What Is a Kamm Tail? The Aerodynamic Trick Behind Some of the World’s Fastest Cars

Aerodynamically, however, it can be remarkably effective.

The idea became famous through the work of German aerodynamicist Wunibald Kamm, whose research in the 1930s explored how engineers could obtain much of the aerodynamic benefit of a long streamlined body without making automobiles impractically long.

The concept later became especially important in racing.

One of its most famous applications was the Shelby Cobra Daytona Coupe, whose unusual truncated rear helped transform the already-powerful Cobra into a car capable of challenging Ferrari on Europe’s high-speed circuits.

Why Is a Teardrop Shape Aerodynamically Efficient?

Air does not particularly like abrupt changes in direction.

As a vehicle moves forward, air has to move around it and then try to reconnect behind it.

A long, gradually tapering rear body helps the airflow remain attached to the surface longer and reduces the large turbulent wake that forms behind the vehicle.

That can reduce pressure drag, one of the major sources of aerodynamic resistance on an automobile.

In theory, the ideal solution would therefore be a vehicle with a very long tapered tail.

In practice, that creates an obvious problem.

Nobody wants a family sedan—or a race car—that extends several extra feet behind the rear axle simply because the air would prefer it that way.

Automotive engineers therefore needed a compromise.

That compromise became the Kamm tail.

How Does a Kamm Tail Work?

Instead of allowing the aerodynamic taper to continue all the way to a point, engineers begin narrowing the rear body and then truncate it.

The resulting vehicle may look blunt from behind, but the preceding taper can substantially reduce aerodynamic drag compared with a conventional square-backed body.

Modern aerodynamic research continues to confirm the underlying principle: tapering the rear of a bluff body can significantly reduce drag, while truncating that taper provides a practical compromise between aerodynamic efficiency and vehicle length.

It is important, however, not to turn the Kamm tail into aerodynamic magic.

A full streamlined tail can still outperform a truncated one when enough length is available. The value of the Kamm concept is that engineers can recover much of the benefit while maintaining a practical vehicle shape.

In engineering, that distinction matters.

The Kamm tail is not necessarily the perfect aerodynamic shape.

It is a very clever engineering compromise.

Who Was Wunibald Kamm?

Wunibald Kamm was a German engineer and aerodynamic researcher whose automotive work in the 1930s helped establish the truncated-tail approach that now carries his name.

He and other European researchers were investigating an increasingly important problem.

Cars were becoming faster.

At higher speeds, aerodynamic drag becomes much more important.

Designers already understood that streamlined teardrop forms could reduce drag, but those shapes were difficult to package into practical road vehicles.

Kamm’s research helped demonstrate that engineers could truncate a streamlined rear section while retaining useful aerodynamic benefits.

A BMW 328-based experimental vehicle developed under Kamm’s direction became one of the best-known early demonstrations of the principle.

The result was not simply a styling fashion.

It was an attempt to reconcile two conflicting requirements:

The air wants a long tail.

The automobile does not.

That is classic engineering.

Why Did the Shelby Daytona Coupe Need a Kamm Tail?

The original Shelby Cobra had plenty of power.

What it lacked was aerodynamic efficiency.

On many American circuits, the Cobra roadster’s combination of low weight and Ford V8 power made it devastatingly quick.

But on Europe’s long, fast straights, Ferrari’s more aerodynamic GT cars had an important advantage.

Shelby needed the Cobra to move through the air more efficiently.

Designer Peter Brock developed a completely new coupe body around the existing Cobra mechanical package.

At the rear, rather than continuing the body into a long taper, Brock used a sharply truncated design influenced by Kamm-tail aerodynamic principles.

The result became the Cobra Daytona Coupe.

The FIA’s historic documentation specifically identifies the Daytona Coupe as a special-bodied aerodynamic development of the Cobra 289 created under contemporary GT homologation rules.

The body looked dramatically different from the open Cobra roadster.

More importantly, it worked.

The Daytona Coupe became one of the most recognizable racing cars of the 1960s and helped Shelby American defeat Ferrari for the 1965 FIA GT manufacturers’ championship.

The tail that looked unusual was there for a reason.

Air.

Why Doesn’t the Air “Notice” That the Tail Is Missing?

Descriptions of the Kamm-tail principle sometimes say that the airflow behaves as though the missing portion of the tail were still there.

That is a useful visualization, but it is a simplification.

What really matters is how the taper influences flow separation, wake size and pressure recovery around the rear of the vehicle.

By tapering the body before truncating it, engineers can alter the size and behavior of the low-pressure wake that forms behind the vehicle.

That can reduce pressure drag.

Modern aerodynamic studies show that the amount of taper, tail length, truncation point and surrounding body geometry all matter. A badly designed truncated tail is not automatically efficient simply because somebody calls it a Kammback.

That is why modern automotive engineers do not simply apply a standard Kamm-tail shape.

They test it.

