Tatra T87, built in Czechoslovakia in the 1930s.
The Tatra T87, built in Czechoslovakia in the 1930s, may be the ultimate expression of the aerodynamic design craze of the period between the two world wars. Blending aero design and functionality is the challenge.

What A Difference Aerodynamics Makes - Part 2

Our continuing journey into the benefits of better vehicle aerodynamics

By John Gilkison and Philip Knox

From Thursday November 13th through Monday 17th of this year I set out on a five day drive to pick up an aerodynamic camper shell and a hitch mounted boat tail box in Little Rock, Arkansas to improve the mileage of my 2014 Ford 150 truck. As per Murphy’s Rule the weather did not cooperate in a spectacular way with my attempts to do MPG testing on my truck driving naked (no aero appliances) and then driving with the aero appliances added.

My story begins September of this year when my wife and I bought our 2014 Ford F 150 4X4 Crew Cab pickup truck with a 6.5 ft bed. The truck has a 3.5 liter V6 EcoBoost engine with variable valve timing, four valves per cylinder, and dual turbochargers. It is capable of 365 horsepower at 5,000 RPM, has 420 ft/lbs of torque on tap at around 3,000 RPM, and a plateau power band runs from 2K RPM’s to 4K RPM’s.

We bought the truck trading in our 2011 Toyota 4 Runner. We plan to buy a 5th wheel trailer and we want to be able to adequately tow it. This vehicle is the only one we own, so it must meet all our regular needs. The crew cab gives us plenty of passenger room; the 6.5 ft bed is long enough for hauling and needed for the sliding 5th wheel hitch for towing. The truck weighs just over 6,100 lbs dry.

Ford F150 with Aerolid installed

Phillip Knox, who was the subject of my last blog about the wind tunnel test of his aero modified Toyota T-100, happened to be visiting us in September when we bought the new truck. Phil knew Brett Herndon who lives Little Rock, AR. Brett has manufactured aerodynamic camper shells for the Ford F 150 w/6.5 ft truck bed. Brett calls his work of art the Aerolid. Brett has had the Aerolid tested in the A2 wind tunnel and it tested out to have a Delta Cd of 0.062. The meaning of this is that the Aerolid would take the 0.402 Cd of my truck down to a stealthy Cd of 0.34. I wanted one, I had to have it!

Brett Herndon worked in automotive and aircraft design for the past 33 years.  Companies Brett worked for include Ford Motor Company, Gulfstream Aerospace, and Raytheon Corporate Jets, just to mention a few.  Brett’s area of expertise is aircraft pattern making and automotive clay modeling.  These abilities allowed him to tool up and construct the aerodynamic peripherals for pickup trucks.

We called Brett and he had a two year old black Aerolid he was willing to sell us. He also had a hitch mounted boat tail which was a one of a kind test item, but it was only painted in a primer gray. We agreed upon a price, and in September we set the travel date to go to Little Rock, Arkansas, for Thursday November 13, 2014. Also I hoped to beat the onset of cold weather. It was “The best laid plans of mice and men, as they say”.

In the mean time we tried to baseline the performance of my truck so we would have something to compare any new numbers after the aerodynamic appliances were attached. This mostly involved using the Instant MPG Readout on the dash to log MPG’s for different speeds from 40 mph in 5 mph increments up to 85 mph. We did this with the AC off and with the AC on. Ford rates the truck at an enigmatic 15 City/21 Hwy/17 mixed. After data logging and looking at the power bands of the engine the EPA label made sense.

A good problem we have here in Radium Springs, NM is that it is at 4,000 feet of elevation, which means we have 12% less air density. This translates into around 8% better MPG’s. Also our driving cycle is more mixed and highway than just city driving. We travel a rural highway at 55 mph to town, or alternately an interstate highway at 70 mph, and then 65 mph to town. To sum up, much of our driving is 40 miles to and from town, and 10 miles in the city. This is an 80% Hwy/ 20% City driving cycle. Neither my wife nor I work as we are both retired, so we do not need to drive on a daily basis.

We were enjoying pleasant fall weather here in the first week of November with daytime highs in the 60’s F and nighttime lows in the high 30’s F. We had not needed to even turn on our furnace yet. Our MPG testing went well, as we had low air densities. This begins to change in the second week of November as Typhoon Nuri moved into the Aleutian Islands. Typhoon Nuri was a Black Swan event the weather people took to calling a “Typhoon Bomb”. The remnant of this Typhoon altered the Jet Stream so that it dipped way south into most of the continental United States bringing polar air into over 90% of the country earlier in the year than is normal.

