Pickup truck aerodynamics

[craveman85]

I'll have to hold off on the half tonneau testing until I get more of a base line with my hard tonneau/ air dam. On a side note, is there an optimal angle range for an aero cap? Id like to build one that sits on top of my hard tonneau and canbe easily broken down to fit inside my bed. That way I can still open up my ladder rack and carry llarge items while giving a big middle finger to aerodynamics but then have the ability to go back to being Eco friendly in a short period of time.

[freebeard]

On a side note, is there an optimal angle range for an aero cap?

You will find a link here, to a paper that answers that question:

http://csus-dspace.calstate.edu/bits...pdf?sequence=1

It's 119 pages. TL;DR: 12°

So you're saying you'll have a full tonneau, aerocap and roof rack? Or one thing that morphs into each item?

[craveman85]

I have a full tonneau that opens up into a ladder rack. I want a take down aero cover to sit on top when I don't need my bed. Might have to go around 14° with my cover as I want my longest piece to be able to fit inside my bed. In ladder rack form its horribly unaerodynamic but I kinda need my truck to be a truck occasionally.
My only pic of tonneau cover mode


Ladder rack/blind spot/ parachute mode

[craveman85]

Aerohead, have any data for other mods and CD values on pickup trucks like side skirts, air dams and such? Sorry for tthe thread jack.

[botsapper]

when it comes to pickup truck aerodynamics.

...slightly lowered, smooth pans, side skirts but can't get rid of the sweet alloy wheels.

[freebeard]

craveman85 -- Is that a commercial product? If it is, is there a video of it expanding and contracting?

There's a lot of potential for commercial signage there.

[aerohead]

Originally Posted by craveman85

Aerohead, have any data for other mods and CD values on pickup trucks like side skirts, air dams and such? Sorry for tthe thread jack.

The automakers consider pickup trucks to be typically a 2-door sedan sans trunklid.With a full tonneau,a truck would essentially react to mods the same way as a notchback.
An aeroshell would place it as a fastback.
*If you look at the 1991 GMC S-15 Syclone LSR (permalink#7,14,etc..) this is a Cd 0.315 truck,lower than a Corvette of the day.
*wiper delete
*mirror delete
*California aero package:bumper fascia/airdam,fender flares & rocker skirts
*lowered,Bell Tech dropped spindles
*lengthened body 12.2"
*widened body 0.8"
*MOONs
*1/2-tonneau
------------------------------------------------------------------------

This is the T-100 at Bonneville in 2012:

*sealed bulbous nose fascia/with integral airdam/grille-block/plex. headlight covers/turn indicator covers
*front wheel opening gap reducer (driver side)
*articulated front wheel skirt (passenger side)
*hood blister with side Plex. diverters
*full-depth rocker panel extensions
*aspirated full-coverage wheel covers (for the road)
*rear wheel skirts
*compound-curvature aero shell with stinger
*30-inch boat tail
*Front wheelhouse trailing flow blenders
*tail light Plex. fairings (off)
*Belly pan (partial)
*rear wheel trailing fairings (off)
The T-100 is estimated at around Cd 0.16 from the MPG data (362,000-mile database).With the missing bits she would do 32 @ 75-mph,up to 37 mpg @ 65-mph.I'll try for the Darko Technologies wind tunnel in September if my world doesn't explode.
------------------------------------------------------------------------
I'm compiling pickup data.We can make this THE official pickup thread.I'll try 'n get some things scanned and posted this coming Saturday.

[craveman85]

Quick truck belly pan question. Let's say you were to build a 2/3 belly pan back to your rear axle. Things get tricky back by the axle though. How good would it work to make a v shaped air dam to kinda plow the remaining air sideways out from under the truck so it doesn't hit the axle. Or would it just be better to stop just in front of it.

[freebeard]

IMHO the dam would allow base pressure to reach forward under the vehicle, adding drag. And you leaving the rear unpanned, where you need a good transition to the wake.

How about a full pan with a lateral slot to clear the axle?

[aerohead]

Originally Posted by craveman85

Quick truck belly pan question. Let's say you were to build a 2/3 belly pan back to your rear axle. Things get tricky back by the axle though. How good would it work to make a v shaped air dam to kinda plow the remaining air sideways out from under the truck so it doesn't hit the axle. Or would it just be better to stop just in front of it.

According to Carr's research,I think it was reported by Scibor-Rylski,if you have 2/3rds of a pan (the forward portion),then you'll have most of the pans benefit,excepting that you lose the chance for a diffuser which can really enhance a pans performance.
As for the the axle,I've done what freebeard recommends,just leaving a slot in which the axle can move vertically.Most of the air will just 'jump' the gap.(a fairing could be constructed for attachment to the axle bottom such that at neutral 'trim',would seal the gap).
A V-shaped cattle-catcher airdam would add frontal area,trigger separation,increasing the wake area,would itself be a high drag structure, blocking the path of energetic air which might be converted to pressure for the wake,and create transverse jets,out both sides of the underside which would play havoc with the free stream out there.