Meer Sabahi

Model Aircraft

Project

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Presentation

Meer Sabahi - Model Aircraft.mp4

Capstone Essay

Meer Sabahi

Mr. Coussens

English 8

4 May 2020

Superior Model Aircraft Design

Building a model airplane from scratch could be quite intimidating, costly, and time-consuming. However, the work pays off as the end result is immensely more rewarding than simply purchasing one. Flying model planes is an exceedingly uplifting experience that involves both technical and artistic measures. The hobby can be immersive in a variety of skill sets such as woodworking, 3D printing, electronics, and aerodynamics. At the same time, it lets people encounter the fresh air outside. In the course of this project, I will explore the most efficient aircraft designs, along with their involvement with physics. Furthermore, I will address points more specific to models, such as their electronics and building materials. Enhancing aerodynamics, reducing weight, and selecting the appropriate electronic components can transform an adequate model airplane design into one with superb flight characteristics.

Taking aerodynamics into consideration plays a major role in ensuring a successful aircraft design. Aerodynamics is the subdivision of physics that involves the movement of fluids such as air and water, along with their effects on various objects. It is involved in the function of aircraft, rockets, and projectiles, as well as the construction of cars, vessels, bridges, and buildings to determine their ability to endure long-term environmental conditions (Aerodynamics). Aerodynamics needs to be taken into consideration when designing aircraft wings. The wings, or airfoil, are designed to push higher pressure air below their surface, and lower pressure air above to generate lift. The majority of this air moves at a constant speed and direction and is referred to as laminar flow. However, some of the low and high-pressure air joins, creating turbulent flow (Datta). This force often takes place on the wing-tips and is referred to as wing-tip vortices (Flight). The consequences of wing-tip vortices are their added drag and noise. In my model, I will reduce wing-tip vortices by adding winglets to either end of the airfoil. Aerodynamics is an integral part of reaching a solid airplane design.

During the aircraft design process, factors that resist airflow must also be taken into account. Drag is defined as the mechanical resistance generated by solids as they move through surrounding fluids, which is air in the case of model aircraft. There are several types of drag, one being skin friction. Skin friction takes place on an aircraft’s outer surfaces such as the fuselage, wings, or externally mounted items such as servo motors (Glenn). To minimize skin friction on my model, I will place the servos and wiring within the fuselage rather than onto the airfoil. Next, induced drag is that which occurs due to the differences in pressure over the airfoil. It cannot be eliminated on airplanes since the differences in pressure are required to sustain lift. Lastly, ram drag is generated when air is let into the aircraft, such as through cooling vents (Glenn). On full-scale airplanes, it is beneficial to use cooling vents that channel air into the engines, as opposed to installing a cooling system that will increase weight, reducing efficiency. Electric models do not usually require cooling, as their power system is highly efficient. To maximize efficiency, resistance to airflow must be avoided whenever possible.

Most radio-controlled planes are powered by brushless motors due to their high torque and minimal weight. Brushed and brushless motors are the two most commonly used electric motor types, found in a variety of applications. They can often be seen in the medical, robotic, aeronautic, and automotive industries. In a brushed motor, brushes provide electricity to the stator, which creates an electromagnetic field allowing the armature or rotor, to rotate the output shaft. However, friction between the brushes and the stator prevents the motor from generating high torque and causes wear and tear over time. Therefore, brushed motors are advantageous in areas of work with small movements and precision, as they are inexpensive and easy to repair. On the other hand, brushless motors have a permanent magnet on the rotor itself, eliminating the need for brushes. This makes them long-lasting and is the reason they are used on electric cars, bikes, or fans (Dirjish). Since the goal of my project is to create an efficient model, I will use a small brushless motor to ensure long flight times while maintaining sufficient power output. Model aircraft frequently utilize brushless motors due to instant torque delivery, high RPMs, and minimal components that reduce weight.

Weight distribution and center of mass play key roles in providing the desired aircraft performance. Although center of mass is a primary aspect of flight, it is often overlooked. During flight, an aircraft continuously rotates on its center of gravity, which refers to the point of the aircraft at which its weight is evenly dispersed. This distribution is based on the location and mass of the aircraft’s individual parts (Hall). The farther back an item is placed on the aircraft, the greater effect it will have on the center of mass. If the center of mass is pushed too far forward or backward on the aircraft, its control surfaces will not be able to counteract, most likely resulting in a crash (Hall). In commercial airliners, individuals are seated in a way that maintains the aircraft’s center of gravity. When there are fewer passengers, most are seated close to the center of the plane, leaving open the front and rear areas (Balance). Similarly, one needs to keep in mind the center of gravity of model airplanes. Due to their small size, the placement of electronic components such as the receiver or battery will be very influential to their flight characteristics. Knowledge of center of gravity can be used to sustain balanced flight.

