Preview: Gumotex Rush 1 and 2 IKs

Gumotex Rush

Interesting discussion

Gumotex are moving on up with hybrid drop-stitch technology, originally showcased in last year’s Thaya – basically an old Solar 3 with a D/S floor to make it more stiff. The new-for-2020 Rush 1 and 2 (left) is the ‘Swing Evo’ mentioned in that Thaya article.

‘Hybrid’ is a cool word for a kayak which isn’t full D/S like a Sea Eagle Razorlite and all the clones; assembled from three flat panels of D/S which make boxy hulls (right) and which, according to the graphics on this page, can be sub-optimal in choppy waters. Me, I think the flat, raft-like floor is more of a real-world problem, but read on to see how they addressed that on the Rushs.

Derived from iSuP boards, D/S has become a blessing to IK floor design which hitherto had to use I-beams of parallel tubes (left) which complicates assembly and is prone to ruinous rupture if over-pressured, unless fitted with a PRV or the IK is exceptionally well made.

A Gumotex hybrid IK (below) retains the regular round side tubes of a classic IK for better secondary stability (afaiu) but features a D/S floor for rigidity. However, unique to Gumo, D/S panels are also used on the bow as well as shorter and less obvious panels at the stern. Until I see a boat it’s still unclear to me if this section of the boat is connected to the D/S floor or the lower pressure side tubes. You’d think the floor, so this must help brace the hull structure to reduce longitudinal flex in wave troughs and so enhances rigidity and overall performance – a better, hardshell-like glide. As Lee at The Boat People wisely observes, any hybrid IK with an integrated D/S floor is miles better than boats with separate/removable D/S floors which slip into a sleeve (some Sea Eagles and Advanced Elements). It’s an easier way of doing it, but one which can see potentially ruinous grit collecting between the sleeve and floor.
A word about this fabric paraphrased from here:
Nitrilon-Dropstich is composed of a core of 1100 dtx polyester fabric made up of two sheets joined by a mass of threads exactly 10 cm long. Unlike regular PVC-based iSuPs and D/S kayaks, this durable elastomer plastic is not glued to the fabric, but ‘pressure-impregnated’ which eliminates delamination risks more common with bonded PVC coatings. An additional layer of polyester-reinforced Nitrilon is vulcanised to the floor bottoms making them double thickness.”

The Rushs differ from the Thaya (1st gen Gumo D/S) with the panels forming a more ‘hydroformed’ bow – another weak point with regular blunt-nosed tubed IKs. The Rush’s flat floor extends into two bow sides which join up to make a water-slicing wedge sharp enough to cut ripe avocados into wafer-thin slices.
This construction is a bit more complex than just a D/S floor attached to two side tubes (like the Thaya and some Aquaglide IKs, for example) and which may help explain the high price.

The vital stats on the tandem Rush 2 are said to be 4.2m long x 82cm wide. Compare that to my Seawave at 4.5 x 78; the Seawave has an 11% better length/width factor (LWF) of 5.77 vs 5.12 over the Rush 2, but those are my Seawave measurements. The side tubes are said to be 19/20cm on the Rush compared to 22 on my Seawave. This and the length may contribute to the load rating dropping to 195kg vs 250 on the longer Seawave. That’s still plenty, unless you’re hauling a moose carcass out of the Yukon.
The official weight varies between 15.5 and 17kg, depending on where you look online. The higher figure is the same as my modified Seawave with packraft seat mod.

Pressures are another obvious difference with the Seawave. The 6cm D/S floor runs at 0.5bar (7.2psi), actually a modest level for D/S, but an IK doesn’t need to be as stiff as a iSuP board. The slimmer side tubes are now 0.25 bar or 3.75psi (same as the Seawave) – well, according to the table from the online manual shown below. When I originally wrote this outlets and even the Gumo website listed the usual 0.2 bar/3psi of regular Gumotex IKs but Gumotex just confirmed this was incorrect.
0.25 is a higher than normal IK pressure but not quite as high as 0.3 in a Grabner or the 0.33 bar on my modified Seawave. When you combine that with the stiff D/S floor, the 0.25 bar sides must make the Rush IKs Gumo’s stiffest IKs by far. The difference is, I added PRVs to my Seawave sides before running them at 50% higher pressure to automatically protect them. The Rushs don’t seem to feature any PRVs which explains the warning in the manual, above right. It’s odd but worth remembering that my super-stiff Grabner Amigo didn’t feature any PRVs eitherl, not even in the floor. Quality of construction (gluing assembly) must have a lot to do with it.

