Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-23-2010, 07:09 PM   #1 (permalink)
Master EcoModder
 
Big Dave's Avatar
 
Join Date: Jan 2008
Location: Steppes of Central Indiana
Posts: 1,319

The Red Baron - '00 Ford F-350 XLT
90 day: 27.99 mpg (US)

Impala Phase Zero - '96 Chevrolet Impala SS
90 day: 21.03 mpg (US)
Thanks: 0
Thanked 186 Times in 127 Posts
Tonneau With Steps

I have a makeshift aerolid. It is suboptimal in my view. Too steep (17 degrees) and I'm blind as a bat to the rear, thus married to big side mirrors. But at the same time, it was a 1.5 MPG improvement over a hard flat commercial tonneau, so the thing had some virtue. Therefore I'm on the lookout for something different: Better smoothing of air flow and better visibility.

Back in younger days I had a Z-28 that had a rear window cover that was a bunch (8 - I think) of stepped louvers over the rear window. Mostly, it was there to keep snow off the rear window.

This is what I'm thinking:

I still have the flat fiberglass tonneau. Why not fot it with three of four flat plates stepping down from the top of the cab. The plate would be paralell to the tonneau, so could see out; and the steps would approximate a aeroshell.

The top of my cab would be about 22 inches above the top of the tonneau. I'm thinking three 12 gauge aluminum plates. Only the top plate need ride close to the top of the cab. The lower ones would progressively begin farther back from the cab and would be attached to the tonneau with some sort of strut.

My only worry is the truck winds up looking like a Fokker DR1. But, then, it is the Red Baron.

__________________
2000 Ford F-350 SC 4x2 6 Speed Manual
4" Slam
3.08:1 gears and Gear Vendor Overdrive
Rubber Conveyor Belt Air Dam
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-23-2010, 07:56 PM   #2 (permalink)
(:
 
Frank Lee's Avatar
 
Join Date: Jan 2008
Location: up north
Posts: 12,762

Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
90 day: 21.24 mpg (US)
Thanks: 1,585
Thanked 3,555 Times in 2,218 Posts
Might work as long as the "virtual" angle is shallow enough... and to fix that if needed you could hang a shelf out the back. I don't know if it would work better/worse/same if the sides were enclosed.

Were I to build an aerocap I'd put a one or two step rear window in it.
__________________


  Reply With Quote
Old 07-24-2010, 01:02 PM   #3 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
go for it

Dave,I'd be very inclined to believe that you'll see some benefit.My original shell ( pre-goats ) had a step for the 3rd brake light and another for a vertical rear backlight.It was still good for 13%.
Both Ferrari and Porsche have used the multi-step backlight louvered cover.
And Ford's patented bi-wing spoiler ( Probe-III,Sierra,Merkur XR4Ti ) is kind of a cruder version,but with good effect.
Your steps should provide for re-attachment and creation of locked-vortices which will help smooth the outer flow.
And thinking about Frank's comment,if your cab-to-bed tailgate ratio is 'fast',the rear shelf would help shape the vortex closer to the 'template' curve.
I'd do it.
  Reply With Quote
Old 07-25-2010, 08:47 AM   #4 (permalink)
Recreation Engineer
 
KamperBob's Avatar
 
Join Date: Dec 2009
Location: Somewhere USA
Posts: 525

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
Thanks: 333
Thanked 138 Times in 103 Posts
I'm a little confused here.

1. BigDave, I thought you had a 3/4-ton diesel. Am I confusing you with someone else?

2. Phil, Dave feels 17-deg slope is too steep but that's less than 22. Any comments on that?

I'm not sure if filled or open sides would be better. If you can compare both and report results, that would be awesome!

Thanks
KB
  Reply With Quote
Old 07-25-2010, 02:09 PM   #5 (permalink)
EcoModding Apprentice
 
Join Date: Jan 2008
Location: Chicagoland
Posts: 204

- - '10 Toyota Prius III w/Navi
Thanks: 4
Thanked 12 Times in 12 Posts
Hi All,

All pickup trucks should have rear-view cameras and sonar sensors anyway. Just add one. They are cheap enough....
  Reply With Quote
Old 07-25-2010, 04:38 PM   #6 (permalink)
Pokémoderator
 
cfg83's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
Thanks: 439
Thanked 530 Times in 356 Posts
Big Dave -

In another thread I made this for aerohead, and I think he approved it :



CarloSW2
__________________

What's your EPA MPG? Go Here and find out!
American Solar Energy Society
  Reply With Quote
The Following 4 Users Say Thank You to cfg83 For This Useful Post:
aerohead (07-26-2010), KamperBob (07-25-2010), Phantom (07-28-2010), TEiN (07-26-2010)
Old 07-25-2010, 05:33 PM   #7 (permalink)
Recreation Engineer
 
KamperBob's Avatar
 
Join Date: Dec 2009
Location: Somewhere USA
Posts: 525

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
Thanks: 333
Thanked 138 Times in 103 Posts
Interesting! Steady state fields look very similar.



