I have been trying to research how I can improve the aerodynamics of my 26' enclosed car-hauling trailer. It is a model with rounded front corners already, but I'm sure there is still room for improvement. The truck by itself only gets around 11.5mpg ('95 F250 7.5L gas/automatic/4.10 rear). Towing the open car-hauler with a 4000# car only dropped it to 10-10.5mpg.

Maybe a 'nose cone' or similar added to the front? Curved airflow scoops or 'guides' at the rear corners?

Most of this aero research is targeted at OTR Semi-truck-trailers, but research is research, and much of it is still valid for our pickup-pulled trailers/campers. The articles I'm seeing that with my rounded-front corners, the addition of a nose cone has little overall effect. What surprises me is that aside from frontal area, the largest source of aero drag is the flat rear of the trailer. Anything that helps guide the air at the rear results in a 3-5% reduction in drag. I've seen those folding air guides on the rear of a few semi-trailers, but I guess they are a PITA for door operation for loading/unloading, especially with side-opening doors that they need to swing 270° when backing up to a loading dock. So much like the old '60s-70's station wagons that had an air deflector at the rear of the roof rack that directed air along the tailgate window, I'm going to try to make something similar to not only the top but the sides of the trailer as well. Nothing that sticks out to the side any farther than the wheel arch fenders, and will also still allow the rear ramp door to open freely. The stand-off brackets to be 3D-printed, and probably the scoop formed from .080 aluminum (same material as the fenders). Will it be worth it? We'll see!

Oh, and for the geeks out there, drag is computed like this:
These are also the 3 main parts of the aerodynamic drag equation.

This equation says the Drag Force (Fd) is equal to a Coefficient of Drag (cd), (multiplied by) Density of the air (ρ (greek letter Rho)), (multiplied by) Velocity through the air, squared ( V*V ), (multiplied by) the Frontal Area of the object, (divided by 2).

(Just me geeking out on a cold winter day here in Northern Ohio... Yeah, I went to school for engineering... ...50 years ago! Note my avatar, LOL! )

 

I have put air tabs, which are designed to reduce drag, on the top only of my truck cap. I checked the mpg only once on my 2016 F350 which I originally put them on and noticed a minimal improvement and now have them on the top only of my 2023 F350. Have them on the top only on our camper also, 34’ Jayco 33RBTS. Could be my imagination but it did seem to improve the handling when towing it. The site says to put them along the sides also, which I didn’t want to do on my truck and because no smooth surface on the camper.

I tried these because there does appear to be engineering data behind them.

Purdue Mechanical Engineering Technology 1980!

https://www.airtab.com/

 

After my last-minute rejection from the USAF Academy in late April 1976 (only six weeks before reporting to Basic), Purdue was my next choice, but already missed the admissions date, so Ohio State Mech E it was for me, and even at that I was on a stand-by for dorm space - on a temporary cot for the first three weeks... That what doesn't kill us makes us stronger, eh? Then my money ran out after that first year, so I worked two years to build up savings, Cleveland State for another year, plus random classes here and there as money/time allowed... I ended at just short of Senior year before the proverbial 'Life comes at you fast'..and moved on... But I'm still an engineering geek at heart!

...and Yuengling Light? Seriously? that's OK for a 'domestic', but I prefer Warsteiner myself... only because they quit importing Kulmbacher Edelherb Pils into the US....

Airtabs? I know about vortex generators because I'm also a pilot....

 

I'm a beliver that Aero is the biggest thing that messes up trailer towing fuel economy, so it makes sense that there's areas for improvement. Slowing down 5 MPG will probably make a bigger difference, but these are low cost and low risk so why not?

 

I only wish I had 10mpg towing. I get about 7mph towing a 5th wheel.

 

Air tabs seem like the science is behind them, so I'm interested . . . but I have yet to see someone do a real-world test with numbers recorded, something like this:

Test 1: No alterations, recorded speed, distance, and temperature on a day when air is essentially still, in a loop like the TFLTruck guys do.
Test 2: Air tabs added, recorded speed, distance, and temperature on a day when air is essentially still, in a loop like the TFLTruck guys do.
Test 3: Air tabs removed, recorded speed, distance, and temperature on a day when air is essentially still, in a loop like the TFLTruck guys do.
Test 4: Air tabs added, recorded speed, distance, and temperature on a day when air is essentially still, in a loop like the TFLTruck guys do.

Maybe same four tests as 55, 60, and 65MPH.

Not the kind of test that Joe Average would do. This is more something that someone selling Airtabs or other fuel-economy improvements would do if their stuff works. That's where my suspicion starts to override my optimism. Maybe they are selling at their production capacity so they aren't worried about making more?

And then there's the semi trucks. I occasionally see air tabs on a semi here and there, but it's very rare. In the meantime, the big trucking companies have traversed decades of fuel prices fluctuating up and down, and have added aerodynamic wheel covers, body fairings, other aerodynamic aids on the tractor and trailers, aluminum wheels, ground effects, etc. etc. to gain fuel efficiency, but have never added air tabs in any noticeable numbers. Is this because they don't work? Is this because they'd be hard to implement? Is this because of some other reason? Maybe no trucking companies have heard of them yet? I don't know, but it adds to my suspicion.

Anyways, I'd love to see some real testing of these.

 

The amount of times most of us are traveling the freeways and the amount of time/money it will take to implement all these aerodynamic do dads, it's a waste of money. There will be no scientific proof that it works or not for you. 99% of us just don't put thousands of miles on a trailer a year. There are just too many variables to prove it works or does not.

