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Old 01-22-2011, 10:24 AM   #21 (permalink)
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t vago, what's the benefit of the tight-radius inside corners and flat tonneau-like surface between the raised portion and bed walls. I'm skeptical flow would attach that deeply into those gullies. Why not use larger fillets instead?

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Old 01-22-2011, 11:09 AM   #22 (permalink)
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Quote:
Originally Posted by BamZipPow View Post
Are you gonna put in a rear window? Is this one gonna be hinged/have a hatch so you have access to the bed?
Eventually. The foam shape has to be made, and that will not have any of the functionality you mentioned. However, the foam shape can be removed in about 20 seconds, and can be lifted with 1 hand. Version 1 fit this requirement rather easily.

Hm... Just had the strangest idea for using my existing tonneau side rails to secure the aerocap, so that it could be removed in 2 seconds instead of 20.
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Old 01-22-2011, 11:15 AM   #23 (permalink)
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Quote:
Originally Posted by KamperBob View Post
t vago, what's the benefit of the tight-radius inside corners and flat tonneau-like surface between the raised portion and bed walls. I'm skeptical flow would attach that deeply into those gullies. Why not use larger fillets instead?
Heh... See, now you're picking on my poor man's CAD program. There's only so much I programmed into that Excel spreadsheet.

You'll notice that the curves on version 1 were a bit gentler than in the Excel workup.


Excel workup


Real life 1


Real life 2

That was one of the reasons I decided to use FoamulaR sheeting. It can be curved to form compound curves fairly easily, as long as the underlying frame shape can support the minimum bending requirements.
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Old 01-22-2011, 11:28 AM   #24 (permalink)
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I tend to agree with Bob -- the trailing shape of the tailgate would be "cleaner" I think if the entire surface of the cap was tapered down; so the air flow over the truck as a whole was improved. Like the shape that others have done -- though I do like the look of this project. So, maybe a combination?

I'll attempt something is SketchUp -- which has an excellent free version, by the way. And, this would deepen the ribs nearer the back, too I think?
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Old 01-22-2011, 11:38 AM   #25 (permalink)
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There's an engineer at work we like to pick on for doing all of his analytical work in Excel. But Excel as a CAD program? That's ... very MacGyveresque.
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Old 01-22-2011, 12:49 PM   #26 (permalink)
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A spreadsheet is the Swiss Army Knife of application software. From poor man's database to poor man's CAD. Two plus decades ago I used spreadsheets to clean up the coordinates of industrial robots for example.

t vago, I wasn't picking at all. I would like to understand your motivation for gullies on the sides. Is the ole tear-back look an aesthetic goal for example? Inquiring minds want to know.
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Old 01-22-2011, 01:07 PM   #27 (permalink)
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Quote:
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I tend to agree with Bob -- the trailing shape of the tailgate would be "cleaner" I think if the entire surface of the cap was tapered down; so the air flow over the truck as a whole was improved. Like the shape that others have done -- though I do like the look of this project. So, maybe a combination?

I'll attempt something is SketchUp -- which has an excellent free version, by the way. And, this would deepen the ribs nearer the back, too I think?
Neil, like this?

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Old 01-22-2011, 01:39 PM   #28 (permalink)
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Quote:
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t vago, I wasn't picking at all. I would like to understand your motivation for gullies on the sides. Is the ole tear-back look an aesthetic goal for example? Inquiring minds want to know.
I know, I was just trying to make a funny.

Anyway, I have noticed in the past, when my tonneau cover was covered with snow, the obvious thing that air wants to flow down from the roof of the cab. I also noticed that air wants to flow back toward the centerline of the bed from the sides. Who am I to argue with Mother Nature?

Also, from reading that other grad paper that was posted yesterday in this forum, I noted that the traditional 12 degree sloped aerocap was good for a reduction in C(d) of 16.2%. Sloping the sides, like what I am going to do, resulted in a reduction in C(d) of 19.8%. To me, the math makes sense.
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Old 01-22-2011, 01:55 PM   #29 (permalink)
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This guy had a similar idea for his Nissan. I think, though, I could live without the huge wing.

And Ecomodder member ChazInMT had a similar idea, too.

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Old 01-22-2011, 02:32 PM   #30 (permalink)
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The Nissan rally truck didn't always sport the rear wing...

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