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Old 12-09-2007, 06:02 PM   #4 (permalink)
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Join Date: Dec 2007
Location: Melbourne
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The Mighty Mira - '92 Daihatsu Mira
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Originally Posted by SVOboy View Post
Do you think adding some sort of curve to the boattail would lower the drag a bit or are you getting attached flow even with that angle between the roof and the boattail?
I'm not sure what you mean... the boattail is already curved, and if there is an angle between the roof and boattail it is very slight. See the second of the original photos, and this other one.

The reason that in some photos it appears as if there is an angle is because the top two lengths of aluminium also point inwards somewhat. This only happens with photos that aren't taken directly from the side, e.g. in front a bit.

The tuft testing in that region confirmed that flow is most likely attached everywhere, the only possible hazy area would be right near the end, and even then I'm doubtful (no looping back observed, just wild oscillations from side to side, never towards the front of the vehicle and never away from the plane of the boattail).

There is a curve to it, An initial curve to break away from the roofline, and a curve at the end to get the flow to approach horizontal again. Most of the curving happens in the end thirds if you look closely.
"Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed." - Isaac Newton
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