Aerodynamics

[RClark]

Since i tow a 5th wheel I sintalled a "V" box at the back of my bed. After i removed the tailgate (anybody want to buy it?). To be cool, beecause it looks good and protects the bed when not towing i installed a LUND Elite bed cover.

This leaves an exposed area at the back where the tailgate was.

Does this affect the aerodynamics of the vehicle when not towing?

Would making a fill piece out of 1/4" plywood make any difference?

 

[Steve Campbell]

You are asking the wrong crowd....

... . wasn't the Long Beach Grand Prix held there yesterday. Now those boys would have the answer.



My simple opinion... . I do not feel there would be any measurable detrimental effecta on fuel mileage.

 

[BCFAST]

This is pretty much the wrong crowd to ask... . except perhaps me!

I'm a long time racer and have always enjoyed reading between the lines in the rule book to find aerodynamic aids As for our beloved Rams, there was a thread a long time ago that included a link to a thesis project by a couple of grad students. This site included photos of a regular-cab Ram being 'smoked' in a wind tunnel with a variety of shells, tonnoa covers and tail gates. What they proved was that the WORST profile to run in an empty pickup was with NO tailgate. The next worst was with a 'flow-thru' tailgate (popular with the RV crowd). The best config with an open bed was with the tailgate down. This shape had the smoothest airstream and least lift. The shape that produced the best overall aerodynamics was a topper that was cab-high at the back window, sloping down toward the tailgate top, then a slight up-flare in the last 8" or so. To answer your question: no, covering the little opening wont help you; fashioning a rear lip spoiler would do wonders!



Brian

 

[RClark]

I just went for a Freeway drive.

Sealing off the rear might not change mileage , but it would probably stop the cover from flaping with the breeze. It would prevent the wind from getting underneath the cover.

 

[Dave Zuber]

I'd keep the tail gate to help brace the sides of the bed. Depending on your 5 wheel hitch type and the amount of time on rough roads, the bed may start to twist.

 

[FAllen]

Ditto on what Dave said!

 

[Doc Tinker]

It took me a while, but I found the project that BCFAST mentioned.



http://mars.wnec.edu/~ehaffner/did.htm



I find it interesting that leaving the tailgate down decreased drag, but taking it off increased the drag





Doc

 

[Chipstien]

Very interesting.

 

[jsimpson]

Aerodynamically, the underside of your truck is the dirtiest. A really low front spoiler (a la racing trucks) would help the most and hit things the most often!

 

[Rammin]

Thats interesting I read in the Dodge owners manual that the pickup was aerodynamically designed to run empty with the tail gate up.

 

[Mundgyver]

I read the same thing about the tail gate being up. I forget where though. I'm interested in the areodynamics of the one cap shown in the link. I saw this a few months ago. 30% is alot. Do we know if anybody builds that style of cap. I do lots of long runs and a 30% reduction in drag would pay big for fuel saving. Oo.

 

[RKohn]

How about putting an Avenger body on a 2500???

maybe have to raise the hood a little.

 

[RClark]

Since i don't have a tailgate on my truck i can't leave it up or down. I removed it because with a 5thwheel it it a pain when hooking or unhooking. If you are not straight in line, a problem in some parks, it wont work.

I had a back flap made that connects to the cover and the back of the truck.

It seals the rear. It will be at MM in Paharump.

 

[BK]

I totally agree with Dave Zuber , I've seen the old 70's fords tear welds in their side bed walls from not having the tailgate in place and up.



As mentioned above I too read an article that spoke about the p/u bed and tail gate Vs no tailgate and such.

When the boy did windtunnel testing for the craftsman truck series they found that with the tailgate closed, an air bubble formed in the bed and rose to the hood of the cab. . the bubble stay and formed a nice ramp for the departing air to flow down and off the truck. With the tail gate down, a vacum formed to just behind the cab which hurt laminate air flow over the bed.



It help it, they closed the bed, decrease the amount of air that is need in the bed to form the bubble.



I see that if you don't have the rear tail gate on, not only are you in for a structural issue, but you will form a vacum under the bed cover by the air that's trying to leave the rear of the truck. Which will cause a dirty air flow off the back. The "thinner" the rear is, the more controlled the air departs and allowed to reform with the other air... .



A truck that as a front/rear that looks like this < > would be best (best I can do with the keyboard).