The plastic (GRP) construction at Storebro started in 1954. Although Ivar Gustafsson did not like the plastic material, it was recognized that certain parts were difficult to form in two directions with plywood. So they were looking for alternatives to wood construction particularly for small moldings.
At the time, Volvo developed the P1900 passenger car with plastic body. Volvo then offered their best customer for boat engines the american plastic experts of Glasspar (Santa Ana, CA), which were already paid but no longer needed, for the introduction in the GRP-processing.
Storebro accepted this offer and used the new technique for canopies, air scoops and other small parts.
Before Storebro starte producing complete plastic hulls, 1960/61 they tested the mixture of wooden hulls of boat building plywood, which received a plastic cover. The test boats were built in different configurations - both as an open boat and with a cabin (see plywood/plastic boats).
Unfortunately, the reservations against this technique were confirmed, so that the yard continued to rely on the construction of massive wooden hulls. Complete plastic hulls were only manufactured from 1968 onwards. The first ship with a complete plastic hull was the Royal Cruiser I/Solö Lyx II.
In 1976 the Storebro Royal Cruiser 31 was introduced, whose superstructure was made of plastic, in addition to the hull. Only the hardtop was still made in wood (sometimes painted in plastic tone). The first ship, which was made entirely of plastic, was then the Storebro Royal Cruiser 40, which was presented in 1979.