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Old 05-22-2011, 07:49 PM   #11 (permalink)
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thanks for those pictures. I think if I scaled them right that last one is about ten inches long? do you happen to know if thats correct?

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Old 05-23-2011, 01:35 AM   #12 (permalink)
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scottoriou -

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thanks for those pictures. I think if I scaled them right that last one is about ten inches long? do you happen to know if thats correct?
I don't know but I did some pixel calcs and the agree. The SC2 is 180" long and the car picture is 478 pixels wide :

478 pixels / 180 inches = 2.66 pixels per inch

The last spoiler is about 26 pixels wide :

26 pixels / 2.66 pixels per inch = 9.79" => almost 10"

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Old 05-23-2011, 06:53 AM   #13 (permalink)
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Check out this thread for a sedan boattail (or wingtail). The one pictured eventually blew off the car so use that as a learning experience. It gives 10 to 20% improvement in mpg.

http://ecomodder.com/forum/showthrea...-a-7489-4.html

When I finish my current boat project, I have another wingtail design in mind. With the trailer hitch receiver as the mounting point, use a "tee" welded up from 1-1/4" square tube and from that frame build up a thin plywood boattail using stitch and glue boatbuilding techniques.
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Old 05-24-2011, 08:01 PM   #14 (permalink)
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Old 05-28-2011, 03:08 PM   #15 (permalink)
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that nature

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Hello everyone, I want to boat tail my saturn. I would like to just build it off of my trunk instead of from the roofline. Would I be wasting my time to build a boat tail of that nature?
scottoriou,there are many instances documented that show a drag decrease from just about anything which filled in some of the turbulent wake.
For lack of an official term I call it stuffing the wake.
If you begin the boat tail where you want to, you'll lose some potential energy due to the overhead turbulence but I do believe you'll see re-attachment and drag reduction,depending on length.Kinda like the difference between an Audi TT and a New Beetle.The Audi is still an aerodynamic compromise but its far and away superior to the VW.
GM did what your doing with the Impact/EV-1 and set a land speed record.It would have also extended the battery range.
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Old 06-02-2011, 01:11 AM   #16 (permalink)
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So what if instead of an entire boat tail I created sort of a prius shape to the rear of the car. It would possibly increase the rear section area which could possibly hurt the performance but if clean separation was induced with sharp corners on all parts would it be helpful? here are some pictures of things i was thinking.
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Old 06-02-2011, 06:44 PM   #17 (permalink)
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what if

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So what if instead of an entire boat tail I created sort of a prius shape to the rear of the car. It would possibly increase the rear section area which could possibly hurt the performance but if clean separation was induced with sharp corners on all parts would it be helpful? here are some pictures of things i was thinking.
This is kinda where Kamm and Korff were going with their recommendations.They realized that a full tail was 'impractical' with respect to driveways and parallel parking and such,and advocated that the tail be truncated at a point where the wake area equaled 50% of frontal area.
There's still 50% of the drag left on the table mind you ( good for another 25% mpg ), but your not strapped with an enormous cantilevered tail hanging way out there.
Adding only a foot to my CRX was good for Cd 0.235 and 60+ mpg @ 55 mph,52 @ 70.
I would not be concerned with 'burst'.Your Cd is fixed at about 20 mph and the separation point at the rear isn't moving around.That's straight from Hucho.
I would encourage you to do a shorter tail exactly on the 'Template' rather than a longer one which either falls above or below it.
--------------------------------------------------------------------------
The Renault Vesta II is an example of a "Template" car.She's good for 138 mpg @ 100 Km/h.
The Mercedes 'Boxfish' is also a "Template" car.
Both have Cd 0.19 and are very short for their Cds.They have only about 32% of aft-body.( the New Beetle,also a 32% aft-body car suffers with Cd 0.38 due to the pseudo-Jaray 'fastback' roofline,which breaks all the rules of streamlining )
------------------------------------------------------------------------- The other thing is, that these cars are 'plug and play.' If you want more mpg at a later date,you just plug in a longer tail.Modular!
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Old 06-02-2011, 07:25 PM   #18 (permalink)
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"The Renault Vesta II is an example of a "Template" car.She's good for 138 mpg @ 100 Km/h."

Hardly, 4.25 l/100 km = 55 mpg city/83 hwy for a 1000 lb 700 cc car. mpg by French standard not EPA
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Old 06-03-2011, 12:42 PM   #19 (permalink)
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Quote:
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"The Renault Vesta II is an example of a "Template" car.She's good for 138 mpg @ 100 Km/h."

Hardly, 4.25 l/100 km = 55 mpg city/83 hwy for a 1000 lb 700 cc car. mpg by French standard not EPA
But Vesta 2 was run from Bordeaux to Paris using only 1,94 l/100 km @ 100,9 km/h - that's 121 mp(US) @ 62.7 mph

Slowing down to 50 km/h or 31 mph , it used 1.6 L/100km or 147 mpg.

Imagine what it'd do with EFI and LRR tires.
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Old 06-03-2011, 04:35 PM   #20 (permalink)
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Hardly

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"The Renault Vesta II is an example of a "Template" car.She's good for 138 mpg @ 100 Km/h."

Hardly, 4.25 l/100 km = 55 mpg city/83 hwy for a 1000 lb 700 cc car. mpg by French standard not EPA
The first article I saw for the Vesta II had to do with the Paris/Bordeaux run,and 138 MPG.
I later wrote to Renault and they mailed me a press kit for the car.I believe they offered the same numbers as in the initial article.No mention of any EPA protocals,just steady-speed driving,two passengers and luggage.

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