Kamm Tail vs. Flick Tail: What Is the Difference?

A Kamm tail and a flick tail are not the same thing.

They can both affect airflow at the rear of a vehicle, which makes the terminology easy to confuse.

The simplest distinction is:

A Kamm tail describes how the overall vehicle body ends.

A flick tail describes an upward turn or lip at the trailing edge.

A Kamm tail usually involves an aerodynamic taper followed by an abrupt truncation.

A flick tail is typically a smaller local feature in which the rear bodywork turns upward. It can act somewhat like an integrated spoiler, influencing airflow separation, lift, downforce and stability.

So think of it this way:

Kamm tail = body architecture.

Flick tail = trailing-edge feature.

A vehicle can even incorporate aspects of both.

That is why the two terms should not be used interchangeably.

Is a Kamm Tail the Same as a Spoiler?

No.

A spoiler is an aerodynamic device intended to deliberately alter airflow around a vehicle.

It may be mounted on top of the body or integrated into it.

A Kamm tail is primarily the shape of the vehicle body itself.

A spoiler can be added to a Kamm-tailed vehicle, but adding one does not automatically improve the aerodynamics. Depending on its geometry, it may increase drag, change rear lift, improve stability or create an undesirable tradeoff.

The entire aerodynamic system has to be evaluated together.

That is another reason modern CFD has become so valuable.

How Do Engineers Design Kamm Tails Today?

Wunibald Kamm and early automotive aerodynamicists relied heavily on physical experimentation, scale models, wind tunnels and road testing.

Modern engineers have another enormously powerful tool:

Computational fluid dynamics, or CFD.

A modern development team can build a digital vehicle model and examine how air moves around it before the first physical prototype exists.

Engineers can investigate:

• rear-body taper angle,
• truncation length,
• roof curvature,
• underbody airflow,
• rear lift,
• pressure distribution,
• wake size,
• crosswind stability,
• cooling airflow,
• and overall drag coefficient.

A designer might begin with CAD geometry created in tools such as CATIA, Siemens NX/Designcenter or Creo.

That geometry can then be analyzed using CFD platforms such as Simcenter STAR-CCM+, Ansys Fluent, SIMULIA or other automotive aerodynamic tools.

Dozens—or hundreds—of rear-body configurations can be evaluated digitally.

The promising designs can then move into wind-tunnel and track testing.

The underlying engineering goal is still remarkably similar to the one Kamm was pursuing nearly a century ago:

How do we make the vehicle aerodynamically efficient without making it impractical?

The tools changed.

The compromise did not.

Are Kamm Tails Only Used on Race Cars?

Not at all.

Kamm-tail principles have appeared on road cars for decades because reduced aerodynamic drag can improve more than maximum speed.

Lower drag can contribute to:

• better fuel economy,
• increased electric-vehicle range,
• lower energy consumption,
• reduced wind noise,
• improved high-speed stability,
• and better overall aerodynamic efficiency.

That makes the concept arguably even more relevant in the era of electric vehicles.

An EV does not have unlimited energy available.

Every aerodynamic improvement can help extend driving range.

For that reason, today’s aerodynamic engineers spend enormous effort optimizing seemingly small details around the roofline, rear glass, tailgate, spoiler and rear corners.

A few percentage points of aerodynamic improvement multiplied across millions of miles can matter enormously.

Why Do Some Cars With Kamm Tails Look So Strange?

Because air does not care what people think a car is supposed to look like.

Automotive design is always negotiating between aesthetics, packaging, manufacturing, aerodynamics, safety and customer expectations.

Sometimes aerodynamic optimization produces shapes that initially look unconventional.

The Shelby Daytona Coupe is a wonderful historical example.

Peter Brock’s rear-body treatment did not resemble the graceful long-tailed sports cars many people expected.

But Brock was not primarily trying to make the rear of the car beautiful.

He was trying to make the car faster.

Eventually, the unusual shape became beautiful precisely because people understood what it accomplished.

That pattern appears repeatedly in engineering.

Function creates a strange shape.

The strange shape works.

Eventually the shape becomes iconic.

Why Does the Kamm Tail Still Matter?

The Kamm tail is a useful reminder that some of the best engineering ideas are not perfect solutions.

They are intelligent compromises.

A theoretically ideal automobile might have an enormously long aerodynamic tail.

A real automobile needs to fit inside a garage.

It needs cargo space.

It needs rear seats.

It needs manufacturing tooling.

It needs bumpers, lights and crash structures.

And if it is a race car, it needs to fit the rulebook.

Wunibald Kamm’s work helped engineers ask a more useful question than:

What is aerodynamically perfect?

The better question was:

How much of that aerodynamic benefit can we keep while still building a useful car?

That question remains central to engineering today.

And more than 80 years later, engineers with enormously more powerful tools are still working on essentially the same problem.

Only now they can watch the air move on a computer screen before they ever cut the metal.