Tag Archives: drop stitch kayak floor

TPU Inflatable Kayaks: the Mis ing Link

See also: Advanced Elements 2021 AirFusion Evo

Pictures from Zelgear and Marcin S

These days IK are mostly made from PVC, be it the hull or the bladders. Just three main IK brands still using old school synthetic rubber: Gumotex (CZ), Grabner (AT) and NRS (US). PVC gets recycled, is made everywhere and so is cheap off the roll and easy to heat weld. But is it only me who finds something unpleasantly ‘plasticy’ about PVC: the stiffness, the texture, the smell and maybe the eco-stigma.

The only PVC IK I’ve ever owned punctured on the slightest thorn and went on to do that with the next owner. And this was supposedly quality Mirasol PVC from Germany (to be fair, a mate with an older K40 had no puncture problems whatsoever). I can’t imagine any Gumotex or Grabner I’ve had ever doing that. That’s why I persevere with synthetic rubber IKs, even if it’s becoming an expensive dinosaur fabric.

Synthetic rubber coatings like Nitrilon and EDPM are derived from the original DuPont hypalon. Boats must be entirely hand glued which adds to costs. But, just as nothing man-made has managed to beat the properties of leather for crashing fast motorbikes, compared to PVC, synthetic rubber remains more durable and more resistant to UV, lighter, more supple, easier to glue and easier fold compactly. After 15 years there was no noticeable deterioration in my Sunny, (below) other than a decade and a half of paddling wear and tear. A synthetic rubber IK will easily outlive a similar PVC IK.

Packrafts, meanwhile, are mostly made from TPU (as well as PVC), a different sort of polymer coating which has many of the benefits of synthetic rubber: odour-free, smooth texture, light, UV resistant, supple (crease-free), not environmentally toxic. But, like PVC, it too can be heat welded. Since Alpacka got the ball rolling, there are now loads of brands banging out TPU packrafts left, right and centre. In this time the fabric and seam technology have proved themselves to be as durable as PVC or rubber, and capable of running higher pressures too. As someone on the internet observed: ‘Thermoplastic Polyurethane (TPU) is the link between rubber and plastic’.
For inflatables TPU is clearly superior to PVC in all ways except price and stiffness (but this works both ways). “It has properties between the characteristics of plastic and rubber. So, it is flexible without plasticizers, and its flexibility does not affect the design or its strength and durability.” Link

In a way, my 3-metre MRS Nomad packayak (above) was as much a TPU kayak as a packraft. With just 2psi or so, it was able to hold its shape (under my weight), but now costs nearly €1400 in the decked version.

Advanced Elements 2021 AirFusion Evo with a PU shell.

The only PU (same as TPU; not sure) IK I know of was NRS’ discontinued Bandit series. It was made in China but was still dropped, I presume due to cost reasons before they started making many more models with PVC. Since I wrote that the Advanced Elements AirFusion Evo with a PU shell has come out.

Zelgear TPU IK

While researching the Zelgear Spark 450 preview I found a 2018 ZelGear catalog. It states their now discontinued 5.2m PVC Igla IK can be requested in TPU (or the similar and much stronger Vectran which Alpacka use for their top-of-the-range packrafts). There’s more here. The weight of this long boat: is said to be just 15kg. The cost? $2000 I was told.

You may wonder if relatively thin and flexible packraft TPU could support a 5-m IK? TPU coating is also said to be more elastic than PVC, but it can’t be any more elastic than rubber. And anyway, a stretch-free scrim (woven core) takes care of that; the coating is primarily for impermeability.

An IK needs to be a lot more rigid than a relatively short and squidgy packraft. A lot of that is down to the fabric as well as the psi. That’s one good thing about inflated PVC: it’s stiff. You’d think a TPY IK would require high pressures to support a long boat which would then require bombproof seams. But add a drop-stitch floor (left) in TPU to take the load and the tubed sides would be under less pressure, so to speak. This Zelgear blog post from 2018 mentions some “some technological issues are being resolved“. I’m told Zelgear are on it.
Pictures below by Marcin S from a boat show in 2018.

With all these Asian-made TPU packrafts knocking about, some using locally sourced fabric whose quality – in my experience – is as good as the Alpacka stuff, the cost of TPU fabric may drop to a level matching the few ‘hypalon’ IKs still available.

