The trailer is a 24ft Haulmark car hauler. My truck is a F250 with just a tonneau cover on the bed. Would putting a camper shell on the back help with gas milage while towing? My thought is that is will since the air is much higher coming off the shell than the top of the bed, there may be less resistance. Thoughts, experiences? TIA,
No, for two reasons. 1. The wind still has to travel over the camper, sure it is more sloped than the trailer but it's almost as bad. 2. What slight gain you may get from a more sloped camper vs. the flat front trailer will be more than offset from the extra weight of the camper itself. The more weight, the harder to push the rig around.
I think I used the wrong wording, I meant to ask if a truck "cap" would help milage, not a camper. Something like this, http://www.snugtop.com/products/expo.php
Hmm thats a good question. You would think it would help because the air wont go down to the bed and back up over the trailer, just strait over your truck and over the trailer.
I can say yes it will. I had a 96 F250 that came with a high top (about 6" higher than the cab) Glasstite cap. I had the same thought - since it was high, the air flow would already be higher when the trailer hit it. I used it for 2 years when towing my RV trailer on vacations to North Dakota and to Colorado. I left it off last summer, and it cost me an extra 1 mpg to run with out it. I have a different truck this year, and it also has a cap. Lesson learned - I will leave the cap on for vacation this summer.
assuming the shell is even with the top of the cab and stays flat or elevates to the top of the trailer, then absolutely it will. the smoother you can make the air run over the total rig the better off you are. Kenworth's website has some great stats on the percentage fuel milage improvements you get by improving how the air flows over your rigs appendages. Years ago one of the car mags did a pickup road test comparing mileage with a) tailgate up, b) tailgate down, c) tonneau cover, d) cab height truck cap and guess what. The cab height cap was a clear winner and they weren't even towing. Its all about keeping the airflow smooth. Remember a jumbo jet is huge but it still flies.
One of the diesel mags did a test on this issue. The Dodge gained the most, I think around 1 1/2 mpg. The problem with tonneau covers is they create the "station wagon effect" of trapping air against the rear window which slows the vehicle down. When Bill Elliot came out with his slope-backed Ford he ran away from the field. The other teams went nuts trying to figure out where his advantage was because he always cleared post-race inspections. Took 'em all year to find it.