On the Thursday morning when I was set to leave for Little Rock the night time lows were in the 20’s F and the daytime highs were in the 40”s F. Winds were out of the North from 5 MPH to 10 MPH depending upon the time of day and location. Not good weather for aerodynamic testing at all.

Air densities in much of the country I was to travel in were only slightly above sea level to below sea level in some locations. Texas, Arkansas, and Oklahoma only range from 500 feet to 1,000 feet of elevation. High barometric pressures and the cold only compounded the problem.

My dash has a transmission temperature read out and it can take as much as 20 or more miles to warm up to the 197 degree F operating temperature in cold weather. The differential can take even longer to warm up depending.

On my 700 mile first day trip to Denton, TX driving seat time was over 13 hours. I did get to fill in my 80 MPH and 85 MPH data for the truck semi legally on a section of I-10 and I-20 that runs from Fabens, TX (3,900 ft) to Monahan’s, TX (2,600 ft) where the legal speed limit is 80 MPH. All speeds we set using my Garmin Navi which is more accurate than the on board speedometer. We were interested in the higher speed data because our look at the engine graph tells us the power laden Eco-Boost engine of the Ford truck was not really working very hard at all below 1,700 RPM. When an engine is outside and below its Map of Performance, internal friction reduces its efficiency.

At 60 MPH the truck only required 40 HP in my test at home. Since the engine is capable of 365 HP this means the engine is capable of 9 times this much power output. The problem with using all this entire power would be that I would be driving at speeds of up to 150 MPH, if this were possible. Even at around 3,000 RPM where the engine develops its peak torque of 420 ft/lbs I would still be doing a leisurely 120 MPH. Not practical for the wallet or my freedom. This is good for a tow vehicle though.

At 80 MPH the truck pulls 1,950 RPM and logged around 15 MPG. This means it took 58 HP. The way we were calculating this is 80/15 = 5.3 gallons of fuel per hour. Five point three gallons of fuel weigh 33.5 lbs. My engine is rated at .625 lbs of fuel per Brake HP hour. So 33.5/0.625 = 53.6 HP. Factoring in transmission losses of 0.9 you have 53.6/0.9 = 58 HP. This is a rounded off number, but 58 HP is a good working assumption. I had at least a 5 MPH wind vectoring out of the North so my effective speed through the air may have been around 85 MPH actually.

My 85 MPH data logging came up with 13.2 MPG. As you will be able to see an extra 5 MPH at these speeds is a whole other kettle of fish. The truck was requiring 70 HP or another 12 HP to do the extra 5 MPH. Even so there was five times more power on tap. The truck was really stable at these speeds and the engine just loved it. If engines could talk (and they do) my engine was saying “Oh boy, happy, happy, happy, I got some work to do, let’s go John”. My effective air speed at 85 MPH was 90 MPH requiring 2,050 RPM.

The next day after staying with Phil Knox in Denton TX, I got on the road to Little Rock, AR. I arrived around sunset and met Brett Herndon at his house. It took about 90 minutes to install wiring for the high center brake light, then we installed the Aerolid, and lastly the hitch mounted boat tai

Ford F150 with prototype Aerolid and bobtail installed

Wake up time was 6 AM to leave for the second leg of my journey with the aero appliances installed. I refueled a few blocks from the motel with that gasoline replacing all the fuel I had burned the previous day. The Ford truck has a Trip A and Trip B dash read out. I was using the Trip B read out for my composite average of the whole of the first leg of the trip with the truck running naked. It recorded 1,070.3 miles using 66.822 metered gallons for a 16.1 MPG composite average.

The drive to Fayetteville, AR was singular in its beauty. I was tired, but excited at the same time, running on adrenaline. At one point I micro slept at the wheel for a brief moment, so I got off immediately looking for coffee. The truck stop had a brand of brew labeled “Turbo Coffee” and that was for me. I filled my thermos and set out again for Monett, MO.