A few years ago I predicted that full drop-stitch IKs would become the new thing. This has happened and has driven IK design and sales a long way forward . But, PVC aside, I’m still not convinced by the boxy profiles and packed bulk of FD-S IKs. Until FD-S forms can evolve (as the Itiwit X500 has shown), I think drop-stitch floors (D-SF) are certainly the way to go, if an IK is to stay undecked, unlike the X500.

There will always be a demand for cheap vinyl or PVC IKs but I predict the next big thing in high-end IKs will be TPU, including removable D-S floors in TPU. TPU is now well proven with packrafts and blends the heat-welding benefits of PVC with nearly all the better attributes of ‘hypalons’.

Preview: Gumotex Thaya IK

See also:
More about Hybrid IKs
Gumotex Rush

Since 2019 the Gumotex Thaya sits alongside the near-identical and 20% cheaper 4.1-m Solar 3 (aka: ‘Solar 2‘ or ‘Solar 019‘) on which it’s based, but with a drop-stitch (DS) floor to greatly improve rigidity. The Solar was not unlike my old Sunny, running just 3psi (0.2 bar) all round. As you can see on the left, that can get a bit saggy with a well-fed solo paddler. This was the first of Gumotex’s DS-floor boats, but a basic exercise in simply replacing a floor rather than trying anything more fancy like the Rushs of 2020.

decpump

Drop-stitch fabric now makes the complicated hand assembly of pressure-vulnerable I-beam floors (left) redundant. A DS floor is a flat panel with effectively 3-4 zillion ‘I-beams’ (see top of the page) all spreading the pressure load evenly to constrain the form into a plank shape, but at a much higher pressure than an I-beam floor can safely handle. In an IK, high pressure = a more rigid hull = better glide/less effort with barely any additional weight. The only drawback is that you need a more powerful high pressure barrel pump (above right). The old Bravo foot bellows won’t do anymore.

DS is normally PVC and made in China, but Gumotex have found a way to manufacture the threading and bonding a D/S floor with their durable, flexible and environmentally right-on Nitrilon rubber fabric. It can’t be that hard. The regular, normal-pressure 3psi sidetubes ought not need the higher pressures I ran on my adapted Seawave because the 7psi (0.5 bar) DS floor greatly aids rigidity (see action video below). Gumotex’s new tag line rubs it all in:
Made in EU [read: ‘not China’], made from rubber [read: ‘not PV … spit … C’].

thaya-family

The promo video below suggests something revolutionary, but combining DS with Nitrilon can’t be that much different from doing the same with PVC. It will certainly simplify or speed up assembly. One assumes drop-stitch floors supposedly don’t need a PRV necessary to protect I-beam floors from internal ruptures when they overheat in the hot sun. Some UK outlets where claiming the Thaya has a “Safety relief valve [PRV] in the bottom of the boat” but it’s probably just a copy and pasting error. I can’t see one in any pictures and have yet to see a DS panel with a PRV until the AE AirVolution came out in 2020. The assumption is they don’t need it if tey run a modest 7psi but some claim high-pressure DS floors won’t last as long as I-beams. Without a PRV, that may be true and much will depend on running the correct recommended pressure, the quality of manufacture/assembly and where possible, leaving the boat in the water on hot days so the large water-contact area keeps things cool.

One positive thing about I-beam floors is the parallel I-tubes (left) probably don’t hurt tracking (even without a skeg). They also enable the desirable curved hull profile of a boat rather than the flat floor of a barge (for the moment DS panels can only be flat or maybe with a slight curve).

Payload ratings seem to have settled at 230kg and the movable seats are also made from DS panels. Initially I thought why? For the backrest and footrest that makes sense but who wants to sit on DS seat base on a DS floor? Of course you don’t have to pump DS up to the max to get its flat form constraining benefits and it looks like valves are regular twist-locks so you’d couldn’t get more than a couple of psi in there. Footrests are the usual inflatable pillows, but possibly also DS. I’d replace them with a section of sawn-down plastic drainpipe so you get a solid block to brace against. It makes efficient paddling much easier.

thaya-red-l

I’ve never tried one, but I do wonder how a flat-floored DS IK might handle in windier, choppier conditions where an IK isn’t exactly a hydrofoil at the best of times. A flat, raft-like floor will be stable, sure, but it will roll and pitch about more. Also, according to the specs (left) at 89cm the Thaya is a disappointing 6 or 9cm (3.5″) wider than the all-tube Solar 3 (Actual verified width seems to be 34″ or 86cm). Great for family-friendly stability; not so good for solo paddling speed and efficiency. My Seawave is 2cm narrower than a Solar 3 and with the usual care getting in, stability is not an issue. Out at sea my Seawave will swamp long before I’m tipped out. But then again, the near-rigid floor may cancel out the drawbacks of the greater width. At 18kg the Thaya is heavier than a Solar 3.

