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#26 |
Eat My Rust
Join Date: Jan 2007
Location: Cypress, Texas
Posts: 3,362
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Re: Aero difference between 67/8 and later hoods?
In theory, the 69 and up hoods are less aerodynamic, forcing the flow of air to separate from the body. Basically, meaning it bounces off the hood's leading edge, and falls back near the cowl. In the pages I have down on this post, page/image A4-fig.16, bottom left corner illustrates this well.
Read your hearts out: Loads of stuff about front-end design on boxy things. Aero development on the VW Rabbit, loads of info of how the design of the nose effects air flow. A1: http://i42.photobucket.com/albums/e3...ROFILES/A1.jpg A2: http://i42.photobucket.com/albums/e3...ROFILES/A2.jpg A3: http://i42.photobucket.com/albums/e3...ROFILES/A3.jpg A4: http://i42.photobucket.com/albums/e3...ROFILES/A4.jpg A5: http://i42.photobucket.com/albums/e3...ROFILES/A5.jpg A6: http://i42.photobucket.com/albums/e3...ROFILES/a6.jpg Air flow on box-shaped vehicles B1: http://i42.photobucket.com/albums/e3...ROFILES/b1.jpg B2: http://i42.photobucket.com/albums/e3...ROFILES/b2.jpg |
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#27 | ||
Senior Member
Join Date: Jan 2005
Location: Raleigh, NC
Posts: 894
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Re: Aero difference between 67/8 and later hoods?
Quote:
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In the lab you could probably measure the effect of the angle of the two hoods. In the real world I would expect very little difference.
__________________
-Chris Building a stripper, one part at a time: 1969 K5, 307, 3spd, 3 seats, hard top. Added Pwr Discs, Pwr Steering, Aux Battery, T-case Skid, Lighted Sidemarkers, HEI, Lock-Right Diff, ECE Class IV Hitch, 32" MT/Rs. Parts to Install: Hand Throttle, Console, Tow Hooks, Dual Horns, AM-FM, Dealer Swing-Away Tire Carrier, Gas Tank Skid. Also building a 1950 Willys CJ-3A and off-roading a 2001 Nissan Frontier on 1-Ton Portals... |
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#28 | ||
just can't cover up my redneck
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
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Re: Aero difference between 67/8 and later hoods?
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Last edited by LONGHAIR; 09-02-2008 at 08:04 PM. Reason: spelling? |
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#29 |
Well, Whoop-dee-do!
![]() Join Date: Mar 2003
Location: Easton, Mo. pop.- me & scarcely a few others
Posts: 2,302
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Re: Aero difference between 67/8 and later hoods?
While you guys are getting technical, I'll throw in what I know to be true. I have both a '68, and a '72. Both on 33 x 12.50 tires, at nearly identical ride height. The '72 has FAR less wind noise & turbulence. You can feel & hear the difference as the air comes over & around the windshield. Windows up or down, same difference.
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'68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD ![]() '72 K20 500 Cad/TH400/NP205 SOLD ![]() '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car ![]() |
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#30 | |
LAIDOUT
Join Date: Jan 2005
Location: NW Montana
Posts: 928
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Re: Aero difference between 67/8 and later hoods?
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#31 | |
LAIDOUT
Join Date: Jan 2005
Location: NW Montana
Posts: 928
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Re: Aero difference between 67/8 and later hoods?
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#32 |
Project underway - finally.
Join Date: Feb 2007
Location: Greenville, SC
Posts: 493
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Re: Aero difference between 67/8 and later hoods?
Longhair, the engineers listening perked up solely because you used the term "frontal area" which is defined as the cross sectional area. What 69towrig said was absolutely correct, there are basically three factors, frontal area, drag coefficient and speed that determine the drag force. There was indeed a change, but it was not in frontal area. He originally said there was little change to drag coefficient and you disagree if I understand correctly. Interesting problem. Easy solution. Do a coast down test with hood one (multiple passes in both directions for consistency) and repeat with hood two. This is a surefire way to eliminate all other variables, and is a time tested way to measure your drag coefficient.
-Brian (yes, an engineer)
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1972 GMC Pre-resto... awaiting allocated funding. |
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#33 |
Eat My Rust
Join Date: Jan 2007
Location: Cypress, Texas
Posts: 3,362
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Re: Aero difference between 67/8 and later hoods?
If some one could be so kind as to provide a large pic of the 67-68 hood, from the side (basic side profile) I can create a video to show the effect of air moving over it...
Same program as I did for this using my 69. I can create one to compare the 67/68 hood to the 69-72. It's not 100% accurate but provides a good visual tool to compare the two. Last edited by texanidiot25; 09-04-2008 at 04:57 PM. |
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