The 2nd Pacific 1,000 km Motorboat Marathon Race was held in the open ocean between Osaka and Tokyo over three days beginning July 7, 1962. Coming off its overwhelming victory in the previous year’s race, Yamaha entered two new motorboats. Bad weather conditions during the race forced 16 boats to drop out due to capsizing or water leaks. The only boats that completed the entire race were Yamaha’s two entries. The boats that participated in this race became the model for the Yamaha Stripe 18 series, which was produced for 13 years.
The 1960s were a critical period that saw the birth of models like the HIFLEX and Stripe that would set the direction for Yamaha design in the years to come. Japan’s oceans are marked by extreme variation in weather and surface conditions due to the nature of the currents and topography. Days in which smooth, calm conditions prevail are rare. To ensure safe and quick travel across such waters, Yamaha had to develop boat designs suited to Japan’s ocean conditions.
Yamaha first introduced the HIFLEX boat design in January 1962. Presentation of the Stripe design followed at the 19th Tokyo Motor Show in October, where it was exhibited in a pool in the motorcycle hall at the show.
Development of the HIFLEX design began based on the concept of “the fun of boating.” To bring out the pleasure of boating on the ocean, Yamaha fully leveraged the advantages of FRP shell construction to create a smooth, beautifully curved shape for the cross section of the hull. The width was set at 1.5 meters to enable compact automobiles to pull it on a trailer. Handling was substantially improved so that the boat could be freely maneuvered on the water like flying in a jet fighter. President Genichi Kawakami saw the boat’s crisp, highly flexible maneuvering and christened it the HIFLEX 14 (H-14).
The Stripe boat design was based on Yamaha’s experience in open ocean racing and shattered the stereotypes held by boat designers.
A hull capable of riding over large waves is necessary to win demanding races in the open ocean. Until the development of the Stripe, designs used a large rise in the hull bottom at the bow in order to mitigate impact from the waves and a gentle rise from the center to the stern. This was because the flatter the bottom rise, the less the resistance and the greater the acceleration. However, this design caused speedboats to jump whenever they raced between waves. To lessen the impact when striking the water, a large bottom rise could be used at the stern, which would provide better cushioning when hitting the water, but the efficiency of the bottom surface would be diminished. For this reason, many designers were convinced speed and cruising comfort could not coexist in the same boat.
The boat that overturned this commonly accepted perception was the Bertram 31, which was actively used for open ocean racing in the US. The aft portion of the boat’s hull was pitched at 25 degrees. A forerunner of the deep-V design, gentle curvature of both the sheer line (curvature at the fore and aft of the boat) and chines (ridges running the length of the hull), as well as spray rails on the bottom, made it possible to achieve both speed and cruising comfort.
Based on the Bertram 31, Yamaha’s engineering team created an original prototype and entered it in motorboat marathons. The boat was commercialized after verifying its performance in the races. The eight spray rails on the white hull were so conspicuous that President Kawakami named it the Yamaha Stripe 18.