Tag Archives: drop stitch flooring

Preview: Gumotex Rush 1 and 2 IKs

Gumotex Rush

Interesting discussion

Gumotex are moving on up with hybrid drop-stitch technology, originally showcased in last year’s Thaya – basically an old Solar 3 with a D/S floor to make it more stiff. The new-for-2020 Rush 1 and 2 (left) is the ‘Swing Evo’ mentioned in that Thaya article.

‘Hybrid’ is a cool word for a kayak which isn’t full D/S like a Sea Eagle Razorlite and all the clones; assembled from three flat panels of D/S which make boxy hulls (right) and which, according to the graphics on this page, can be sub-optimal in choppy waters. Me, I think the flat, raft-like floor is more of a real-world problem, but read on to see how they addressed that on the Rushs.

Derived from iSuP boards, D/S has become a blessing to IK floor design which hitherto had to use I-beams of parallel tubes (left) which complicates assembly and is prone to ruinous rupture if over-pressured, unless fitted with a PRV or the IK is exceptionally well made.

A Gumotex hybrid IK (below) retains the regular round side tubes of a classic IK for better secondary stability (afaiu) but features a D/S floor for rigidity. However, unique to Gumo, D/S panels are also used on the bow as well as shorter and less obvious panels at the stern. Until I see a boat it’s still unclear to me if this section of the boat is connected to the D/S floor or the lower pressure side tubes. You’d think the floor, so this must help brace the hull structure to reduce longitudinal flex in wave troughs and so enhances rigidity and overall performance – a better, hardshell-like glide. As Lee at The Boat People wisely observes, any hybrid IK with an integrated D/S floor is miles better than boats with separate/removable D/S floors which slip into a sleeve (some Sea Eagles and Advanced Elements). It’s an easier way of doing it, but one which can see potentially ruinous grit collecting between the sleeve and floor.
A word about this fabric paraphrased from here:
Nitrilon-Dropstich is composed of a core of 1100 dtx polyester fabric made up of two sheets joined by a mass of threads exactly 10 cm long. Unlike regular PVC-based iSuPs and D/S kayaks, this durable elastomer plastic is not glued to the fabric, but ‘pressure-impregnated’ which eliminates delamination risks more common with bonded PVC coatings. An additional layer of polyester-reinforced Nitrilon is vulcanised to the floor bottoms making them double thickness.”

The Rushs differ from the Thaya (1st gen Gumo D/S) with the panels forming a more ‘hydroformed’ bow – another weak point with regular blunt-nosed tubed IKs. The Rush’s flat floor extends into two bow sides which join up to make a water-slicing wedge sharp enough to cut ripe avocados into wafer-thin slices.
This construction is a bit more complex than just a D/S floor attached to two side tubes (like the Thaya and some Aquaglide IKs, for example) and which may help explain the high price.

The vital stats on the tandem Rush 2 are said to be 4.2m long x 82cm wide. Compare that to my Seawave at 4.5 x 78; the Seawave has an 11% better length/width factor (LWF) of 5.77 vs 5.12 over the Rush 2, but those are my Seawave measurements. The side tubes are said to be 19/20cm on the Rush compared to 22 on my Seawave. This and the length may contribute to the load rating dropping to 195kg vs 250 on the longer Seawave. That’s still plenty, unless you’re hauling a moose carcass out of the Yukon.
The official weight varies between 15.5 and 17kg, depending on where you look online. The higher figure is the same as my modified Seawave with packraft seat mod.

Pressures are another obvious difference with the Seawave. The 6cm D/S floor runs at 0.5bar (7.2psi), actually a modest level for D/S, but an IK doesn’t need to be as stiff as a iSuP board. The slimmer side tubes are now 0.25 bar or 3.75psi (same as the Seawave) – well, according to the table from the online manual shown below. When I originally wrote this outlets and even the Gumo website listed the usual 0.2 bar/3psi of regular Gumotex IKs but Gumotex just confirmed this was incorrect.
0.25 is a higher than normal IK pressure but not quite as high as 0.3 in a Grabner or the 0.33 bar on my modified Seawave. When you combine that with the stiff D/S floor, the 0.25 bar sides must make the Rush IKs Gumo’s stiffest IKs by far. The difference is, I added PRVs to my Seawave sides before running them at 50% higher pressure to automatically protect them. The Rushs don’t seem to feature any PRVs which explains the warning in the manual, above right. It’s odd but worth remembering that my super-stiff Grabner Amigo didn’t feature any PRVs eitherl, not even in the floor. Quality of construction (gluing assembly) must have a lot to do with it.

