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Old 09-27-2016, 09:20 AM   #91 (permalink)
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Quote:
Originally Posted by gumby79 View Post
Any open back with sides will have an eddy. Eddy=fuel economy reduction, you don't get to spin the air for free. I'll be it it would be a smaller eddy ,their for a smaller penalty.
Dreem big chisel down to reality
I think that "Box Cavities" can be made to work.

There was a thread on it a while ago, several articles/PDF's were posted.


Box Cavity for a pick-up truck

http://ecomodder.com/forum/showthrea...uck-26367.html

In that thread above is one of my favorite images discovered by participating this forum.

Automotive Aerodynamics: Drag Area – Size Matters


The VW van tail does not follow the aero-template and is open ended, yet I am told by a forum member familiar with the project that it worked quite well.

EDIT: gumby79, your description is similar to Aeroheads, net positive gain I think?

http://ecomodder.com/forum/showthrea...k-26367-3.html

Quote:
Originally Posted by aerohead View Post
I think that it will definitely show at the gas pump.
As long as the trailing edges are round about where Mair's boat-tail profile would be,the air will separate at the tailgate area,then swirl into a captured-vortex;stuck against the tail,with the outer air streaming by.
It's that outer air which will have a chance to decelerate to a higher pressure before it does break away,which will raise the base pressure back there.

........................The air immediately separates at the beginning of the cavity but does re-attach at the back,capturing a vortex on top,both sides,and bottom.

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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html

Last edited by kach22i; 09-27-2016 at 09:27 AM..
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Old 09-27-2016, 01:50 PM   #92 (permalink)
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Wickerbill?

To test you premise you could tuft test the bed gap.
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Old 09-27-2016, 08:22 PM   #93 (permalink)
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Originally Posted by freebeard View Post
To test you premise you could tuft test the bed gap.
The bed gap is a dead pocket of air and can be sealed up with a foam rubber gasket.

The area above the bed can also be sealed flush, but like I said I favor an aileron/flap/flaperon/slat type gap which induces venturi type flow (in theory).

Wings - THE ZENAIR STOL CH 801-HD



It does look like any type of air gap increases drag however.

http://ecomodder.com/forum/showthrea...n-32407-2.html


I suppose one could just tape it sealed.

http://ecomodder.com/forum/showthrea...ail-33283.html


Interesting graphics.

http://ecomodder.com/forum/showthrea...fo-2072-2.html

Quote:
Compared to the standard blunt end (a), adding what they call attikas (fascias or parapets; flat, parallel panels) (b) delays separation and moves the tail vortices back (reduces Cd by up to 10%); these can be set inward (c), further reducing the size of the „dead zone“ (reduces Cd by 0.06, which is about half as good as the ideal tapered tail); the open-ended Kammback made of flat panels (d); and „Fluid Tail" (e).
http://theaviationbusiness.blogspot....end-stall.html
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Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html

Last edited by kach22i; 09-27-2016 at 08:48 PM..
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Old 09-27-2016, 09:06 PM   #94 (permalink)
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Quote:
It does look like any type of air gap increases drag however.
That's my point, although longitudinal ducts appear to be effective (Ford GT40, VW GTI W-650, any late Ferrari), lateral ducts like your wing slots add drag. With tufts in the gap you could tell if the air is rising, falling, exhausting out the sides, whatever. Then decide when and where to block it.




Look how close that is!

Morelli used turbines in the wheels to pump air into the wake of the rear tires. The Vanagon pumps [at least] 1500cfm of hot air under the back bumper. If that was ducted into the wake of the rear tires, Morelli's kludge wouldn't be necessary (except for EV conversions ).

Truncating with a flat plate, a box cavity or a perforated base plate all work to some extent.
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Old 10-01-2016, 12:48 PM   #95 (permalink)
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Vanagon box cavity

Quote:
Originally Posted by kach22i View Post
I think that "Box Cavities" can be made to work.

There was a thread on it a while ago, several articles/PDF's were posted.


Box Cavity for a pick-up truck

http://ecomodder.com/forum/showthrea...uck-26367.html

In that thread above is one of my favorite images discovered by participating this forum.

Automotive Aerodynamics: Drag Area Size Matters


The VW van tail does not follow the aero-template and is open ended, yet I am told by a forum member familiar with the project that it worked quite well.

EDIT: gumby79, your description is similar to Aeroheads, net positive gain I think?

http://ecomodder.com/forum/showthrea...k-26367-3.html
That was my neighbor's,the late Bob Parsons.It had curvature in plan and elevation.1/2" EMT skeleton,covered with doped Dacron,sewn by his wife Jacque.
Bob 'n wife went to the Yucatan Peninsula each year in it.He saw upwards of 28-mpg.None of the other Vanagon owners (mostly Germans) believed his claim.
I've never heard of another Vanagon getting over 24-mpg.
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Old 10-01-2016, 03:15 PM   #96 (permalink)
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Quote:
I've never heard of another Vanagon getting over 24-mpg.
Possibly because nobody has gone full diverter/bellypan/wheel spats and put a little boat tail on that retracted awning?
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Old 12-08-2016, 10:54 AM   #97 (permalink)
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I did not want to start a new thread, so I'll just add to this old one.

The rust holes on my truck became to large they were adversely affecting the aerodynamics.

Holes so large you could pass a new born baby though them, and the rear wheel flares were completely gone.

Here is a thread in another forum with more photos:

Rusty old pickup truck - Razzle Dazzle Camouflage

Rusty old pickup truck - Razzle Dazzle Camouflage - Pelican Parts Technical BBS
Before:


After:


Photobucket Gallery:
S10 4x4 Pick Up by George Kachadoorian | Photobucket

Expandable foam (Great Stuff), 2-part epoxy, Micro-balloons, masking tape and spray cans...............and lots of time.

The actual tapping and spraying took a single day, most work was either before or after.

I had some fun with the details.



I also silicone caulked up some cracks and joints near the chin spoiler, it's amazing how these little details add up in the handling and performance department.

Cheers, George/kach22i
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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 12-08-2016, 02:08 PM   #98 (permalink)
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Quote:
Holes so large you could (very carefully) pass a new born baby though them
Fixed that. It looks good.

All the time is always in the prep work.
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Old 12-09-2016, 08:40 AM   #99 (permalink)
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Once the lose thin stuff was cleared out a toddler could of nestled in there.

S10 4x4 Pick Up by George Kachadoorian | Photobucket


It's all foam filled now.



I think once the rust starts to become an aerodynamic issue something as radical as this must be done. It is not as radical as that guy in Russia making a whole car out of this method, but it is transforming, and can be part of an Metamorphosis .
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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 12-09-2016, 02:23 PM   #100 (permalink)
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Tell us what we're looking at. My guess is that you taped black polyethylene, injected the foam behind it, and it expanded until the plastic ruptured. And you put tape over the first pinholes that opened up.

Close?

I've often thought of injecting foam into the door pillars and window headers in a VW Beetle body (plus one bar across the center roof) to make a non-NHRA/NORRA/SCTA-legal roll cage.

What do you think is the future history of the repair? Delaminates and traps water? Outlasts the pyramids?

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