For most recreational, flatwater users the Thaya ought to be a nice family boat, but then so is a Solar 3. The Thaya costs 20% more than the Solar 3 whose days may be numbered.
One assumes this

Full Dropstitch (FDS) Inflatable Kayak Buying Guide

Updated October 2021

See also
Book
Other IKs
Full review: Shipwreck ArrowStream Full DS
Guest review: Aqua Marina Tomahawk Air-K 375
Paddling with a Yakkair Full HP2
• Preview: Advanced Elements AirVolution
• Preview: Decathlon X500
Preview: Gumotex Thaya
Preview: Gumotex Rush
• Preview: Advanced Elements AirFusion
• Preview: Aquaglide Chelan 155
• Buying direct from China

As predicted here years ago, eventually someone was going to find a way of making a decent inflatable kayak entirely from dropstitch panels. Something a bit more sophisticated than a SUP board or the three-plank bathtub, below left. As things stand, with a couple of innovative exceptions, most Full Dropstitch (FDS) IKs are made with three panels.

There’s more interest in FDS than ever, because buyers view them as superior to a traditional round tubed IK. But this technology is still in its infancy with a lot further to go. Certainly they’re miles better than just about any low-end, low-psi Sevylor or Intex, nor do they have the days-long drying issues of your Shell & Bladder IKs (but see below). And right now you can buy a two-seat, obscure-brand, China-made 3-panel FDS for just £600, including paddles and pump, or a SUP-with-a cockpit-cavity for under £300.

Some Solo/Tandem FDS IK specs

WeightLengthWidthPayloadPressureIncluded**Price
Advanced Elements
AirVolution 2
52lbs 23.5kg4.5m 14.5′94cm
37 inch
249kg
550lbs
10 psi
0.7 bar
Pump£1499.00
Allroundmarine
Force L
19.5
43
4.73
15.5′
86cm
33.8
350
771
13
0.9
Pump€790
Aqua Marina
Tomahawk AIR-C
24.7
54.5
4.78
15.7′
88
34.6
260
573
10
0.7
2 skegs
Pump
£1000
Aqua Marina
Tomahawk AIR-K
20.3
44.7
4.4
14.4′
76
30
210 46310
0.7
2 skegs
Pump
£950
AquaTec
Ottowa
23
50.7
4.26
14′
83
32.7
270 59510
0.7
Pump
2 paddles
£899
BIC Yakkair
HP2
15.5
34.2
4.1
13.4′
85
33.5
210
463
8
0.55
Pump£1300
Bluewave
Glider
18
39.6
4.73 15.5′85
33.5
317
698
10
0.69
Pump
2 paddles
£660
DS Kajak
465 FLex
20
44
4.65 15.2′78
30.7
250
551
10
0.7
Removable
floor
€1300
Kxone
Slider 410
15.5
34.2
4.1
13.4′
85
33.5
210 4638
0.55
£1050
Sea Eagle
Razorlite 473
17
38
4.73 15.5′76
30
340
750
10
0.7
Pump
2 paddles
£1490
Shipwreck
Arrowstream
*
25.4
56
4.31
14.1′
83
32.7
340 75010
0.7
Pump
2 paddles
£849
Story22
48.5
4.7
15.4′
82
32.3
220 48510
0.7
Pump
2 paddles
£600
ZPro Drift24.8
54.7
4.26
14′
81
31.9
220
485
8
0.55
Pump
2 paddles
£580
Shorter (solo) and longer 2-3 seat models also available • Prices will vary • Weights can be in-the-bag or on-the-water so not really comparable • Payload claims also unreliable • **At the very least all come with a bag/backpack (some with wheels; quality varies) and a repair kit • You’ll need a high-pressure barrel pump.

What is Dropstitch?

