Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Minimizing Aerodynamic Effect for Trailer Towing

ByDesign · 11-23-2015, 11:27 AM

Second trip. 166.2 miles. Without even looking at the fuel numbers, I could tell it made a difference. On trip #1 I had a hard time holding speed, and 80 mph was pushing it. With this (except going up a few of the hills) I was able to cruise at 75 mph. I sped up to test it at one point and did 90 on the flat without much trouble.

The tape held on the way there, but came undone at the bottom on the trip back (some loss of effect for sure). This photo, taken out the back window driving at dusk shows the tarp being pulled by the wind (note the lower corner where the black trailer is visible). Interesting, because it's the wind from below causing much of the turbulence -- more perhaps than from the sides.

This photo shows the trailer the next morning with the tarp loose.

Final fuel numbers gave minus 1.5 MPG for the trip over normal driving without the trailer -- 0.7 MPG improvement over the trailer by itself. Interesting mod, but not very practical (limited access to the truck, really hard to use the tongue jack) though nice for security since the hitch and tongue jack are near impossible to access and popping a tube would make a huge noise! Anyway the Ghetto look has to go and I need the functionality.

The fuel economy numbers are not scientific. Conditions were similar, but not exact. Secondly, we traveled faster (7 mph faster average) on trip #2 than on trip #1 (because we could), so that distorts the values.

The take away: substantially filling much of the void changed fuel use ~5%. I'd guess if the top of the tubes had been covered, including a proper slope up to the trailer top along with better accommodation near the bottom, (and real tests at the same speed) that number would rise to something closer to 7 or 8% -- in line with the numbers Aerohead has posted from books about tractor-trailer combos. Cool.

By the Way, Thanks to Aerohead for the above images. Most of them I've seen posted in other threads, but a couple were new to me. Thanks for posting.

Another interesting point -- not one comment or question from any observers about it. I can't believe it looks normal, but .... I didn't have a black tarp, and the blue is obnoxious. I was ready for criticism and weird questions.

Finally, it will get decals. I've been slow, but got some quotes. It's more fun to mod than to decorate.

11-23-2015, 11:27 AM	#20 (permalink)
ByDesign Eco Dabbler Join Date: Oct 2015 Location: Colorado Posts: 45 Thanks: 33 Thanked 33 Times in 19 Posts	Second trip. 166.2 miles. Without even looking at the fuel numbers, I could tell it made a difference. On trip #1 I had a hard time holding speed, and 80 mph was pushing it. With this (except going up a few of the hills) I was able to cruise at 75 mph. I sped up to test it at one point and did 90 on the flat without much trouble. The tape held on the way there, but came undone at the bottom on the trip back (some loss of effect for sure). This photo, taken out the back window driving at dusk shows the tarp being pulled by the wind (note the lower corner where the black trailer is visible). Interesting, because it's the wind from below causing much of the turbulence -- more perhaps than from the sides. This photo shows the trailer the next morning with the tarp loose. Final fuel numbers gave minus 1.5 MPG for the trip over normal driving without the trailer -- 0.7 MPG improvement over the trailer by itself. Interesting mod, but not very practical (limited access to the truck, really hard to use the tongue jack) though nice for security since the hitch and tongue jack are near impossible to access and popping a tube would make a huge noise! Anyway the Ghetto look has to go and I need the functionality. The fuel economy numbers are not scientific. Conditions were similar, but not exact. Secondly, we traveled faster (7 mph faster average) on trip #2 than on trip #1 (because we could), so that distorts the values. The take away: substantially filling much of the void changed fuel use ~5%. I'd guess if the top of the tubes had been covered, including a proper slope up to the trailer top along with better accommodation near the bottom, (and real tests at the same speed) that number would rise to something closer to 7 or 8% -- in line with the numbers Aerohead has posted from books about tractor-trailer combos. Cool. By the Way, Thanks to Aerohead for the above images. Most of them I've seen posted in other threads, but a couple were new to me. Thanks for posting. Another interesting point -- not one comment or question from any observers about it. I can't believe it looks normal, but .... I didn't have a black tarp, and the blue is obnoxious. I was ready for criticism and weird questions. Finally, it will get decals. I've been slow, but got some quotes. It's more fun to mod than to decorate.