Catamaran made of… foam

In recent years, foam catamarans have begun appearing on the water bodies of the Urals. They are unsinkable, convenient to operate, durable, and simple to manufacture. The figure shows the design of such a catamaran. Its dimensions: 3750X1600 mm, plate thickness from 40 to 150 mm, float height 200 mm and width 400 mm. The weight of 1 m³ of foam is about 20 kg. The plates are cut on a special device with nichrome wire heated to 200—250°, or on a special machine, the design of which is described in issue No. 9 of the “Modelist-Konstruktor” magazine for 1971.

The bow diaphragm (2 pcs.), partitions (4 pcs.), and frames (4 pcs.) are made from 12 mm thick plywood. The tie rods, which serve to fasten the parts, are duralumin, although thin-walled steel ones are also acceptable; duralumin rods Ø 10—12 mm are also suitable for tying. Threads on Ø 1/2″ pipes are cut with a die or tap, and on rods—with a tap with standard metric thread (M10). Before assembling the floats, the wide surfaces of the plates are coated with oil paint or epoxy glue and tightened with steel pipes using nuts. Then the outer surfaces are covered with thin calico or fiberglass in two to three layers on epoxy resin or oil paint. The bow part of the catamaran floats is made separately from 25X25 mm aluminum angles and sheathed with thin (0.5 mm) sheet aluminum. The metal structure has a plywood diaphragm fastened with M5 bolts to the angles; the aluminum sheathing parts are connected with rivets.

Covers made of plywood or sheet duralumin 1—1.5 mm thick are attached with screws to the bow angles. The bow part is mounted on the ends of the tie rods and secured with nuts, as shown in the figure. Then it is filled with pieces of foam and closed with a cover.

The superstructure (deck) is assembled from wooden beams and battens. The entire structure is fastened to the frames with eight bolts and nuts. For movement on water, a boat motor with a power of 1—5 hp (for example, “Chaika”, “Salut” or “Priboy”) is installed in the stern. You can also row using oars made from thin-walled duralumin tubes. It is also possible to install a fore-and-aft sail with an area of up to 3 m² on the catamaran.

«M-K» 9’74, A. KOPYLOV