When you add any colour you want as long as it’s black, you do wonder if no PRVs is a good idea because in the sun black things get hotter, faster. Black is great for Cockleshell saboteurs, not so good for visibility at sea and it kills photos stone dead. It’s true the Innova-branded Swings in North America have long had black hulls and no one complained. But they run 0.2 bar so could do with some help in stiffening up in the hot sun. They also have fixed decks in red. I also see that many Grabner IKs are now made with black exteriors (right).
One assumes the Rush’s grey, lowish-psi D/S floor can handle increased pressures from passive solar heating, especially as it’s in the water most of the time. But the black side tubes will get taught which becomes a nuisance to manage (or worry about), even if tubes/cylinders handle high pressures better than flat slabs. In fact, as you’ll see from the comments below, Gumotex have found that black is not notably worse than red or green in absorbing solar heating and dangerously over-pressurising. And if you’re that worried it would be just as easy to install PRVs in the Rush side tubes, as it was on my Seawave.

Because a D/S floor is flat, one imagines it will hinder effective tracking, despite having a skeg at the back. The flat hull will plane over the water and wander off to the sides like a packraft – the so-called ‘[windscreen] wiper-effect’.

So, similar to Sea Eagle‘s patented NeedleKnife Keel™ (right), Gumo have added a more discrete ‘keel hump‘ under the bow (left) to compensate for the lack of old-style parallel I-beam floor tubes which added a directional element. You can see from the overhead image above that this keel hump is mirrored on the floor inside the boat, either by design or need. This protuberance makes a high-wear point on the IK in the shallows so it’s just as well the floor is double thickness Nitrilon, as mentioned above. It’s the same on any boat. On my Seawave I pre-emptively added a protective strake – a strip of hypalon – to the central tubed rib, though to be honest it never got much wear as i try and be careful. Mine was hardly worn in five years of mostly sea, but you could easily do the same to your Rush if you expect to do a lot of shallow rivers.

Rushs can be fitted with optional decks (green on the R1, above, red on the R2, below), using the same velcro system as the Seawave, with those horribly bulky alloy spars (right) supporting the decking (surely a flexible rod like tentpole material wouldn’t be hard to make). I read on other reviews that they’ve greatly improved the coaming (hatch rim) so that spray skirts attach more securely.
The footrest appears to be the usual rubbish cushion but can be adjusted by strap (another idea I like to think Gumo have pinched off me!) and seats can be moved to a variety of positions, too. Seats are now foam, but the base looks a bit thin/low to me. A stiff foam backrest (with side bracing straps) is good, but an inflatable seat base is much more comfortable to sit on because you can vary the pressure to suit the height. Unlike anything inflatable, foam eventually loses its cushioning. But an inflatable seat just doesn’t need to be made of hefty hypalon, as on previous Gumo IKs (more in the vid below). But anyway, a seat is easily changed to suit your prefs.

Below, a review of a Rush by Austrian Steve. Can’t understand a word but some observations: I like his convertible Eckla Rolly trolley/cart/camp chair; also love the lovely long canoe chute at 20:40. Have to say though, I winced a bit at some boat dragging here and there. Do the right thing, Steve; it only weighs 12kg! Note also this shortish boat seemed to track pretty well without a skeg – the frontal keel-hump may be effective in leading it by the nose, after all. But in the comments Steve admits the stiff, flat floor slaps down hard on wave trains coming out of rapids and I suppose would be the same at sea. It’s a drawback of flat, raft-like D/S floors I’ve not considered.
See this for an easily translatable written review also in German.

The price of an R1/R2 is a hefty £900/£1200 in the UK, plus decks going from £200/310/370 (tandem). There’s also a rudder kit (price unknown) which will be similar to the Seawave unit. IMO it’s not so useful, even on the longer R2. But like decks, some may like the option.