With semi's, they can take hundreds of their trucks, over millions of miles, and have plenty of data to prove if it actually helps. We will never have that luxury.

I don't trust anyone. Just because the person has a great way of talking does not mean any of it is true. I've been around the automotive industry so long and I know, the best talkers sold the most cars and rarely ever knew how the car worked. So, if they sold aero do days, they would be just as rich and still have no clue what they were selling.

If you think this works and you got the money, do it. I just accept that when I get to the pump, it will cost me a pretty penny, and the easiest way to get better fuel economy is not to start the truck.

 

When we bought the former '97 F250HD 7.5L new waaaay back then, I did notice an almost 10% improvement in gas mileage at highway speeds simply by putting on a tonneau cover. It went from 10.5 to 11.5. The tonneau cuts down on the turbulence behind the cab. Wife spent three years of that time commuting 55mi each way on the Ohio Turnpike with the truck at 65-70mph. 110 miles round trip = ~10+ gallons/day would use almost all of the available gas in both tanks in just three r/t s! We then got her a car that got over twice the fuel economy... I took over the truck for two years, and my commute was ~55mi/rt, Interstate highway all but 2 miles.. The $250 spent for the tonneau cover paid for itself many times over in fuel savings in the 124k miles we put on that truck.
Calculating 124k mi / 10.5mpg = 11,800 gallons used.
Calculating 124k mi / 11.5mpg = 10,780 gallons used.

Savings is over 1000 gallons!

And Aero DOES sell to the truckers!. Aero-shaped tractor bodies, 'ground effects' on the cab, side skirt on the trailers (cuts down on undercarriage drag), smooth-sided trailers, full wheelcovers, retractable tarping systems on flat-beds, and sometimes even those pesky rear fairings.

 

I don't think the topic is about large items you can bolt on your car/truck. My understanding is the topic is putting on a bunch of warts and expecting a huge MPG increase.

I'm sold that if they did something, my wallet won't know. I'm not sold that it's a 4% improvement [like the site says]. If you are, great.

According to their site, I can save 500 gallons but I need to travel 75k miles to save that. That would take me over 50 years. More like 70+ years. I don't know about you, but with AI here, I think Skynet will fix all of our problems before I can save 500 gallons.. I think you're better off spending your money at the Indian Casinos or lottery tickets.

The other weird thing is that there is no price for them. The reviews are over 10 years old and based on people saying it helps. Absolutely no real proof that I see. With all the aero do dads they have on semi's, I never see these warts. I suspect the trucking companies already know it's fake.

But that is just me. I just don't sweat MPG. Sure, everyone wants more, but I'm not going to be scammed.

 

Exactly my point!

If the big trucking companies saw a benefit that makes them worthwhile, they'd do it. Even if they did, the benefit they'd see would pay for them a lot faster on their all day every day driving than on our RVs.

Yet they never use them.

Even still, I'd love to see a real test.

 

I've seen vendors of those tabs claim the trailer is more stable. I believe the stability is while other vehicles are passing in the same direction. That is one of the few situations that I've had problems with.

 

Aero DOES work, but like you've said, it is cost vs gain. My real-world savings example from adding a Tonneau increasing MPG by 10% is still valid. The Semi-trailer -'tails' yields only about 3-5% reduction in aerodynamic drag, and as we know from the formula above is that drag is related to the square of speed... so let's just say at 50mph, the aerodynamic drag is almost half what it is at 70mph. The BEST way to reduce drag is to go slower. OR you can try to reduce the coefficient of Drag. Aero features help with that.
Our cars typically don't even get into Overdrive and converter lock-up until around 40-45mph, so the best economy is generally achieved by going around 45-50mphwhen we're in the highest gear. If you have a vehicle with 'instant MPG' display, check it out for yourself. 45-50mph is probably where you get the best MPG (engine RPM, manifold pressure and the engine's volumetric efficiency comes into play) From that point and faster, the MPG drops as aerodynamic drag increases. This is ONE of the reasons we were saddled with the 55mph National Speed Limit for so many years, starting in the 1970s. Cars back then did not have overdrive transmissions, nor did they have electronic fuel injection that optimized fuel burn for a certain power output, AND generally, they were big and boxy - as aerodynamic as a brick. Much like our pickup trucks!!!! Our trucks pilling a big square brick-shaped box behind them is even worse. Anything we can do to help aerodynamics will help!! If I was an aeronautical engineering type, I'm sure they have models for airflow/aerodynamics of various shapes moving through the air. The most aerodynamic shape for a specific weight is a teardrop. Rounded front and tapered rear. Likewise, if I can 'guide' the airflow around the rear (flat) end of a square trailer, it should improve the cD (Coefficient of Drag)

 

Yes it does.

I ride bicycles and I do know power it takes to maintain 25mph. I notice a big difference with my climbing wheels [lighter, less aero] vs my aero wheel [heavier, more aero]. It's a difference of about 1mph with the same power output with the aero wheels.

 

Visit your optometrist. That is Yuengling. I do not know what this “light” is you mentioned!
Can’t say I’ve heard of Warsteiner. Will keep my eye open for it!

 

Yuengling Lager comes in maroon cans around here


Yuengling light comes in white/tan cans



Warsteiner is a German import



Edit: My bad... I see Yuengling changed their cans.



They're always messing with my head! LOL!!!