the money issue with the other half of the H2’s crew who happens to also be the purser. She too wanted to keep the H2 and was not as appalled by the cost as I was, so after a short deliberation we decided to proceed.
Three weeks later my local reseller informed me enthusiastically that my H2 was here and beautifully refurbished. Save for the numerous patches it looked like new.

The Grabner folks had done a great job; even the foredeck grommets had been neatly repaired.

All backrest brackets had been replaced with new parts of a much better design. A new pair had been added at my request to enable solo paddling from a central position. Up till then I’d sat in the back of my H2 when solo.

Most cockpit fittings like footrest and D-ring brackets which had started coming loose had been reglued.

There was a keel strip on the bottom as well. Surprisingly the Austrian guys hadn’t paid attention to the colour of the patches (left). While the inside the H2 is yellow, they applied patches in external red. I should have supplied them the yellow patches I’ve got in my repair kit. Anyway, I’m happy the boat is in such great shape again, if not better than before. I can’t claim it’s worth as much money as I’ve spent on it, but I’m sure my H2 will go for another 12 years.

Inflatable kayak construction. Part 1: fabrics and fabrication

Updated January 2020
I’m not an expert on any of these matters; it’s just what I’ve learned over the years.
I update these pages as I learn more and welcome your corrections.
This original article got a bit rambley so was split into two.
Part 2 covers hull forms and rigidity.
And you can read about glues and repairs here
A ‘PVC vs rubber’ article from 2011 by Lee from the Boat People.
PVC vs PU vs Synthetic rubber: a good if slightly biased page: skip to: 2. Characteristics of the Material to read about PVC (vinyl’), TPU (polyurethane’) and synthetic rubber (‘hypalon, etc).

Broadly speaking, quality inflatable kayaks are made from two types of material: a woven fabric core coated in ‘rubber‘ or ‘plastic‘. ‘Plastic’ can further be split into PVC (cheaper) and TPU – more modern. And IKs are fabricated or assembled in two ways: either with ‘inner tubes’ which inflate a fabric shell to give a rigid form like a bicycle tyre inner tube – or panels of hull fabric carefully glued together making a fully airtight load-carrying monocoque. I call this ‘tubeless’ and the pros and cons of both are outlined below.

hypalon fabricSynthetic rubber

nylonpolyThese use a nylon or polyester (PES) woven fabric (see right. Nylon is more stretchy which is good for impacts punctures but less good for rigidity. It is coated with tough natural and/or synthetic rubber and sometimes a softer neoprene on the inside surfaces. Examples include the original hypalon, invented decades ago by DuPont, no longer made or fab-grabtrademarked but actually referring to the coating, not the finished material. Hypalon fabric is composed of three plies all bonded together:
• an inner coating of neoprene makes it airtight and easy to glue
• a fabric core of polyester or nylon weave gives tensile strength and resists tearing
• the hypalon outer layer resists UV rays and chemicals

A near-identical product is now supplied, among others, by Pennel in France under the ‘Orca‘ brand (graphic, above left) as used on US-made NRS IKs.
gumotexfabrics18Gumotex’s various Nitrilons (left) are similar, as is EPDM aka: ‘Nordel’ used by Grabner as well as some folding kayak makers and raft manufacturers. In 2012 Gumotex brought out a material called Hevealon based on their single-side coated Lite-Pack (renamed Nitrilon Light and since dropped). It had EDPM on the outside of the hull and a teflon treatment on the inside of the boat to repel water and so speed up drying. This is a problem with the former Lite-Pack material as used in their original Twists, compared to the classic, full coat Nitrilon which dries fast on both surfaces. Other problems with earlier Lite-Pack boats may explain the renaming as Nitrilon Light. The Swing models use Hevealon and the Twists use Nitrilon Light (NL) but are much cheaper than the Nitrilon models. As you’ll see in the table, NL has only a third of the tensile strength of Nitrilon, which can only be down to a less robust and thinner polyester core but is 30% lighter. In 2018 it was dropped and all IKs used Nitrilon or more.

semp-glue

A 40+ year-old Hypalon IK. I repaired an L tear (inset) but then found the old rubber coating had porous areas so the boat was a write-off. With nothing to lose, I sawed the boat in half to inspect the I-beam floor construction and also tried to pull off the Hypalon patch I had glued on a few days earlier. I needed heavy pliers to do this. The Polymarine glue heard together. Instead, the Hypalon coating of the patch (pink, left) and bits of old orange boat Hypalon pulled came away from the nylon core or skrim. But the glue did not separate.