As you can tell, I’ve been comparing the Rush 2 with my 5-year-old Seawave and wonder if it might be time (or an excuse) to change. An unprecedented five years of ownership proves there’s nothing wrong with my Seawave [anymore].
What are the benefits of a Rush 2? Having outgrown my stealth-gothic phase, black is not such an attractive or useful colour for a boat, and neither is losing a foot in length or 50kg in payload over the Seawave – at least at sea. On a river the greater nippiness from less length will have benefits, but for that I have my Nomad pakayak. As for greater rigidity, it looks pretty good in this clip but my adapted HP Seawave was very good compared to the lower-pressure Gumboats, and it seems the speed (see below) is no greater. Being a bit shorter, I wouldn’t expect it to be.
The word is a Seawave hybrid with a D/S floor will be out later in 2020 but that will cost a pretty penny. Maybe I’ll sling my brilliant Seawave out onto eBay and see if anyone bites. [I did and it went within hours. Oh dear.]

The test by Yves Samson, also the Seawave’s first tester, in Saint-Malo in November 2019: Test conditions: in the open sea on the coast exposed to the east of the Grande-Plage, wind force 5, gusts to 6.
First impressions: it is well designed, aesthetic, (which was not the strong point of Gumotex), a well-conducted research for the seat and footrest adjustments, which can be adjusted very easily when sailing. Rigid and light, it seduces from the start. On the water its behaviour is very healthy, I dreaded the wiper effect, but thanks to the small inflatable keel from the front, it behaves very well. I have the impression that the side tubes are smaller than those of the Seawave because there is more room inside and it is lower on the water. In navigation, with a good wind of 3/4 before, you go straight without any problem, much less hard to stay the course than with the Seawave. It climbs well on the chop, I have 11km on board very little water (without a deck). You feel like on the Seawave and in total safety.
In summary: a very healthy kayak, I think very suitable for solo itinerant trekking. For double use, it is for day trips only, too small for 2 + over night gear. The more negative points: I was a little disappointed by its speed which I hoped to be much higher than that of the Seawave. It is in fact in these rough sea conditions it was barely higher: I averaged with GPS, 5.9 kph over 11km with 5.1 kph against the wind and tide. (BUT I paddled at cruising speed as if I was going on a 30km stage, I never “PLF’d”!).


Another detailed online review (German).

Drop-stitch IKs: Razorlite, KXone, Yakkair, etc

Updated summer 2020

• Read also Decathlon X500 and Gumotex Thaya and Rush
• … and this illuminating post
Slider discussion on French forum

As predicted in IK Construction a few years ago, before long someone was going to find a way of making a decent IK entirely from drop-stitch panels.

Sea Eagle in the US, and KXone and Airkajak of Germany plus Bic Yakkair in France were among the first to do just that, with three-chamber DS IKs made entirely from Selytech DS PVC developed by Woosung in South Korea. Woosung is the world’s biggest manufacturer of IKs and sell their own boats as Zebec Pro (Z-Pro and KXone). The boats are actually manufactured just over the Yellow Sea in Shandong, China. 

There are now several full D/S IKs to be found on eBay under various brands you’ve never heard of. The Bluewave Glider left is an 18-kilo 4.7m footer that’s 76cm wide and goes for just £659 for the full kit, or 3.9-m singles from £550.

Below, Allroundmarin out of Austria are another importer bringing in the same Chinese-made full D/S IKs re-branded under their name and adapted with their own colours and features such as a footrest strap and what looks like a drain hole through which you can clamp an electric motor. Their 4.7m F D/S IK goes for around the same price as a Glider.
In 2020 I took a punt and bought an inexpensive, unbranded full D/S IK (right) off Ali Express in China (it never got sent; refunded).

A fully drop-stitch (DS) IK is made of three flat panels which each run at least 10psi – three times more than a regular tubed IK. In a way, D/S IKs resemble a simple, self-assembled three-board canoe, as shown left. This gives the boat the rigidity (if not the streamlined form) of a hardshell, while retaining an IK’s light weight and portability. Full description of D/S here or keep reading.

D/S IKs started with easy-to-make drop-stitch floors (derived from iSUP boards) but retained regular round side tubes. Some floors were a removable option (Advanced Elements), on others the floor is integrated (Sea Eagle 385; Gumotex Thaya and Rush). The boats on this page are the first generation to be made entirely of D/S panels. See image below for the three types of IK: tubed; D/S floor; full D/S.

Sea Eagle’s tandem 473RL RazorLite, the two larger Kxone Sliders (below) and the Yakkair Full HP are a slick and lean group of full DS IKs. And setting aside the fun element of speed, a fast IK is an efficient and safe IK on which you can range further or retreat quicker if conditions change.

