Partial Boattail/Kammback on a sedan?

[kach22i]

Found something a bit more than a "leading edge slot".

I'd call it a true roof wing, and not a spoiler.

2011
Proton R3 Satria Neo – short test drive impressions
https://paultan.org/2011/03/09/proto...e-impressions/




A different car and wing/spoiler, same color?

https://www.tokopedia.com/m-center/m...ky-qdjn519n0pz

[freebeard]

Diverging duct over a wickerbill?

[mpg_numbers_guy]

Originally Posted by 19bonestock88

So I’ve noticed my Kamm lifting as I drive... as speed increases, the trailing edge rises... I still think I have more drag than without the visor/Kamm... in the rain the water seems to be moving almost horizontally across the backlight...

Did you tape the gaps between the kammback and the car--and any other gaps in the kammback construction--to avoid a possible parachute effect?

[19bonestock88]

I did seal all the unnecessary gaps when I built my Kamm and it provided a loss of about 4%, as it was built... I meant to revise and retest it but never did, focusing on measuring the gain from lowering the car...

[MetroMPG]

Originally Posted by Ecky

@MetroMPG, what were your construction materials for that kamm?

Oops - didn't see this question. Late reply, sorry!


Like almost everything I make: plastic-wrapped cardboard.

[mpg_numbers_guy]

Originally Posted by 19bonestock88

I did seal all the unnecessary gaps when I built my Kamm and it provided a loss of about 4%, as it was built... I meant to revise and retest it but never did, focusing on measuring the gain from lowering the car...

From reading up on kammbacks and stuff on this site your results make sense now. With most sedans (unless yours is abnormally boxy) air remains attached for several inches down the window before detaching, with more aerodynamically shaped cars such as the '01 and newer Civics having more of this (tuft testing revealed ~50% attached airflow on my own Civic). With having the kammback on there you aren't adding any attached flow that isn't already there, and the flow is then detaching further away from the glass surface than is was without the kammback, and thus creating greater drag.

It seems that unless 100% perfectly designed, kammbacks don't really help sedans that much unless they extend beyond the rear of the car and lower than level with the trunk; essentially a mini-boattail.

Just my $0.02...and all from Ecomodder research too.