Pickup Cab Wing Angle - Measure from Where?
 

I'm modding a '99 Ford Ranger and need help setting the correct angle of the wing. I read in a post here that a 12 or 11 degree wing approx 19" wide used in conjunction with a half bed cover on a short bed truck would give close to the same benefits as an aerocap. My truck has a 6' bed and an 18" wing, but my question is where do I measure the 11 degrees from? The top of the cab is a gentle curve, so that's not much help. I ended up parking my truck on a level surface and then using a gauge with a bottom-weighted needle to get my 11 degrees. I ran a string along the top of my wing and the string passes 7" over the top of the tailgate.

Advice?

Edit: Now that I look at my pics I can see that any movement between the bed and cab is going to damage the wing. I'll make new support poles and run them to the cab near the bottom corners of the window.

Here is my modding thread:
http://ecomodder.com/forum/showthrea...ger-25320.html


http://i424.photobucket.com/albums/p...psd4f3e572.jpg

http://i424.photobucket.com/albums/p...ps864733f0.jpg

It's looking good, you might be the first in the forum going this route, as my effort has a leading edge slot and no angle at all.

The 7" should be fine, although I'm not sure what Texas Tech and others have used. If you had a rear spoiler at the end of your tailgate for down-force (like mine), then I could see increasing the angle to engage it in the flow.

Test it.

Good idea, although isn't that wing spoiler hinged connected with duct tape/foil tape?

I'm actually getting some down force at the tailgate. My plastic bed cover ends just short of the tailgate and at speed I can see the plastic flexing downward about half an inch.

The wing is bolted on with six brackets. The tape is just to seal the gap and smooth the transition.

I need to do some research on testing.

In my estimation, you'd be better off being too flat rather than too steep. What you have seems right, I certainly would not go steeper. If too steep, it would create a large vortex due to the downwash from the top hitting the air coming in from the sides which would then be sucked in and set to whirling, this type of vortex would be like adding a drag chute to your truck. Not good.

advice
 

Shooting from the hip,the 7" sounds 'bout right with the short bed.
Project looks mpg to me!:thumbup:

Yeah, trucks are work vehicles, not ego-boosters. So aero changes are like a rotating amber warning lamp . . something is happening! Gets my attention every time (as in, is that an "edge" that can be exploited).

Hard to make money with a car. Not so with a pickemup. :thumbup:

.

Just posting this in this thread because it was the last roof wing thread.

Cab Spoiler 1994 to 2003 Chevy S10 or GMC Sonoma Pickup with Std Cab 531007 | eBay
http://www.truckaccessorizer.com/ima..._nitrowing.gif
http://i.ebayimg.com/t/Cab-Spoiler-1...oKQ~~60_35.JPG

Looks like a nice drag generator more than anything else, but maybe something someone wants to get involved in.

Update:

I taped four rows of tufts to the bed cover. The leading row (nearest cab) was pulled forward and down strongly while the remaining rows were pulled backwards but wagged side to side.

I waited for a very windy day (30 ish mph), parked my truck into the wind, and threw handfuls of sawdust on the windshield and watched it flow it over the cab. After flowing over the wing the sawdust took a sharp turn downward and a lot hit the leading edge of my bed cover, with the bulk of it hitting the bed cover and flowing off the back.

I then changed the angle of my wing to about 7 degrees. This equates to about 11" above the tailgate. The wind and my free time haven't coincided since, so I sort of repeated the sawdust experiment by having my wife release a handful of sawdust as we were driving down the road. The sawdust now missed the bed cover and passed over the tailgate a few inches above it.

The tufts now show the leading row of tufts to pull weakly forward and slightly down. The second row flops around but mostly rearward, and the last two rows are pulled back fairly strongly.

So what did this do for mileage? Don't know. I had to replace the EGR feedback sensor and the spring weather has been erratic so I can't be sure. My next step is to build adjustable supports, find a long hill, and do some coasting tests at different angles. May also build a rig to release sawdust/flour/cornmeal ahead of my windshield so I can see airflow as I drive down the road.

Very creative.

I wonder if anyone has used a leaf blower?

Interesting. I'll borrow one and give it a shot.

Keep in mind, the air affected by your mod extends up several feet above and around, so unless your leaf blower was originally used on the set of the movie "Twister", it really won't tell you much.

I think the reason your tufts point forward is due to your lack of a smooth transition, your flat wing creates this by default. I think it helps control the air in a good way for you. Short of building a complete cap, this seems to be the best you can achieve.