I don’t claim to have any experience of these new boats yet: it’s all the usual online speculation IK&P is so well known for. I did try to buy one direct from China as this guy did, but got no reply. Sea Eagle and KXone make some hugely wide bladder tubed ‘American’ IKs – recreational boats which are great for standing up and fishing from while your dog scratches its ear, but are less suited to all-day IK touring which is the niche activity we like here at IK&P.

Sea Eagle’s 473RL RazorLite double is 4.73m (15.5′) long and just 76cm (30″) wide. Weight is claimed at just over 17kg (38lbs). The DS panels run at 10psi (0.67bar) and are 10cm thick, giving a massive claimed payload of 340kg.


KXone’s two similar boats (right) are designed in Germany but made at the same Chinese factory in Weihai for Woosung in Korea and are rated at 8psi (0.55 bar):
Slider 445 (14′ 7”) • 85cm (33.5”) wide • 17kg • 225kg
Slider 485 (16′) • 85cm (33.5”) wide • 20kg • 250kg

BIC Yakkair Full HP 2  4.1m (left; 13.5′) • 85cm (33.5”) wide • 15.5kg • 210kg • 8 psi • Video below: barely a millimetre of sag!

Air Kajak’s 10psi Airtrek 465 is 79cm wide and weighs 20kg + seats.


You notice the two Sliders and BIC are 10cm wider than the Sea Eagle RL. This may be because the 2017 models at least, are pitched as SUP IKs, in that you can stand in the boat and work those core muscles! With the popularity of iSUP boarding, this is quite a clever sales gimmick and an activity which is easier to do with a wider floor, although sit-down paddling performance will suffer.

Lined up against my latest IK compassion table (below), all those dimensions are very much in the ballpark, with the slim Razorlite getting a very high L/W Index of 6.22. The RazorLite 473 is over 20cms longer and a couple of cm narrower than my old Seawave (among the faster touring IKs). The longer but wider 485 Slider has an LWI of 5.7 – same as my Seawave. The shorter BIC comes in at 4.82 – not so good and a bit more than a ‘hybrid’ Thaya.

These DS IKs are simply three flat slabs of DS fabric. Conventional tubed IKs like old Gumotex can vary the diametre each chamber (floor and two sides) to help give a curved hull in both axes, particularly each end of the floor. Somehow, even with the formed hull and stern pieces, the plank-like floors of a DS IK have zero rocker, suggesting these boats will track very well, but may be hard to turn.

One French Kxone owner admits that after a year of use… son défaut c’est qu’il est hyper directeur, même sans dérive … [‘It always wants to go straight, even without the skeg’] and he’s thinking of installing a rudder. Another reviewer from the US says:
‘The 393 RL tracks very well, almost too well. I trimmed 3″ off the skeg for better clearance in shallow water and it still tracks straight and true. It’s easier to turn now as well, another nice improvement.’ Here’s another short review from the UK.

This is because some of these boats effectively have a frontal keel (right: Sea Eagle Fast Track) or a very sharply defined bow piece. I can’t help thinking that having to fit a skeg to the front of a boat is an admission that a flat hull won’t track well, even with a conventional skeg at the back. A frontal keel or skeg-form bow will make a boat track very well but make it very hard to turn, especially when it’s over 4.5-m long.

And the flat floor and box profile (left) may make edging – leaning on one edge as you turn or counterbalance on waves – trickier; the secondary stability (leaning right over) may be on a knife-edge. You’d need thigh straps to manage that, but anyway, it’s all speculation – the proof is in the paddling.

What is Dropstitch?
For the full story on drop stitch (D/S) click the link
Short version: the mass of non-stretch ‘space yarn’ stitched between the two woven fabric surfaces of a hull panel (above left) enable much higher pressures while crucially constraining the panel from ballooning out. We’re talking up to 15psi (1 bar) which is four times more than what even the better regular tubed IKs run. Pressure has long been the weak link with traditional ‘lilo’ IK floors which need I-beams (above right; a similar idea to DS), to retain a flat shape. I-beams are expensive to make and – without PRVs – vulnerable to damage or rupture when over-pressurised through neglect or when left in the sun.

Easy-to-make round side tubes can handle high pressures fine, but take up a lot of space which makes for a wide and tall but also a cramped IK – one of their biggest failings. DS panels get round some of this. High pressure is also desirable in an IK to reduce longitudinal sagging under a single paddler’s weight (above). Some manufacturers use metal frames to minimise this, but in my experience it’s a clumsy solution.

