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Old 12-24-2013, 06:43 PM   #1 (permalink)
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Tonneau cover extension/spoiler

I washed my truck today and noticed that my tailgate was the dirtiest part of my vehicle. I think this is a bad sign for aerodynamics, and indicates that my airflow is not detaching cleanly at the rear. I have a tonneau cover and want to try extending it about 6" either straight back or with a small angle.

Any advice for the angle of such a spoiler?

This is a rough idea of what I have in mind.



Not my truck but the same cover I have.

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Old 12-25-2013, 12:57 PM   #2 (permalink)
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If you get that to work out for you please let us know.

I did not see any mpg improvements when my adjustable rear spoiler was flat out, but the transition was not idea, and the devil is in the details.

However, I believe the theory you have is sound, it just does not add to down-force as I once desired, in fact I think it contributed to uplift if anything at all.

See this thread:
Rear Spoiler on Pick Up Truck - Experiment - Page 2 - Pelican Parts Technical BBS
Quote:
Originally Posted by kach22i View Post
A cotter pin wiggled out and was lost, so I pulled the other one. I soon discovered this was a method for recording pressure/suction on the rear spoiler.

The rear spoiler is originally set near straight up, it takes less than one pound of pressure to get it to move, a couple of pounds to flatten it out all the way. Photos taken after max speed listed on picture.





I will be installing a rubber cork plug with a hole in it on the tail of the cotter pin to keep it from riding up again.
NOTE: The adjustable angle is adjustable no longer, the piano hing has long rusted into a set position. Photos are almost 5-years old now.
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Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

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http://ecomodder.com/forum/showthrea...1-a-19525.html
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aerohead (12-26-2013)
Old 12-25-2013, 01:08 PM   #3 (permalink)
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There was some discussion in the forum of including the tailgate and sides into the equation.

This was a mark-up I did for such a tailgate.
http://ecomodder.com/forum/showthrea...tml#post381583
Quote:
Originally Posted by kach22i View Post
Cut & Paste re-post from the Aerodynamic section:
http://ecomodder.com/forum/showthrea...k-26367-2.html
This is totally a KISS method, might try it on my own truck. Is it crazy or what?

Modified a random image off the Internet, should work on any pick-up truck.

Cant corrugated plastic in 10-degrees from top and both sides, with tailgate down.

Automobile 2 - Odds And Ends Photos by kach22i | Photobucket


Might have to put a cargo net back there, could be trouble otherwise.

Inspiration was this:
Automotive Aerodynamics: Drag Area – Size Matters
More here, including actual built projects + Patent.
http://ecomodder.com/forum/showthrea...k-26367-2.html
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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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aerohead (12-26-2013)
Old 12-26-2013, 04:42 PM   #4 (permalink)
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advice

Quote:
Originally Posted by nathan01xl View Post
I washed my truck today and noticed that my tailgate was the dirtiest part of my vehicle. I think this is a bad sign for aerodynamics, and indicates that my airflow is not detaching cleanly at the rear. I have a tonneau cover and want to try extending it about 6" either straight back or with a small angle.

Any advice for the angle of such a spoiler?

This is a rough idea of what I have in mind.



Not my truck but the same cover I have.
The base pressure of your wake is determined by the pressure at the line of separation,top,sides,and bottom.
An upper spoiler will do nothing to lower this vacuum behind the tailgate as you've still got 'forward' separation aside,and below it.
Either a proper boat tail or box cavity is the only thing which is capable of any meaningful drag reduction.
Also,the end of the tailgate may already be in the 'ideal' position with respect to the 'roofline.' A comparison to the Aerodynamic Streamlining Template tool at the top of the Aero Forum would tell you where you are now.
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Old 12-26-2013, 08:35 PM   #5 (permalink)
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Quote:
Originally Posted by aerohead View Post
The base pressure of your wake is determined by the pressure at the line of separation,top,sides,and bottom.
An upper spoiler will do nothing to lower this vacuum behind the tailgate as you've still got 'forward' separation aside,and below it.
Either a proper boat tail or box cavity is the only thing which is capable of any meaningful drag reduction.
Also,the end of the tailgate may already be in the 'ideal' position with respect to the 'roofline.' A comparison to the Aerodynamic Streamlining Template tool at the top of the Aero Forum would tell you where you are now.
Well that answers that question Thanks for the knowledge
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Old 12-27-2013, 11:14 AM   #6 (permalink)
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Quote:
Originally Posted by nathan01xl View Post
Well that answers that question Thanks for the knowledge
It does answer your question, but if you lower your expectation to just wanting a clean release of air off the rear of the bed cover (which is a step in the right direction), then following what the latest truck designs are doing may help.

PickupTruck.com - First Look: 2009 Ford F-150

Quote:
The lines flow around to the truck’s new tail lamps and curve up at the top to form a prominent spoiler that helps improve the truck’s aerodynamics.
I think that you were just asking too much of too little in your original post.

Here is an aftermarket installation with a camera:
How To: Install Tailgate Spoiler With Back-Up Camera - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums


Lots of other types too: "tailgate spoiler"
https://www.google.com/search?q=tail...h=677#imgdii=_
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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html

Last edited by kach22i; 12-27-2013 at 11:23 AM..
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Old 12-27-2013, 05:26 PM   #7 (permalink)
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latest truck designs

I just wanted to mention that the automakers have commented that the tailgate spoiler itself has very little if any actual streamlining benefit.What they're hoping for is that Joe Six-pack will remember to keep the gate up where it can do the most good compared to gate down,or gate off,which I see locally on a daily basis.
You can bring a brain to a cerebrum, but you can't make it think.
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Old 12-27-2013, 06:12 PM   #8 (permalink)
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I imagine an extended spoiler would be effective if it was integrated into an aerocap. Similar to the rear spoiler on the Prius.
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Old 12-28-2013, 10:20 AM   #9 (permalink)
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I noticed a pick-up truck parked near my house yesterday, I think it was a recently produced F-150.

The rear tailgate spoiler was complemented by a matching plastic cap on the top of bed each flank.

The overall view of a "U" shape comprising of horizontal 3-inch wide plastic cap gave a very solid feel and perhaps provides a flat surface for attachments, loads or just to sit on.
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Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 12-28-2013, 01:55 PM   #10 (permalink)
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extended

Quote:
Originally Posted by nathan01xl View Post
I imagine an extended spoiler would be effective if it was integrated into an aerocap. Similar to the rear spoiler on the Prius.
Yes,anything which extends the length along the streamlined contour is beneficial.

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