After tossing around the idea of a trailer to carry our two Pungoes on my new Mazda 3 hatch, I’ve decided to go with a roof rack. On my previous car I had a Thule which worked fine, but those square bars were so noisy that I couldn’t open the sunroof while the rack was on.
Any recommendations for something quieter? I see that Thule now has aero bars-- are they better?
How are the round Yakima bars?
Anyone seen/tried WhispBar?
http://www.whispbar.com/
I have never seen them
but they look very similar to the stock units on my Hummer. My bars do not make any noticeable noise at all. However, my wife has Yakima bars on her Hummer and it is quite loud. We added the fairing in hopes that it would help but it only made it worse when the sunroof was open. I think the oval bars are great for strength and wind noise.
I have yakama round bars on both my
truck and my car and I never get any noise.
A few years back, I drilled a few holes in the bars to mount some other tubing (a stabilizer rack for a 23 foot long kayak) and when I didn’t have that rack on and the holes were open, I would get a whistling.
I covered the holes with tape and now they are quiet again.
I have always liked the round bars, since there is so much less surface to scratch the wooden gunnels on our canoes when we are sliding them on and off.
Cheers,
JackL
One solution that worked for me
on Yakima bars was to wraps a long bungee cord, spiraling around each bar and hook the ends. It only needs to wrap around each bar maybe 10 times to make a difference. This apparently breaks the air flow pattern around the bar and cuts the noise down significantly - at least in my case. Very inexpensive thing to try
Avi
i have thule and
never have any noise. sometimes it’s a little loud when the kayak is in the rack, but i just don’t open the sunroof with a boat on the top.
force a transition to turbulent flow
Whistling can occur because you have laminar (streamlined) flow of air over your bars. Thus the solution is to “roughen” the surface of the bars to create a transition to turbulent flow, which will reduce whistling. The bungee suggestion above will work. I have used many other solutions over the years, such as a small bead of caulking on the bars, or a piece of twine wrapped around them, or just erratic layers of duct tape.
I’ve used a couple of Windjammer
plastic airfoil add-ons. Two is enough to cut the moaning. They are overpriced, but they probably cut wind resistance a bit.
Same experience as g2d
NM
Jim
All turbulent
– Last Updated: Apr-14-10 10:11 PM EST –
Actually, at highway speed, flow over roof rack bars will be turbulent, whether or not they have a wrap. The wrapping around the bar breaks up the turbulent (but organized) Von Karman vortex street being shed by a cylinder.
The street consists of long vortices shed alternately from the top and bottom of a cylinder. This is what causes the noise - it's only audible when the vehicle speed and cylinder diameter is such that the vortex shedding frequency is audible (e.g. at low speeds, you usually can't hear anything). Spiral wrapping on the cylinder effectively disrupts the organized vortices, stopping the noise.
Here's a nice photo of a vortex street behind a cylinder, flow left to right:
http://www.math.ucdavis.edu/~fannjiang/home/tea/221/karman-streamlines.jpg
Examples in nature, large scale:
http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/vonKarman_vortices.shtml
SQUARE OR ROUND
Those bars ALL make that danm sound. We have a 3 hatch, but our hauler is a 6 -and for that -and the preceeding haulers we’ve had, we slit pool noodles lengthwise and put them over the bars, taping them to the bars with clear packing tape.
-It cuts the howling;
-It provides a nice, padded surface for your boats (we now cradle ours because they’re glass & vacu-thermo-plastic, not roto poly), and you can load most plastics and canoes upside down without needing cradles or Js;
-It allows you to much more easily spot your car in a large parking lot. (A small one, too!)
As you’ve seen, this is just another approach, but our favored one, for eliminating wind howl as we tote the boats to & from our fun as we
PADDLE ON!
-Frank in Miami
^this works
Turbulent, laminar…all I know is it works great.
lucky here
my Yakima bars are very quiet with no whistling at all even w. the sunroof slid back.
