I would imagine that the underside of something like this vehicle is already extreamly smooth, after all the engine is in the rear, right? so why would they creat a bumpy underside?
tires should be 80-100psi tires, you might be able to find some low rolling resistance tires, altho tires for that thing at all are going to be hundreds of dollars each I suspect, I like the hub cap idea, the moon hub caps might work, but remember to cover the back side of the wheel as well, not just the part you see.
not sure if air tabs are enough, you have a flat rear end that is like a wall for air to come around, get some discounted plastic christmas trees, and plant them with the tips pointing back, the needles will grab the passing air, and pull it in, creating a rear boat tail in the air, reducing uncontroled rear turbulance.
of course the biggest thing you can do to improve your mileage, is ask your self the question "why not stay where I am"
The worst thing about campers that I've noticed (other than the huge frontal area) is all the CRAP sticking out all over! Look on top- there's probably one or two big ol' a/c units up there, plus luggage racks, ladders, skylights, antennas, huge mirrors, brackets for this 'n' that... all that junk is certainly creating turbulence over and above the form drag that the square box already has.
Seconded. Maybe some kind of spoiler or cover to move the air around all that stuff? I coulda swore I saw a chopped RV the other day, but maybe it was just my eyes playing tricks. I can think of worse uses for a rolled salvage title.
Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
The underside of an RV is an an aerodynamic nightmare, since it is a mismash of water and holding tanks, the undersides of the "basement" storage bins, various framing members, etc., so underbody panelling would help a lot. Also wheel well skirts, wheel spoilers, front and side skirts, and low drag fairings around the AC unit, skylights, and canopy struts. Also the interior of a sturdily designed tail cone could be be used for additional storage space (which is always at a premium on an RV).
Another area for drag reduction would be the radiator. If they also made your RV in a version with a gasoline engine, they probably sized the radiator intake for the worst case heat output for the gas engine. Since a diesel engine produces less heat for the same power output than a gas engine, you could probably get away with a smaller radiator intake. The thing to do would be to start taping over parts of the intake with clear packing tape until you start to see a temperature rise on your engine's temp gauge (then open up the intake somewhat at that point). After you have determined your engine's exact intake air cooling requirement under your worst case driving situation of hot days and/or steep climbs, you can make a permanent grill block for the intake. A further refinement of the grill block would be to install louvers in the grill block that you could adjust from your driver's seat to reflect current cooling requirement (similar to adjusting cowl flaps on an aircraft).
I don't really want it to look too freaky, so no nose cone or giant wings!
Crap, there goes my grafting a Corvette nose cone idea. What about small wings?
Seriously, at the speeds that you'll be driving (most of these that I see are going something like 55-60 the big square nose probably won't be as big of an issue as you might think. The trick will be to reduce the other "parasitic" drags; from the wheels/tires, tire/road friction and the underside of the vehicle. I see in the photo that that particular one has rear mud flaps. Be a shame if they just like fell off and you got better mileage....
Proud owner of Stinkerbutt!
-Air Raid cone filter, direct to TB
-Homebrew front air dam
-Homebrew side skirt
-Torza top bed cover
-Now featuring front wheel canards!