Updated and revised May 2018
Most pics from Sea Eagle and KXone
Read also 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 an IK entirely from drop-stitch panels. It seems Sea Eagle in the US and KXone and Airkajak of Germany are among the first to do just that, with three-chamber DS IKs made entirely from Selytech DS fabric developed by Woosung in South Korea. Woosung are the world’s biggest manufacturer of IKs and sell their own boats as Zebec Pro (Z-Pro). The products are actually manufactured just over the Yellow Sea in Shandong, China.
A fully drop-stitch (DS) IK is made of three flat panels which each run at least three times the pressure of a regular tubed IK. This gives the boat the rigidity (if not the streamlined form) of a hardshell, while retaining an IK’s light weight and roll-up portability. Full description of DS here, or keep reading. In a way, DS IKs resemble a simple, self-assembled three-board canoe, as shown right, rather than a bloated IK-like RIB, like the Bombard (top left).
DS IKs started with easy-to-make drop-stitch floors (derived from iSUP boards) but with regular round side tubes. Some floors were a removable option (Advanced Elements), on others the floor was integrated (Sea Eagle 385). The boats here are the first generation to be made entirely of DS panels. See image right for the three types of IK: tubed; DS floor; fully DS.
Sea Eagle’s tandem 473RL RazorLite and the two larger Kxone Sliders are a slick and lean trio of bladderless (non-envelope) boats that might well be fast 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: it’s all the usual online speculation. I did try to buy; try & sell 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 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
Air Kajak’s 10psi Airtrek 465 (blue boat below) is 79cm wide and weighs 20kg + seats.
You notice the two Sliders are 10cm wider than the Sea Eagle RL. This may be because the 2017 models 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, but paddling performance will suffer.
Lined up against my latest IK compassion table (left), all those dimensions are very much in the ball park, 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 current Seawave (among the faster touring IKs). The longer but wider 485 Slider has an LWI of 5.7 – same as my Seawave.
These DS IKs are simply three flat slabs of DS fabric. Conventional tubed IKs like 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 (right and left; full assembly video) 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 these boats effectively have a frontal skeg or a very well defined bow (right: Sea Eagle Fast Track 465; DS floor). I can’t help thinking that having to fit a skeg to the front of a boat is an admission that the hull will not track well, even with a conventional skeg at the back (also on the 465, right). A frontal skeg 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 (right) 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 actual paddling.
For the full story on drop stitch (DS) click the link. Short version: the mass of non-stretch ‘space yarn’ stitched between the two woven fabric surfaces of a hull panel (above right) enable much higher pressures while crucially constraining the panel from ballooning out. We’re talking up to 10psi (0.67 bar) which is more than double what even the better regular tubed IKs can run. Pressure has long been the weak link with traditional ‘lilo’ IK floors which need I-beams (right and below left; 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 (left). Some manufacturers use metal frames to minimise this, but in my experience it’s a clumsy and not so effective 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 high density of evenly spread space yarn and the gluing can handle over-pressurisation when a boat is left in the hot sun. Some to have clear warnings at the valve not to exceed pressures some 50% over recommended. These boats’ smaller volumes also mean they’re a bit quicker to inflate than a comparable regular IK, despite the effort in reaching 10psi which will require a hard-bodied barrel pump.
The Sea Eagle features two drain valves in the floor – I’m not sure why unless it is genuinely self-bailing? To drain an open IK, you simply flip it over. Drain valves seem another thing to go wrong, as RazorLite owners have already found (see below). It’s not like these are truly 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) which makes much more sense. stand it up and let it drain. 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 one 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 molded ends in the one-piece body to help slice the boat through water. This element of streamlining is typically a weak point on ‘broad nosed’ IKs (right) where a sharp bow and stern are difficult to fabricate purely from inflatable tubes. The grey Incept on the right (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 DS panels, may make the DS 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, without knee braces, a footrest (right) is all the more useful. Even then, I’d say both these DS IKs would benefit from thigh braces, especially the slimmer Sea Eagle. Both boats are spacious inside, with little chance of feeling nicely wedged in.
The KXones are pictured with an optional 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 a waves a little – a stiff DS IK will cut in and swamp, especially if loaded.
Over in Canada IK World ran a comparison between her old style DS-floored Sea Eagle FastTrack and the 393 solo Razorlite (left and right; their photos), 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 DS boat was less stable, but to me the ‘stability’ of the yard-wide FastTrack is beyond the pale. Look at the photo left. I am by no means at ease in tippy kayaks, but 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 sides actually taper inwards towards the floor, so they’re narrower than they look.
And both come with an easily fitted slip-in skeg that’s pretty tall so will drag in the shallows. Perhaps that pancake-flat floor needs a big skeg to keep it on track.
I’ve never been a great fan of Sea Eagles’s regular, PVC watersofas (exemplified by that 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 and many people are already mistaking them for hardshells.
Today the Razorlite 473 is listed in the US as a $1900 ‘package‘ reduced to $1300. In the UK the same package with two paddles, pump and bag goes for £1300 – £100 off.
In the UK the KXone Slider 485 goes for £1250 with paddles and pump, or €1300 in Germany, same as the Airtrek 465. That is a lot of money for a kayak but they’re fast, light, easy to inflate and spacious, plus you can carry on a plane or stuff in the back of a car. One of these days I might actually try one.