What’s That Thing? Truck Fins Edition 

By Mark Vanhoenacker April 3, 2013

イメージ 5Our latest effort to dispel the mysteries of the modern visual landscape takes us back onto the great American road. For previous columns, click here; to submit your own suggestions, email us.
Do you like driving on highways crowded with big trucks? I’m guessing not. Maybe you’ve seen Steven Spielberg’s Duel (tagline: “Fear is the Driving Force”) or Stephen King’s Maximum Overdrive (“Evil’s Wheels”) one too many times. Whatever the reason, just know that the feeling is mutual. 
But still, in a country that worships movement, there’s more than a little romance to the grueling lifestyle of America’s long-distance truckers. Many truckers are owner-operators, each driving his own (97 percent are male) small, independent business. Just listen to the Modest Mouse song “Trucker’s Atlas” (or, even better, the cover by Sun Kil Moon). Or consider the hardworking, honest heroism of Optimus Prime, the robotic truck who leads the Transformers. (Motto: “No sacrifice is too great in the service of freedom.”)
Lately, trucks have been undergoing their own transformation. On a recent drive on I-40 between Memphis and Little Rock, Nathan Hamilton, a resident of North Little Rock (and a Slate reader), saw a truck with some funky panels on the side and back, and sent What’s That Thing an email.

What are these panels called, and what’s their purpose?

The panels under the body of the truck are called aerodynamic panel skirts, side panels, or side skirts. The panels that hang off the back are often called rear tail fairings, trailer tails, or sometimes boat tails. Whatever you call them, their purpose is to reduce drag and save fuel.

According to Susan King, a spokesperson for the American Trucking Associations, side panels “reduce drag on the undercarriage and wheels of the rig, thereby improving fuel efficiency,” while tail fairings reduce drag around the rear of the vehicle. How much fuel do they save? Between 5 percent and 15 percent, with 10 the average, according to King.

How do you unload the truck? You fold the panels out of the way.
ATDynamics, the manufacturer of TrailerTails, a brand of rear tail fairings, has a useful graphic that shows the reduction in “low-pressure suction drag” behind a trailer:

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So were these panels invented in response to rising fuel prices and growing environmental concerns? Yes—but not recently. Numerous patents, starting in 1935 for rail cars, attest to decades of ongoing efforts to streamline vehicles. Crystal Arvigo, a spokeswoman for ATDynamics, says that side skirts started to become more common in the U.S. between 2003 and 2005, but really took off in 2008.
These panels don’t make sense for every truck. Rather diabolically, drag increases with the square of velocity. So reducing drag becomes much, much more important as the average speed of a truck increases. King points out that these panels really start to come into their own when a truck is averaging 60 to 65 mph. “So you wouldn’t see these panels on trucks that handle local area deliveries.”

How green, exactly, are side skirts and tail fairings? Crystal Arvigo told me that tail fairings on a long-haul trailer that does 60,000 miles per year can save 480 gallons of diesel fuel, which equates to 10,752 lbs, or 4.9 metric tons, of CO2 that is not emitted. According to the EPA, the average car emits about 5.1 metric tons of CO2 per year. So each time a long-haul trucker installs tail fairings, that’s the rough global-warming equivalent of taking a car off the road.

If side skirts and tail fairings are so great, why doesn’t every long-haul truck have them? Price is one reason. A set of TrailerTails costs around $2,200, according to Arvigo, though volume discounts are available to fleets. Uncertainty about fuel prices is another. Long-term investments in fuel efficiency—especially those undertaken by small businesses, like owner-operators—make a lot more sense when high fuel prices are a long-term certainty. That fundamental truth of energy policy has long been obvious to many economists and environmentalists (if not, it seems, to politicians).

Have a favorite trucking movie, aside from the top ten listed here? Add it to the comments. And if you’ve wondered about something, on or off the great American road, send it with a pic to whatisthat@markvr.com.


 一般社団法人 日本流体力学会
 plaza.rakuten.co.jp 研究者の独り言

 truckinginfo.com High-Tech Trailer Aero Systems Nov. 12, 2010
 nytimes.com Stretching Trucks’ Mileage Dec. 28, 2012
 greencarreports.com Aug 26, 2011
 gajitz.com August, 2011
 government-fleet.com Nov. 12, 2010 and Oct 25, 2010
 ccjdigital.com ATDynamics debuts TrailerTail Model 2011 Oct. 19, 2010
 vehicleservicepros.com Oct. 10, 2010
 fleetowner.com A tale of trailer tails Sep 16, 2010
 trailertail.blogspot.com April 3, 2008


 Transport Canada
 California Environmental Protection Agency

 gii.co.jp 世界の市場調査資料 総合サイト
  世界のトラック用省エネ技術市場 (出版日 2016年02月01日)
  Truck fuel efficiency: trends, challenges and emerging technologies
  (USD1,145 (税抜 約13万円) PDF by E-mail (Single User License)

  Before Stemco’s subsidiary, ATDynamics Inc.

  • 顔アイコン



    [ よんちゃん ]

    2017/5/28(日) 午前 9:55

  • 顔アイコン


    ”お魚フィン”は知りませんでしたが、小さな突起がある事は知ってました。 成型上の理由かと思ってましたが、空力だったのですね。F1並みの細かい造り込みに驚きました。ドアミラーの代替は技術的には可能なんでしょうが、アナログ機能をどこまで削ぐかの見切り/判断が難しそうですね。パナメーラのギミックな羽は運転者からは良く見えないんで、動作をダッシュボードのモニターで表示して欲しいです。(笑)



    2017/5/28(日) 午後 9:45

  • 顔アイコン

    生物の形や仕組みを真似て技術開発するバイオミミクリー。これを用いた商品が増え始めましたね。 形や表面加工に応用されたモノを多く見かけます。自然界の動植物が幾何、物理、化学、数学などの高度な技を持っているのは、全く不思議です。



    2017/5/28(日) 午後 9:47