Half tonneau / Bonneville spoiler
 

I'm not exactly sure it's called a Bonneville spoiler, but I thought I had seen a picture of what I'm thinking about in a thread here years ago. Searching "Bonneville spoiler" didn't turn it up so.........?

This is probably more of a mental exercise, but I don't think I've seen it discussed before. Maybe there's a reason for that?

I understand how the half tonneau and cab wing works, with the low pressure zone being transmitted into the bed and creating a pressure difference on either side of the tailgate. But most tailgates come up short of the "template". I had seen pictures of a bed cover "extension" that went beyond the tailgate and ended where it would intersect with the "template". Some were even curved like a D with the straight part being at the tailgate.

Would this work with a half tonneau, also? A bed cover that starts halfway down the bed and extends to a point where it will meet the "template"? Would it negate the pressure difference because of it overhanging the tailgate? Amplify it? If I could figure out how to attach a cab wing I think it would be interesting to try. One sheet of plywood first long and squared off. Then long and D shaped at the rear. Then cut down to be even with the tailgate.

Would it work without the cab wing, just not as well?

My old vinyl tonneau has seen better days. The Velcro doesn't hold anymore and the vinyl had to be screwed to the rails. The catches that keep it taught have failed and it is beginning to rip at some of the screws. With my work commute being so long (110 miles round trip) and this job being so long term, I was hoping it might make a good test platform for some "outside the box" ideas. It's an old Ranger, and I won't mind drilling a few holes in it here and there. LoL.

Any thoughts on this tonneau idea?

Perhaps the size of the un-tonneaued portion depends on the height and shape of the cab. I suspect the cab wing and half-tonneau work against each other.

The picture you describe may be aerohead's waterbed inflatable.
https://ecomodder.com/forum/attachme...p;d=1203131237
ecomodder.com/forum/showthread.php/inflatable-boattail-896.html#post9948

I found this pizza delivery truck with a half-tonneau/spoiler.

https://ecomodder.com/forum/member-f...02-5-26-32.png

They said it improved the gas mileage but they didn't know how much. It reaches aerohead's Template line. He added length to get a similar result.

What would you think of a lockable storage box with end plate fins?

Working from my old Kindle is not making this easy. Copying pictures to post isn't very easy.

If I remember the picture that has the pickup truck designs, the cab spoiler/half tonneau was nearly as aerodynamic as a full aerocap. The D shape I'm thinking of is ironically, very similar to the shape of a roof spoiler built by Kachi22. I think he links that thread to most of his posts.

Just to throw another twist into this mental exercise, I found this quote while following different links from the Kachi22 links.

"a shallow (20 degree) spoiler as long as 60mm is capable of actually reducing the car’s drag while reducing rear lift or creating modest downforce".

It comes from this thread.....
Rear Spoiler on Pick Up Truck - Experiment - Page 2 - Pelican Parts Forums

Now, I wonder if this type of spoiler on the end of a half tonneau (or extended half tonneau) would have the benefit of reducing drag without increasing lift.

Information overload.........help !

Same thing happening in Phase's Rear Diffuser? thread.

Conflicting sources.

'Bonneville' spoiler
 

1) for the 'Bonneville' spoiler you'll want to look at HOT ROD Magazine's Project Red Hat Camaro, GM's 2006, Chevy Cobalt ECOTEC Bonneville race car, and Ford's 2007, Fusion 999 Hydrogen LSR Bonneville race car.
2) they all use a form of the 'Bonneville' spoiler.
3) all the spoilers terminate along a 'template' contour.
4) the spoilers reduce drag, reduce lift, add high spe4ed directional stability, and provide a more turbulence-free wake in which the drogue parachutes can safely deploy.
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5) GM's patented half-tonneau was based upon the pre-1986 C-10, long-bed pickup. The top of its tailgate happens to coincide with the 'template.'
6) This truck was Cd 0. 535.
7) with the half-tonneau it was Cd 0.491.
8) with full-tonneau, Cd 0.513.
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9) For Texas Tech's 1988 SAE Paper, they used a circa 1987 F-150 long-bed and short bed.
10) As your memory is 'good', the combination cab-wing, plus half-tonneau was almost as good as the GM' 'aeroshell', delta-18% vs delta 20% drag reduction. Around 60% of rear lift was killed.( for the long-bed ).
11) Optimum wing 'size' and angle depended on bed type/ length.
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12) All modern low-drag concept cars are using aft-body contours close to, or dead on the 'template' contours, depending on 'aggressiveness.'
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I don't have a 'blueprint' for your Ranger, so I don't know it's particular architecture.
For a first approximation, you might start with a wing and cantilevered half-tonneau which mimicks the contour of the #3 'template.'
RIVIAN is using it, and until CYBERTRUCK hits the market will be taking top honors for lowest drag pickup.
If you want to get laughed at, you can add a 'blister' on top of the half-tonneau, to fill in some of the vortex void above it. AeroStealth and I tested one back in the 90s on SPIRIT, and it showed the highest mpg increase, short of a 3D aeroshell.
A 'wing' will help by itself.
Same for the tonneau.
Both together is better.
I'll check at home for the wing lengths. Maybe have them Thursday.