Gumotex in Czech Rep. produces Nitrilon fabric in their factory as well as various other rubber-based sheeting and products besides inflatables. The tougher boats in their inexpensive recreational gumoglubiIKs are made from regular Nitrilon (see graphic above) and are glued together by hand. The gluing of some of these boats limits the operating pressure to 0.2 bar (2.9); still-impressive by the standards of many well known American-branded IKs which run as little as 0.1 bar. But notably, a couple of Gumotex IKs including the long-established and expensive K whitewater series and the Seawave sea kayak run 0.25 bar (3.6 psi). It is possible that these boats are not hand-glued, but heat vulcanised, a join that can contain higher pressures.
heatrweldAustrian fab-frabGrabners say their EPDM boats are heat vulcanised which can be compared to heat- or radio-frequency (RF) welding of plastics like PVC. Heat welding PVC is so easy and effective you can do it yourself with roller and a heat gun fitted with a flat nozzle (left), though trying to make an IK like this would be quite a challenge (as would be gluing up an IK from Nitrilon sheet).
doudoufeatherfApparently, heat welding PVC was invented in 1948 in Vitry, France by SEVY, the company that went on to become Sevylor (‘Sevy of gold’). They produced an inflatable PVC bath that became a hit in post-war austerity France. A velour coated air mattress followed and since that day Sevylor has never looked back.

Vulcanising is a chemical reaction which either molecularly bonds rubber to itself or makes a rubber product, such as a tyre more durable. In a bonding sense, vulcanisation is what happens when your punctured tubeless car tyre is professionally repaired on the inside surface, whereas gluing is like sticking a patch on an inner tube (stop me if I’m going too fast, here). Assuming I have the right end of the sticky stick, that means Grabners have a superior construction process to most Gumotexs, and may also explain how, despite running 50% higher pressures, Grabner boats don’t feature pressure release valves (PRVs); their boats are so well bonded there’s little risk of them bursting if left in the hot sun. But that’s still not recommended.
Don’t be put off by the picture of delaminated Grabner on the left – it’s from a 12-year-old Grabner Holiday 2 and occurred at a point where a metal eyelet on the demi-deck didn’t get on with the EPDM fabric (that boat has since been renovated). It’s there to illustrate the densely woven and stretch resistant underlying fabric. On full inflation a good IK doesn’t want to stretch hypaalike a balloon (or a PVC Slackraft come to that), it wants to be taught like a basketball. As folding boat makers, Pakboat put it on their website: ‘The abrasion resistance [and so, waterproofing] is in the coating, and the tear strength and tensile strength are in the woven fabric.’

hypa

Huge sheets of Hypalon lining this salt pond near Moab, Utah. (And above right).

PVC and TPU

Otherwise, IKs are made from a cheaper but stiffer PVC-coated fabrics or more expensive and pliable polyurethane, the former: Kokopelli packrafts; the latter like Incept, Alpacka, Antibio and most other packrafts and a few more listed below. Remember, with PVC this is not the plastic film of the pool toy and Slackraft, but PVC coated onto a nylon or polyester fabric base, just like Hypalon. The difference is like a tent made out of a plastic bag; light and waterproof yes, durable no. Or a tent made of normal woven fabric with a PU waterproofing coating: much more durable. TPU is superior in all ways bar price to PVC but is less well familiar as a brand name. It’s also superior in some ways to synthetic rubber. Again, this page is good.
contubesIn environmental terms, PVC has become a bit of a dirty word (Greenpeace report) which is why Gumotex US make such a song and dance about their IKs not being made from PVC. Apparently toxic chemicals leach out of the material and it degrades internally over time.
It’s staggering to note the lengths that boat makers like Ally Canoe, Pakboat, Sea Eagle and even Aire will go to not to mention ‘PVC‘ by name. They will just describe hull material as ‘1100 Decitex Reinforced’ or ‘Base Fabric Denier 650/1000’, but the cells (see below) are identified as urethane. This because 
US vendors are now required to post a warning (below) if they dare sell PVC products in California.

pvcwarning

Rubber vs plastic
Synthetic rubbers like Nitrilon and EPDM are both tough, durable and more expensive than PVC, metre for metre. On a same-sized boat, they’re also more pliant and will roll up much more compactly than PVC (below right, a 4-metre Nitrilon Sunny). Importantly, this means creases and folds cannot develop into cracks and leaks.
Synthetic rubbers also have very good resistance to UV and solvents, are heavier than comparable PVC/PU and come is fewer colour options. Rubber used to be the classic material for river-running rafts (as pictured left at Lees Ferry near the Grand Canyon) that put in years and years of reliable service. But being a form of rubber, not plastic, it cannot be heat welded in a machine like PVC/PU; it must be labouriously glued which, when done right, increases costs. It can also be heat vulcanised which might be regarded as a form of heat welding.
This is why Grabners, NRS MaverIKs and proper river running rafts all cost so much. They’ll easily outlive your pet and might be considered over-the-top for a recreational IK’ing. Inexpensive recreational IKs are made from PVC-coated fabrics. Polyurethane (PU) approaches the better characteristics of rubber and it’s likely that not all PVC is nasty, toxic crap, just as not all alloy bicycle frames are the same quality. In the hands of a careful owner – as opposed to the hard use from a rental- or river-running outfit – with 303proper care and maintenance involving anti-UV 303 protectorant (right), thoughtful handling, drying and storage, a PVC or PU IK should still last for years provided the initial material and quality of manufacture is high. And while suitably chunky PVC or PU IKs like my old Incept K40 are hard to fold, that stiffness translates to a more rigid and therefore faster boat on the water without needing to resort to high pressures. This was apparent when I first tried a K40 after running a Nitrilon rubber Sunny for years.

vanguard

Table lifted from: http://www.vanguardinflatables.com
Bear in mind, like the link at the top of the page, it may be a little biased to validate their choices of material.

