car top carrier vibration problem

Just bought a Hobie Revolution Kayak, 13', 58 lbs. Have a Mazda MPV with
built in car rack. When we put the kayak on top and securely strap it
down I was shocked by the vibration noise at speeds > 30 mph. Can't see
any noticable vibration on the kayak when we're traveling.

We have the 8" foam blocks over the car top runners and 2 rachetting
straps front and rear. Different strap tensioning seems to have only a
very slight effect. At 40 - 45 mph the vibration noise is very un-
nerving.

Is this vibration we hear normal and is there any way to reduce or
eliminate it?

TIA

Scotty wrote:
> Just bought a Hobie Revolution Kayak, 13', 58 lbs. Have a Mazda MPV with
> built in car rack. When we put the kayak on top and securely strap it
> down I was shocked by the vibration noise at speeds > 30 mph. Can't see
> any noticable vibration on the kayak when we're traveling.
>
> We have the 8" foam blocks over the car top runners and 2 rachetting
> straps front and rear. Different strap tensioning seems to have only a
> very slight effect. At 40 - 45 mph the vibration noise is very un-
> nerving.
>
> Is this vibration we hear normal and is there any way to reduce or
> eliminate it?
>
> TIA

If this is the roof drumming, congratulations! You've found the natural
frequency of the roof, driven by the turbulence of the boat. ;>D This
is not easy to fix without replacing the rack. The most direct fix
(maybe...) is to make a support system that rotates the boat 90 degrees
so that it sits on edge. An example:

http://www.thuleracks.com/product.asp?dept_id=10&sku=835PRO

No guarantees... I would make a makeshift setup to try before I
committed, unless I could get a promise of a refund.

You might also ask over on the MPV club forum.

http://www.mpvclub.com/