Are your tie down straps made of some flat webbing material? If so,
the vibrations can be eliminated by putting a few twists in each
strap when you are snugging things down, rather than trying to keep
the straps flat and straight. The twist lets the straps slip the
wind evenly rather than letting them act like a wing.
Flat is OK where the straps bear on the hull, but between the hull
and the edge of the car roof, where the straps are in the slip stream
and acting like a wing, put in a few twists. That will keep the
straps from vibrating and you can then do without the extra bungee
I've used this trick for years, both when transporting cartop boats
and when cartopping boatbuilding materials. It works every time. I
often drive at Interstate speeds with boats or materials on the roof
of my Buick Century (probably not too smart) and there is no
vibration from my tie down straps at those speeds, when I put the
twist in the tie down straps. If I forget the twist the straps let
me know about it at 30 mph.
--- In Airolite_Boats@yahoogroups.com
, "Elliot Mednick" <elliot@...>
> I do find that the straps themselves vibrate, so I use a bungie to
> toward each other at the sides, on both sides, which adds enough
tension to eliminate the vibration.