When you add any colour you want as long as it’s black, you do wonder if no PRVs is a good idea because in the sun black things get hotter, faster. Black is great for Cockleshell saboteurs, not so good for visibility at sea and it kills photos stone dead. It’s true the Innova-branded Swings in North America have long had black hulls and no one complained. But they run 0.2 bar so could do with some help in stiffening up in the hot sun. They also have fixed decks in red. I also see that many Grabner IKs are now made with black exteriors (right).
One assumes the Rush’s grey, lowish-psi D/S floor can handle increased pressures from passive solar heating, especially as it’s in the water most of the time. But the black side tubes will get taught which becomes a nuisance to manage (or worry about), even if tubes/cylinders handle high pressures better than flat slabs. In fact, as you’ll see from the comments below, Gumotex have found that black is not notably worse than red or green in absorbing solar heating and dangerously over-pressurising. And if you’re that worried it would be just as easy to install PRVs in the Rush side tubes, as it was on my Seawave.

Because a D/S floor is flat, one imagines it will hinder effective tracking, despite having a skeg at the back. The flat hull will plane over the water and wander off to the sides like a packraft – the so-called ‘[windscreen] wiper-effect’.

So, similar to Sea Eagle‘s patented NeedleKnife Keel™ (right), Gumo have added a more discrete ‘keel hump‘ under the bow (left) to compensate for the lack of old-style parallel I-beam floor tubes which added a directional element. You can see from the overhead image above that this keel hump is mirrored on the floor inside the boat, either by design or need. This protuberance makes a high-wear point on the IK in the shallows so it’s just as well the floor is double thickness Nitrilon, as mentioned above. It’s the same on any boat. On my Seawave I pre-emptively added a protective strake – a strip of hypalon – to the central tubed rib, though to be honest it never got much wear as i try and be careful. Mine was hardly worn in five years of mostly sea, but you could easily do the same to your Rush if you expect to do a lot of shallow rivers.

Rushs can be fitted with optional decks (green on the R1, above, red on the R2, below), using the same velcro system as the Seawave, with those horribly bulky alloy spars (right) supporting the decking (surely a flexible rod like tentpole material wouldn’t be hard to make). I read on other reviews that they’ve greatly improved the coaming (hatch rim) so that spray skirts attach more securely.
The footrest appears to be the usual rubbish cushion but can be adjusted by strap (another idea I like to think Gumo have pinched off me!) and seats can be moved to a variety of positions, too. Seats are now foam, but the base looks a bit thin/low to me. A stiff foam backrest (with side bracing straps) is good, but an inflatable seat base is much more comfortable to sit on because you can vary the pressure to suit the height. Unlike anything inflatable, foam eventually loses its cushioning. But an inflatable seat just doesn’t need to be made of hefty hypalon, as on previous Gumo IKs (more in the vid below). But anyway, a seat is easily changed to suit your prefs.

Below, a review of a Rush by Austrian Steve. Can’t understand a word but some observations: I like his convertible Eckla Rolly trolley/cart/camp chair; also love the lovely long canoe chute at 20:40. Have to say though, I winced a bit at some boat dragging here and there. Do the right thing, Steve; it only weighs 12kg! Note also this shortish boat seemed to track pretty well without a skeg – the frontal keel-hump may be effective in leading it by the nose, after all. But in the comments Steve admits the stiff, flat floor slaps down hard on wave trains coming out of rapids and I suppose would be the same at sea. It’s a drawback of flat, raft-like D/S floors I’ve not considered.
See this for an easily translatable written review also in German.

The price of an R1/R2 is a hefty £900/£1200 in the UK, plus decks going from £200/310/370 (tandem). There’s also a rudder kit (price unknown) which will be similar to the Seawave unit. IMO it’s not so useful, even on the longer R2. But like decks, some may like the option.

