06-08-2013, 12:12 AM
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#191 (permalink)
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Master EcoModder
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Quote:
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I bet adding those would probably help the U.F.O.'s aero, and if doing so means the underside of the tail then technically becomes a diffuser (if un-befinned), so be it!
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Difflow use 5 -7 fences. I suspect they channel turbulent air and equalize it across the rear.
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06-08-2013, 02:00 AM
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#192 (permalink)
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Cyborg ECU
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Quote:
Originally Posted by euromodder
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Yes, but it seems without "fins" like I think Metro is referring to, right? Here is another angle that I don't think is in the thread you linked to... but maybe that open box/wing thing is about the same idea as "fins."
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06-08-2013, 02:45 PM
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#193 (permalink)
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Strakes? Fins? Fences?
We need a Glossary.
Skegs? |
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06-08-2013, 04:14 PM
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#194 (permalink)
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solar car
Quote:
Originally Posted by jime57
I tend to agree with you overall observations. I was just kicking the idea around.
Formula 1 cars have been productively using various diffuser fins for several years now, but I'm not sure that the 150-175 MPH difference in speed makes that comparison relevant.
And, yes I remember seeing that solar car. As I recall, the fins were small and at the very rear.
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That might have been the 1987 GM/AeroVironment SunRaycer.
Crosswind stability near the Australian land trains was a prerequisite for racing qualification and that car had already 'flown'.
The 'strakes' added under the tail were a solution which Dr.Alberto Morelli had come up with in 1978 with the CNR 'banana' car.The stabilizing tailfin was placed low,behind the wheels to mitigate a roll-moment,while moving the center-of-pressure well aft,giving it a nice weather-vaning.
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06-08-2013, 11:23 PM
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#195 (permalink)
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My CarBEN EV5 has a three straight diffuser fins, though I have no idea if they wil help or hurt or be meaningless. They provide downforce, I think? I'm hoping that the fins on CarBEN will "straighten out" the air flow so that it swirls less as it exits - maybe?
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06-09-2013, 02:33 AM
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#196 (permalink)
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My understanding would be that the downforce would be affected by the angle of the plate/bottom of the boattail. There is a diagram that indicates the angle is sensitive to the upper rear body shape (which I apparently don't have), i.e., fast/notch/kamm-back, over a range IIRC of 0-10°.
I agree they would reduce turbulence, but I'm curious about how they act in cross-wind conditions. And I think Difflow is onto something with the fan shape.
[post contains much opinion]
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06-09-2013, 08:18 AM
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#197 (permalink)
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Cyborg ECU
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Quote:
Originally Posted by freebeard
My understanding would be that the downforce would be affected by the angle of the plate/bottom of the boattail. There is a diagram that indicates the angle is sensitive to the upper rear body shape (which I apparently don't have), i.e., fast/notch/kamm-back, over a range IIRC of 0-10°.
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Is this the graphic/table you are referring to?
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.
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06-09-2013, 11:53 AM
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#198 (permalink)
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Not Doug
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Quote:
Originally Posted by California98Civic
Is this the graphic/table you are referring to?
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I think that is it!  Will someone please explain it to me?  |
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06-09-2013, 01:17 PM
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#199 (permalink)
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Cyborg ECU
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Quote:
Originally Posted by Xist
I think that is it! Will someone please explain it to me? |
Maybe. Let's see: Cx is another way of noting Cd. The "Y" axis, therefore, is measuring change in Cd (Cx) +/- and the "X" axis is charting different angles for the different body shapes' diffusers. Body shape A and B are shown to have their best diffuser angels at 3 or 4 degrees and the wagon ("C") seems just to suffer.
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.
Last edited by California98Civic; 06-12-2013 at 08:23 PM..
Reason: three intrusive typos (shakes fist at spelling gods)
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06-09-2013, 08:50 PM
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#200 (permalink)
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Not Doug
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Quote:
Originally Posted by California98Civic
Maybe. Let's see: Cx is another way of noting Cd. The "Y" axis, therefore is measuring change in Cd (Cx) +/- and the "X" axis si charting different angles for the different body shape's diffusers. Body shape A and B are shown to have their best diffuser angels at 3 or 4 degrees and the wagon ("C") seems just to suffer.
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So, once again, I am doomed?
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