Ducktails
 

Can you advise if ductails promote "significant" increase in MPG?

How about spoilers?

Stock spoilers (and goofy aftermarket ones), no. Ductail, potentially but not by much.

ducktail
 

Ducktail is a new expression to me.Can you help me out with that?

I think he's talkin about a flat extension off the back of a car to lessen the roof-to-trunk angle

*edit* see this thread.

http://tbn0.google.com/images?q=tbn:...-SPS-CF-BK.jpg

http://www.aj-racing.com/catalog/files/t_1027.jpg

OOOOOH, ok....no they won't help.

ducktails
 

Thanks for the images! Without a windtunnel or tufting it's hard to say what the upkick does to the wake.I always lean towards the teardrop form,however in light of the VOLT rear spoiler mods(with the 5mm kick),if it works,it works!Some rally cars use extensive upward angles for rear downforce at the expense of drag.It's hard to know where the boundary is.

opel insignia

Cd 0.27
http://i77.photobucket.com/albums/j5...atchback-1.jpg

the initial concept car didn't have the "ducktail" so i don't think it was added for looks alone

What about a ducktail, angled down about 12 degrees instead of up, off the cabin roof of a conventional sedan?

What you call 'ducktail' is a trip spoiler. It's used to keep at bay aerodynamic lift at the rear of the car, which can be dangerous when cornering at high speeds if the stern loses grip.

The 'ducktail' trips the boundary layer prematurely, assuring no aerodynamic lift would be generated.

This can be critical at high speeds. The original Audi TT had an aerodynamically poorly designed very rounded tail that in itself generated lots of lift at high speed. Audi screwed big time on this. The first production models, without rear spoiler ...

http://www.automotriz.net/images/mod.../auditt7_2.jpg

... suffered some fatal crashes while cornering at high speed (180kmh/112mph +) in the Autobahne. Even a known race driver was killed. Audi was forced to recall and fit an inprovised spoiler ...

http://www.lotpro.com/themes/Default/cars/5678.jpg

In the 2nd generation TT they solved the problem with a retractable spoiler, which deploys at high speed:

http://z.about.com/d/cars/1/0/E/x/ag_08ttr_spoiler.jpg


Unless you need them to corner at high speeds, these devices just increase drag (by enlarging the wake area) and fuel consumption. At 55mph they are perfectly useless.