SAE Paper# 881874 and cab wings
 

https://ecomodder.com/forum/showthre...ics-20744.htmlhttp://https://ecomodder.com/forum/m...ng-results.jpgFound PhD Timothy Maxwell et al.'s paper from Texas Tech.
Full-scale, wind-averaged ( 0-degrees-to-10-degrees ) tunnel testing at Lockheed, Marrieta, Georgia revealed:
Short-bed pickup:
* 19" wing @ 8.2-degrees down angle= negative delta-Cd 4.17%
* 22" wing @ 5.0-degrees = negative delta-Cd 4.6%
* 24" wing @ 8.2-degrees = negative delta-4.73%
* The 19" wing was 'okay' up to 13-degrees
* The 22" wing was in burble point by 12.0-degrees
* The 24" wing was burbling @ 12.0-degrees
* The 24" wing was @ stall @ 18-degrees.
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The Long-Bed pickup:
* 22" wing @ 3.0-degrees= negative delta-Cd 3.64%
* 28" wing @ 5.0-degrees = negative delta-Cd 4.19%
* 32" wing @ 8.0-degrees = negative delta-Cd 4.37%
* The 22" wing was in stall @ 13.0-degrees
* The 28" wing was in stall @ 13.2-degrees
* The 32" wing was in stall @ 13.0-degrees
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The combination, cab-wing & half-tonneau maximum drag reduction was 17%.
Lift was reduced by 30%.
56% lower lift compared to a no tonneau and gate down configuration.
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here's the table ( rotated )
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here's a link to the 'blister half-tonneau', 3rd & 4th images from top

My thoughts would be to use the 22" wing at 5*. It's nearly as good as the "best" option listed and I think 5* (maybe) fits the template better. I have a short bed truck. It also looks like 12* is the "fail" point of the 22" wing. Thinking about the measurements and math I did on my aerocap frame for the old truck, maybe a 22" wing at 8* would fit the template even better and be the "sweet spot" between the last two options.

Even though I'd love to test some different tonneau options, I think my thoughts at the moment are to put on a half tonneau that stops at the tailgate with the option to build a 3"/20* rear spoiler at the tailgate end. Then trying to figure out a way to mount a 22"/8* wing at the cab. I have a couple of ideas how to mount it, but I need to go out to the laboratory (the local pick-n-pull) and do some real world mock ups.

Any thought from the collective on this plan?

My only other question is this......

With a 22" wing and a half tonneau of 36", that leaves only 14" of gap before they overlap in the side view. How do these two surfaces interact to create the differing pressures? I guess I always thought the bigger the "opening" in the side view (less overlap), the greater the pressure difference. Is my thinking backwards?

22" @ 5
 

If we wanted to split hairs, we'd have to accept that these quanta are technically valid ONLY for a 1987 F-150 Short Bed.
Just for my own curiosity, I'm gonna see if there are blueprints available for the '87 long bed and short bed, and all the exterior dimensions. This would put Texas Tech's quanta into context.
And keep in mind that, they just essentially used a piece of plywood, hinged at the bottom, with no pains made to integrate the wings into the cabin's architecture. And there was no 'curvature', just a simple angled panel.
I suspect that a blended wing, which marries perfectly to the cab, with a contoured surface, will out-perform Tech's rudimentary form.
When tilted down, their panel created a 'bulge, presumably acting as a crude airfoil, actually adding some lift. An integrated, curved panel would not, and it would have given superior pressure recovery compared to the flat panel.
But as a 'first approximation' I'd be doing exactly as you plan.
Tech's 32" wing lowered the cab's separation line almost 4.5-inches. That's all pressure recovery. When the flow left the trailing edge of the wing, it was moving slower, and at a higher pressure, closer to that of the flow coming off the sail panels. Shearing forces would be lower, and with that, weaker vorticity, and a higher 'base' pressure behind the cab.

wing / tonneau gap
 

On the long-bed with 32" wing and 48" tonneau they had a 16" gap. So it kind of 'scales.'
Your tailgate is much closer to the rear of the cab, so all the body proportions are different than the long-bed.
And Ford never published a Cd for the short bed F-150, so it's an unknown quantity.
Presently, the RIVIAN pickup has the lowest Cd. And it's cabin upper trailing edge to tailgate proportion happens to intersect the AST-III projection perfectly, so that's a clue for us ( GM's long-bed C-10 Pickup used in their tonneau cover research happened to match the AST-I contour. Their aero-shell, which Texas Tech also researched, would have also fit under the AST-I , their Cd 0.14 Aero 2002 concept was also AST-III, also their Cd 0.137 EV-1, 183-mph LSR ). They're smart folks!
I wouldn't be concerned with the gap.
That opening is part of the mechanism which transmits a lower pressure from the bed vortex core to the inner face of the tailgate, which is the 'secret sauce.'