Not for the first time I will boldly speculate that the Austrian-made Semperit Forelle (‘trout’) was the first serious modern IK, designed in the 1960s from tough hypalon ‘rafting’ fabric. Around the same time Sevylor released the PVC Tahiti watersofa in North America and maybe worldwide. I bet the Tahiti has outsold any Semperit 1000:1. I know which one I’d rather own.
According to my measurements the Forelle 2 is 3.56m long, 70cm wide and weighs 10.5kg + seat. This guy says Semperit were last made in 1983 at which point (or soon after) Grabner (also Austrian) bought the rights.
Grabner then got Gumotex, in Braclav just over the border (and behind the Iron Curtain, back then) to produce a cloned Forelle called the Grabner Fun (left), but made from Gumotex’s hypalon-like fabric called Nitrilon. Back in the 1980s I’m sure Commie Nitrilon would have been cheaper and probably as good as DuPont hypalon made in western Europe. The Fun was discontinued (or stock ran out) a few years ago.
Grabner Fun: 365 x 75 cm; weight 12kg; payload 170 kg; pressure 0.2 bar; fabric 1100 dtex Nitrilon
Not being one of their boats, the Fun was undersold by Grabner (notice the table, above). Instead, the similar but longer Holiday range got the fanfare and is still made today with few changes.
Grabner boats are made from a hypalon-like fabric called EPDM which, combined with Grabner’s hot vulcanising method, explains how their boats managed to run 50% more pressure (0.3 bar) than the Fun and other Gumotex IKs at the time. Gael A. paddled an aged Grabner H2 along the Scottish Sea Kayak Trail a couple of years ago. Among others, Incept also used the twin-side beam design to produce a 70-cm wide K40 which is also 70cm longer than the Forelle II, and one of the fastest IKs around.
I would say the obscure and expensive K40 and the more popular but also expensive Austrian Holiday 2 and 3 IKs are modern iterations of the twin side tube Forelle design, with the Holidays (below) right down to the wooden bow clamp (right).
You can occasionally find aged Forelle IIs for around €300 in Germany; a new H2 goes for €1900, while Funs were being discounted for as little as €400 new, but seem much rarer now. I was curious about tracking down a Forelle recently (I succeeded) and below are a few shots I picked up off the web and from some sellers. Apart from the odd repair, the indestructible hypalon fabric stands up well (or does it?) and the seats may well have been improved (Grabner’s still use crude and bend-prone alloy bars).
Some boats come with a huge wooden rudder which might be replaced by a skeg, but one off-putting aspect are the basic inflation ‘lilo plugs’ (left); no better than an old Gumotex seat. These could easily be cut out and replaced with proper Gumotex valves (right), maybe in a more accessible position, too.
It seems older versions (grey and orange, below) have a half-inch deep keep strip right along the bottom (as well as a rudder fitting) while later ones like the yellow one, do not.
One thing that can’t get avoided is that a Forelle (and a Fun) still run only 0.2 bar pressure. Same as most ordinary Gumos, like the Solar 3 though the stiffer twin side beam hull helps. Modern Grabners run 0.3 bar which makes a big difference. Some newer Gumotex IKs now run 0.25, though that can be pushed to 0.3 bar with care.
Thanks to Gael and OP for extra details. Most pics lifted from ebay sellers.