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 dropstitch panels. Something a bit more sophisticated than the short-lived and basic ‘three-plank’ bathtub shown on the left.
Right now there’s a lot of interest in these types of kayaks. Buyers view them as more advanced and ‘less blobby’ than a traditional round tubed IK. Certainly they’re miles better than just about any Sevylor or Intex, but prices are high and at this level, there’s still something to be said for a high pressure tubed or DS-floor IK, especially those made from synthetic rubber rather than PVC, and those nor using separate air bladders.
What is Dropstitch?
For the full story on drop stitch (DS) click this.
Short version: a dense mass of non-stretch ‘space yarn’ is somehow stitched evenly between two fabric sheets which, once coated in PVC and sealed round the sides makes a flat, board-like panel. When inflated via the usual valve, this panel can take much higher pressures than a normal IK without ballooning out or deforming. We’re talking up to 15psi (1 bar) which is four times more than even the firmest tubed IKs and which, as we know from iSUp boards (right), can be as stiff as a hardshell. The huge popularity of iSUPs has helped advance DS technology.
Pressure has long been the weak link with traditional IKs once lengths increase. Floors need I-beams (above left), to act like space yarn to make a flat panel similar to DS, but they’re expensive to assemble and – without pressure release valves (PRVs; more below) are vulnerable to damage or rupture if over-pressurised through neglect or when left in the sun.
Dropstitch technology produces rigid kayaks, eliminating longitudinal sagging, commonly experienced under a single paddler’s central weight in a longer boat (left). Improved rigidity enables sea kayak-like lengths of 4 metres (13′) which adds up to greater speed or simply a better glide (less effort). It’s the same energy saving gained by pedalling a pushbike with hard tyres instead of soft. Dropstitch is far more effective than using metal frames to support saggy IKs. In my experience this is a poor solution.
Round side tubes also take up a lot of space inside. DS panels get round this while retaining all the benefits of IKs: light weight, transportability and buoyancy.
Usually a full dropstitch (FDS) IK is made of three flat panels. In a way they resemble a simple, self-assembled three-board wooden canoe (right).
They’re all almost certainly all made from Selytech DS PVC (left) 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 Bic Yakkairs are made in Vietnam; most of the rest are assembled just over the Yellow Sea in and around Shandong, China and once they get to western markets typically go for around £1000 for a double – a lot compared to a used plastic hardshell.
DS IKs actually started with easy-to-fit dropstitch floors (derived from iSUp boards) but retained the round side tubes. Some IKs are still made this way but all the boats on this page are FDS. See image below for the three types of IK: tubed (bladdered – can also be ‘tubeless’); DS floor or Full DS.
Among others, Sea Eagle in the US, KXone and DS Kajak in Germany (same factory) plus Bic Yakkair in France and maybe Kraken in the UK all produce FDS IKs.
There are others sold on eBay, some offered direct from China where all FDS kayaks are made. Aquamarina Tomahawk is one, Bluewave Glider (below left) is another; an 18-kilo 4.7-m boat that’s only 76cm wide and goes for around £650 for the full kit, or 3.9-m singles from £550. That’s about as cheap as an imported FDS gets. You can take the risk and buy direct from China as JtB did without regrets. I’ve tried twice off madeinchain.com and AliExpress: either no answer or payment immediately and suspiciously cancelled. If doing so, use a credit card so you have some protection.
Below, Allroundmarin is an Austrian importer bringing in the same re-branded Chinese-made FDS IKs customised with their own colours and features like a footrest strap and valves in the floor to help drain the floor cavity (and through which you can clamp an electric motor). Their 4.7-m model goes for around the same price as a Glider but consider the floor cavity drying issues…
Floors: Read This
Broadly speaking, these boats are assembled by wrapping and gluing the three DS panels in a reinforced skin of PVC which protects the panels from wear and abrasion.
Some boats have removable floors, a bit like a footbed slips into a shoe. This makes the floor skin interior accessible for easy cleaning, rinsing and drying before storage – an important part of IK care.
Less good but almost universal is a DS floor permanently fitted to the floor skin or side panels, but not fully sealed. Water and debris get down in the gaps so some drain valve arrangement as below left is needed to allow water to run out when flushing or disassembling. This is not a self-bailing outlet, no matter what vendors may claim or owners may think. Open the ports and the boat will pool with water for sure. Until I realised this, I was puzzled by these drains. So it seems are actual owners.
