# Semi's Trailer Undercarriage Airfoil **URL:** \ **Category:** General Discussion\ **Created:** [May 16, 2013, 8:18am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338 "2013-05-16T08:18:40Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![longprime](https://avatars.discourse-cdn.com/v4/letter/l/e79b87/32.png) [@longprime](https://community.cartalk.com/u/longprime)\ **Post date:** [May 16, 2013, 8:18am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/1 "2013-05-16T08:18:40Z")
Amazing that a simple device as the undercarriage has saved the longhaul-hiway trucker, 5% in fuel efficiency. What took us so long to invent this device? ---
**Author:** ![kmccune](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/kmccune/32/1237_2.png) [@kmccune](https://community.cartalk.com/u/kmccune)\ **Post date:** [May 16, 2013, 12:56pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/2 "2013-05-16T12:56:59Z")
wouldnt helped much back in the 70s,with the speeds they run now makes a difference-Kevin ---
**Author:** ![dagosa](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dagosa/32/9837_2.png) [@dagosa](https://community.cartalk.com/u/dagosa)\ **Post date:** [May 16, 2013, 4:17pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/3 "2013-05-16T16:17:23Z")
Blind luck and ignorance. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [May 16, 2013, 10:01pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/4 "2013-05-16T22:01:30Z")
It simply wasn’t time yet. ---
**Author:** ![longprime](https://avatars.discourse-cdn.com/v4/letter/l/e79b87/32.png) [@longprime](https://community.cartalk.com/u/longprime)\ **Post date:** [May 16, 2013, 10:53pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/5 "2013-05-16T22:53:27Z")
Something you and I could have invented as a 10 year old. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [May 16, 2013, 11:48pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/6 "2013-05-16T23:48:47Z")
Things that seem obvious today weren’t long ago. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [May 17, 2013, 1:43am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/7 "2013-05-17T01:43:17Z")
I’m just waiting for those flimsy things to start flopping around and flying off like the tires and mud flaps. ---
**Author:** ![DrRocket](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/drrocket/32/2603_2.png) [@DrRocket](https://community.cartalk.com/u/DrRocket)\ **Post date:** [May 17, 2013, 2:29am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/8 "2013-05-17T02:29:56Z")
I drive 61 miles each way to work, all on interstate, so I see a LOT of semi tractors. One device I’m beginning to see more of is what’s known as a “tailwind” fairing. It consists of a set of panels mounted to the back of a trailer that form sort of a “cone.” It’s supposed to make quite a bit of difference by cutting down on the turbulance at the back of the truck. the obvious drawback is that the driver must disconnect all of the supports struts and swing the panels around out of the way before they can back up to a loading dock and open the doors. For a truck that must make frequent stops, it’s probably not worth the trouble, but I can see how this would appeal to long haul operators. ---
**Author:** ![longprime](https://avatars.discourse-cdn.com/v4/letter/l/e79b87/32.png) [@longprime](https://community.cartalk.com/u/longprime)\ **Post date:** [May 17, 2013, 6:43am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/9 "2013-05-17T06:43:32Z")
Tail cones. Why haven’t they appeared earlier. We know they work on ships and airplanes. And lower tail drag prevents anyone from drafting behind the big rig. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [May 17, 2013, 8:37am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/10 "2013-05-17T08:37:52Z")
I just read in this months Popular science where some kid came up with a plastic bubble to mount on the top os school busses that would save the schools about $500 per year/per bus in fuel costs. The bubble costs about $30 to make. Its still undergoing safety testing but we should be seeing it in a year or two. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [May 17, 2013, 4:49pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/11 "2013-05-17T16:49:54Z")
I have to laugh when reading this thread and realizing at the same time that the new C7 'Vette has a flat rear end. I know many disagree, but in my mind that ain’t progress. ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [May 17, 2013, 5:32pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/12 "2013-05-17T17:32:23Z")
The flat tail on the 'Vette is in the same category as pickup tailgate up vs down. The wind tunnel may tell a very different story than your intuition. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [May 17, 2013, 6:01pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/13 "2013-05-17T18:01:13Z")
It might, but whether it’s aerodynamically efficient or not, it’s very different from the pickup truck tailgate dynamics. That box changes everything. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [May 17, 2013, 6:13pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/14 "2013-05-17T18:13:33Z")
Actually, a flat rear end (also called a “Kammback”) improves aerodynamics over many alternatives: “A Kammback is a car body style that derives from the research of the German aerodynamicist Wunibald Kamm in the 1930s. The design calls for a body with smooth contours that continues to a tail that is abruptly cut off. This shape reduces the drag of the vehicle.” ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [May 17, 2013, 7:02pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/15 "2013-05-17T19:02:38Z")
" it’s very different from the pickup truck tailgate dynamics" The point I tried to make is they are similar in that people have an opinion on which is more efficient based on appearance. In the case of the tailgate in some cases at least it’s more efficient to have it up even though it **looks** like there would be less drag with it down. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [May 17, 2013, 10:25pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/16 "2013-05-17T22:25:31Z")
Form before function for me. I could give a hang if it gets .0005 better mileage if it looks like heck. Styling is very important in cars and they shouldn’t all look the same. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [May 17, 2013, 10:52pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/17 "2013-05-17T22:52:16Z")
I’m more of a “form follows function” guy. I have to admit, though, that some of the most gorgeous cars were designed the way they were purely for the aesthetics. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [May 18, 2013, 5:58am UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/18 "2013-05-18T05:58:54Z")
You do remember that Corvette’s road race and the body is almost identical to the stock one. Oh, and they win, too. What was that about aerodynamics again? ---
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [May 18, 2013, 2:58pm UTC](https://community.cartalk.com/t/semis-trailer-undercarriage-airfoil/79338/19 "2013-05-18T14:58:45Z")
Gee, and making airplanes fly was easy once the Wright Brothers showed everyone how.