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Old 02-14-2012, 06:36 PM   #242 (permalink)
aerohead
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where are the

Quote:
Originally Posted by ERTW View Post
Re: the template - where are the vertical % to match the horizontal %? In other words, what are the X and Y coordinates for the template? Does the spline have an equation?

Doesn't the data show that an ellipsoid has virtually the same Cd as the teardrop?

What's the Cd down to 55% template? This is where I see a pickup terminating. It'd be handy to determine point of diminishing returns.

I've observed snow on my car. I hypothesize that sharp corners discourage atmospheric pressure side air from moving towards the lower pressure area above the car, and reduces vortices. If no vortices are created above the roof, then it's even less likely imo to create vortices at the trunk edge. I think that a polyellipsoid reduces the lateral pressure gradient - which also prevents vortices.
ERTW,I've never finished the thread so,so far there is no data for what would be happening in plan view.I hope to complete it within my lifetime.
As it is based on a streamline body of revolution,the 'Template',in theory would begin plan taper at same point as the roofline.
Of course it would make the vehicle too wide.
I'm compiling plan views of vehicles to post at some date,so members can get a sense of what has already been done with this 'pumpkin seed ' form.
As to your 55% question.If your vehicle was completely cleaned up,then at 55% of 'Template' you'd have a potential for around Cd 0.16.
To fully exploit the 'Template' with a pickup would require that the truck box roll into tumblehome as it progresses rearward,allowing the elliptical cross-section to evolve.
I was in the process of doing this to the Dodge pickup when the T-100 showed up in my driveway.So this project has languished since 2005.KamperBob is the only person who has seen it.
The boat hull "poco-loco" which replaced the original aeroshell has both elevation and plan taper,mimicing the 'Template' best I could.She produces no vorticity and by itself is good for 13% better mpg (hwy).
With the full kit on the T-100,by the delta-fuel economy/delta-drag coefficient method,she's estimated at Cd 0.18.
There is a tuft-testing photo of it at the "Full-Boat-Tail with Gap-Fillers for T-100 Pickup' thread.
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ERTW (02-14-2012), KamperBob (02-17-2012)