Fabrication ‘air tube’ or ‘tubeless’ airecell
Sometimes an IK’s hull form is a shaped, casing or ‘envelope’ made of PVC, Cordura or any similar hard-wearing fabric into which slip light, removable sponsons or air bladders, made either from stiffer, ‘brittle’ vinyl, more durable and flexible urethane, or PU-coated nylon. Examples include Aire (an Aire ‘cell’ or bladder pictured above left), bladdioAdvanced Elements and the BP Trinity II (see Other IKs). I call this the ‘American’ method. Pictured on the right, vinyl and urethane may just all be plastics, but might be compared to Platypus water bladders (vinyl, stiff, slippery) and the blue Camelbak (more soft and rubbery). That is why in bladder boats like Aires PVC is good for the shell and urethane makes an ideal, very slightly stretchy bladder.
pointerdiagramCompare that to the Gumotex, Grabner, NRS and Incept style of fabrication which is like a tubeless car tyre: the perfect gluing of the tough hull sections keeps the air in. Aire-style is like a tyre with an inner tube that pumps up to give rigidity and form to the outer cover or hull casing. Both are repairable with patches in broadly speaking the same way. I notice my ‘tubeless’ analogy has now been adopted by Innova, the US Gumotex importers, except that they try to make out that ‘tubeless’ is superior. It certainly is for automotive tyre use, but with IKs it’s more down to manufacturing ease and therefore, costs. PVC (welded is best,
like Incept or some Aires, not glued like Advanced Elements or sewn like Tributary) is stiffer once pumped up, less durable, doesn’t abrade so well on grit (out of the water), but is less expensive than synthetic rubbers, quicker to weld together, and is slipperier in the water, so giving better response when combined with the superior stiffness. The difference between the ‘tubeless’ or ‘tubed’ construction style is merely down to the cost of manufacture and materials.
yakkistanBladder boats can use PVC shells and so save costs (or spend it on design) because fully sealed welding of the hull sleeves isn’t critical; they can just be easily heat welded, sewn, glued, or even zipped together and the sponson ‘inner tubes’ can be slipped in and pumped up. But durability of the outer hull is a factor in how the panels fit together to make the sleeved hull, and here quality heat welding is best, certainly compared to vulnerable stitching. I also read that on cheaper IKs sponsons can get twisted in the sleeves during unrolling and inflation which can get to be a faff. That and that much quicker and easier drying is another reason I prefer tubeless IKs. If your boat is in and out of your car boot or motorhome hatch, then tubeless won’t give those problems. If you’re more into multi-day trips, a bladder boat has no disadvantages dsfabriconce pumped up correctly.

Drop-stitch fabric (right) – a type of construction from flat tubeless panels – is discussed in the next article.

Conclusion
sempauto - 1
Nitrilon/EPDM ‘tubeless’ construction seems to be the traditional or ‘European’ method, and if well made will last for decades as rafters know well (left, a hypalon Semperit probably from the 70s or 80s). Our Nitrilon Gumotex Solar looked as good as new when  I sold it some nine years on, and if my former Incept K40 had been made from the same material I’d have probably kept it. Bladder boats seem to be a cost-saving way of doing it and are popular in North American. All cheap IKs use bladders, but not all bladder IKs are cheapies. A top of the range, 18-foot Aire Sea Tiger costs $2650.
bladderboyThe problem with bladder boats is that although the best-made ones may perform better, it’s normal for some water to get inside the hull sleeves which contain the pumped-up bladders. Result: the boat takes ages to dry. This may not matter in sunny Californi-yay, but it sure does in Scotland or Scandinavia. Packing a wet boat is as undesirable as packing a wet anything, not least if it’s seawater. Mildew may develop, grit may get in and who knows, something may rot and shorten the life of a boat (although Aire says that a little water in the chambers does no harm, even long-term). When I come back from a sea paddle I always hose my IK down.
gumk44I’ll admit I like the simplicity of the tubeless style of IK fabrication – a tough outer shell that is well sealed; there is no cheap way of doing it and so any tubeless IK ought to be a well made IK. In my experience in the US, IK rental outfitters tend to use tubeless Hypalon IKs even if most recreational IKs sold are bladdered. Tubeless will cost much more but they’ll last much longer, especially if made from synthetic rubber.

Part 2 covers hull forms, rigidity and drop stitch IKs