Add air dam to my RV?

[Snowman9000]

I have this exact model of motorhome. Would an air dam be worthwhile?
How about anything in the rear tires & wheelwell area?

[BabyDiesel]

Yessir!!!

An air dam is a good start, especially since the truck is more than likely "dirty" aerowise underneath. I use lawn edging material from Wal-Mart on my vehicle. Works like a charm Anything, no matter how insignificant it seems, you do to help out aero on a rig such as that will be ubberly beneficial.

If you feel more smitten, I would look at deleting the front mudflaps and making wheelwell and rear wheel coverings.

Kammback can come later

[freebeard]

A 'yes' answer by itself isn't all that helpful, is it? There's always the next question. How big? How attached? What color?

An airdam probably won't hurt, it depends. How does the bottom of the bumper compare to the overall low point of the chassis (brackets and so forth don't count, maybe the frame rails and axles)? How gnarly is the underside?

I'd say airdam, and/or bellypan and/or airbagged suspension so you can lay frame and then pick it up to drive and let it grind. But there's also wheel spats and fences.

Apparently, one of the best things you could do is this:



Soften the radius on the front edge. The rule of thumb is 4% of the gross width, that's 3.3" for a seven foot wide vehicle.

Turn the mirrors upside down and hang them from the lower front corners of the van.

[Cd]

http://ecomodder.com/forum/showthrea...d-e-18151.html
http://ecomodder.com/forum/showthrea...lly-13149.html

I too agree about the edges and an air dam. That would be the easiest things to see results with.

( To me it looks as though the top half is already smooth, but the area just behind the cab has edges that are too sharp. )

[Snowman9000]

Yes, well, it's a brick for sure.
I won't be doing any mods to the body itself which couldn't be removed without a trace. Which is another way of saying no mods to the body. I could do something like air dams in front of the rear tires, or a removable cover for the rear wheel wells. The roof is not really clean, the air conditioner is the biggie up there. I'll find a side profile photo on the net and post it.

Our previous small MH had a much more aero overhead cap and transition from the cab to the body. Same chassis and motor, 1 fewer speed on the trans, and it got at least 1 MPG better. I'm not obsessed over the mileage, but I do like to tinker and look for ways to beat the system. This one only has 5K miles on it, and so far it averages right at 10 MPG at 65 MPH. It's better at 55 MPH, of course. As gas motorhomes go, this one is at the high end of the MPG scale. Most, almost all, of them get in the single digits, even at 55-60.

[Snowman9000]

This one is a Ford, so the nose is a bit flatter than my Chevy. Otherwise it is the same model exactly. I don't have the TV antenna you see on the roof, the front-most object, ahead of the A/C. My TV antenna is the old style which cranks down flat. Works better too. Yay.

[BabyDiesel]

Originally Posted by freebeard

A 'yes' answer by itself isn't all that helpful, is it? There's always the next question. How big? How attached? What color?

Correct freebeard, I was tired and gave a lazy answer

To the OP, the rule of thumb on an airdam is to make it as low as the lowest under hanging piece of your vehicle. Say the lowest point on your truck is the front axle and it is 8" above the ground. You would make the airdam stop 8" above ground level. Black coroplast would match the airdam color you have now and you would be able to tailor it to the desired length.

I believe BigDave had his go nearly all the way to the ground at one point. He has since trimmed a few inches off, I believe -> http://ecomodder.com/forum/showthrea...up-3171-3.html

Snowman, are you okay with putting screws into your ride? I don't see any other way of putting on an airdam or tire splats.

[Snowman9000]

I'm okay with screws in hidden or hard to see places, sure.

[Sven7]

The running boards probably hold you back as well. If you can get in and out without them, take em off! I think it's safe to say none of that RV stuff was wind tunnel tested, so it's probably all taking a toll.

Maybe you can use some clamps or stock bolt holes inside the rear wheel housings to add skirts to them. Make sure you can take them off easily if you need to change a tire.

Cliffs Notes on the air dam would be, as others said, to drop it as low as the lowest component. You may be able to score some really tall lawn edging, but otherwise black coroplast is good. To shape it in plan view, here are some quick ideas-

lawn edging: either attach aluminum bar behind it and create brackets to mount it to the car, or cut a wide wooden board to the shape you like and drill the edging to it.

coroplast: either use the aluminum bar method or buy some long steel rods from a hardware store and slide them into the plastic's channels. This way, when you bend the piece it will stay bent. I've yet to see anyone use this method for an air dam, so you might want to put a lot of rods in to start.

Of course "Preparation H" (When Preparations A through G have failed) would be to find and modify an aftermarket or special bumper or air dam designed to fit your vehicle. This would be a good start.

[ennored]

Top picture, the Chevy chassis, is exactly what you have? Looks like there is already a pretty good airdam there.

What was the old motorhome? What are the two engines and transmissions? You should plug both of them into the Aerodynamic & rolling resistance, power & fuel consumption calculator, in the Tools section, and see if the differences agree with your observed MPG. You could then tweak your current setup in the tool and see what gains you can make.