Complex sentence: The circular arc hull was created by the Swedish engineer Fredrik Ljungström, who, in the 1930s and 40's, successfully used his sailboat designs to build boats, commonly called the Ljungstrom sailboat.
Split into simpler sentences: The circular arc hull was created by the Swedish engineer Fredrik Ljungström. In the 1930s and 40's Ljungström successfully designed and built sailboats, commonly called the Ljungstrom sailboat.