Yea, could be right.

I think you would need another large fan behind the truck for drawing air in.

I tested different wing angles today. I built adjustable braces and found a hill that is .9 miles long. My procedure was to put it in neutral at a mile marker at the top of the hill while traveling 55 mph, and then see how much speed I gained by the bottom. To make a long story short, at the low and high end of my adjustments I could reach 60.9 mph, but I found a sweet spot right around 10 degrees that would take me to 62.8 mph. I made about 20 runs in order to be sure my results were repeatable.

In my final run I removed the wing entirely and hit 65 mph. :(

Back to the drawing board.

http://i34.tinypic.com/vhg678.jpg

Well I think it's fantastic that you got out there and really put it to the test, unlike so many who just hem and haw and never try to discover the real results with a legit test.

Ten stars for you!:thumbup:

Just my two cents, perhaps you are befitting from some down-force which has yet to be measured.

I'd rather have down-force than any kind of lift in a pick-up truck.

Next ice storm, just see which vehicles are in the ditch on the side of the road.

In SE Michigan they will be pick-up trucks (suffering from tail lift) and a few surviving Geo Trackers which are short wheelbase and perhaps of the 2WD variety.

Thanks. I'm trying to figure out where to go next. I wish I could see that study that tested pickup truck bed drag. I wonder how they built their wing and arrived at their conclusions?

kach22i - I'm purely interested in increasing mpg. I'll leave my truck at home when the weather gets bad - or throw some weight in the bed. I wouldn't want to drive fast enough in an ice storm for my spoiler to create down force. :) But, yes, traction is horrible in a rwd pickup with an empty bed.

I'd hate to dig up an old thread but Id like to know why this didnt work? From my standpoint theres no reason this shouldn't of worked. Is the space forward of the half-tonneau cover creating a negative pressure under the kamm back and thus making it act like a wing providing downforce or is it just turbulent drag? How could the design be fixed?

I may be able to get a hold of a Ranger and would of loved to do this to it

In advance, great job Bruce and great thread!

Was the gap at the gate causing problems?

Very possibly. I wonder if he did this, if it would change anything? The Salt Flat Gm Cyclone had a half tonneau but it extended down to the bed as-well.


http://i.imgur.com/0g25Cis.png

UPDATE 2020


Was this project perhaps scrubbed prematurely because of dependence on on coast-down testing?

Would have Throttle Stop Testing or another means be a better indicator of success or failure?

I just got an email notification of the latest response to this thread.

Hard to believe it's been nearly eight years.

The main reason I scrubbed the project was that I needed the truck to be a truck. Attachments over and on the bed were a real pain because I need to be able to throw stuff in the bed. Animal feed, building supplies, etc. I also built a cage that my wife and daughters use to haul their goats. It fills the whole bed.

All of that aero stuff just got in the way.

Which makes an eight hour response time impressive. :)

The question remains, was there a better way to test the results?

Is gravity not the most consistent power input known to man?
It takes out many of the variables that impact the engines power output at a consistent throttle position( yes these are variables /inconsistency that are relatively small ,so are some of the changes that are being chased).

Sounds like the OP did throttle stop testing.
setting there stop at 0 % throttle position. , in Neutral (this negates weather the computer is programmed to lock the torque converter clutch or have it in free spool for slower speed testing. Eg. GMC/Chevy Allison program running the TCC open till 5th[1st overdrive 0.71:1 ])

Gravity Drop Testing aka a more consistent version of Throttle Stop Testing was what I used to determine the air dam prototype that I built had a negative impact on my aero. I noted a reduction in speed on my 6% grade that is 3 miles long, this test was confirmed when Arrowhead ran my truck at Darko. Ditto for the bug deflector big negative (negated the 24% Improvement of my 3D boat tail canopy)

I thought his answer was pretty clear on additional testing is no.
For 2 reasons
1 Julian hook wasn't published yet nor was he participating in sharing his knowledge on this website yet . As well as Julian gets mad at me when I try and talk to him about pickup trucks as his book and I quote was specifically written for cars nowhere in the title does it say anything about trucks leave me alone." (Bitter taste words off most predators)

2 the concept proved unusable/ too troublesome in real life therefore was abandon.

The white paper is a good starting point for Research into where someone elce thought to look to correct the deficiencies of the produced 3 box pickup done to SAE standard, and of course lots of testing on these and more variables to find your best use case scenario of Form and Function.

Not sure how I come into this but I describe using gravity testing in my book (page 104).