Roof Top Tent Fairings - Anyone Using them? Any improvement in MPG?

[Bravo1782]

Hey Everyone!

I've got a CVT Mt. Rainier that i have mounted to a Vantech P-3000 Topper Rack of the topper of my 2011 F-150 Crew Cab Short Bed. I usually get a 2-3MPG hit running the RTT, and I'm curious if it's possible to mitigate that with a fairing? Does anyone make anything that would work, or is this going to have to be a creative DIY project? Any suggestions?

As a side note, I'm considering switching to a Leitner ACS system which would bring the tent lower to bed, but still above the roof line. The tent is too big to run with a lower-profile bedrack (without sticking WAY off the back of the 5' 6" bed) and I'm not interested at downsizing to a smaller tent at this time.

 

[Theoretician]

I added polycarbonate roofing panels to the sides of my leitner rack to enclose the bed and that added 15% back to my gas mileage after driving around with just the frame and tent, so it's not impossible to see a gain. I wouldn't expect to see a whole lot from ordering the airflow over the top though.

I have been thinking about adding such a fairing to mine, but more from the perspective of concealing and protecting some lighting and antenna up there and the aerodynamics would simply be a bonus. I see no reason why I wouldn't use the same polycarbonate roofing panels again for that.

 

[ghostshaper]

I've been thinking about mounting my recovery boards at an angle to a cargo rack over the cab. My other idea is to use foam to make a triangle fairing that would velcro to the tent cover.

 

[Kmrtnsn]

A fairing in front isn't going to do anything. It's the dirty, disrupted airflow BEHIND your RTT and vehicle that is causing the increased drag and diminished MPG.

 

[Bravo1782]

That's an interesting point. So what can be done about it? Anything? Or am I just stuck with crappy fuel economy if I run it "full height?"

 

[fredgoodsell]

That's an interesting point. So what can be done about it? Anything? Or am I just stuck with crappy fuel economy if I run it "full height?"

Something utilizing this concept? http://www.stemco.com/product/trailertail/

 

[Finlay]

A fairing in front isn't going to do anything. It's the dirty, disrupted airflow BEHIND your RTT and vehicle that is causing the increased drag and diminished MPG.

This runs contrary to my experience. The fairing not only helps with MPGS (especially in a headwind) but also drastically reduces the number of bugs splattered on the tent cover.

 

[Kmrtnsn]

This runs contrary to my experience. The fairing not only helps with MPGS (especially in a headwind) but also drastically reduces the number of bugs splattered on the tent cover.

View attachment 418726

View attachment 418725

It's not my principle, it's Bernoulli's.

 

[Finlay]

You are correct that fluid dynamics are complex and often non-intuitive. I had a class on it as part of my engineering degree. Even our best computer simulations require modeling to confirm efficacy. It's a super complex field.

The point I was making - A fairing may do the job. It very clearly did in my case. And it's not a super expensive mod - mine cost ~70 bucks - and it's highly unlikely to make the instant problem worse. And if it does, it's easy to go back.

To be sure - when I attached the fairing, my goal was bug gut reduction. I was less concerned with the MPG loss, and thought the fairing was too far forward to have any positive effect on that. But truck actually does 2ish better with the RTT/Fairing and about 400 lbs of gear (slight rearward squat) than it does unloaded.

 

[spagthorpe]

I'd be happy if I could quiet down the wind noise from my rack. It's just enough over the driving area that I get a pronounced buffeting sound.

 

[Chili]

You are correct that fluid dynamics are complex and often non-intuitive. I had a class on it as part of my engineering degree. Even our best computer simulations require modeling to confirm efficacy. It's a super complex field.

The point I was making - A fairing may do the job. It very clearly did in my case. And it's not a super expensive mod - mine cost ~70 bucks - and it's highly unlikely to make the instant problem worse. And if it does, it's easy to go back.

To be sure - when I attached the fairing, my goal was bug gut reduction. I was less concerned with the MPG loss, and thought the fairing was too far forward to have any positive effect on that. But truck actually does 2ish better with the RTT/Fairing and about 400 lbs of gear (slight rearward squat) than it does unloaded.

I bet that gap is really what is helping you.. Have you seen the way air flows in a pickup bed that is empty with the tailgate up? It causes a little bubble circulation of air in the bed that keeps the majority of the airflow from being interrupted, and the air can flow right over the tailgate. I bet you are getting the same effect between your fairing and the tent. The squat would only enhance that effect allowing more air to clear the front of the RTT.

 

[MANUCHAO]

I built my own to deal with wind noise...
don't know if it helps with fuel efficiency, but my RTT is bug-splatter free and wind noise is minimal.

Fairing follows the same 47º angle as the windshield...

 

[nonhog]

A thread I started on Eco Modders..... http://ecomodder.com/forum/showthread.php/roof-top-tent-flow-question-34433-4.html

I'm still scratching my head.

A very good overlay program(on that site) to get the flow best at the rear as previously mentioned.

 

[acg]

This is for those with a hard shell RTT.... I mounted a Road Shower in front of my Baroud tent. It acts as a wind fairing. Certainly less wind noise at highway speeds. The Road Shower with its rounded front profile reduces the airflow going between the roof of the Land Rover and the bottom of the roof rack. There is about 0.5 MPG improvement in gas mileage.

 

[80t0ylc]

This is for those with a hard shell RTT.... I mounted a Road Shower in front of my Baroud tent. It acts as a wind fairing. Certainly less wind noise at highway speeds. The Road Show with its round front profile reduces the airflow going between the roof of the Land Rover and the bottom of the roof rack. There is about 0.5 MPG improvement in gas mileage.......

I like that shower & your idea! I recently added a front extention to my modified Yakima roof rack system that runs in front of my CVT hard shell that, I think, might be able to accommodate that shower. Thanks for posting!