Bluewave Gliders are like this, so are Allroundmarin, Sea Eagle Razorlite, Kxone and anything else with the telltale drain ports, either in the floor or at the stern, as below right on a Bic Yakkair HP.
Such a boat is as much of a pain to dry as the bladdered IKs I go on about. There will always be moisture in the inaccessible cavity alongside the DS floor which you may struggle to dry properly, even if you can rinse and flush it. Proper rinsing and drying matter, especially after you’ve been at sea, or when sand and other debris gets in the boat. Seawater causes mildew, staining, odours and possibly rot, so does trapped organic matter, while in the long term trapped grit might rub unseen against the soft PVC until it wears right through (this will probably take years).
A way to eliminate these issues is by fully sealing or ‘wallpapering over’ the side and floor DS panels where they join inside the boat. To drain and dry such fully sealed boats, you simply flip them over to let excess water fall out, then deflate, spread out and wipe dry like the Grabner on the left.
A boat like this would have no crud-trapping, moisture retaining cavities which can’t be accessed to dry properly (unless the floor is removable). The problem would be the air trapped in this sealed-off cavity would make the boat bulkier to pack, like trying to roll up a partially deflated inner tube. A simple plug would get round that. Pull out to deflate, plug in once pumped up, but this is all hypothetical.
In 2020 Advanced Elements introduced the innovative two-panel AirVolution FDS IK which seems to have no crack between the upper and lower panels. Good for them because, apart from the added labour, sealing the insides is not exactly rocket science. For the moment it seems other manufacturers are happy to settle on removable floors or fitted floors with drain valves, just as some buyers are either oblivious or happy to own bladdered IKs with the same tedious drying issues.
Actually their is a worse option: supposedly ‘self-bailing’ F DS IKs which have little side cavities on the edge of the fitted floor and simple drain holes in the outer skin. There are no closable drain valves.
The tellingly unused and unbranded F DS IK (left) I saw on eBay the other day was like this. I had to check with the seller as there were no photos of the floor. Within an hour it sold for £700, but once on the water the new owner will find their boat filling up from below. It may only be a couple of inches but that water will slosh back and forth as you paddle along, adding several kilos of weight. You could easily tape up the holes in the outer skin, but this is why such boats are unbranded and without guarantees. No brand would risk doing it this way and get rightly hammered by negative customer feedback.
One benefit of having the floor panel loose above the PVC outer skin is you get can a thin inflatable tube in there to give the hull more of a V-shape. The AirTrek FLex 465 by DS Kajak (and the same-but-different Kxone FLex) have these optional shallow inflatable keel tubes (‘AirBone’) under the removable but clamped-down floor which you quickly inflate via a loose hose. It changes the hull shape from flat to V. More speed and a bit less stability is what they claim, and you can easily deflate the keel tube on the move if conditions get tippy. An FDS IK’s flat floor is one of its less good features, so this sounds like a clever idea. And as said, the floor is removable so it can all be cleaned and dried easily. See the video below or here.
What are they made of?
Nearly all brands are cagey about the 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 crap, 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 ‘rubber’ is in hypalon and its derivatives.
Tracking (maintaining a heading)
Many of these boats feature rigid moulded ends to help slice through the water (good images here). This element of hydrodynamics is typically a weak point on broad-nosed tubed IKs (left) where a sharp bow and stern are difficult to fabricate solely from inflatable tubes. The grey PVC Incept on the left (based on the old Semperit) did a pretty good job and was a fast boat.
Hardshells and conventional tubed IKs like old Gumotex can have a curved hull in both axes, particularly bow and stern uplift which is called rocker. The more banana-like profile the more rocker. Even with a formed hull and stern pieces, the plank-like floors of an FDS IK has zero rocker, suggesting these boats may track well (especially with the formed plastic bow pieces) but will be hard to turn without a rudder, especially when when over 4.5-m long.
One French Kxone owner admits that after a year of use… ‘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 or a very sharply defined bow piece. Even with a conventional skeg at the back, a flat hull needs help to track well, but this can make turning much harder, as we found on a DS-floored Moki II. And the flat floor and box profile 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 this but anyway, it’s all speculation. The proof is in the paddling.
