I am going to buy one of these

http://groups.msn.com/TREKTracks/tre...to&PhotoID=576

It's a shoebox shaped 28' RV. Does anyone see anything that can be done to help? They claim 15 mpg. I am going to run it on waste vegetable oil, my fuel will be free but it will be hard to fill-up for free on the road. That's why I want better MPG. I plan on putting in as big a tank as possible in it, maybe 200 gallons, which at 15 mpg will get me to Florida and back, but every little bit will help.

I was thinking airtabs on the back?

I will get it on April 10th

Peter

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83 Mitsubishi Mighty Max

92trek-1.jpg

It might get crappy mpg as a car, but 15 mpg is FANTASTIC fuel economy for a house!
I'd say your only hope is Engine Off Coast whenever possible (although I hear that diesels use very little fuel at idle).

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thats awsome! ide say weight reduction and maybe a a belly pan

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Rear wheel skirts seem easy enough (front wheel skirts too).

I think air tabs are a good idea too.

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Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)

I think wheel skirts an a belly pan are some good ideas. It already is pretty low. I have to take a good look at it once I get it. I don't really want it to look too freaky, so no nose cone or giant wings! It only has 16" wheels so maybe I will get some racing hubcaps, if they will fit over the nuts.

I think also because it is so flat and square, I will have to cruise at only 55 mph.
Keep the ideas coming!

Peter

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83 Mitsubishi Mighty Max

A roof faring, perhaps? Rear panels that can be opened up and extended out at highway speeds? If you want an idea of techniques to try, take a look at various concept aerodynamic big rigs and steamlined busses that have been built.

I remember reading in an SAE manual that a bus with a rounded rear end(bluff end I think it was called?) can achieve a .30 drag coefficient. If you can somehow get your camper into the low .4 range, you'd be in good shape.

That thing gets almost the same mileage as the jeep......

A front air dam would probably help, you've got plenty of room to mount one. Maybe some kind of cover to cover the support beams and the roll of the awning?

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Put a big old cone on the back and something on the front to soften the blow? Make it look more like a cross-section of an airplane wing, I guess, even if just a bit. It's not like RVs have to look pretty anyway,

A belly pan will do wonders under an RV. Those things have alot of things on the bottom that create alot of drag. Apart from that, ou need something on the back other than air tabs. You need something that doesn't cut off. A cone is a bit dangerous on something that size, but if you have a car in tow, it might be possible to do some sort of rear taper.

Hello -

Someone else posted this somewhere else in GasSavers :

http://www.dfrc.nasa.gov/Gallery/pho...L/E-38096.html
nasa_truck.jpg

But what are all those "hairs" for ?

CarloSW2

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I just did a search for aerodynamic trucks and RV's, and found a few things that you might want to look into adding.

http://images.google.com/imgres?imgu...US203%26sa%3DG

http://images.google.com/imgres?imgu...US203%26sa%3DG

http://images.google.com/imgres?imgu...US203%26sa%3DG

http://images.google.com/imgres?imgu...US203%26sa%3DG

050106113455.jpg

That's quite the 'spoiler' that rig has there. I still don't understand how spoiler's are supposed to reduce drag. Wouldn't it just be more frontal area for air to hit?

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Thats hilarious!

I'll get right on building that huge tail cone! The wife will love it.

Thanks

Peter

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83 Mitsubishi Mighty Max

I imagine that it acts as a large vortex generator that makes the low pressure area in the back a little smoother.

That one was designed at Georgia Tech, so I assume that the kids there put it on for a reason other than looking cool.

Tuft testing. If you can get photos of the vehicle moving with pieces of yarn taped to it, you can see where turbulence are being generated.

This allows you to make modifications where there is turbulence, so that you're not doing it blindly.



Next to a wind tunnel, it's the best you'll get.

As noted above, a lot of things could be done to improve the MPG .

Rolling resistance is going to be high due to the weight of the RV, so, see if you can get lower rolling resistance tyres, and pump them up a bit more (but, not crazy-high as some of the cars on here, as you don't want to blow one of them on a vehicle that size).

Front (if they wheels on full lock don't protrude from the wheel arch) and rear wheel skirts will also help, as will a full belly pan. These would have to be removable, at least in the areas where you need to change wheels and tyres.

Finally, the cone mentioned above is a good idea - if you had enough time you could design a cone shaped attachment at the back, which if made well enough, could even be used to store (lightweight) items while you are travelling around e.g. spare bedding and the like.

With the above mods, which won't really affect the appearance (apart from the cone, but, if done well, this would not look odd at all - you could have a 'square cone', to more closely match the style of the vehicle), you should get a big improvement in MPG!.

You could also try the trick of disconnecting the fuel lines (after depressurising them), and having a small container of diesel. Idle the RV on that, and see how long it takes to drain it, then work out the fuel consumption at idle. If it is very low, then you can engine-on coast whenever possible, to save fuel that way, and reach the top of hills at 20mph (if not holding up traffic), so you can then roll back down the hill and be at 60 by the bottom of the hill - that RV will have a lot of momentum for this kind of driving!

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Hypomiler

Mmmm. How about fitting a larger front bumper (not freakishly large) so that a lot more air flows over the vehicle rather than under - this should make a difference surely?

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Team GasMisers5 - #1 for first three rounds of the original GS Fuel Economy Challenge
Miles displaced by e-bike since 1 Jan 2008: 62.6 (0 kWh used)
Hypomiler

The first thing that came to mind is a rounded cone design that I've seen on the side-load, tractor-trailer rigs:



The green cone should help finish the air, and is probably a commonly available product that could be cut/customized, if you don't need that area back there (or hook-up a swinging hinge to open it up).

"Swift" Trucking Company uses these (usually white) on their side-loaders. They also have a 61mph governor on their tractors, so they're usually looking for ways to save fuel. They're currently working with the EPA in other testing. Look for these on the road.

Of course the next simplest thing to do is keep the speed as close to 55 as possible. On long trips that might mean a significant time distance to the destination, but it's not being there, it's getting there, right?

RH77

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repete86 -

I really like this last URL you posted because of the massive rear-wheel mod.

aero_truck.jpg

CarloSW2

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Great suggestions, But obviously I was kidding about building the rear cone. Here is another shot, it may be 15 years old but still in good shape so I can't turn it into a Franken-car (franken-rv?)

Can't cover the tiger!

Thanks

Peter

Attached Images

tiger2.jpg (54.4 KB, 41 views)

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83 Mitsubishi Mighty Max

OK crappy picture, but there is a big tiger mural on the back ! I will try to post better pictures

Peter

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83 Mitsubishi Mighty Max

Not to mention, it looks like a Rear-View camera is back there too...

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So you need for the big bubble on the rear to be transparent. No problem! :-)

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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"

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.

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Two things are needed:
1, a sign painted on the rear reading: "Caution Tandem Trailer"
2, A grapple on the front to hook onto the ICC bar of the semi trailer ahead.

O.K.,
2.5, a willingness to arrive where ever the semi unknowingly tows you.

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).

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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).

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aerocivic.com

This is probably a dead thread by now. These have sort of been mentioned elsewhere but this is something to consider.

These look way better than golf ball tape. This might be legitimate.

http://airtab.com/

http://airtab.com/video.htm

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usedgeo

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....

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-Homebrew front air dam
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-Now featuring front wheel canards!