Composite Davit Case Study
CSS' challenge was to design and develop a lightweight, durable, low cost, visually appealing FRP composite davit that could safely hoist 350 lbs from a boom tip positioned 12 ft above and 6 ft away from its base. In addition to a compact shipping size mandate, the davit had to be easily assembled by 2 or fewer people without the use of a lift or crane.
Several davit design configurations were presented to the Client; each design was backed by Finite Element Analysis (FEA) derived maximum load carrying capability and tip deflection predictions.
The Client selected a three (3) section davit assembly; two straight tapered hollow sections and a curved tapered center section with tight tolerance dry fit ferrule socket joints between sections to efficiently transfer load through the davit assembly. The lightweight individual sections and two different ferrule socket joint shapes made for ease of assembly. The multi-section davit design also broke down into a reasonably small shipping package.
Composite Davit CAD Model
The davit's composite layup designs called out conventional fiberglass fabric reinforcements for the straight section preforms and a combination of fiberglass fabric and braided sleeves for the curved center section preform.
Section preforms were infused using Vacuum Assisted Resin Transfer Molding (VARTM) in OML clamshell tooling to produce a smooth, well defined exterior surface. Tooling inserts were employed to define critical IML end detail such as the joint sockets.
The combined weight of the molded GFRP composite sections was approximately 90 lbs making the individual sections easy to handle despite their size. Field assembly consisted of bolting the bottom section to a steel base, assembling the center and upper sections while standing on a ladder, and attaching several davit function components to the composite structure.
Composite Davit Proof Test
The multi-section composite davit design passed static and dynamic proof testing with test loads exceeding 3 times the designated safe operating load and tip deflections well within design limits.