For the full story on dropstitch (DS) click thisShort version: a dense mass of non-stretch ‘space yarn’ is magically stitched between two fabric sheets at thousands of stitches per square metre.
The dimples you see on an inflated panel surface are the space yarn inside, under tension, a bit like on a mattress. Once the outside of the sheets are coated with PVC and sealed round the sides, on inflation you get a stiff, board-like panel. The huge popularity of much more easily made iSUP boards in recent years has helped advance DS technology, and an FDS can end up nearly as stiff as a hardshell while packing into a bag, like a regular IK, even if there’s more to a kayak than that.

When inflated via a raft valve, this panel can withstand much higher pressures than a normal round-tubed IK. We’re talking up to 15psi (1 bar) which is four times more than even the firmest tubed IKs. In fact, on an FDS IK, half that is plenty, as you’re not standing on it, like a SUP.

4.3m long and stiff as you like.

It is the ability to make a stiff form from an inflatable chamber which has long been the weak link with traditional tubed IKs, especially once lengths increase. Floors made of parallel tubes need I-beams in place of space yarn to make a flat, wide floor. But I-beams are 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 out in the hot sun.
Running 8-10psi, dropstitch technology eliminates the longitudinal sagging commonly experienced under a single paddler’s central weight in a longer, old-style boat (below). This rigidity enables sea kayak-like lengths of well over 4 metres (13′) which adds up to more room inside as well as a much better glide (less propulsion effort). It’s the same energy saving gained by pedalling a pushbike with properly inflated tyres.

Most full dropstitch (FDS) IKs are made of three flat panels, resembling a simple three-board wooden canoe (left).
On a regular IK, round side tubes up to 30cm in diameter take up a lot of space inside. DS panels are typically just 10cm/4″ thick while retaining all the benefits of tubed IKs: light weight and buoyancy. The only downside seems to be bulk: there’s up to four kilometres of space yarn in a typical 4.5-metre FDS. Add stiff PVC which is hard to roll up and an FDS ends up twice as bulky as a similar-sized tubeless rubber boat. Nevertheless, dropstitch is at least as effective as using metal frames to support saggy IKs. In my experience this is a poor solution.
Dropstitch in IKs actually started as easy-to-fit DS floors (derived from iSUP boards) with round side tubes retained. These are still popular and are now called hybrids; seen by some as the best of both worlds. But all the boats on this page are Full DS. See image below for the three types of IK: tubed (bladdered – can also be ‘tubeless’); DS floor (‘hybrid’) or Full 3-panel DS. There are also SUP FDS IKs; see below.

Floors: Read This

Broadly speaking, 3-panel FDS IKs are assembled by gluing the three DS planks into a wrap-around envelope of PVC which holds the panels in a boat-like shape and which offers additional protection from wear and abrasion.
Some floors are removable, a bit like a footbed slips into a shoe. This makes the hull skin’s inner floor accessible for easy cleaning, rinsing and drying before storage: an important part of IK care. Not everyone may see drying as the deal breaker I make it out to be. Much depends on where you live in terms of climate and storage space.

Unless a glued-in floor is fully sealed along the sides, water and grit will collect in the side cavities. But for deflation reasons, this cavity cannot be airtight.

Less good but almost universal is a DS floor permanently glued to the floor skin but not fully sealed to the side panels. See the two images above: at the bow and stern where the tape stops, water and debris can get down in the cavities. A drain valve helps water to run out of the cavities when flushing before deflating. Some boats feature several capped drains along the sides, which is odd, or a ‘more-looks-better’ marketing gimmick as one will do, same as your bath has one plug hole.
These multiple drains are not self-bailing ports, no matter what clueless vendors may claim or owners may think. Open the drains when afloat and the boat will part-fill with water for sure. Until I realised this, I was baffled by these drains. So it seems were actual owners.
Bluewave Gliders are like this, so are Allroundmarin, Sea Eagle RazorLite, Tomahawk, KXone, Shipwreck and anything else with the telltale drain ports. Even hybrid IKs like the Aquaglide Chelan have multiple (but closeable) ‘self-bailing’/drain valves along the sides of the floor.

Such a boat is nearly as much of a pain to dry properly as the bladdered IKs I go on about. There will always be moisture in the long, inaccessible side tunnels along the floor edge which you will struggle to dry properly. Proper rinsing and drying matter if you want your IK to last a long time, especially after you’ve been at sea when sand and other debris can get in the boat. Seawater causes mildew, staining, odours, 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).

