Raft on a Highline: Loads and Trim

This study examines the loads associated with the positioning of a 4.5m raft on a high line in moving water. Testing was conducted within a flow-calibrated channel demonstrating representative stream velocities typical (0.6 – 5.4ms/ also MPH) of those encountered during water related rescues. The raft was positioned from a high line mid-stream, and a load cell was utilised to collect force/time data. The independent variables of trim (relative positioning of the load within the boat) and average stream velocity were investigated. The findings challenge assumptions regarding the impact of trim on the loads within a highline, the relationship between flow rate and loads on highline and make recommendation for training and practice. The study contributes to understanding the loads placed on high lines by representative rafts during operational rescues. KEY WORDS: High line, trim, force, current vector, water rescue training.