Tailgate "wings" on a tonnau cover?

[Blu3Z3rg]

For various reasons, I need to have my fiberglass tonnau cover. Storage, lockability, etc. Sure I may upgrade to a custom made fiberglass aero cap some day, but money won't allow it atm.

On the Chevy's and Dodge's they add these plastic tops to their tailgates that have a small wing to them. Ford also puts a small wing incorperated into the tailgate as well. It's apparently effective to a small amount.
Proof???

http://www.youtube.com/watch?v=1YL423MHtLc

My question:
If i have a hard fiberglass cover, would it be worthwhile to mount one of these chevy or dodge bolt on types to the cover? If not, i'm adding on a handle anyways. I need something because it doesn't have a handle atm and every time I lift the cover it greases up the paint all over the back. Quite annoying. I thought if these "spoilers" are effective at ALL, that it would make for a good handle as well.

Let me know what you think!
Blu3

PS. My watching snow/rain/etc. shows that the wind on highway hits cover about 3/4 of the way back, not at the very end. This is at about 60 mph. Perhaps at 70 it's closer to back. Dunno if this is relavent.

[t vago]

It was my understanding that those types of spoiler were mainly effective at hinting at the truck owner to keep his tailgate up. They appear to do next to nothing for fuel economy, otherwise.

That was a rather intriguing demonstration of airflow around the lower front nose of that Ford, though... Might look into that one of these days.

[Blu3Z3rg]

Originally Posted by t vago

It was my understanding that those types of spoiler were mainly effective at hinting at the truck owner to keep his tailgate up. They appear to do next to nothing for fuel economy, otherwise.

That's what I had read as well, however, ford believes it helps aerodynamics. Would it be something specific to that truck? Or would it work better on mine since the air hits the cover before the tailgate, THEN would use the spoiler? Would it just create downforce?

So many questions... it's really fairly specific to my case i think, but if the big 3 decided to put it on their trucks, and now Dodge and Ford both actually make it in the sheet metal on their tailgates instead of just the plastic parts on top now... well... it makes me think it's gotta do SOMETHING.

[KamperBob]

Blu3Z3rg, it depends. If your flat tonneau cannot reattach flow then a wing can do good. If flow already reattaches then a wing could do harm. Tuft testing can help answer that question. If you're good enough you can imagineer flow attachment given key geometry and dimensions of your truck.

[BamZipPow]

Chevy called theirs a tailgate protector and support bar. Not sure why Ford chooses to call theirs an aerodynamic aid. To me...it's just some styling eye candy that they decided to give it a working purpose.

If you go with the notion that it's there to protect the top of the tailgate...then putting it on the tonneau cover sort of defeats that approach. If you put it on the tonneau cover then you'll need to find out what angle will best provide you the results yer looking fer. It will take a little time/effort as well as an adjustable tail/wing to determine the proper angle.

[gone-ot]

...if nothing else, you've captured the Cd values for the 2008-2009 Ford F150s "...directly from the mouth of their aerodynamics engineer..." (ha,ha).

[KamperBob]

Originally Posted by Old Tele man

...if nothing else, you've captured the Cd values for the 2008-2009 Ford F150s "...directly from the mouth of their aerodynamics engineer..." (ha,ha).

Good point. I wonder what Cd=0.4 plugged into an MPG calculator turns out, and how that compares to EPA numbers and member reports...

(I vaguely recall Tundra Cd is closer to 0.35 but don't have a reference.)

[some_other_dave]

From that video, it looks like they have the "spoiler" there mostly to make sure that the air coming over the top of the cab doesn't wind up down in the bed. And the tonneau cover should already do that...

-soD

[Blu3Z3rg]

So I'm wondering, if the air is hitting my cover about 3/4 of the way back, what WOULD the best solution be back there?

[KamperBob]

Originally Posted by Blu3Z3rg

So I'm wondering, if the air is hitting my cover about 3/4 of the way back, what WOULD the best solution be back there?

If you do tuft tests and confirm that flow has reattached before the rear of the tonneau then do nothing. If the air hitting it is turbulent then a wing can help.