Angle of truck with camper vs mpg?

gbopp wrote:
Just my opinion, I don't think you would see enough of a difference to really do a good calculation.

Ditto. Maybe .1-.2 is all I'd expect, but there's so many variables, that a truly scientific analysis would be pretty much impossible to achieve.
Things like temperature, variations in humudity, wind, fuel.

I included a thread that included Sleepy's thread earlier, but here it is again. http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/23645900/srt/pa/pging/1/page/1.cfm

Potential Fuel savings/yr (L)

OEM Side Mirrors
-938

OEM Bug deflector
-903

OEM fender mirrors
-588

Blocked Engine Inlets
6

Sun Visor/windshield brow
54

Truck and trailer hubcaps
120

“Deer” Bumper
120

Wrap-around splash guards
292

Prototype roof deflector filler
825

Gap reduction of 10 inches
982

OEM cab tank skirts
1596

OEM Side extenders
2499

OEM Roof Deflector
4318

DWeikert, I agree about those 2 areas being bad for air flow. Semi truck tractors sometimes have air foils added to the back of the cab on each side, to help direct air around the front wall of the trailer, which is wider than the cab of a conventional tractor, similar to our campers being wider than our pickups.

There is a 3rd area, between the cab roof and camper overhang, which member Sleepy developed an air foil for a few years ago. I think his write-up was saved in the truck camper help section.

Forum won't let me quote

I agree, Silversand!

I have doubts lowering the nose of the truck would make a measurable difference in mileage. I have thought about this though and it seems, on my camper at least, I have 3 main wind resistance areas that I'd like to deal with. The first is the camper that extends beyond the cab on either side. The other is the rear wrap around the tail lights.



Both of those represent a vertical surface with the air hitting it at a 90* angle. Adding some sort of rounded surface that deflects instead of impacts the air is bound to help, or maybe something like the panels they're hanging under the trailers of 18 wheelers deflecting air away from the rear axle.. The other and most likely worst offender is the huge area of negative pressure directly behind the camper as your driving down the road. Some deflector along the side and/or roof of the camper would direct air into that low air pressure space and significantly reduce drag.

I agree that you likely won't see a measurable increase in fuel mileage from the truck riding a couple inches higher or lower in the rear.

....I think that your proposed aerodynamics mitigation would probably be completely swamped by numerous other issues: driving style (good/bad); perfect tire inflation; perfect/terrible wheel alignment; perfectly/imperfectly tuned engine; weather conditions (extreme cold, strong headwinds, etc, etc, etc); terrain slope (flat/hilly/downright mountainous); and many, many other issues.

I think that it would be practically impossible to tease-out any canted rig aerodynamic benefits from all the above situations (unless you were testing in a 100% controlled environment).

Trucks and SUV's are built high in the rear when unloaded, so that when they are carrying a load, they ride level, in theory. In reality, the manufacturers do not spec enough rear spring rate in the trucks and they end up riding low in the rear, rather than level. Anyways, aerodynamics isn't the reason.

I agree that you likely won't see a measurable increase in fuel mileage from the truck riding a couple inches higher or lower in the rear.

Keep your tire pressure up, your road speed down, your foot out of the go pedal and your engine tuned up and maintained and that will be the best increase in mpg you will experience with a truck hauling a camper, which has the aerodynamic characteristics of a brick wall going down the road.

gbopp wrote:

jimh425 wrote:
I'm not sure why I'm not supposed to be able to measure it, but I'm thinking I can measure as well as I'm measuring now. ;)

You can measure the mileage as well as you are now measuring it. :)

I just don't think it will make enough of a difference to accurately show an increase (or decrease) in mileage if you change the angle of the RV.

But, if you raise the rear you will be going downhill all the time so, it may help. :B

Probably be harder on the brakes also. May have to install an Exhaust Brake. :D

jimh425 wrote:
I'm not sure why I'm not supposed to be able to measure it, but I'm thinking I can measure as well as I'm measuring now. ;)

You can measure the mileage as well as you are now measuring it. :)

I just don't think it will make enough of a difference to accurately show an increase (or decrease) in mileage if you change the angle of the RV.

But, if you raise the rear you will be going downhill all the time so, it may help. :B

I think you can see the angles in the picture below. I'm not sure why I'm not supposed to be able to measure it, but I'm thinking I can measure as well as I'm measuring now. ;)

Older thread that includes the sleepy air deflector.