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General Discussion & Feedback => Just Chat! => Topic started by: dentstudent on 03/08/2007 10:42:18

Title: How can you stop your roof bars and box whistling?
Post by: dentstudent on 03/08/2007 10:42:18
And I don't mean by teaching them to sing instead.....

As we're approaching the holiday season, and travelling by car is just one of the options, we've bought a roof bars and box. When we took it out for a test (to make sure I'd actually put it on properly and it wasn't about to fly off into some poor unsuspecting bystander's head), it was whistling in that kind of sitting in the middle of a hurricane kind of way.

Any top tips for whistling reduction?
Title: How can you stop your roof bars and box whistling?
Post by: Karen W. on 03/08/2007 10:52:50
Hummm I never thought about that as you formed kind of a tunnel under neath it that allows the air to whistle through... hummmm how much space is between the rack and storage space. Could you put some kind pf rubber deflector across the front of the rack that would attach to the front of rack and run all the way across and slightly around the corner do deflect the wind, like a small mud flap or something. pretty stiff rubber I would think! You've seen deflectors on the front of trucks, right? It should deflect the wind enough to lesson the whistle of it whipping under and through the rack I would think.. although I am no engineer just a thought!
Title: How can you stop your roof bars and box whistling?
Post by: Karen W. on 03/08/2007 10:53:23
Can you post a picture later of your rack?
Title: How can you stop your roof bars and box whistling?
Post by: dentstudent on 03/08/2007 11:03:08
It's a Thule Ocean 100 (I'm sure George Clooney's in there somewhere) with some Thule bars. I think I might have to jiggle it about a bit to reduce it as much as possible, but you're right - some sort of windshield would be a good idea!
Title: How can you stop your roof bars and box whistling?
Post by: Karen W. on 03/08/2007 11:09:17
Hey Stuart is this it?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi17.photobucket.com%2Falbums%2Fb73%2Fkarenw44%2FroofrackThuleocean100.jpg&hash=cf4b73da64c23700c38563f99d42d18c)

Here is another type roof basket for this thing supposed to add more space but the front has a solid bad I wonder if that would help?

Its called a:    
Inno INNO Roof Basket - INA501

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi17.photobucket.com%2Falbums%2Fb73%2Fkarenw44%2FRVInnoINA501.png&hash=669c4c18078e0e1c268a87e0d97cc964)
Title: How can you stop your roof bars and box whistling?
Post by: Karen W. on 03/08/2007 11:22:49
Do you have a cargo rack safari stlye or one like this? I found this in their overstock items they say it is lighter weight and more efficent..
Title: How can you stop your roof bars and box whistling?
Post by: dentstudent on 03/08/2007 11:26:18
Hey Stuart is this it?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi17.photobucket.com%2Falbums%2Fb73%2Fkarenw44%2FroofrackThuleocean100.jpg&hash=cf4b73da64c23700c38563f99d42d18c)

Yes, that's the one. It's mounted on 2 transverse bars much as the box appears to be in the photo.
Title: How can you stop your roof bars and box whistling?
Post by: another_someone on 03/08/2007 16:13:10
From what you say, you seem to be implying that the noise is wind noise, rather than the box vibrating on the mounting bars.

One question - can you isolate where the sound is coming from?  Is it in the tunnel between the box and the car, or the wake behind the box?  I expect the former, but ofcourse lots of theoretical possibilities might exist.

If this is the case, then the only course of action I can think of is trying to break up the air flow (maybe have lots of small pieces of foam suck onto the box, particularly on the underside, so the box, and roof of the car) so as to break up the airflow, and at most, what sounds might be created may be in the ultrasonic range.

One thing you will have to test out is to ensure that any change you make in the airflow does not create undue lift, and so impair the stability of the car while driving.

Ofcourse, if the whistle is predominantly in a single frequency (unlikely), you could always look at employing anti-sound to cancel it out (maybe a bit complicated, but a thought anyway).
Title: How can you stop your roof bars and box whistling?
Post by: dentstudent on 06/08/2007 08:16:03
Thanks for all the thoughts and replies. After some messing around with them at the weekend, it transpires that where the brackets fit ito the bars, a small aperture is left on either side of the bars. The wind goes across this like a flute, and the covering of this stopped the external noise. Now I need to work on the internal noise - boys that want to share the same toys!
Title: How can you stop your roof bars and box whistling?
Post by: Karen W. on 06/08/2007 16:38:27
Good job! LOL I am glad you stopped it. What did you cover them with?