Preview: Zelgear Spark 450 inflatable kayak (D-SF)

Photos by Marcin S and ZelGear
See also: Zelgear TPU IK

Zelgear is a Ukrainian outfit producing PVC rafts, folders (under the Neris brand) and outdoor gear since 1999, as well as some IKs with innovative ideas.
Their current tubeless PVC IK line up includes the drop-stitch floor (D-SF) Alpha-Z II and Spark in three sizes: 370, 450 and 520cm. Zelgear are sold in Russia, Poland, Germany, the US and maybe elsewhere. As with some other importers, the ZelgearUK website currently only features the discontinued Alpha and Needle (‘Igla’) models. A Spark can be hard to find.
Recently, Gumotex Solar owner Marcin S from Poland pointed me to his detailed review of his new Spark 450 IK which has led to a closer look at this brand.

The new Alpha-Z and Spark look similar but the Alpha-Z II has round sidetubes; the pricier and heavier Spark. has twin sidetubes, like my old Incept, the discontinued Gumotex Seaker or of course the Grabner Holidays based on the old Semperit.
Stacked sidetubes provide more space inside – always useful with tubed IKs – as well as less overall width, good for speed at a slight cost to stability. In 450 and 370 sizes, the Spark is just 83cm wide vs 87 in the Alpha-Z II (according to online specs). That’s still 7cm more than my single-sidetube Seawave so there sure is lots of room in there: 43cm width inside – same as a Holiday 2 and 10cm more than a Seawave. That’s a length-width ratio of 5.42. See the full comparison table here.

Twin sidetubes are more complicated to make as they need an internal I-beam to form the tall but narrow ‘8’ profile. Although Grabner manage without, I-beams (used in non drop-stitch IK floors) benefit from a pressure release valves to protect the I-beams from rupturing if the tubes get too hot and pressures climb. Round tubes spread pressure loads evenly so can withstand over-pressure. That’s why pressurised gas cylinders are cigar-shape. But in fact the Alpha gets side PRVs too. PRVs make over-pressure worries a thing of the past, whatever your sidetubes.

It’s also possible that at the same pressure, stacked sidetubes flex less longitudinally than a round tube, but I doubt there’s much in it. Stiffness is primarily down to psi, although PVC fabric is innately more stiff than synthetic rubbers. Good on the water; less good for folding up when cold. PVC is Heytex or Valmex from Germany (or German branded, at least). PVC is said to be less durable and UV resistant than rubber in the very long term. The plasticisers evaporate (that distinctive PVC smell) and the fabric hardens. As Marcin observes at the end of his post: Spark in Nitrilon would be less bulky but costlier. That boat is the (still unavailable) Gumotex Rush 2 or the D-SF Seawave which is due in 2021.

You’ll see from the video still and above that Zelgear uses an unusual and removable D-S floor. AirBoard or AirDeck, they call it, with the unusual ‘horns’ or spars poking out to make sharply formed prows to the stern and bow – another failing with tubed IKs. It looks like the floor’s flat and wide section is D-S, the neck may be just an empty round tube and the end pieces have a couple of I-beams in them.

This is a much more complex assembly than a regular iSUP-like D-S floor panel, but the benefits are clear: a hardshell like prow without resorting to plastic mouldings or worse still, alloy ‘backbones’. Clever. The sidetubes run a very firm 0.3bar (4.3psi) and the floor is rated up to 0.6 bar (8.7psi) making a very stiff boat. (Other sources say 0.25 and 0.5).

In the video the chappy mentions opening the PRVs on inflation, and the online specs also say leave them open during use. Why would you want to close PRVs? Or does the cap push open once pressure climbs? Who knows.

Marcin mentions his Spark is a lot quicker than his old Solar. Not hard to believe when you consider the Solar is just a long Sunny, still running just 2.9psi. But the difference is quite dramatic, and so is the effect of using thigh straps on a firm D-S floor: all the energy gets transferred to better propulsion or less effort.

The Spark floor has tabs for mounting a footrest, but only when sat in the rear. As Marcin observes, another set is needed for solo paddling when sat in the middle. But that would be quite easy to make and glue on.
Talking of which, I came across this interesting footrest idea (left), possibly from a discontinued Igla. Similar to the Gumotex skeg mount, that could also be dead easy to make for any IK, and you wouldn’t have to use shin-gashing bent and riveted alloy either.

Other features with the Spark include loads of D-rings, a velcro paddle holder; seats with an inflatable base and foam backrest; thigh straps!; a generic rudder mount and fittings plus Seawave-like velcro to fit an optional deck (left).
There’s no skeg (an optional order or easy glue-on) but Marcin says the boat tracks very well thanks to the prow forms.

A fly in the ointment is the boat’s weight at 23kg in the bag where my similarly long and wide Nitrilon Seawave is 19kg. That’s PVC for you, but see this. And the PVC becomes hugely bulky once rolled up. Look at this picture of Marcin’s massive bagged-up Spark alongside his old Solar.

A Spark 450 is listed at 23,000 grn from Kiev, which works out at £800. Prices in Poland are about £940. It’s hard to find Spark prices elsewhere, everyone’s still trying to clear out the old models. Compare that to a 4.2m, round-tube D-SF Gumotex Rush 2 direct from CZ (were it available) at 30,000 CZK (£1015) and probably higher still by 2021.

I must say I’m quite impressed with the Zelgear D-SF IKs: stiff hulls, thigh straps included and tubeless, too. In a vast sea of Asian-made Shell & Bladder bloats, only Sea Eagle and the Intex K2 Excursion Pro are tubeless PVC. I still think I’d rather run a D-SF IK than a full drop-stitch floating box. But I’ve yet to try either. For more on the Spark, including pictures,, read Marcin’s kayaking blog.