I had a timeline to meet, so I drove to Monett, MO to visit my daughter and family and thence to Chandler, OK to visit my two brothers Jim and Norman. I did not get to Chandler until around dark. Another long day but there was a hot meal waiting on me. I had told my brother Jim about the Aerolid and Boat Tail project but asked him to keep it a secret from Norman so I could surprise him. The look on my Brother Norman’s face was priceless.

In the morning I let Norman drive the truck to take us to breakfast. He punched it when we were on the highway as any red blooded American male would. When we reached 70 MPH in short order, he shut it down satisfied that my new truck had passed the test. The weather news was not sounding good as Oklahoma had snow coming that day, and since I was traveling south I wanted to get out of there. So, sadly I left early.

By the time I reached OK City, OK it was blowing snow across the highway and visibility was down to a mile or less. When I turned south to Denton, TX the winds became a five mpg tail wind for me. I recorded a 22.3 MPG at 70 MPH. Temperatures were in the low 30’s F and the baro was at 29.3 inches. This comports with mpg figures I recorded at 60 mph at home without the aero under much better air density and temperature conditions. This 197 mile stretch of road was really the only favorable conditions encountered during the whole trip and even then temperatures were in the low 30’s F and I had to climb over the Arbuckle’s.

Arriving at Denton earlier than planned Phil and I unloaded my personal gear and went to town. We weighed the truck and its front axle. The truck came in at 6,360 lbs v 6,120 lbs naked. The front axle weighed 3,420 lbs which means the weight distribution is 53% front/47% rear. Good numbers for a pickup truck. The truck’s weight distribution is 54%/46% without the boat tail

It was 25 degrees F in the morning when I got on the road for my 700 mile trip home. The truck did not really come to operating temperature until I got to Weatherford, TX. Once I got past Fort Worth, TX I began to be able to do 70 MPH. At Mineral Wells, my first refueling stop, winds were 3 MPH out of the North, the temp was 28 F, and the Barometer was at 29.52. I was averaging 18.6 MPG at that juncture as compared to the low 16’s MPG on the trip in.

Things had warmed up a little by the time I reached Monahan’s, TX where I could begin to do 80 MPH. Temps were in the low 40’s F when I started the 80 MPH testing regime. By the time I had reached Fabens it had warmed up to 48 F. With the more moderate quartering winds of only a few MPH the truck had reached 18 MPG at 80 MPH. This is a 16.7 % improvement using only 48 HP v the 58 HP over I saw traveling east with the truck naked. The truck was losing elevation going east but gaining 1,300 ft going west which makes these higher numbers even more significant. The faster you go, the more important aerodynamics becomes.

At 85 MPH I recorded a 16.2 MPG v 13.2 MPG with the truck naked. This is an 18.5 % improvement using only 58 HP v 70 HP naked. I really enjoyed my time traveling at these higher speeds. The truck was extremely stable. So stable in fact, after I trimmed the wheel and let go of the steering wheel it was a full 12 seconds before it begin to drift. My truck was passing semi trucks effortlessly and going uphill and down without losing or gaining more than 1 MPH in cruise control. If my truck had the speed rated tires and it was legal, I would have no qualms about traveling at 100 MPH as we wrote about in our blog “100 MPH at 32 MPG”. MPG’s at 100 MPH would be around 9.5 MPG according to my calculations v 7.8 MPG without the aero appliances.

I got into El Paso, TX around sunset and pulled into a Valero just as my dash readout flashed “You Are Low on Fuel” and I had to press OK to remove it. The 36 gallon tank still had about 4.1 gallons of fuel left in it. The tank holds 220 lbs of fuel. I had 25 lbs of fuel left. It took $86.64 to refuel my vehicle. I had traveled 566 miles from Mineral Wells at 17.7 MPG and technically could have made it all the way to Las Cruces, NM, but I did not want to test that theory after such a long and arduous day.

The Trip B registered 1,437.7 miles on 79.034 gallons of gasoline for a composite average 18.19 MPG. It took an additional 3.5 gallons of gas to get home from El Paso. I trust the computer in the truck more than I do the pumped gas readings. There are just too many variables in pumping gas unless you fill the tank to the neck and measure the fuel temperature. Personally I did not want to stand around in the cold doing this. I did not record odometer readings when pumping gas which confuses the issue even more.