Cheers
KB
  Reply With Quote
Old 07-25-2010, 05:44 PM   #8 (permalink)
Master EcoModder
 
Big Dave's Avatar
 
Join Date: Jan 2008
Location: Steppes of Central Indiana
Posts: 1,319

The Red Baron - '00 Ford F-350 XLT
90 day: 27.99 mpg (US)

Impala Phase Zero - '96 Chevrolet Impala SS
90 day: 21.03 mpg (US)
Thanks: 0
Thanked 186 Times in 127 Posts
Kamper Bob:
1. Mine's always been a one-ton. You must have me confused with someone else.

2. I have no intention of going to 22 degrees. I have to step down a total of 22 inches in an 80 inch run.

3. I'm gonna do open sides. I'm looking for some visibility so I can cut down or eliminate my side mirrors.


CFG:
Thanks. That's what I'm looking for. I'm thinking two flat plates attached parallel to the top of the hard tonneau. Use the top of the tonneau as the zero datum, I thought the first one might be set about 14 inches above the datum and the rear one 7 inches above the datum.

I'm thinking 14 gauge aluminum with some welded longitudinal stiffeners. I'll also need stronger gas struts for the lift mechanism as the tonneau top gets heavier.
__________________
2000 Ford F-350 SC 4x2 6 Speed Manual
4" Slam
3.08:1 gears and Gear Vendor Overdrive
Rubber Conveyor Belt Air Dam
  Reply With Quote
Old 07-25-2010, 06:01 PM   #9 (permalink)
Recreation Engineer
 
KamperBob's Avatar
 
Join Date: Dec 2009
Location: Somewhere USA
Posts: 525

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
Thanks: 333
Thanked 138 Times in 103 Posts
Dave, thanks. It IS you. Right, full not three-quarter ton. I knew it was heavier than half. I'm seeing that in your sidebar stats now. It was actually your thumbnail that threw me. The cap on back looks familiar but for some reason the truck looks like a mini. That's where I went wrong. No insult intended it just confused me.

I'm also puzzled by your angle comment. Why do you say 17 degrees is too steep?

Maybe I'm just not having an off day. (shrug)

Cheers
KB

Last edited by KamperBob; 07-26-2010 at 06:57 AM..
  Reply With Quote
Old 07-26-2010, 06:23 PM   #10 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
results

Quote:
Originally Posted by KamperBob View Post
I'm a little confused here.

1. BigDave, I thought you had a 3/4-ton diesel. Am I confusing you with someone else?

2. Phil, Dave feels 17-deg slope is too steep but that's less than 22. Any comments on that?

I'm not sure if filled or open sides would be better. If you can compare both and report results, that would be awesome!

Thanks
KB
KB,this is going to be all speculation on my part and here's how I'm looking at it.
If we place Dave's truck under the template and look at the slope of the tangent at the tailgate,we might find that,while short of Mair's 22-degree maximum angle,we're to 'soon' along the template line to support 17-degrees.
If you look at Mair's boattail in the archives,you'll notice that he doesn't hit 22-degrees until at least a full diameter ( 2-truck body heights ) behind the point of max. roofline camber.
So 17-degrees may be two 'fast.'
As far as the sides are concerned,I'm going out on a ledge.They should behave exactly like a roofline excepting that the flow is less energetic and cannot support as radical a divergence as the roof and even with a windtunnel,would require very careful integration so as not to introduce attached vortices where they 'blend' into the roof sides.
The other thing is the fact that Dave's will be an 'open' structure,something we don't have a lot of published data on.
I do have Ford's patent for their bi-wing spoiler and they go into the aerodynamics of it's performance.Even though their spoiler has 'open' architecture it can still develop some tasty bound-vortices which are capable of modifying the outer field flow in a beneficial manner.
I've found about a dozen cars which have used the 'multiple-rear-facing-step' backlight cover and it appears that they take the bound-vortex from the macro,to the micro level.
I have a very strong suspicion that Dave will see a benefit but I have no way to put any quanta with it.
When Lamborghini,Ferrari,Porsche and others adopt this technology as they have,you've got to figure that they did not arrive at the decision in a haphazard fashion.I've no crystal ball but I'm giving it my thumbs-up.
One upshot is that Dave will 'know' at some point and have something to report.

  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
KamperBob (07-26-2010)
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to improve fuel economy with a tonneau cover MetroMPG Aerodynamics 67 04-14-2022 03:16 AM
Partial Tonneau cover on pickup (plus cab extension - cab wing) bennelson Aerodynamics 61 08-27-2014 01:12 PM
Truck Aero, Bed cover DIY tonneau? Chris D. Aerodynamics 84 11-04-2010 11:56 PM
aerocap or tonneau? (build thread?) ModelE Aerodynamics 9 01-04-2009 09:36 PM
Full Tonneau vs Partial Jim Allen Aerodynamics 4 07-14-2008 05:52 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com