Builders' Forum Archives
Re: cartopping long boats
Posted by Jim E on May 9, 2007
Umm.. Firstly, the kayak in water is only partly in water, which has a stabilizing effect on it's motion. On the cartop it's fully immersed in a 70-mph fluid. Secondly, the forces are proportional to the square of the speed. Thirdly, the kayak's long axis is accurately in line with the waterflow, whilst on a car it's always skewed. the airflow is not straight, but flows over and around the car. This causes a fierce lifting force which tries to peel the kayak off the rack. Mercedes did some measurements using windsurfers in the 1980s, and discovered that the lifting force was enough to dangerously interfere with the car's handling at high speeds.
In summary: Use bow and stern lines, and drive a bit slower than you normally do.
In Response to: Re: cartopping long boats by Laszlo on May 9, 2007