Bubbling / Shuddering Tonneau cover while driving

[Back2Trucking]

I have little experience with tonneau covers, but I wonder if the emphasis on air infiltration that I see in many of the posts might be overblown (yes, bad pun). But seriously, even if the truck bed/box and cover were perfectly sealed, there would still be a tendency to billow because the air below the cover would be still and the air on top would be flowing. That reduces the pressure on top, creating lift (as happens with an airplane wing where the air on top flows faster than the air below). That would contribute to the billowing. The flapping would come from fluctuations in the air speed and turbulence of flow over the cover (the shape of the cab and bed/cover is not especially aerodynamic and the flow will change as truck speed, wind speed and direction constantly shifting.
That doesn’t mean that air infiltration doesn’t contribute to the problem. Maybe what’s needed is MORE air flowing under the tonneau to equalize pressure — maybe with an air scoop built into the side of the truck bed, or a hood air scoop installed in the middle of the tonneau, facing forward? (Yes, I’m kidding about that.)

Sponsored

 

[Scupking]

I have a Gator SFX tri-fold. It flaps around. It has since day one 2 years ago. Does it bother me? No. Can I hear it flap around. No. It's a soft cover it's going to flap around...

 

[Bilbo_B]

I have little experience with tonneau covers, but I wonder if the emphasis on air infiltration that I see in many of the posts might be overblown (yes, bad pun). But seriously, even if the truck bed/box and cover were perfectly sealed, there would still be a tendency to billow because the air below the cover would be still and the air on top would be flowing. That reduces the pressure on top, creating lift (as happens with an airplane wing where the air on top flows faster than the air below). That would contribute to the billowing. The flapping would come from fluctuations in the air speed and turbulence of flow over the cover (the shape of the cab and bed/cover is not especially aerodynamic and the flow will change as truck speed, wind speed and direction constantly shifting.
That doesn’t mean that air infiltration doesn’t contribute to the problem. Maybe what’s needed is MORE air flowing under the tonneau to equalize pressure — maybe with an air scoop built into the side of the truck bed, or a hood air scoop installed in the middle of the tonneau, facing forward? (Yes, I’m kidding about that.)

This is exactly what I feel is happening. Anyone can feel this happening at times when they are traveling behind a semi-tractor box. (Not that I recommend tailgating )but not only can one increase mileage by 'drafting' as race cars do but behind the semi-tractor box you can feel the buffeting causing your vehicle to jerk just a bit to the left and right.

I have some experience with sailing and this same effect with a badly trimmed sail is called luffing.

One way to reduce this is to mount spoilers on the cab to direct air from the roof or sides of the cab behind the rear window. The tonneau scoop might work but the only thing that a hood scoop would do is supply weight and provide a hole to neutralize air pressures. negative is that rain would come in. I still believe that the Tonneau is essentially sucking air into the bed via any drain holes and especially from the area to the sides of the tailgate.

I'm going to try adding a pipe insulator or pool noodle to my cross bars. This can raise up the fabric to about where it ends up when moving at speed. Alternatively, I may go to Home Depot and buy one of their nicely arched (warped) 1X2 pine boards, trim it down for weight and try replacing the cross bars. They're just mounted with velcro straps anyway.

 

[Back2Trucking]

Ah hah! A creative use for those awful warped boards — I like it!

 

[Bilbo_B]

I I haven't tried it at speed but I suspect that for a 1.25@ investment at the dollar store it reduces the fluttering.

 

[Maxximus]

I really appreciate all the positive feedback. For those that say it's a cover and it's going to flap, like I stated at the beginning of this thread, I have owned many trucks with many different brands of covers. It's the manufacturing of the entire unit that either makes it good or bad and whether it allows the cover to flap terribly while driving. The better companies have figured it out. Having the cover secured to the crossbars stops all the flapping. Allowing it to flap around and raise horribly is not only going to wear it out prematurely but in my opinion it just looks terrible seeing it in my rear view mirror as well as what other people see as you're on the road, and lets face it, we all want our vehicles to look awesome or we wouldn't spend all the money we do on accessories right? Thanks again!

 

[Bilbo_B]

I really appreciate all the positive feedback. For those that say it's a cover and it's going to flap, like I stated at the beginning of this thread, I have owned many trucks with many different brands of covers. It's the manufacturing of the entire unit that either makes it good or bad and whether it allows the cover to flap terribly while driving. The better companies have figured it out. Having the cover secured to the crossbars stops all the flapping. Allowing it to flap around and raise horribly is not only going to wear it out prematurely but in my opinion it just looks terrible seeing it in my rear view mirror as well as what other people see as you're on the road, and lets face it, we all want our vehicles to look awesome or we wouldn't spend all the money we do on accessories right? Thanks again!

I agree that having the cover secured to the crossbars will make a lot of difference. I'd rather not sew anything but is there a glue that would hold a pocket for the crossbars in place?

Sponsored