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
• I bought an unbranded full D/S IK from China. Impressions shortly

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.
And I’ve finally just taken a punt and bought myself an inexpensive, unbranded and incomplete full D/S IK (right) off Ali Express in China. We’ll see if it turns up and if it’s any good, or if I merely got what I paid for.

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.

slides

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.

kzostand

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.

Selytech-DS-Fabric-Construction_2-yellow-1024x569

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.

sai13

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.

iu

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.

5 thoughts on “Drop-stitch IKs: Razorlite, KXone, Yakkair, etc

  1. Stuart Holmes

    Thanks for the excellent report, we have just bought one of the new (2019) versions of KXone Slider Flex 485 and have already had some fun trips around the Scottish coast. We did get quite a bit of water in on a particularly rainy and wavy day and are looking at getting a spray deck to prevent spray and waves getting in. How do they work for attaching along the sides of the boat and are they still susceptible to waves getting in the sides? Do you think they are worth their weight or are we better to just bail out when necessary?

    Reply
    1. Chris S Post author

      Hi Stuart, congrats on your new boat. Is the 2019 any different, or just graphics? It looks like there are tabs along the sides. Possibly glue-on velcro? So it won’t be a full seal but better than nothing. A deck ought to keep you drier but I find [usually out alone] that if it’s choppy enough to be coming over the sides more than a little then it may be too windy to be out in an IK.
      Also, there do not seem to be any supports visible to keep the deck convex so water rolls off. You definitely want that so you’re not to be distracted doing it yourself. Maybe knees will do? (see added picture of decks, above)
      As expected, I did not get on with the deck on my Seawave. I like the ease of getting in, wear a drysuit if needed and come back if it’s too gnarly., but not all think like me. Much depends on the cost and effectiveness. A bilge pump will be a handy accessory, either way.

      Reply

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