Using DS technology these kayaks can easily attain hardshell sea-kayak-like lengths (and so, speed) because the high-pressure DS hull makes a rigid box-like structure; the boat won’t ‘taco’ or fold up between waves as most long 0.2 bar/3psi IKs like a Gumotex Solar 3 will do.

It’s notable that there are no PRVs on these boats, presumably because the very high density of evenly spread space-yarn and the can handle over-pressurisation when a boat is left in the hot sun. Some do have clear warnings at the valve not to exceed recommended pressures (left). You’d think the pressure increase in smaller volume D/S floors will be less extreme than fatter I-beam floors. These boats’ smaller volumes also mean they’re notably quicker to inflate than a comparable regular IK, despite the effort in reaching 10psi which will require a hard-bodied barrel pump.

Some claim D/S floors won’t last as long as I-beams with PRVs. That may be true and much will depend on the quality of the original manufacture/assembly, maintaining the correct pressure and where possible, leaving the boat in the water on hot days to keep things cool.

The Sea Eagle features two drain valves in the floor – I’m not sure why. To drain an open IK, you simply flip it over, like emptying a bowl. Drain valves seem another thing to go wrong, as RazorLite owners have already found (see below). It’s not like these are self-bailing boats – open the valve and you’ll be sitting in water. Kzone and Airkajak now have the drain plug right in the stern (left) but it still makes little sense. As for the red Kxone graphic above; I’m not sure I fully understand it, but there appears to be a water-collecting cavity between the floor and the sides which requires draining, once deflated.


Both brands are cagey about the actual Selytech fabric. There seems to be a word missing and that missing word is of course ‘PVC‘ – poly vinyl chloride: the Devil’s Fabric! But not all PVC need be nasty slackraft material, as this page explains.
It may not be considered very green, but the PVC is applied as an air- and watertight coating over a polyester fabric base, just as with ‘rubber’ hypalon.


These boats also feature rigid moulded ends in the one-piece body to help slice through the water. This element of streamlining is typically a weak point on ‘broad-nosed’ IKs (left) where a sharp bow and stern are difficult to fabricate purely from inflatable tubes. The grey PVC Incept on the left (based on the old Semperit) does a pretty good job and was a fast boat. The bulk of these rigid fixtures, as well as the dense D/S panels, may make PVC D/S kayaks less easy to pack compactly than regular synthetic rubber IKs.

Not for the first time I see an IK manufacturer use ideas I’ve tried on my own IKs. In Sea Eagle’s and Airkajak’s case it’s a simple footrest tube with an adjustable strap which I came up with a years ago. It’s so much simpler, versatile and more effective than some of the mushy ideas I’ve seen used on IKs. Kxone use a padded strap; less good IMO.
In any kayak, a solid footrest helps you connect with the boat and pull in powerful strokes. And as an IK doesn’t have the benefit of a hardshell deck to brace knees off, a footrest is all the more useful. Even then, I’d say both these D/S IKs would benefit from thigh straps, especially the slimmer Sea Eagle. Both boats are spacious inside, with little chance of feeling nicely wedged in, like a packraft.

The KXones are pictured with a removable deck for single or double paddlers. Once you realise this boat is as rigid as a sea kayak but with no deck, adding one (or at least some sort of deflector at the front) may be a good idea for managing waves more than a metre high. A regular IK will bend with waves a little – a stiff D/S IK will cut in and may swamp, especially if loaded.

Over in Canada IK World ran a comparison between her old style D/S-floored Sea Eagle FastTrack and the 393 solo Razorlite, as well as giving a fuller recreational review of the 393.

You may like to scroll down and read some of the reader’s comments about issues and returns they’re having with early Razorlites. She mentioned the new D/S boat was less stable, but to me the ‘stability’ of the yard-wide FastTrack is beyond the pale.
About 76-cm on the 473 is still 30-inches and I felt quite safe in my 69-cm wide K40 right up to the point when it was coming in over the sides (thigh braces helped greatly, I admit). 
Both boats appear wide but the D/S sides taper inwards towards the floor, so they’re narrower than they look. And both come with an easily fitted slot-in skeg that’s as tall as a dorsal fin so will drag in the shallows. Perhaps that pancake-flat floor needs a big skeg to keep it on track, but of course it’s easily trimmed.


I’ve never been a great fan of Sea Eagles’s regular, PVC watersofas (exemplified by that hideous thing on the right), but good on them and KXone for upping the game with the full DS IKs. It’s a big step in making IKs less ‘bloat’ and more boat. Many people are already mistaking them for hardshells.