Wave height from planing and semi-planing small boats

Abstract

The increasing number of small boats has raised concerns about their effects on the environment, particularly their waves. Bank erosion is one of the foremost concerns of boat waves but disruption of habitat, resuspension of bottom sediments, and damage to aquatic plants are other areas of concern. A large programme of field measurement of boat waves was conducted on Johnson Lake in Alaska to evaluate boats typically used on the Kenai River. The boat wave study compared wave characteristics of four boats under a variety of loadings, speeds, distances and motor powers. Over 400 tests were run on Johnson Lake with each test providing wave measurement at four locations. Two measures of waves and two types of tests were used in the study. MAXPOW was the wave height at the maximum power of the motor. MAXWAV was the maximum wave height produced by the boat which required runs at a range of speeds to determine the MAXWAV. While the MAXWAV data herein have considerable scatter in magnitude, the conditions at which MAXWAV occurs are consistent from boat to boat. To prevent generation of maximum wave heights, small boats should operate as far as possible either above or below length Froude number of 0.6, displacement Froude number of 1.3, or beam Froude number of 1.0. A general boat wave height equation was developed for the four boats based on boat speed, volume displaced by the boat and distance from the boat, and are applicable to semi-planing and planing boats based on MAXPOW and MAXWAV data. The predictive equation for V-hull boats was compared to independent data not used in the development and was found to be in agreement with the data. The predictive equation is limited to depth/boat length greater than 0.35. Published in 2005 John Wiley & Sons, Ltd.