Pickup truck aerodynamics

[aerohead]

Just a quickie,based on T-100/Dodge research
*Flatbed --------------------------------------- Cd 0.668
*Suburban type roof (Lear cap)------------------ Cd 0.39
*Pickup bed (open)------------------------------Cd 0.44
*Full tonneau ---------------------------------- Cd 0.415
*GM' Half-tonneau ------------------------------Cd 0.357
*Texas Tech (GM) Aero Shell ------------------- Cd 0.352
*ITworks double-geometry shell ---------------- Cd 0.325
*Spirit of Ecomodder.com----------------------- Cd 0.268-0.267
*Spirit of Ecomodder.com with folded mirrors----- Cd 0.251
*Spirit of Ecomodder.com with mirror delete (est.) Cd 0.24
*Complete boat-tail on custom truck box--------- Cd 0.12?
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Here's a semi-recent photo of a pickup chassis (Chrysler) illustrating the 'body-on-frame' nature of most trucks.The Ridgeline,VW,Subaru Brat, Dodge Rampage,etc. would be exceptions

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Here's the all-new for 1986 GM pickup revealing the deep chassis of which the airdam or belly pan will help with,drag-wise

Here is a shot of the blistered half-tonneau cover.It's the rear half of a plan-tapered aeroshell

Here is the blistered half-tonneau in combination with a very rudimentary cab-wing

Here is a shot which shows the aft-body more in true length

Here is a tuft study of the aft-body near home back in the day

[Sven7]

The GM half tonneau is the rear half covered?

What are the Texas Tech Aero Shell and the ITworks double-geometry shell?

How far back does the noted boat tail go? All the way to a point?

Pics, or at least links!

[Frank Lee]

The half tonneau by itself is that much better than a full tonneau?

[slowmover]

Originally Posted by aerohead

Just a quickie,based on T-100/Dodge research
*Flatbed ------------------------- Cd 0.668
*Suburban type roof (Lear cap)---- Cd 0.39
*Pickup bed (open)---------------- Cd 0.44
*Full tonneau --------------------- Cd 0.415
*GM' Half-tonneau -----------------Cd 0.357
*Texas Tech Aero Shell ----------- Cd 0.352
*ITworks double-geometry shell --- Cd 0.325
*Complete boat-tail -------------- Cd 0.12

I'm surprised that a bed topper (cab-height, flush-fit) shows so well. I was under the impression it was "worse than" a full tonneau cover.
.

[skyking]

Thanks Phil. I have a shell in mind with an extension back about another foot. I could keep the tail lights exposed that way.

[KamperBob]

This is a great thread - thanks, Phil!

Grain of salt: not all pickup trucks are the same. Differences in height, width, length, cab shape, step vs. fleet side, weight, driveline (gearing, horsepower, valves per cylinder, fuel type & delivery, aspiration, two vs. four vs. all wheel drive) vary across make, model and production year. For trucks X and Y the optimal aero-mod may not be the same solution.

[BackroadBomber]

Originally Posted by Sven7

What are the Texas Tech Aero Shell and the ITworks double-geometry shell?

*also interested. Any pics or links?

[aerohead]

Originally Posted by Sven7

The GM half tonneau is the rear half covered?

What are the Texas Tech Aero Shell and the ITworks double-geometry shell?

How far back does the noted boat tail go? All the way to a point?

Pics, or at least links!

The GM 1/2-tonneau is just the rear half.It was tested on a C-10 pickup of Cd 0.535.I had to haul a workmate this morning which required emptying out the cab,and with it my workbook with GM's patent which has a performance curve for different configurations of a tonneau.I'll have it for next time,Sorry!
In 1988,Texas Tech University's Dept.of Mechanical Engineering Aero Lab published an SAE Paper on pickup truck aero.It is here that we're introduced to 'aeroshell' for the first time.In the 'photo-albums' under documents,there is an image of their drag table which depicts the aeroshell.It was good for a 20% drag reduction and 10% HWY mpg.
Itworks is me (Independence Technological Works).When I do public presentations people seem to be attached to officialdom,so I created ITworks to connect with the displays.
My cover simply combined the elevation contour of the Texas Tech Aeroshell with some plan taper to cheat a little extra mpg out of the device.It demonstrated a 13% HWY mpg improvement,which according to GM Aero Lab equates to a 26% drag reduction.
As to the boat tail length,70% = 100% as far as the drag eduction goes,as from 70% on,truncation of this structure is duplicated aerodynamically as a 'phantom-tail.'
Fachsenfeld was doing this.This is what Kamm premised his work on.Alberto Morelli did likewise with the CNR car of 1976-78.
I have the GM patent and I'll try and get it scanned this Saturday.AUTOWEEK carried an article for a Gale Banks GMC LSR pickup which sported the 1/2-tonneau for it's 211-mph run at Bonneville.If it isn't in the photo-album I'll dig that out.
The ITworks aeroshell should be in the photo-album as well,or you can just GOOGLE Phil Knox,for the EV World article by Jessica Savage about the T-100 from a few years back .
Hope that helps!

[Sven7]

So this is the TIworks shell?


I looked on the SAE's website for the papers but they are not available for free.

[Sven7]

AUTOWEEK carried an article for a Gale Banks GMC LSR pickup which sported the 1/2-tonneau for it's 211-mph run at Bonneville.

If this isn't it, the thing uses the same principle.


Here's the Banks Sidewinder. Notice the half tonneau.


The next question is, why? It would seem that this opening would impede the vortex that leads high speed air over the virtual template.