As you can tell, I’ve been comparing the Rush 2 with my 5-year-old Seawave and wonder if it might be time (or an excuse) to change. An unprecedented five years of ownership proves there’s nothing wrong with my Seawave [anymore].
What are the benefits of a Rush 2? Having outgrown my stealth-gothic phase, black is not such an attractive or useful colour for a boat, and neither is losing a foot in length or 50kg in payload over the Seawave – at least at sea. On a river the greater nippiness from less length will have benefits, but for that I have my Nomad pakayak. As for greater rigidity, it looks pretty good in this clip but my adapted HP Seawave was very good compared to the lower-pressure Gumboats, and it seems the speed (see below) is no greater. Being a bit shorter, I wouldn’t expect it to be.
The word is a Seawave hybrid with a D/S floor will be out later in 2020 but that will cost a pretty penny. Maybe I’ll sling my brilliant Seawave out onto eBay and see if anyone bites. [I did and it went within hours. Oh dear.]

The test by Yves Samson, also the Seawave’s first tester, in Saint-Malo in November 2019: Test conditions: in the open sea on the coast exposed to the east of the Grande-Plage, wind force 5, gusts to 6.
First impressions: it is well designed, aesthetic, (which was not the strong point of Gumotex), a well-conducted research for the seat and footrest adjustments, which can be adjusted very easily when sailing. Rigid and light, it seduces from the start. On the water its behaviour is very healthy, I dreaded the wiper effect, but thanks to the small inflatable keel from the front, it behaves very well. I have the impression that the side tubes are smaller than those of the Seawave because there is more room inside and it is lower on the water. In navigation, with a good wind of 3/4 before, you go straight without any problem, much less hard to stay the course than with the Seawave. It climbs well on the chop, I have 11km on board very little water (without a deck). You feel like on the Seawave and in total safety.
In summary: a very healthy kayak, I think very suitable for solo itinerant trekking. For double use, it is for day trips only, too small for 2 + over night gear. The more negative points: I was a little disappointed by its speed which I hoped to be much higher than that of the Seawave. It is in fact in these rough sea conditions it was barely higher: I averaged with GPS, 5.9 kph over 11km with 5.1 kph against the wind and tide. (BUT I paddled at cruising speed as if I was going on a 30km stage, I never “PLF’d”!).

http://www.canoekayak.fr/kayak-haute-pression-drop-stitch/356-rush-2.html


Another detailed online review (German).

13 thoughts on “Preview: Gumotex Rush 1 and 2 IKs

  1. pankanel

    Hi Chris
    Don’t disappoint us. Buy the new Rush, do your magic, and let us know if a prv can be installed on the ds floor.
    I ‘m afraid that without one, it will be unusable in the greek summer (you may remember the problem I had with the side tube of my sw).
    Keep up the good work
    Panagiotis

    Reply
    1. Chris S Post author

      The problem is we are stuck in London this summer, not anywhere interesting, like Greece (where we toxic Brits are currently banned ;-)
      Plus it is quite a lot shorter than a Seawave but no shop in UK will let you try it or even see it right now.
      Fyi: I don’t think a PRV is needed in a modern D/S floor. (I see old Sotars had D/S with PRVs in the 90s).
      I am pretty sure if you run them at the recommended pressure they could handle some overheating with the usual precautions. Also, cutting a hole into DS is not so simple; it will imbalance the evenly spaced tension on the strands (but then I suppose a PRV will stop pressures getting high and staring them).
      I have read that D/S does not last as long as regular tubeless with good care (but I still think it’s many years).

      Reply
      1. pankanel

        Well Chris you see, in the greek summer with temperatures not falling from 30 c and sometimes up to 40 c, we don’t talk about some overheating. When the side tube of my sw opened, I was constantly relieving pressure from them. With no luck. I think that if I think about getting a ds boat I will discuss it first with the lady (professional) who repaired my sw. I would be very sceptical to buy a ds boat if I wouldn’t be able to install a prv on the ds floor. Especially in a boat like Rush, with an integrated ds floor, any problem with the non replaceable floor will mean the end of the boat.
        Regards
        Panagiotis
        PS Regarding your comment about toxicity, I would wait to see what happens. I have the feeling that since the end of a very effective quarantine, people here behave like if nothing happened.

