Truck Airfoil

[The_Works]

Does the cost of installing a airfoil on the cab roof of my truck offset any increase in gas mileage because of the aerodynamics? Does the airfoil effect handling of the truck while hauling a 35 foot 5th wheel? Thanks for your thoughts and input.

[Me_Again]

06Fargo wrote:
The more you can do to have a large frontal area vehicle combination only make "one hole" through the air the better = why it's harder to pull in a cross wind than head wind - the wind gets at all the gaps and clutter. The pointier the front and the more shaped like a fish the stern the better. The closer roof top fairings are to a trailer the better.

And that is the problem with pickups and 5th wheel trailers. You can not get it close enough to gain any advantage!

That is why the Glendale Titinum trailers work!

I went from a square corner flat rear 26 foot fifth wheel to a 29 footer that weighs 3K more and get better fuel mileage. The new trailer has both a front and rear cap with nice rounded corners.

Chris

[noteven]

The more you can do to have a large frontal area vehicle combination only make "one hole" through the air the better = why it's harder to pull in a cross wind than head wind - the wind gets at all the gaps and clutter. The pointier the front and the more shaped like a fish the stern the better. The closer roof top fairings are to a trailer the better.

[Me_Again]

arnko37 wrote:
The reason 18 wheelers use them is the payback is there due to the high milage the truck puts on. Over the road trucks will drive between 100K to 300K per year. A small increase in mpg multiplies very fast at that rate. For an RV it may not pay. I do however think they do increase the mpg if set up right.

If set up right! That is within a few feet of the trailer. Remember the OTR trailers have square corners. Some have/had bumbles on the front!

Due to the distance from the front of a 5th wheel and the fact that they are making them more aerodynamic all the time, one will see little or no charge. People use to report they helped handling in cross wind. If you bobtail a lot, even with it folded down you will loose mileage.

They are a solution looking for a problem, not a solution for a problem. There was a thread here 6 or 8 years ago where guy did a lot of testing and the result was they do not do much for the average 5th wheel trailer.

Rounded corners both front and back on the trailer will make much more difference. Few trailers now a days have square corners on the front.

Chris

[arnko37]

The reason 18 wheelers use them is the payback is there due to the high milage the truck puts on. Over the road trucks will drive between 100K to 300K per year. A small increase in mpg multiplies very fast at that rate. For an RV it may not pay. I do however think they do increase the mpg if set up right.

[TimnJo]

laknox wrote:
Anyone had a Titanium, with the "double step" front end want to chime in? I'd think they'd have an advantage over a similarly-sized rig with a more "standard" front end.

Lyle

Yup, I went from a 29 foot 'regular' profile to a 37 foot Titanium and my mileage went up.
We regularly travel to my wife's sister's place about a four hour tow away (360 Km).

With the old trailer I couldn't make it without a fill up, with the newer, longer, heavier, but more aerodynamic trailer I still had almost a quarter tank upon arrival.

[waltbennett]

I've one that I picked up originally to help with a large and very tall Leer cap on my short bed Chevy gasser. It worked spectacularly at that, boosting mileage by over 2.5 per gallon. With my new/old Ford dually and 5er, I get almost a full mpg improvement at the same speeds and over the same highway (~100 mile trip done twice). I'm certain the previously talked over reason (too far away on a long bed crew cab) is why I don't get more, but since it's already paid for, I'll take the savings.

[Impulse24]

They work......

My wing was on the truck when I bought it, I took it off and averaged 8.5 mpg so I put it back on and I got 10.2 using 87 octane gas and a Wing adjusted to push the air over the trailer. I will add I calculate my MPG every fill up.

If the wing is at the back of the cab and aligned with the top of the hood and top of the trailer the air will flow over the trailer with little resistance.
For some to say the small advantage isn't worth the cost of the wing, you need to recheck your math. If you get and extra 1/2 mile per Gallon, that means on a 3000 mile trip you save about $50 the cost of a wing is around $300, there for 12000 miles will pay for the wing or approx. after 1 year.

For many years people used to drive a truck with the tailgate down claiming it helped fuel economy, It was later discovered having the gate up made no difference, the design of the vehicle is what counts, Aerodynamically I foresee the area between the cab and the 5ver being streamlined in much the same way as Semi's now streamline the underside of there trailers.

