Kammback vs spoiler-or both?

[oldschooleco]

hey y'all
which would net the most mpg gain? a spoiler of some sort or a kammback?ill try to post some pics- thank you

[cowmeat]

I had a detached wing for months that didn't seem to do anything at all mpg-wise.

I replaced the detached wing with a small Kammback halfway through the last tank, and saw about 2 mpg gain. Coincidence? Maybe, it may be just from me getting better and better at hypermiling, but I was never able to reach 60 mpg before.

[aerohead]

Historically,with the exception to wing-form bodies,the K-form aft-body continues to demonstrate the lowest drag.
*It has no separation
*It generates zero lift
*It's modular.Once you've established the essential Kamm architecture,you can simply add additional elongation for additional savings.
*You will have a blind spot on the passenger side unless you provide for a fenestration there.
*And the new backlight,if part of the roof,will be so steep as to block outward vision.A vertical backlight,with louvered cover has been a repeated solution.
*Rear camera systems are a big plus.

[oldschooleco]

Originally Posted by aerohead

Historically,with the exception to wing-form bodies,the K-form aft-body continues to demonstrate the lowest drag.
*It has no separation
*It generates zero lift
*It's modular.Once you've established the essential Kamm architecture,you can simply add additional elongation for additional savings.
*You will have a blind spot on the passenger side unless you provide for a fenestration there.
*And the new backlight,if part of the roof,will be so steep as to block outward vision.A vertical backlight,with louvered cover has been a repeated solution.
*Rear camera systems are a big plus.

ok that sounds good, i may try and get something mocked up/together tomorrow, would 18in make a noticeable gain? ill post pics when i get something set up. thank you very much

[freebeard]

Hey, is that a '65 Dodge Dart?

18" behind the backlight? Not so much. It would depend on the fit and finish. Think sail panels, like the Dodge Charger, so you don't lose rear visiblity.

18" behind the bumper? Now you're talking. You could halve the wake.

[oldschooleco]

Originally Posted by freebeard

Hey, is that a '65 Dodge Dart?

18" behind the backlight? Not so much. It would depend on the fit and finish. Think sail panels, like the Dodge Charger, so you don't lose rear visiblity.

18" behind the bumper? Now you're talking. You could halve the wake.

ok, would it be more effective with a spoiler if i only did 18in? i don't want this thing looking to crazy

[freebeard]

Originally Posted by me

Hey, is that a '65 Dodge Dart?

Sometimes I'm too cryptic. That was me mocking you for starting two threads in two days on the same subject. Sorry.

which would net the most mpg gain? a spoiler of some sort or a kammback?ill try to post some pics- thank you

Either would help a little. Both could be better; there are other things (lower the stagnation point, spats, skirts, belly pan, rear diverter) that could make as much difference or more.

ok, would it be more effective with a spoiler if i only did 18in?

Again, 18" from where?

i don't want this thing looking to[sic] crazy

And why not? Did you see the Blowfish in the other thread? here's the Stupidbaker:

[oldschooleco]

Pics as promised, i would like suggestions for the rear end and anything else you would do. thank you, you've all been very eye opening

[freebeard]

It has a particular style going already, some things might clash like stripes and plaid. Fender skirts and peep mirrors would fit right in.

Things you do underneath or in the engine compartment could make a lot of difference. That deep airdam makes sense if there's no bellypan, but if you smooth out the underside you could trim it. How is it on speed bumps? Shrouding the radiator might be needed. If you have an air cleaner with a snorkel intake, just putting a bellmouth on that will help. See Autospeed.


As for the rear: Dodge Charger sail panels? If you built a boattail that covered the stock taillights you could do something like this:


How about fender skirt and a diverter that tie together as a single shape by material or color change; sort of a combination of these:


To get started on the details, ponder this:


My best guess is it says 2-4° is the sweet spot between lift and drag. And little circles are better than little triangles.

[oldschooleco]

hmmmm i like the idea of fender skirts, i can definatly make something work. what about sail panels? coming from the side edges of the roof?, or on the edge of the the body near the tail lights?