Tubeless rubber IK: dead easy to dry

A theoretical way to eliminate these issues is by fully sealing or ‘wallpapering over’ the floor gaps: usually the bow and the stern as shown in green above. To drain and dry such fully sealed boats, you simply flip them over to shed the excess water, then deflate, spread out and wipe dry, just like the round-tube Grabner on the left.
A boat modified like this would have no crud-trapping, moisture-retaining cavities. The flaw with this idea would be the air trapped in this sealed-off cavity would make the boat impossible to pack compactly: like trying to roll up a partially deflated inner tube. It needs a breather hole: a simple plug would work. Pull out the plug when deflating, plug up once inflated to keep water out.
Fyi: this is all hypothetical but an Italian chap with a BIC told me he had just this problem: gravel and grit collecting in the cavities. One solution of his was to stuff the openings with a dense sponge. Water may still get in but bigger grit won’t. Good idea.
For the moment it seems most manufacturers are happy to settle on removable floors or fitted floors with drains, just as some buyers are either oblivious or contented with bladdered IKs, despite their greater drying issues.

Protracted KXone cavity drying instructions using what seems to be a hidden floor drain valve (6, 7).

Actually their is a worse option: supposedly ‘self-bailing’ FDS 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 FDS IK (left) I saw on eBay 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 and upsetting stability. You could easily tape up the holes in the outer skin, but this is why what look like FDS bargains come unbranded and without guarantees. No brand would risk doing it this way and get hammered by returns or negative customer feedback.

Keel tubes

One benefit of having the floor panel separate above the PVC outer skin is you can stick a thin inflatable tube in there to give the hull more of a V-shape. The AirTrek FLex 465 by DS Kajak (and possibly the same-but-different KXone FLex) have these optional shallow inflatable keel tubes (‘AirBone‘) under the removable but clamped-down floor which you can easily inflate by mouth 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 iffy.
An FDS IK’s barge-flat floor is one of its less good features, so this sounds like a clever idea. And as said, the floor is removable so everything can all be cleaned and dried easily. Sounds like a win-win to me. See the video below or here.

SUP IKs: the other type of FDS

In 2020 Advanced Elements came up with the AirVolution innovation (left): more or less wrapping two SUP planks together, the top one having a central cockpit aperture and set at a bit of an angle to make a tiny space between the two slabs and to help water run off.

Sandbanks Optimal Double

Most others like Aquatec, Sandbanks and the inexpensive GoPlus are simply two sandwiched SUP panels with no cavity in between, and with a cockpit cavity built into the top panel. Each panel or chamber has its own raft valve.
Immediately these FDS SUP Sandwich IKs give an impression of greater stability compared to some of the slimmer, boxy FDSs above, but as a cost of interior storage. As a day tripper, that may not matter to you. You might even be able stand up in them and SUP along, if that appeals. They’ll be dead easy to get back aboard, that’s for sure.

Another good thing is that the two layers are sealed along the insides, leaving no annoying cavities to retain water and grit to complicate full drying. Just flip them over to drip-dry then wipe, or use the floor drain which some have if turning the kayak over is not possible.

Floor of an AE AirVolution

Like the boxy FDSs, these two-chamber FDSs have next to no rocker (longitudinal curve, like a banana), but for swiftness and agility in choppy conditions you want to hope the floor somehow creates a bit of a boat-like profile. The AE AirVo’ on the left appears to have a less wide floor board, but that would work well enough and once wrapped in PVC ends up not much different in profile from my all-tube Seawave.

GoPlus – under 300 quid

The orange GoPlus does have an upturned bow but is otherwise flat as a board. That boat has a single chamber hull with the cockpit cavity built in and a sheet floor, like a packraft. You then fit the separate DS floor panel. There’s no drain but it will be easy to clean and dry.
As with all IKs with DS floors, you’ll be fitting on a hard surface and so the seatbase becomes more important. A think bit of foam won’t be comfortable for long; an inflatable cushion or similarly soft foam will improve matters and also set you higher for a better paddling posture. raised seats can add instability, but at a yard wide at the water, that ought not be an issue with these SUP FDS IKs.

Tracking (going straight)

Just about all of these FDS IKs come with an easily fitted slot-in skeg or tracking fin that’s often as tall as Flipper’s flipper. Like a fixed keel or rudder, they help the boat go straight. Some even have more than one under the assumption that again, more must be better. A tall skeg will drag in the shallows and the boat can’t easily be sat on flat ground without stressing the fitting. But a skeg is easily trimmed – or you can buy a spare and cut it down for shallow paddles. More about skegs here.
FDS boats also feature rigid moulded bow and stern pieces (below right) to help slice through the water. This is typically a weak point on broad-nosed tubed IKs (below left).