After thought,

$50 buys around 15.8 gals of Gas @ 3.15 per gal at 10.2 mph that's around an extra 160 miles per tank.

$50 buys around 13 gals of Diesel @ 3.85 per gal, as most say they average 10 mpg plus Diesel works out at about 130 to 160 per tank.

So on price per gal it doesn't matter if you use Gas or Diesel you will benefit a lot using a wing..

***prices used for this calculation are averages across Florida including the Keys.

[tegu69]

Since an airfoil is basically a wing and can be used to create down force, it should also be possible to create lift, which should then take weight off the tow vehicle (if you drive that fast). Just saying.

[fpresto]

Even if they did work which is very doubtful for most truck/5th combinations, they hurt your mileage when not towing which is probably the majority of the time.
I knew several guys who had jobs towing 5th wheel from the factories to the dealers and from the dealer to RV shows. Most of them had the deflectors at first but over time most removed them. When I asked they said that they gained little in gas mileage and while they did raise the bug line higher that was not necessarily an advantage as they were required to wash the 5th before delivery and a thick line at the top took longer to clean.

[stripit]

I'm not an engineer, but I do know the airfoil is used as a down force on race cars to help hold the car down on the track. I have to believe just because it is now mounted to a truck the same dynamics are now still in place. In essence it makes you move more weight with the down force if your moving at speed, my opinion. In talking to many folks we have seen over the years with those foils most have said no change in fuel usage, just helps keep the front of the 5'er cleaner from bugs, the foil is catching the bugs the 5'er would have.

[laknox]

Anyone had a Titanium, with the "double step" front end want to chime in? I'd think they'd have an advantage over a similarly-sized rig with a more "standard" front end.

Lyle

[ol_Bombero-JC]

The Works wrote:
Does the cost of installing a airfoil on the cab roof of my truck offset any increase in gas mileage because of the aerodynamics? Does the airfoil effect handling of the truck while hauling a 35 foot 5th wheel? Thanks for your thoughts and input.

.

No.

Don't waste your money.

.

[Desert_Captain]

As I noted 9 posts back they work better the further back - closer to the trailer you can mount them. Most of this discussion has been about their use with a fiver but given the success I had with my TT I have to believe that with an optimum mounting location they would work just as well for a fiver. For the record I could always tell when I had the optimum attack angle on the deflector as there would be no bugs on the front of the trailer....now if the bugs weren't hitting the trailer it stands to reason neither was the wind that carries them.

I really don't have a dog in this fight as we recently traded our TT in on a nice class C and sold the truck but.... unlike many here I have been there, done that and know for a fact they can and do work. Maybe 1.5 to 2.0 additional mpg doesn't mean much to some but it translated into about $400 a year (we averaged about 6,000 miles a year towing), that we had to spend on campgrounds and cold beer. :B

You can probably get the same result by slowing down 5 mpg but since I already do that (towing at 55 to 60), this was just free money after the first year of recouping my original investment. I wish I could squeeze 12.5 out of my V-10 in the C but will have to settle for 9.5 to 10 (still traveling at 55 to 60), and the freedom that comes with the 55 gallon tank. :C

[John_Bridge]

What we are really talking about is, or the object should be, reducing drag. Drag is caused by air turbulence. It occurs between the truck and the trailer, along the sides of the trailer, over the roof of the trailer, under the trailer and behind the trailer. It is worse when there are square corners on trailer. Just rounding them makes a significant difference, and that has largely been done on fivers.

The truck cab is too far away from the front of the fiver to employ a foil that will help improve the turbulence situation. In fact, additional turbulence will be created between the truck and trailer, which in turn will increase drag.

The best way to reduce drag on a fiver would be impractical. You would have to eliminate everything on the roof, awnings and other obstructions on the sides of the trailer, spare tires, steps and other obstructions under the trailer, etc.

One thing that everyone could do is not carry spare tires, bicycles, ladders and other clutter on the back of the fiver. It all causes turbulence. If the back of the trailer is at right angles to the sides and roof, rounding them would make a difference. Think jumbo jet when you think of improving trailer aerodynamics. The front of a jet is rounded in a dome shape, and the rear is brought to a diminishing point or "boat tail." That would be the best shape for the trailer. Then all you would have to do is conquer the truck.

The air foil won't help. 🙂