      2. Chris S Post author

        Morning Panagiotis, it sounds like summers get very hot in Greece but can it be that different from some other countries where Gumotex are sold? You’d think a 1000-euro IK could handle such pressures providing the usual care is taken on land. Some smaller Grabners like the Holidays (or my old Amigo) run 0.3 bar but have no PRVs at all (Grabner give all sorts of air-down warnings when on land). I think if I owned a no-PRV Grabner again I would fit 0.3bar PRVs all round simply for the worry-free convenience.
        Also, you must have iSUP boards in Greece which run much higher pressures then most D/S IKs and yet, as far as I know (and the one I tried once) they do not have PRVs (I am not sure they even make PRVs which go that high). I suspect modern D/S fabric is much stronger than what was made in the Sotar-with-PRV days and by spreading the load is able to safely sustain take much higher pressures than an I-beam floor. I would feel more confident with a D/S with no PRV than an I-beam floor with the same.
        Interesting iSUP articles
        http://www.windsurfer.co.uk/SUP_iSupConstruction.htm
        https://www.airhead.com/blogs/news/an-inside-look-at-the-technology-of-inflatable-paddle-boards

        (The ‘toxic Brits’ comment was a small joke on the vastly different outcomes to the epidemic between UK and Greece ;-)

  2. Garrett Wong

    Hi Chris, long time reader first time poster. Saw your recent post about selling your seawave! I guess on to better and bigger things? Just purchased one myself and about to embark on new PRV. Btw do you choose to allow comments on some posts but not others?

    Reply
    1. Chris S Post author

      Hi Garrett. Should have kept the SW for the summer – it was a clear-out spasm! – but there will be another IK. You will enjoy yours.
      You saw the new super valves, I take it. Let us know if they fit. With comments, happy to receive but I usually forget to tick some box on some posts. If it’s automatic the spam folder gets clogged.

      Reply
    1. Chris S Post author

      Thanks J-F. yes I saw that video while writing the Rush story but it seems odd it’s the only mention and it was last year when the Rushs were coming. Could it be the new D/S Seawave? It also seemed odd that he said it was self-baling but that it was also meant to have a cockpit. Usually you only have one or the other. We shall see.

      Reply
      1. azgorh

        Hi Chris, first of all congratulations for your blog, I have been reading from a time.

        Let me ask you if you dont mind because I am now confused. I have been saving money to buy an inflatable kayak and I was convinced to buy a Seawave because I only use it for long distances in the sea. My problem now is that i dont know if its better to buy the Rush 2, the actual Seawave or maybe would be better to wait an update of a new Seawave with drop stich. In your big experience what do you think would be the most wise decision?

        Thanks for you blog and your adventures.

      2. Chris S Post author

        I think you can’t go wrong with the original Seawave if you can find a good price.
        Same weight, cheaper, 30cm longer, 5cm narrower than Rush2.
        If you add the high pressure PRVs in the side as I did (see the page, i updated it) + add better seats and thigh strata you have a great sea IK which I think becomes nearly as stiff as a Rush. But if you can get to try both (difficult, I know), so much the better.
        The new D/S floor Seawave will be expensive – let’s hope the size and weight are the same.

  3. Roberto Muzzetto

    Hi Chris,
    sorry for my personal translation, for zip-colander I meant zips which let a great quantity of water in, even if Gumo state “The enclosed deck prevents water getting in” for Swing models. I replaced the footrest with the one from Twist 2/1 and it seems to work.

    Reply
  4. Roberto Muzzetto

    Hi Chris,
    quite an interesting review, as usual, even if with no real testing, but reach in interesting details. I do agree with you about the black colour being not visible and attracting solar rays which implies pressure increase, especially in southern regions like mine (Sardinia); moreover I don’t like that colour for a boat (but it’s my personal taste!) otherwise I could think of buying one. I reckon Gumo will not deliver Rush in different colours in the near future, this is their reply to my doubt on colour: “Regarding Rush, I can guarantee that you do not need to worry about colour, because we use black colour in USA for ages now and nobody complained on problem. They use kayaks in Florida, California, Oklahoma,…. in all US states. Rush has great characteristics and we received only best feedback on it”.
    Besides, they seem not to be prone to changes or improvements on their models (i.e. the zip-colander or the useless footrest on Swing models).
    Thanks for your useful reviews
    Regards
    Roberto

    Reply
    1. Chris S Post author

      Hi Roberto, shame to hear Gumo has no plans to make other Rush colours. A quick Google shows that actually heat build-up is not so great (15% more black vs white car) so red will be less. And I just read Steve’s video comments (some in English): “… Gumotex said they measured the temperature of the black material in the sun and its almost identical with the dark green, they have for Scout and Baraka.”
      Which leaves personal taste, dull photos, and safety/visibility benefits. Oh well.
      Not sure what a zip-colander is but yes, footrests have long been a weak point, and Rush gets the same old rubbish cushion. Easily replaced by a piece of plastic drainpipe.

      Reply

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