Mattress catamaran

For weekend hiking enthusiasts who prefer relaxing on the water, an unusual lightweight catamaran design published in the Hungarian magazine “Ezermester” will certainly be of interest. This is a single-seat recreational “boat” with a pedal-powered rowing drive, based on two inflatable beach mattresses. They are used without any modifications, so they fully retain their traditional purpose. And to set off on a short trip — for example, to fish or just ride around — it is enough to place a small wooden frame on top, with a standard folding chair attached to it, popular among summer residents and retirees.

Since inflatable mattresses are purchased ready-made products, let us look in more detail at the catamaran base frame. It is assembled from wooden slats with a 40×20 mm cross-section and consists of two longitudinal supports 1700 mm long and crossbars connecting them: one front crossbar 640 mm long and two more of 1100 mm each. The supports and crossbars are connected with furniture bolts and wing nuts for convenient assembly/disassembly. The front and middle crossbars are mounted flat (the first above the supports, the second below), while the rear one is mounted below and on edge so that it fits into the transverse gap between the inflatable tubes of each mattress. This fit is sufficient to avoid extra frame-to-mattress connections (though they can be added if needed).

After the base frame is assembled, a folding chair is mounted on its middle and rear crossbars and fixed with metal clamps made from steel or duralumin strip.

It remains to install the mentioned rowing drive — two foot pedals that move two blades back and forth, the blades being folded in half from thick rubber cut from automobile inner tubes. The pedals are metal plates with a hinge made from a small window hinge, which in turn is attached to the front crossbar. The plates are connected to the blades in a special way — by bent (see figure) metal rods made from 6 mm diameter bar, whose hook-shaped ends are bolted with M4 bolts. For easier assembly/disassembly, the pedal hinges can also be attached to the crossbar using bolts with wing nuts.

Final catamaran assembly is performed in shallow water near the shore: the inflatable mattresses are placed on the water, and then the frame with chair and drive is carefully lowered onto them and aligned accordingly.

To protect the wood from excessive moisture, all frame elements are thoroughly impregnated with drying oil and painted in several coats with oil paint or waterproof varnish.

“Modelist-Konstruktor” No. 6’2008