JimL wrote:
A note about webbing tie down, when spanning some distance (more than a few inches). ALWAYS twist free runs of webbing into a spiral (the longer the reach, the more twists required). This method keeps the flat strap from getting into high frequency vibration (and the horrid buzzing that goes with it!) caused by high speed air flow.
That vibration is transferred into the kayak, the rack, the rack mount hardware, and into the car. It is, effectively, high speed, repeated, tensioning applied to everything in the system. The kayak will be fine, probably....no bets on the rack, or rack mounts, or retaining hardware. You may, unfortunately, find the weakest link!
You may have noticed the spiral wound pattern on all modern automobile mast-type antennas? That's what the spiral is for...to keep the antenna mount from coming loose in the fender or roof, and prevent cracking of the body sheet metal. This is especially true when driving in rain (which adds a whole 'nother layer to the buffeting frequencies!)
Regards, JimL
You are correct. The vibration can cause failure easily. The webbibg will begin to tear at stress points. I have used the twisting method and have also tied a string around the midpoint in runs of webbing straps. That will also work to eliminate the vibration. At the very least, it can be greatly annoying.