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Old 09-10-2012, 02:19 PM   #471 (permalink)
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I'm always reluctant to guess, but 5-10% @ 55 mph seems reasonable based on what we've seen.

But I do wonder about the bottom angle you've got there. Are you going to have attached flow? Are you going to have sharp or radiused corners on the top-side-bottom transitions?

Wake reduction formula: haven't seen that specifically. But you could pretty much extrapolate from the studies that compare various lengths of boat tails, truncated at various points vs. full length. (Though they seem to assume attached flow on a body of rotation.)

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Old 09-10-2012, 04:15 PM   #472 (permalink)
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Sounds good; thanks for the guesstimates. The top and bottom angles should come out to approximately 15 degrees. If it doesn't work I can always add an inch or two under the back plate and lower the bottom. Tuft testing will happen as soon as I get it together.

I'll have to look up the boat tail data, or maybe just wing it and see what happens.

I picked up a fiberglass temporary fence post, small hinge and angle bracket at Fleet Farm. Should be able to mock up that backup aid after some other details are worked out, but before I skin the tail. Still need to get more 8' aluminum bar but everyone's sold out (I wonder why )
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Old 09-10-2012, 05:15 PM   #473 (permalink)
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looking good!

i might have missed it but what the skin going to be made of?
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Old 09-10-2012, 09:01 PM   #474 (permalink)
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...and radiused transitions, yes?

FYI, the bottom of my prototype tail went from 4 degrees at the back of the car to 6.5 degrees at the end of the tail, and the flow under there was attached but really turbulent, even with a smooth belly pan. I'll be surprised if it stays attached at 15 degrees!



from: http://ecomodder.com/forum/showthrea...tml#post156960
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Old 09-10-2012, 09:46 PM   #475 (permalink)
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Spotter, I scored four 4x8' sheets of coroplast for $30 so I'll be using those.

Metro, what about the AeroCivic? That has at least 15*, so basjoos must be doing something right.



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Old 09-10-2012, 09:58 PM   #476 (permalink)
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I'd bet against attached flow underneath AeroCivic's tail (at the end).

But Mike has said before that he has studied the tea leaves... I mean dust trails ... left underneath the tail and he thought they looked like things were good.

But the wee beastie has never been tufted, so we don't really know.
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Old 09-10-2012, 10:37 PM   #477 (permalink)
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I'll tuft mine and see!
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Old 09-10-2012, 11:08 PM   #478 (permalink)
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I thought he said he made the bottom part steep so it doesn't scrape on the road going up inclined driveways. I could be thinking of someone else who did a boat tail though.
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Old 09-11-2012, 01:24 PM   #479 (permalink)
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The car is 23% longer than stock but still shorter than Detroit's behemoths.

177" -stock 1G Probe
218" -Anal Probe (adds 40-3/4" or 103.5cm)

232" -2012 F-150 SWB crew cab
222" -2012 Chevy Suburban
202" -2012 Audi A8
189" -2012 Toyota Camry

Put some more bars in this morning and I'm going to put some more in this afternoon. After that the structure should be done and I can put together the rear light wiring, side marker wiring, backup aid and hatch latch. Then coroplast and paint!


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Last edited by Sven7; 09-11-2012 at 01:33 PM..
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Old 09-11-2012, 04:41 PM   #480 (permalink)
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looking good.

Its about time to hold are yearly boat tail members induction

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