As mate was getting out of a current-model full-NitrilonTwist 2 the part of the boat under a jetty rose up into the sharp end of a bolt securing a mooring ring.
.. a two-and-a-half foot rip tore across the top of the hull in both directions with a puff of South Moravian talc. As it’s a largely linear rip in an accessible location, making the repair was fairly straightforward: sew, then patch.
[FYI: I know of two other Twists which have suffered similar long rips: here and here. But not any other Gumotex model].
Because the coated core of the red Nitrilon fabric is a woven mat, sewing is an effective way of holding the two sides of the rip together to reduce the tension on the eventual glued-on patch once the boat is inflated. You need an awl spike to pre-poke each hole for the thick polyester thread. This fabric is hard to cut with sharp scissors, let alone thread with a needle.
Rip neatly sewed up with a special cobbler’s reverse herring backflip cross-stitch. One thing that got forgotten was sanding then cleaning the surfaces alongside the rift before sewing began.
Completed repair. This would work on a PVC IK too, but most of them are shell and bladder or drop-stitch. PVC is a bit harder to glue well.
It’s understandable to worry that something like an inflatable boat is a bit of a liability when out in the middle of a deep lake, hairing down some white-water or when far out to sea. This is especially pertinent if your only experience is a beach toy made of a thin and stretchy PVC film.
Once on the actual water it’s hard to think of anything actually puncturing my full Nitrilon Gumotex IKs or the old Grabner. What more often happens is some kind of accidental wear or rubbing when not paddling or during transportation, like the trolley wheels which wore a hole in my Seawave, or the windy tree branch which rubbed (but did not puncture) my Grabner (left). I also snagged my packraft’suninflated floor on submerged concrete once, then added protection to the outside and padding on the inside to stop that happening again.
I’ve also travelled with cheap slackrafts that have got ruined within minutes and punctured every other day. You do get what you pay for. So when it comes to glue I’ve learned that preparation and application are vital to getting a good repair: rough it up; wipe it down with solvent, apply the right glue to both surfaces, wait, then slap on the patch and press down hard with roller to achieve a long-lasting bond. More below.
Is your boat plastic or rubber? As explained here, broadly speaking IKs are made of either rubber- or PVC-coated fabrics. Rubber-based Hypalon, EDPM or Nitrilon is much less used now and most with the tubeless construction method. On a boat like this, rough up the surface, clean with solvent (see below), apply the right glue and a same-material patch, all which needs to be done well as the patch is vulnerable on the outside. Or, you can just dab some Aquaseal directly onto a small hole in the hull to protect it from wear, as shown above left (not an actual puncture).
One-part glues I’ve succeeded in gluing on non-critical D-rings onto Nitrilon and EDPM (Grabner), as well as PVC to Nitrilon using single-part Aquasure urethane sealant/adhesive (‘Aquaseal‘ in North America). Allowing Aquasure or similar to half-cure in air for 30 minutes, then sticking together and letting it ‘seal’ to itself is a way of bonding anything – even non-compatible rubber-based Nitrilon to PVC, as I did here. SeamGrip is a runnier version of Aquasure to get into cracks and seams. Though I’ve not tried it yet, British-made Stormsure is the same thing. Apply a thin film of Aquasure to both surfaces; wait half an hour, then bond with all you’ve got.
In the UK you can buy Aqausure in 28g tubes from £6, or 250g for around £24. Unless you have a lot to glue/seal jobs, be wary of saving money with the big, 250-g tube. Give it a chance and it’ll split and harden before you get to use it all, even if it’s effectively over half price. Alternatively, I’m told a good tip is to store it in the freezer once opened.
The other one-part glue I used on my PU/PVC Incept IK, Slackrafts and used recently on an old hypalon Semperit is Bostik 1782, not least because it once went real cheap on ebay.
I can’t say it worked that well on my Incept; two-part adhesive is always better. Even on the slackraft the Bostik softened and shrivelled the thin PVC. But on non-critical applications (D-rings and none-huge tears), 1782 seems to work well on hypalons (rubber is always easier to glue than plastic PVC) and at £10 for 100ml was good value. Plus it’s a nitrile rubber/resin-based solution and I’ve found won’t go off and harden in the tube like Aquaseal often does. It’s my favourite, do-it-all, one-part glue.
For years Gumotex supplied rubbish Chemopren Universal gluing in their repair kits. It looked like the brown rubber solution you’d use on a bicycle inner tube. I tried to use it on my Gumotex Sunny years ago and found it was crap. Back then it may have been me, but I tried to use Chemopren again recently on my hypalon Semperit and it wouldn’t even adhere to a roughed up, MEK’d surface! To be fair, it might have been many years old, but so are my other glues.
The glue that came with my second Seawave in 2020 was a small tube of Elastick (left). It looks like a generic polyurethane do-it-all glue, like Aquasure. It will probably remain unused with the boat until it turns solid. I’d sooner rely on Nirtile-based 1782 or Aquasure for field repairs. Tbe problem with these urethane glues is once you open them or the alloy casing cracks they dry up and harden.
