Truck Box Caps: Do they help with drag

[herbpagel]

I found over the years that wind direction was a big factor in drag and gas mileage. When I bought a new FR travel trailer with the aerodynamic shaped front, I was amazed at the difference. Adding a topper to the truck never made that much difference.

[Dave Lyon]

[QUOTE=BriaBeck;2036700]I'd say that 250-300 lbs is in the ballpark for a good quality topper like Leer, Sportsman, etc. Fiberglass isn't lightweight.


Yep.....I didn't realize how heavy my Leer was until I removed it.....3 of us could hardly lift it.

[privateer]

My fiberglass top (6.5' bed on Chevy 2500) weights about 200# and has additional hardware so that all windows open (feature will never do without again).

It does make a difference depending on what towing. When I pull my 18' boat, yes the wind is directed over the boat - I can tell as no bugs or trash on my boat windshield. When towing one of the box trailers or my toy-hauler -- I can see the bug line across the front of the trailer. toy-hauler although enormous compared to box trailer does have an air splitter on the nose so is a little better.

does not take a degree in aerospace to simply see that if you can get the airflow over and around the vehicles to be somewhat smoother, you will have a more efficient vehicle. And then we can also discuss the topic of laminar flow and turbulence if you wish...

[tsnell]

You are worrying about a gap that you can't close enough to benefit. Bare pickups do benefit from covering the bed or opening the tailgate. When you put a large object behind it you can only try to smooth the airflow between them.

You are, however, forgetting that the big block you are towing creates drag from the air burble behind it. That is why you see air fairings on the back of the trailer on some of the OTR commercial trucks. They want better milage.

A couple of people have mentioned AirTabs which I personally use on my 2018 FROG class A driveable block. I noticed improvement in handling, an improvement in mileage, and know from 18 years on my previous coach they do help with the mileage. The help you can get is going to come from the back of your trailer.

Smooth the airflow behind your rig and you will improve your mileage. FMCA magazine had an article about AirTabs in a January issue about 2012 - 2015 ( I don't remember which year) where a guy in CA did a recorded test while installing them. He gained 1/2 mile to the gallon with no other changes.

I suspect that you can gain a little help from putting them on the side of your bed at the back to smooth the airflow between your truck and trailer. Some on the top rear of the cab couldn't hurt. The weight to cover your truck and your trailer would be about 5 pounds.

They aren't cheap but they can save you money. Check the website and do your homework, then make your decision.

[NJKris]

Bare pickups do benefit from covering the bed or opening the tailgate.

Studies have debunked this.

[Theo]

Originally Posted by NJKris

Studies have debunked this.

X2.

A memorable test debunking this myth was deftly executed by The Mythbusters in Episode 64. However, they did get good results from using a mesh tailgate.

[tsnell]

Mesh tailgate - open tailgate, what's the difference? Bare pickup - not towing, I will have to check out the Mythbusters episode. Tonneau cover might not improve mileage but it would stop the airflow from hitting against the tailgate causing drag. Why would you want to have air hitting a closed tailgate?

I also mentioned that the big gain would be from having reduced drag at the back of the trailer like the OTR truckers do. Push 18 wheels for a while, that is an education

[BriaBeck]

Originally Posted by tsnell

Mesh tailgate - open tailgate, what's the difference? Bare pickup - not towing, I will have to check out the Mythbusters episode. Tonneau cover might not improve mileage but it would stop the airflow from hitting against the tailgate causing drag. Why would you want to have air hitting a closed tailgate?

I also mentioned that the big gain would be from having reduced drag at the back of the trailer like the OTR truckers do. Push 18 wheels for a while, that is an education

Aerodynamics isn't always obvious to the naked eye, or one's intuition. Air doesn't always behave as we think it does, or as we think it should.

[JohnD10]

This was all hashed out here a few months back...

I remember that it was proven that a pickup gets better gas mileage with the tailgate up that when down or removed

They are designed to flow the air over the top of the cab and over the top of the tailgate...

A flat cover doesn't help, but a topper does.

Don't ask me for a link...

I'm sure Google can find it!

[hshaynes]

Had one on my Titan. Other than additional weight and cost the only down side I found was the restrictions when hauling things. No tall stuff, cant stand in truck bed, limited cargo capacity. Will not put one on another truck. And it did nothing for gas mileage.

[NJKris]

See with your own eyes a wind tunnel test to show how turbulence/drag plays out with tailgate up or down.

https://www.youtube.com/watch?v=oEkiDsVGr9c

[SailorSam20500]

Originally Posted by JohnD10

A flat cover doesn't help, but a topper does.

Guy in the wind tunnel test u-tube said that a tonneau cover is better than an open bed, at least on a F-150.

[Crusader 816]

When we bought our 5ver I had to sell my cap since it wouldn't be used and I miss that cap every day.

[JohnD10]

Originally Posted by Crusader 816

When we bought our 5ver I had to sell my cap since it wouldn't be used and I miss that cap every day.

Same here ..

Thinking about going back to a smaller TT and getting another topper.