The bulk of these rigid plastic fixtures, as well as the stiff PVC DS panels may make FDS kayaks less easy to pack compactly than synthetic rubber IKs, though it’s possible Woosung’s Selytech ULite DS fabric is more pliable.
It’s notable that there are no PRVs on most of these boats, presumably because the very high density of space-yarn means they can handle over-pressurisation when left in the hot sun better than an I-beam floor. The two-panel AE AirVolution above is an exception.
Otherwise, these FDS IKs have clear warnings at the valve not to exceed recommended pressures (left). You’d think the pressure increase in smaller-volume DS floors will be less extreme than fatter I-beam floors. These boats’ smaller volumes should mean they’re quicker to inflate than a regular IK, although the effort in reaching 10psi will require a barrel pump and in the AE, above, requires well over a 100 strokes per chamber.
Some claim DS floors without PRVs won’t last as long as I-beams with PRVs. 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.
Footrests, Decks & Skegs
Not for the first time I see 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 and Gliders use a padded strap.
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 all these D/S IKs would benefit from thigh straps, especially the slimmer ones like the Razorlite. All boats are relatively spacious inside, with little chance of feeling nicely wedged in, as in a packraft.
The KXones pictured left have optional removable decks. 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 bigger waves. A regular IK will bend with waves – a stiff D/S IK will cut in and may swamp, especially if loaded.
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 DS boat was less stable, but to me the ‘stability’ of the yard-wide FastTrack is beyond the pale.
About 76cm on the 473 is still 30-inches and I felt quite safe in my 69cm-wide K40 right up to the point when it was coming in over the sides (thigh braces helped greatly, I admit).
Just about all of these Chinese F DS IKs come with an easily fitted slot-in skeg or tracking fin that’s often as tall as a killer whale’s dorsal fin which means it will drag in the shallows. Perhaps that pancake-flat floor needs a big skeg to keep it on track but it’s easily trimmed – or buy a spare and cut it down for paddles which need it.
Some boat specs
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 Sliders (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). It’s unclear if all current Sliders are now FLex models with the removable floor and keel tube option (as described above), or if FLexes sit alongside the regular flat-fixed-floor Sliders.
Slider 445 (14′ 7”) • 85cm (33.5”) wide • 17kg • 225kg
Slider 485 (16′) • 85cm (33.5”) • 20kg • 250kg
Slider FLex 485 80cm (31.5”) • 20kg • 250kg
BIC Yakkair Full HP 2 4.1m (13.5′) • 85cm (33.5”) wide • 15.5kg • 210kg • 8 psi. There’s also a 4.8m HP3. see video below.
DS Kajak’s extra-long 10psi Airtrek FLex 515 (below) is a slender 78cm wide and weighs 22kg with a claimed load of 300kg. DS K also make a 465 FLex.
You notice the two flat-floor Sliders and the BIC are wider than a Sea Eagle RL, for example. This is because they’re pitched as SUP IKs, in that you can stand in the boat and work that core (left). With the popularity of iSUP boarding, this is another clever gimmick and an activity which is clearly less difficult balancing on a wider kayak floor. But sit-down paddling performance will suffer. Me, I’d sooner have a slim kayak.
Lined up against my latest IK compassion table (below), all those dimensions are very much in the ballpark, with the long Airtrek 515 getting a very high L/W Index of 6.6. The DS Kajak 515 is over 2 feet longer and as slim as my old Seawave (among the faster touring IKs). The short and wide BIC HP2 comes in at 4.82 – not so good and a bit more than a ‘hybrid’ Thaya.
Good on all these brands for upping the game with their takes on full DS IKs. It’s a big step in making IKs less ‘bloat’ and more boat. Many people commonly mistake them for hardshells. I’ve yet to be convinced but then I’ve yet to try one.
Having spent days looking at loads of images and videos of all these boats, at the moment the 20-kilo DS Kajak 465 is the one I’d choose. Pictures seem to indicate a better build quality than most, the removable floor is important for proper drying and cleaning, it’s no wider but half-a-foot longer than my old Seawave and graphics-wise, it doesn’t give me a migraine. But without the chance of a test paddle, €1300 is a bit of a gamble.
Whatever you get, make sure you fully understand any possible drying and grit-trapping issues unless you live in a spacious villa in sunny Tahiti and plan use your boat regularly. Not everyone may see this as the deal breaker I make it out to be.
Spotted a mistake or have something to add? Your comments are welcome below.