Hardshells and conventional tubed IKs can also have a curved hull in both axes: laterally, and bow-to-stern-curve which is called rocker. The more banana-like the longitudinal profile the more rocker and the easier the boat turns and rides over waves.
With the formed bow and stern pieces, box-like profiles and plank-floors, an FDS IK has zero rocker, meaning these boats track well but are hard to turn without a rudder. Many owners report that they glide as straight as an arrow, a real problem with cheapo low-psi vinyl IKs with no skegs which sag, giving too much rocker. One French KXone owner admitrf 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 was my experience too with a DS-floored Moki II and the FDS Shipwreck, but on the latter it was much improved by removing the skeg. The boat’s firm hull innately tracked well enough.

Hull profiles

FDS IKs are still crude box shapes because, excepting the Decathlon X500, making anything other than flat DS boards is too complicated and expensive. The design and handling of these FDS IKs are limited by these constraints: high sides, flat floor, no rocker. Add the fact that the hard floor can make them as uncomfortable to sit on as a hardshell, but when adding a foam seatbase, stability can take a knock.

And the flat floor and box profile may make edging – leaning on one edge as you turn or to counterbalance on waves – trickier. You’d need thigh straps to do this, although I never got that technical with the Shipwreck. This Tomahawk owner said his boat’s initial (or ‘primary’) stability was a bit shaky, but once on edge was quite stable and took a lot to tip right over. This was on flat water. In more kinetic conditions things can happen too fast for you to react.

Pressure release valves

It’s notable that there are no PRVs on most of these FDS boats, presumably because the very high density of space-yarn means they can handle over-pressurisation better than an I-beam floor where the stresses are more concentrated. The two-panel 2020 AE AirVolution is one exception.
Otherwise, better branded FDS IKs have clear warnings at the valve not to exceed recommended pressures (left). Some claim DS panels 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.
These boats’ smaller volumes also means they’re quicker to inflate than a regular IK, although the effort in reaching 10psi requires a barrel pump. Tall and slim barrels work better than short and fat: it’s this shape and not the volume which counts. A 4.4m FDS side panel can be filled to 10psi in just a minute; allow a bit more time for the floor.

Footrests & Decks

Not for the first time I see my ideas adopted by manufacturers ;-). 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 and more versatile and effective than the mushy pillows still used by Gumotex. KXone and Gliders and Shipwreck use a padded strap. Would you have padded pedals on a pushbike?
In any type of kayak, a footrest helps you connect with the boat, execute efficient strokes and not slide down the seat as you do so. And as an IK doesn’t have the benefit of a hardshell deck to brace knees off, a solid footrest is all the more useful.

KXones may come with optional removable decks. Once you realise this boat is as rigid as a sea kayak, adding a deck (or at least some sort of deflector at the front) may be a good idea for managing bigger waves. A regular IK will bend up and over the waves; a stiffer FDS IK will cut through them and may swamp, especially if loaded.
IK World ran a comparison between her old style DS-floored Sea Eagle FastTrack and the 393 solo Razorlite, as well as giving a fuller review of the 393. You may like to scroll down and read some of the readers’ comments about issues and returns they’re having with early RazorLites (the very first FDS IK). She mentioned the FDS 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). Then again, the 83cm-wide FDS Shipwreck is actually more like 60cm at the waterline where it counts, and I (quite heavy and tall) found the 6cm-thick seat base made me feel very tippy. Removing the foam from the seatbase resumed normal service.

You notice Sliders and the BIC are much 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 (left). With the popularity of iSUP boarding, this is a clever gimmick. But sit-down paddling performance will suffer. Me, I’d sooner have as slim a kayak as possible.

Summary
Good on all these brands for upping the game with their takes on FDS IKs. It’s a big step in making IKs less ‘bloat’ and more boat. Many people commonly mistake them for hardshells.
Having spent years 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, except the massive bulk of these things puts me off. The removable floor aids proper drying and cleaning, it’s no wider but half-a-foot longer than my Seawave, and graphics-wise, it doesn’t give me a migraine. But €1200 is a bit of a gamble. The Shipwreck ArrowStream which I did actually try (review here) was half the price at the time.

Spotted a mistake or have something to add? Your comments are welcome below.

Inflatable Kayaks: Hull Forms and Rigidity

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