Traditionally, the drive body for small boats has been made with metals. Manufacturing method of metallic drive body followed with consecutive and accurate process of casting, machining, surface grinding, plating or coating and assembly.
The fabrication of FRP(Fiber Reinforced Plastics) drive body is of great advantage to reduce weight, low vibration transmission, vibration absorption, specific strength, specific stiffness, fatigue resistance and wear-corrosion characteristics in seawater. In accordance with this development, it is easy to increase production rate and mechanical properties, whereas to get lightweight and low vibration than strainless steel and aluminum alloy.
To make specimen, we used glass roving/roving cloth as reinforcements. Hybrid fabric with carbon and aramid fiber in order to protect from rub and impact of floating matter was also used for skeg part. We also used epoxy matrix YD115 which is good for increase fiber area weight, rub property and relatively lightweight and room temperature cure. Eventually, we did co-cure together with fermate as core material.
The resin having a relatively fast reaction was injected by a low pressure machine into the airtight mold, which is RTM(Resin Transfer Molding). For the airtight tooling, a silicon O-ring was used for around the injecting hole. In consideration of multiple functional structure as well as measure stability during second process, various small metallic jigs were also designed and co-cured to be stood up to over pressure properly.
Mold assembly, resin injecting and curing with circulation water at 80℃ during 4hours were conducted. Heating time is suit for ideal combination between resin and glass fabrics, which was easy to release from the mold for from 4 to 6 hours. The released FRP body from the mold was finished by above procedure and continued to be coated and final assembly.
In conclusion, we developed FRP drive body for small boats to reduce weight, to protect vibration, to save production cost, to cut down maintenance charge, thus it became to have properties of higher resistance corrosion and longer lasting mileage than common metallic drives.