The dimensions of both full-scale and model aircraft significantly influence the amount of lift produced due to ground effect. Ground effect is the supplementary lifting force produced during takeoff and landing, and occurs due to air trapped between the aircraft’s wing and surfaces below. It increases the amount of airflow under the wings and allows flight with considerably less thrust than usual (Flight). This can result in a substantial increase in airspeed if the pilot does not reduce thrust in time, narrowing the chance of a successful landing. On the contrary, the pilot must provide adequate thrust during takeoff to be able to sustain flight when ground effect clears away (Ground). The cushion of air also changes the angle of the airfoil’s upwash and downwash, upwash being the air that approaches from below the airfoil, and downwash being that which flows over the airfoil (Flight). Ground effect occurs at the altitude equivalent to that of the airplane’s wingspan, and its authority increases linearly as the aircraft approaches surfaces below. Because of this, an airplane will experience the most ground effect if the airfoil is mounted lower on the fuselage. The wings of my model will be mounted low relative to the fuselage to make use of ground effect when possible. Aircraft design specifications can directly influence lift production from ground effect.

To improve efficiency, the shape of an aircraft’s wings, along with its internal components, can be adjusted for its specific function. Since induced drag is most prevalent on short airfoils with wide wing-tips, one should avoid such designs. Instead, wings that distribute lift in an elliptical shape should be used, as they produce the least amount of induced drag due to a lack in wing-tip vortices (Glenn). The size, shape, and angle of a plane’s airfoil directly affect the amount of lift it produces (Datta). Therefore, the surface area of the wings can be optimized for a specific aircraft’s function to improve efficiency. High-speed airplanes often have slim, aerodynamic wings that produce minimal drag and considerable lift, where most of the flight is centered on the motor. Gliders, cargo, and STOL aircraft have reinforced airfoils that produce more drag but maximize lift (Airplane). In the case of my model, I will have a hybrid of these designs to reduce drag while producing sufficient lift. Since the weight of an aircraft is contradictory to the lift it produces, lighter planes are generally more efficient (Airplane). I will save weight on my model by using foam-board as the primary building material as opposed to heavier alternatives such as wood. This will accommodate a large battery, which will increase flight time. Through changes in airfoil design and overall aircraft weight, satisfactory performance can be achieved.

Propeller design plays a significant role in efficiency, as the thrust it produces is central to powered flight. Propellers generate thrust by creating a difference in pressure within the fluid they are rotating in, resembling the function of an airfoil. When paired with a motor, the usable thrust output of a propellor is its efficiency. Increasing the number of propeller blades reduces efficiency but creates a balanced thrust. Larger propellers will rotate more slowly and produce more thrust, while small ones reach higher RPMs while generating less thrust per rotation. A smaller angle of attack on the propeller blades will work better in areas that lack airflow, such as inside an electric ducted fan (Optimize). A fixed-pitch propeller is one whose angle of attack cannot be changed once manufactured. They are often made of wood or aluminum alloys and are best suited for aircraft that fly at low altitudes, hence their frequent use on models. Next, there are controllable-pitch propellers, whose angle can be adjusted during flight to match surrounding air-pressure. Constant-speed propellers automatically adjust the pitch of propeller blades to assist with maintaining airspeed (Types). This is especially useful during ground effect so that the pilot needs to provide fewer throttle inputs. With all variables in mind, propeller designs must be tested to conclude the power system and rotational speed with which they are most efficient (Optimize).

Resilience to environmental conditions is critical to model aircraft without which its design and efficiency become irrelevant. One can reinforce the leading edge of a wing by gluing to it a piece of wood, such as a barbecue skewer. Paper delamination from foam board can be avoided by spreading a thin layer of hot glue over the edge of the foam. To reinforce the hinges of control surfaces, one can apply and smooth out a thin layer of hot glue inside the hinge. To reduce wear on the axles of landing gear wheels, a reinforcement plate can be made by drilling a small hole in a thin piece of wood and gluing it over the axle. (Speed) In my model, I will use materials that are both lightweight and durable. I will use a carbon fiber rod as the wing spar, and an aluminum alloy for the landing gears to make them long-lasting. Increasing the durability of an efficient model allows for peak performance while keeping the airframe intact.

Through my research on aircraft physics, construction, and efficiency, I have learned a great deal about the technical aspects of this hobby. Model aircraft can be enjoyed by any individual, regardless of age and experience. At the same time, they are used for testing the behavior of full-scale aircraft before they are built. I will apply my acquired knowledge from this topic to explore the possibilities of a long-lasting, efficient, yet high-performance model that can multiply the pleasure and usability of conventional aircraft. This will result in a unique model of my own, which creates something I enjoy while having it last for an extended period of time.

Works Cited

"Aerodynamics." Britannica School, Encyclopedia Britannica, 7 February 2020,

school.eb.com/levels/high/article/aerodynamics/3873. Accessed 21 April 2020.

“Aerodynamics of Flight.” FAA, 23 August 2016,

https://www.faa.gov/search/?q=aerodynamics+of+flight&bSubmit=Search. Accessed 12 April 2020.

"Airplane." Britannica School, Encyclopædia Britannica, 3 December 2018.

school.eb.com/levels/high/article/airplane/110741. Accessed 7 April 2020.

“Airplane out of Balance?” Mentour Pilot. Youtube, Petter Hornfelt, 21 February 2020,

https://www.youtube.com/watch?v=9JS0evmHZDA. Accessed 21 April 2020.

Datta, Sreela. "Aerodynamics." The Gale Encyclopedia of Science, edited by K. Lee Lerner and Brenda

Wilmoth Lerner, 5th ed., Gale, 2014. Gale In Context: Science,

https://bit.ly/3cAkVDw. Accessed 5 April 2020.