More about Hybrid IKs
Since 2019 the Gumotex Thaya sits alongside the near-identical and 25% cheaper 4.1-m Solar 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. 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.
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 for barely any additional weight. The only drawback is that you need a more powerful high pressure barrel pump (above right). Your old Bravo foot bellows won’t do anymore.
DS is normally PVC and made in China, but Gumotex have found a way to manufacture 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’].
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 from the Solar. 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 it runs 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 old-style 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 pillow rubbish, 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.
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 was 2cm narrower than a Solar 3 and with the usual care getting in, stability is not an issue. Out at sea my Seawave would 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 30% more than the Solar 3 whose days may be numbered, but it’s 2022 so maybe not.