For any object to attain flight, it has to overcome drag as it thrusts into the air in order to generate lift. For example, golf balls have dimples on them to create air pockets, which enables them to overcome wind resistance (drag) and boost their aerodynamic properties. This aerodynamic property — the presence of air pockets — is also shared by birds to enable them to solve the aerodynamic problem posed by drag.
However, if drag is such an aerodynamic issue, why aren’t airplanes dimpled? Dimples are used in golf balls to decrease drag by minimizing the wake behind the ball (base drag). Since airplanes already use streamlined bodies, their base drag is already low, and won’t be helped much by adding dimples.
As a matter of fact, adding dimples would increase the drag on the airplane body itself, causing increased drag overall.
Golf balls are designed to spin as they generate enough energy to move through the air and this is where dimples come into play. Golf ball designers create dimples on the surface of golf balls to reduce drag and generate enough turbulence that would be used to keep the ball in motion.
On the other hand, the wings of airplanes are already designed to be aerodynamic, while their engines are designed to create enough turbulence.
Nevertheless, to fully grasp the reasons why airplanes are not dimpled, we must first understand the case against the inclusion of dimples on airplanes as it relates to the challenges it poses to an airplane.
Also, in the course of this article, we would look into other aerodynamic features and design choices found in airplanes that compensate for the lack of dimples.
Why Aren’t Airplanes Dimpled Like Golf Balls?
As earlier mentioned, airplanes are not dimpled like golf balls because dimples are not necessary to enhance their aerodynamic properties. The case against the inclusion of dimples on the surface of airplanes is built on the question of necessity, efficiency, and cost.
When these factors are put on a scale and weighed, it becomes easier to see why airplanes aren’t dimpled like golf balls. The following are the major reasons why airplanes are not dimpled like golf bass:
- Manufacture difficulties: Although carving out dimples on a golf ball is practically easy due to its small surface area, doing the same on an airplane, which has a significantly bigger surface area, is much more difficult. Besides, carving dimples on the surface of an airplane would make it difficult to attach parts to it. Therefore, when compared to the value expected, it is impractical to carve dimples on the surface of an airplane.
- Affinity to dirt: Another factor that works against the case for dimples on airplanes is their attraction to dirt and the challenges dirt poses as regards to repairs and maintenance. Due to the curved design and nature of dimples, they tend to attract and hold a lot of dirt and foreign bodies. This affinity for dirt creates a lot of difficulty in maintaining the airplane and keeping all its parts running.
- Redundancy: A major reason why dimples are not included on the surface of airplanes is that their inclusion makes little or no difference on the aerodynamic property of airplanes. First, airplanes already possess wings that are streamlined to give them an aerodynamic edge. Secondly, dimples tend to attract and hold a lot of dirt, which adds a lot of weight to the airplane surface and undermines the drag-reducing effect of dimples. Taking these two factors into consideration, it becomes very unnecessary to carve dimples on the surface of airplanes.
- Purpose of design: The purpose of a golf ball design is to allow the golf ball spin at thousands of rotation per minute (RPM) as the dimples produce air pressure on the opposing sides of the ball. The generation of air pressure on the golf ball permits an increase in lift and curve-ability. Airplanes, on the other hand, are not designed to spin but travel in a straight line. This means that the presence of dimples would increase the air pressure and drag all through the plane’s surface, which would consequently reduce the plane’s speed and increase fuel consumption.
- Turbulence: Golf ball designers consider the generation of energy by golf balls when carving dimples on them. Dimples generate extra turbulence and in effect more energy as they move through the air. However, when it comes to designing airplanes, laminar flow is more desirable, where a thin film of air sticks to the skin of the airplane and lubricates the airstream. Creating dimples on airplanes will prevent laminar flow.
Other Aerodynamic Design Choices Found in Airplane
Aerodynamics plays a huge role in flight. The more aerodynamic a body is, the more it is likely to fly in the air provided it has enough energy to sponsor this flight. When designing a plane or any other object, engineers pay a lot of attention to aerodynamics and other design features that enhance its aerodynamic property.
We have already established that designers use dimples to enhance the aerodynamic properties of a golf ball, although the same cannot be said for airplanes. As a result, we also looked into the disadvantages of using dimples on airplanes.
However, this leaves us to wonder, if dimples are a no go area for airplanes, what aerodynamic features can be found on a plane? From aerodynamic wings to vortex generators, here are the aerodynamic design features found in airplanes:
Aerodynamic wings
Just like in golf balls, engineers play with curves to affect the air pressure around an airplane and generate lift. However, unlike the dimples on the surface of a golf ball, aircraft engineers increase the aerodynamic properties of an airplane using aerodynamic wings. These wings are designed in such a way that they enhance the aerodynamic property of the plane and allow it to fly.
The wings of airplanes are curved on the top and made flatter towards the bottom in order to make airflow on the top of the wings faster than that below the wings.
This reduces the air pressure on top of the wings as the pressure below the wings increases. As a result of this difference in pressure, the wings overcome gravity and lift off together with the airplane they are attached to.
Streamlined fuselage
Aircraft engineers design the fuselage of an airplane to be streamlined. They achieve this by shaping the outline of the fuselage of a plane into a smooth curve, in such a way that the front part of the airplane is well rounded as it gradually curves back from its midsection to a thinner rear section.
Streamlining the fuselage of an airplane allows it to reduce the resistance to its motion caused by air pressure as the airplane moves through a stream of air. The faster an airplane is expected to be, the more streamlined its fuselage is going to be.
Light materials
Gravity is probably the greatest limitation to flight. The heavier a body is, the faster the earth’s gravity will force it back to the ground. Birds fly because their feathers are light enough to allow them stay in flight. In order to give the airplane an edge over gravity, aircraft engineers make use of very light materials in the manufacture of airplanes. These materials include aluminum alloys such as duralumin, light wood, and titanium.
Powerful engines
As mentioned earlier, drag is another limitation that must be overcome before flight can be attained. For a body to overcome drag, it needs to generate enough force in the opposite direction called thrust.
In golf balls, dimples are introduced on its surface to play with air pressure and generate thrust. However, engineers install powerful engines to overcome drag and generate thrust in airplanes. When the force generated in an engine is pushed out in one direction, the airplane attached to it follows Newtons’ third law of motion and shoots in the opposite direction.
The greater the power of an engine, the more thrust it is likely to produce, and the faster the airplane attached to it will fly.
Winglets
Another aerodynamic design choice used by aircraft engineers to enhance the aerodynamic property of planes are winglets.
Winglets are attached to the tip of an airplane’s wing to reduce the amount of induced drag or drag due to lift. However, this kind of drag is only experienced at very high speeds and as a result, winglets are rarely seen in small airplanes.
Vortex generators
The closest substitute to dimples on an airplane are vortex generators.
A vortex generator is an aerodynamic device in the form of a small vane attached to the wings of an airplane. When an airplane moves through the air, vortex generators create a vortex. The vortex created removes some part of the internal air friction in contact with the wings and as a result, improves the aerodynamic property of wings.
Summary
In conclusion, although dimples actually enhance the aerodynamic property of golf balls by playing with the air pressure around them, they are ineffective and unnecessary as an aerodynamic feature when used in airplanes.
However, thanks to various other aerodynamic design choices found on airplanes, the absence of dimples does not make them less aerodynamic than golf balls.
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