For important jobs use much stronger two-part adhesives suited to actually assembling air boats as well as making more permanent fittings and bomb-proof repairs. At about £15 posted for a 250-mil tin, PolyMarine 2990 Hypalon adhesive is much cheaper per ml than Aquaseal or Bostik 1782. In the UK Ribstore and Ribright sell similar stuff, and Bostik 2402 is the same but prices vary wildly. Just make sure you buy for Hypalon or PVC. I’ve used it to glue D-rings onto my Grabner (more here), floor patches to my Alpacka, latex socks to my dry trousers and patches as well as repairs to my Nitrilon Seawave and Sunny. It sticks like shit to a s***el.
The trick is to measure out the correct quantity. Above: the small bowl about half full of glue and hardener – about 10cc or 2 tablespoons? – was enough to fit two 80mm D-rings. Each surface: the back of the Ds and the hull, need two applications half an hour apart.
In 2017 when I dismembered an old IK, I was easily able to pull off recent patches glued on with Bostik by hand. But I could only pull off Polymarined patches with a pair of Knipex hydraulic trench pliers and even then, the patch coating pulled away from it’s core (lighter exposed weave below) or the patch remained stuck to the boat and instead pulled off the dead’s boat’s hypalon coating revealing the fabric’s yellowed core or scrim. The two recently glued surfaces could not be separated. They say the mixing of the two components causes a chemical ‘vulcanisation’ and molecular cross-linking which creates a very strong bond. Mixing and applying two-part is a pain, but it works.
Get a good roller
Single or two-part, once you apply your patch, roll it very hard with something like the classic Baltic-pine handled Sealey TST15 stitch roller (left) aka: tyre repair roller used for innertube and tyre repairs. The knurled metal wheel set in a solid handle applies much greater pressure than a wide plastic roller I used to use, and they’re only about a fiver on eBay. Buy one now so you’re ready.
Bladder boat and packraft repairs With smooth-skinned Alpacka packrafts, they recommend two-inch wide Tyvec adhesive tape produced by DuPont. Just peel off the back and apply a section to pricks or small tears once the surface has been cleaned and dried. No need for roughing up, but a quick wipe with solvent won’t do any harm. Larger tears can be sewn then taped. Tyvec will work on urethane IK bladders and extra tacky duct tape or gorilla tape will do too, but is unlikely to remain impermeable once immersed for a while.
Aire-style bladder boat repairs are actually easy. According to Aire’s youtube vid, you unzip the hull shell, slap on a bit of Tyvec on the split, tape up the inner side of the hull shell gash to keep out grit, reflate and off you go. You can glue up in the usual way later, if necessary. I had the feeling that on my Feathercraft Java the urethane-coated sponsons made of thin ripstop nylon fabric (like tent flysheet material) couldn’t have been securely repaired with tape. In fact, it would be difficult to bond anything well to the slippery nylon fabric compared to smooth urethane plastic or hypalon-like surfaces, but perhaps once inflated the seal would have been fine.
Once you’ve done your roughing up (sandpaper or a foam abrasive sanding block, left) you need to clean off the residue as well as any oil or grease present. Anything will do in a pinch; alcohol and spirits, after-shave or nail polish remover (acetone), lighter fluid, white gas or petrol of course, but not oilier diesel, aviation fuel or Nivea for Men. Bleaching agents aren’t the same thing. In the end just use water to remove the dusty, post-roughing residue, and on a cold day it can help to warm up the damaged surface to cure the glue more quickly.
For a travel repair kit a tin of lighter fluid (same as white gas) or nail polish remover (acetone) are easy to buy and handy to pack. Back at home I’ve found MEK (Methyl Ethyl Ketone) is inexpensive at £9/ltr and hideously effective. Acetone is even cheaper and perhaps less extreme – all we’re really talking about is cleaning off any grease and the dust after sanding. They say MEK is for PVC boats rather than Hypalon, but on a thin plastic slackraft the PVC will shrivel up before your eyes once MEK’d. Even on rubber-based coatings use MEK or similar toluene sparingly. Expect some colour to come away on the cloth and the coating to soften at bit: good for adhesion. Note the NRS video above specifically recommends toluene (the second ‘T’ in ‘TNT’ explosive, fyi) for hypalon. On ebay uk it’s the same £9/ltr but they won’t post this stuff around the USA.
Huge tears and bear bites
If you have a huge gash, as in the folding Klepper’s hull below, sewing is the only way to contain the tear when applied to an IK. Then apply a huge patch with adhesive, as normal. The boat below caught a cut-down metal fence stake buried in a shallow river bed and was actually sent back to Klepper for professional repair. It’s tempting to think an IK’s pressurised hull would have skimmed over the stake rather than snagged it. The smaller 1-inch L-tear on the left was glued with a 5-inch patch but the 30-year-old IK proved to be totalled.