Kammbacks & tail aero info

[trikkonceptz]

Don't even know if this is possible, but build one like a boat canopy with a light frame and canvas material. Attach a spring to it to retract it automatically on tension, but when the air pushes against it it unfolds on its own.

Now that is assuming that the air force would force such a device open, but when the resistance becomes minimal, the springs would retract it automatically.

Then again, I have been known to talk out of my ass ... LOL

[aerohead]

Originally Posted by apgrok1

So why can't you put steps on the back window? I brought up this topic before and was shot down due to flow separation. It looks to me that anything that has more than a 12 degree slope should have a step or tail.

You can do steps,as Ford/Merkur did this with the Xr4Ti.They got a patent on it.The "steps" need to be pretty close to the glass or circulation will kind of destroy the whole effect,and the trailing edges of the steps need to approximate the form of the ideal roofline.Basically,your using captured vortices to fill the void behind the backlight and the air skips over the vortices as if they were solid.They don't work as good as the totally re-designed roofline,however they're way out ahead of nothing.

[aerohead]

A Massachusetts company by the name of Continuum Dynamics came up with a system as depicted in example-c.They got about $50,000 from the U.S. taxpayer to do the R&D which did show a measurable fuel economy improvement.In a phone conversation to Continuum,They said they were not pursuing commercial development of the device.

[Piwoslaw]

Originally Posted by Bearleener

In 1999 Morelli & Di Giusto modified a Fiat Punto, adding a Kammback and blower-type rear wheels, calling it the Fluid Tail:

[...] Note that their Kammback has a clear plastic partial end cap.[...]

More tail modifications:

Compared to the standard blunt end (a), adding what they call attikas (fascias or parapets; flat, parallel panels) (b) delays separation and moves the tail vortices back (reduces Cd by up to 10%); these can be set inward (c), further reducing the size of the „dead zone“ (reduces Cd by 0.06, which is about half as good as the ideal tapered tail); the open-ended Kammback made of flat panels (d); and „Fluid Tail" (e).

I wonder how much the endcap in the "Fluid Tail" improves over the regular Kammback? Would my Kammie benefit from adding a perpendicular wall around the inside edge? How wide should it be? And does the Kammback have to be of the all-around design, as in the Punto picture, or can it be of open-bottom type?

[jabb]

The most annoying thing about the "Fluid tail" is that even though it's been based on a Fiat Punto, it can't be legally mounted on Punto since it obstructs rear lights totally. What a waste of perfectly weird design.

[Piwoslaw]

Originally Posted by jabb

The most annoying thing about the "Fluid tail" is that even though it's been based on a Fiat Punto, it can't be legally mounted on Punto since it obstructs rear lights totally. What a waste of perfectly weird design.

I wonder if plexi would be legal?
Another option is to get rid of the high-mounted lights and replace them with lights from a different car. It should be legal as long as the replacement lights are certified. (In Warsaw a few years ago I used to see a Fiat 126p with rear lights from a Polonez - now that was ugly!)

[Rokeby]

Anybody else notice the sharp edged anti-diffuser along the lower bumper
line? I guess with the new air fflow pattern at the roof and sides, you would
want the under-car flow to breadk from the body as well.

I would like to see/learn more about the "blower type wheels." Apparently
they are coupled with the wheel well bulges. But there appears to be more
bits and pieces of the system under the car where they can't be seen. Here's
what the patent application says:

Abstract of EP0937633
"A device for reducing drag in vehicles is described and comprises
ventilating means (2) associated with each wheel (1) of the vehicle in order
to create respective auxiliary flows, and directing means associated with the
wheel housing (5) for directing the auxiliary flows, by means of a manifold
having an outlet, so that they pass along the bottom of the motor vehicle,
the device further comprising, associated with each wheel (1), a fixed screen
(20) restrained on the suspension members (21) and situated on the inner
side of the wheel, of which it screens the entire lower portion disposed below
the hub (22), excluding the tyre, in order to direct the auxiliary flow towards
the directing means (6, 7) associated with the wheel housing (5), to force
the whole of the flow to pass over the braking members (23, 24) associated
with the wheel (1), and to act as a fairing for the lower portion of the
wheel."

I just can't picture what all the bits and pieces being described here look like
or are doing.

[Piwoslaw]

I remember reading (10 years ago?) about Mercedes using wheels in which the spokes were shaped like fan blades (wheels on the left and right sides were mirror images of each other). They were supposed to suck air out from under the car to reduce drag. But I always figured that the actual pumping would produce more resistance than the gains from having lower pressure under the car. Maybe it only works when the rest of the car has a particular shape?

[bestclimb]

Originally Posted by Cd

Too bad it can't be translated.


( I wish I was tought more than one language in school. It's as if we here in America expect everyone to speak our language, but we won't speak theirs. )

really? Most schools offer french and/or Spanish as an elective (others are often available mine even offered Latin). It is usually up to the student to decide if knowing another language would be of benefit to them. If one should chose not to learn another language it is that person who may miss out.

back on topic. I keep seeing these neat kammiback shapes, and looking under them at the wasted space that could be used as internal volume with only a minimum of additional materials outlay from the factory. The other thing is that with a negative rear window angle the accumulation of snow and ice would not happen back there.

[Piwoslaw]

Originally Posted by bestclimb

I keep seeing these neat kammiback shapes, and looking under them at the wasted space that could be used as internal volume with only a minimum of additional materials outlay from the factory. The other thing is that with a negative rear window angle the accumulation of snow and ice would not happen back there.

That's exactly what I've been thinking. Check out this thread:
Aftermarket rear hatch with roof extension