Added a fairing cuz I found one on sale ($17 bucks at Moosejaw, yowza!) but it was more about how cool it looked. Maybe it helps a little w. aerodynamics, dunno.
Thule! No noise!
I have Thule bars on a Volvo wagon and use a fairing. I have no noise. I think the vehicle design has a lot to do with the noise issue. On a Hummer what wind noise when you your knobby tires roar!!
I don’t like the Whisper Bar test
It’s not actually proving any bar creates noise. The wind comes out of the nozzle, across a bar, then into an air-recycler. It’s the fact that the bar disrupts the air flow so that it can’t enter the recycler perfectly that is creating the noise. The Whisper Bar is perfectly tuned to align the air flow. I bet in real world applications, like on the roof of a curved vehicle, that the designers haven’t taken into consideration the air flow over the vehicle. And if they have, how useable is the crossbar if it is at an angle to align with the air flow. Further more, if the vehicle speed changes, so does the air flow over the vehicle, so you could have noise at low or high speed.
Having installed hundreds of roof racks, I can tell you from experience, it is the vehicle and where the bar is positioned on the vehicle that creates noise, not the actual shape of the bar.
Look at factory crossbars. Often there is a notation on the rails that warn you not to position a crossbar forward of a certain position. That is because behind that position, the crossbar is in the slipstream, and out of the wind.
Having installed tracks on my vehicle, I can tell you the same is true. Too far forwards, and I hear noise. Move it back a few inches and it will be absolutely quite.
Fairings help direct the air flow over a bar. Because I want my crossbar far forwards on my vehicle, I have opted to use a fairing. However, the fairing only covers the same width as my vehicle, not the bars that extend from the side (using the new Yakima 86" crossbars). This bar in the forward position, but out in the “clean,” undisturbed by my vehicle air, doesn’t make any noise. Again, this reinforces my argument that the position of the bar is more important than the actual bar shape.
But you know that, for some cars, Yakima
and Thule specify exactly where the bars have to go. If they are placed farther back or farther forward, the clip geometry may not work properly.
As for bar shape, if the bars were shaped like airfoils rather than being rectangular or circular, they would be much less likely to cause noise. Evidently this is too much of an engineering challenge for Thule and Yakima.
spacing
An airfoil design wouldn’t be effective at all when it comes to mounting gear in my opinion. It’s like Yakima vs. Thule… you can’t space Thule bars but so far apart on a curved roof before they face away from one another. Yakima can be spaced anywhere (within their specs) and you can still mount a device evenly on the bars.
An air foil design would only work on a flat roof such as an SUV or wagon.
Simple fix for whistling is to wrap a shoe string around the bar in a spiral from side to side and tape it down with black duct tape.
I know the difficulty, but such bars
have been offered in the past.
Yakima’s Windjammer clip ons, while too short and overpriced, are one way to achieve an airfoil shape. I use them on my bars, where they fit between the fore-and-aft struts.
bars
I’ve got the newer thule aero bars on my car and yes they make noise! I can hear some windnoise from the roof but there’s also some noise coming from the door brackets - the door weatherstripping has to go over the bracket which leaves some air space as the stripping goes over the plate. No way to avoid that. I’d say the windnoise is no better or worse with the aeros than the standard thule bars.
My last car was a saab that had built in rack door grommets (no bracket to go over the weatherstripping) - they were much quieter (used regular thule bars). Great car and surfski hauler when it wasn’t in the shop. Tried a fairing too but it just looked cool - no noticeable noise improvement.
With just the Yak Bars
a very loud roar on my PU truck mounted as far back as the door jamb allows. Boat on and it is whisper quite. More an annoyance than anything but always loudest when I have a headache.
Side-track
Seriously - you folks drive two Hummers?!?!
I find filling up my hatchback to be pretty costly.
I once put three canoes on an old Dodge Omni. I wonder how many canoes could be stacked on the wide flat roof of a Hummer, given enough straps and rope.