Does the Kammback have a place in aviation?

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Tiger Tim

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This is just a point of curiosity for me but as the title asks, is there a place in aviation for the Kammback?


In short, it’s basically just chopping the aft end off a streamlined shape and letting the airflow figure itself out. Apparently it has historically worked pretty well for race cars and in the context of airplanes the back end of a fairing can’t weight anything if it’s not there.
 
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Mad MAC

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Stinson talks about chopping trailing edges off square at ?% chord in at least one of his textbooks. Although that is as much about producing reliable control behaviour.
 

rotax618

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From my experience the taper on the rear of the fuselage on pusher aircraft is critical, the inflow to the propeller can effect not only the thrust but yaw stability and noise. During the testing of my first Boorabee aircraft, a slight two phased oscillation in yaw was observed. This was cured through experimentation with the placement and sizing of vortex generators along the sides of the fuse pod, not only did they cure the oscillation but they considerably lowered the prop noise, increased the speed with less prop pitch.
The CFM Shadow and Streak Shadow have a “Kamm” tail, that is the sides of the pod are parallel and the rear firewall is flat normal to the airflow - the Shadow did not suffer from the disturbance in yaw but was considerably noisier and less efficient because of the prop diameter limitation because of the high boom.
 

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Norman

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This is just a point of curiosity for me but as the title asks, is there a place in aviation for the Kammback?


In short, it’s basically just chopping the aft end off a streamlined shape and letting the airflow figure itself out. Apparently it has historically worked pretty well for race cars and in the context of airplanes the back end of a fairing can’t weight anything if it’s not there.
Sure you can if you don't mind a 13% increase in drag. The reason it's acceptable for cars is that the tail cone would be several feet of length added aft of the rear axle.
 
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Norman

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Stinson talks about chopping trailing edges off square at ?% chord in at least one of his textbooks. Although that is as much about producing reliable control behaviour.
The width of the truncated trailing edge should be less than 2% of the chord length. How much less depends on the airfoil thickness to chord ratio. Thin airfoils (say 12% or less) start developing extra drag pretty quickly so the TE thickness should be as thin as structurally practical which usually means two sheets of skin material. Really thick airfoils like those used for wind turbines can actually benefit from off-surface pressure recovery and have a small drag reduction from a 2% thick TE.
 
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mcrae0104

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is there a place in aviation for the Kammback?
No. (Aside from truncated airfoil shapes) Aerodynamic afterbodies are not practical for cars, and bluff (truncated) afterbodies are not practical for GA airplanes. Different requirements, different solutions. Where is a truncated GA fuselage that outperforms one with an afterbody?
 

Vigilant1

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I saw one of these a couple of days ago. Might give some float plane designers some ideas?
Wonder if it works sell enough to justify the cost?

View attachment 129666
Here's a CFD video that the company provides to justify the rear wing.


I didn't get any audio. And I don't know if anything in the video is correct, or what they claim it all means.
 
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Reminds me of the old Reece’s PB Cup ad: “Hey, you backed into my Cessna Skymaster!” “No, you mistook my driveway for a runway!”
It won’t get off the ground, but it no longer sways in a crosswind...
 

Riggerrob

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Here's a CFD video that the company provides to justify the rear wing.


I didn't get any audio. And I don't know if anything in the video is correct, or what they claim it all means.

The original truck suffers massive down-ward airflow immediately aft of the trailer tail, so the new horizontal tail flattens that downward curved airflow.
Vertical fins just "fake" a wider horizontal tail .... similar to the way that winglets "fake" longer wing tips.
 

Riggerrob

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This is just a point of curiosity for me but as the title asks, is there a place in aviation for the Kammback?


In short, it’s basically just chopping the aft end off a streamlined shape and letting the airflow figure itself out. Apparently it has historically worked pretty well for race cars and in the context of airplanes the back end of a fairing can’t weight anything if it’s not there.
A bunch of military, pod-and-boom transports (Arava, Bristol BeverlyC-82, C-119, Nordatlas, etc.) can be flown without the tail fairing cones installed on their cargo fuselages. Removing tail fairings increases drag so much that air forces only ever removed tail cones when they were doing short-range, heavy cargo drops (see the Battle of Kap Yong Hill).
Mind you the tail cones on those military transports is the full width of the cargo compartment, so wide enough to drop a bulldozer.

Blunt, perpendicular trailing edges of flying surfaces prevent air from sneaking around the alternative curved trailing edge. This is best illustrated by the trailing edge of modern, Jalbert-pattern, square, ram-air parachutes and para-gliders. Early square parachutes just had one or two ribs per cell, but now the latest Sabre 3 and pond-swooping competitors sew extra, triangular, mini-ribs into the trailing edge just to "sharpen" it.
 

Vigilant1

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The original truck suffers massive down-ward airflow immediately aft of the trailer tail, so the new horizontal tail flattens that downward curved airflow.
When I saw that, the specific advantage I thought of was "more weight on the rear tires", which could be handy with an empty trailer. Still, only a tiny amount of downforce compared to the existing mass of that trailer.
I'd think something to do with vortices/vortex shedding and trailer stability might be the purpose.

Or, just marketing.
 
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