These numbers amount to a [16.01/18.19 = .88 = 12%] improvement in averaged highway MPG’s over the course of a long distance trip over a five day period traveling 2,528 miles. A 12% improvement translates into a reduction in drag of 24% using the 2 to 1 rule. Since the truck naked has a reported Cd of 0.402 when you multiply the reported drag by [100-24 = 76/100 = 0.76 x 0.402 = 0.3055]. Since we can only claim accuracy at 2 digits we need to round this figure up to [Cd = 0.31]. The two appliances used together have a Delta [Cd of 0.092] in my test.

The next day my wife helped me dismount the approximately 50 lb boat tail. We will be traveling with the Areolid on the truck as a daily driver only using the boat tail for trips. The Areolid weighs around 190 lbs according to our scale numbers. It has a nice locking lift gate which will keep valuables secure in our truck bed in conjunction with the locking tailgate.

Ford F150 with Aerolid installed

The Ford Truck has a frontal area of 36 sq ft. I measured the aft body areas of both appliance and came up with 22.6 sq ft for the Aerolid and truck, the boat tail reduces the wake area to 10.4 sq ft. The tires account for another 3.3 sq ft in both instances. This makes the wake areas 25.9 sq ft and 13.7 sq ft respectively. Using the wake area ratio, I came up with a 52% reduction for the boat tail. A Delta Cd = 0.062 x .48= 0.0297. A Cd of 0.34 – 0.0297 = a Cd of 031. This is a very good agreement with fuel data.

We are very pleased with our purchase. The Herndon Aerolid is painted black and has a quality fit and finish. I want to paint the boat tail black to match it and then install some reflectors on it. We also want to install a hidden door and a swing arm mount to hide the door up against the tailgate. Since the boat tail covers the lock for the Aerolid we think a swing arm mount and faster disconnects for the bumper latches would improve accessibility. Also the addition of some small windows would allow the backup camera mounted in the tailgate to function again. Currently the camera is inspecting the inside of the boat tail.

The Areolid is one of three in the United States so this puts us in a very exclusive club. The hitch mounted boat tail is one of one. My truck with the crew cab and the extra length is one of one with these aerodynamic appliances mounted on it. Ford has set a world speed record of 147 MPH with a Ford Raptor F 150 truck using 411 HP available HP in the installed V-8 engine. This speed record was set on a closed track using speed rated tires and lower viscosity lubricants.

We have calculated that my truck with its 365 HP V-6 engine set up as the Ford Raptor was (speed rated tires and special lubricants) and using the Herndon aerodynamic appliances would be capable of this speed record and possibly be able to break this production pickup truck record. We say this because the aero appliances are worth 50 free HP at speed. At nearly 5,000 RPM my engine would be producing the needed HP (with the appliances) and its peak torque of 420 ft/lbs. It is nice to speculate like this, but we are highly unlikely ever to test this theory out in the real world. However, I may actually own one of the world’s fastest production pickup trucks in theory. Sweet, “Get yourself some of that”!

The Herndon Aerolid passed the Typhoon Bomb Nuri stress test with flying colors. I want to thank Brett for giving me the opportunity of owning such a rare piece of aerodynamic history. We hope Brett will be able to get the Aerolid and boat tail into mass production someday soon. The investment capital to do this could be well over one million dollars, maybe as much as two million dollars. The Chinese have a similar product on the market, but it is sold in Europe and not sold in the United States.

If there are any of you investment capital entrepreneurs out there reading this article here is your chance to get into a wide open North American market that is virtually unexploited right now. Feel free to contact me and I will pass you on to patent holder. It was a rare privilege for me to even test this device.


Our Cd’s calculations are provisional but we think they are accurate to a Cd of plus 0.005 or minus 0.005. We say this because this Cd calculation is in agreement with the wake area proportionality improvements; the miles/MPG data; and it dovetails with the A2 Wind Tunnel numbers for the Aerolid itself. Higher MPG numbers would be seen in the warmer air less dense air of New Mexico in future testing.

Some warm weather and lower air densities for testing would be nice. As the guy I overheard in a rest stop restroom said “I wish someone would turn the heat on back on out there”! My one piece of advice to you aero testers out there is “DO NOT test during Typhoon Bombs”. We had no choice, but the Herndon Aerolid and boat tail just laughs at such global climate weirding weather. “IT (really) WORKS”.

Times Article Viewed: 9761
Published: 30-Nov-2014


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