That is why in bladder boats like Aire, tough PVC is good for the outer shell and urethane makes an ideal, slightly stretchy bladder. Vinyl and urethane (PU) may all be just ‘plastics’, but might be compared to a Platypus water bladder (vinyl, stiff, slippery) and the blue Camelbak PU (softer and rubbery). Examples include Aire, some Aquaglide, Sevylor, Intex, Decathlon Itiwit and Advanced Elements. Inside the casing fit light, removable sponsons or air bladders, made either from more PVC, more durable and flexible urethane, or just PU-coated nylon. It ought to last 20 years I’ve seen cheap vinyl-tubeless slackrafts ruined in less than 20 metres.Īn IK’s hull can be an envelope or shell made of three chambers (two sides and the floor) usually made of PVC, woven nylon or both. A Grabner is made from tough Nordel EDPM, a rubber coating bonded to a woven fabric core, same as a RIB or a white water raft. The difference is the Sevy is made from thin, heat-welded vinyl, like an inflatable globe or a bin bag. Ironically, the very cheapest ‘£99’ Sevylors (as above) as well as the most expensive €4000 Grabners are both tubeless IKs. I call this ‘ tubeless‘ (which is also found on the very cheapest heat-welded vinyl IKs) and the pros and cons of both are explained below.
Or sections of hull fabric are assembled to make fully airtight chambers and a load-carrying monocoque.
IKs are fabricated or assembled in two ways: either with airtight ‘inner tubes’ which inflate inside the floor and side compartments of a (sometimes porous) protective fabric shell to make a rigid form, like a bicycle tyre inner tube. PVC vs PU vs synthetic rubber: slightly biased. A ‘PVC vs rubber’ article from 2011 by The Boat People
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