Introduction: (Initial Observation)
Model airplanes use the same aerodynamic rules as larger airplanes. All new airplane designs start by making and testing a model. Models may be tested in an air tunnel or using small engines. Sometimes the engine is nothing more than a rubber band. Rubber band may be used to eject the model airplane, so it can glide back to the ground. It may also be used to drive a propeller mounted at the nose of an airplane.
The most common material for making model airplanes is balsa wood. Balsa is flexible, light weight and easy to cut.
We usually make model airplane in order to study the effect of different design factors in how stable and efficient an airplane can fly. Models are inexpensive and can be made in a short period of time. In this project I will make a model airplanes in order to see how does the shape, size and location of the wing affect the flight.
Adult supervision and support is required.
Information Gathering:
Find out about airplane parts and their function. Read books, magazines or ask professionals who might know in order to learn about airplane designs, model airplanes and material used in constructing model airplanes. Keep track of where you got your information from.
Following diagram shows the parts of a small airplane.
The following diagram shows the airplane parts as well as their function.
In some airplanes, specially fighter jets, the wings are stretched along the airplane. How does this affect the speed of the airplane?
| Anyone who has seen the B-2 stealth bomber knows that the flying wing isn’t new to military aircraft. In fact, the flying-wing design dates back to the first half of the 20th century.
Search the Internet for flying wings for more information. |
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Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement. Following is a sample of purpose for this project.
The purpose of this project is to experiment and learn about making airplane models. Making model is the first step in designing new airplanes, cars, bridges, buildings and many other complex structures. The experience that I will earn in doing this project can help me design more advanced and more complex models in future.
If you want to do a project in order to find the answer to a question, your question must be very specific. For example you CANNOT have a question like “How does the design of an airplane affect the distance that it can glide?” . The reason is that there are many design variables or design factors that can not be studied or experimented at the same time. Following are sample questions.
- How does the wingspan of the airplane wings affect the distance that it can glide?
- How does the position of airplane wings affect the distance that it can glide?
- How does the surface area of the wings affect the distance that an airplane can fly?
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
If you choose your purpose to be experimenting and learning about making models, you don’t need to identify variables. You may simply skip this section.
If you choose question number 1, you may define your variables as follows:
The independent variable (also known as manipulated variable) is the wingspan.
The dependent variable (also known as responding variable) is the distance that the airplane can glide.
Controlled variables are shape and size of airplane body, wings surface area and wings position.
If you choose question number 2, you may define your variables as follows:
The independent variable (also known as manipulated variable) is the position of the wings (distance from the nose or front of the airplane).
The dependent variable (also known as responding variable) is the distance that the airplane can glide.
Controlled variables are shape and size of airplane body, wings surface area and wingspan.
If you choose question number 3, you may define your variables as follows:
The independent variable (also known as manipulated variable) is the surface area of the wings.
The dependent variable (also known as responding variable) is the distance that the airplane can glide.
Controlled variables are shape and size of airplane body, wings position and wingspan.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. You need to propose a hypothesis only if you have a question for your project. Following is a hypothesis if you choose the question number 1.
My hypothesis is that as wingspan increases, the airplane flies slower and can glide a longer distance. My hypothesis is based on the pictures that I have seen from different airplanes. High speed fighter jets have the lowest wing span.
Using the above sample, make up your own hypothesis for any other question.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1:
In this experiment you will make a simple balsa wood airplane. The purpose of this experiment is learning about making models. You may purchase a simple balsa wood airplane kit (about $5.00) or you may purchase balsa wood and cut it yourself as described here.
A kit is recommended for younger students. Even if you want to cut balsa wood and make your own model, it is still good to have a kit for your initial experiments. Following is a sample instruction on how to make a model.
Procedure:
Get two pieces of 3″ x 24″ balsa wood with 1/32″ diameter. You can purchase this from craft stores, art stores or hobby stores.
Cut one of the pieces to two equal pieces of 3″ x 12″. These pieces will be used to form the sides of the fuselage or the main body of the airplane.
Balsa wood can easily be cut by a utility knife. (Cutting must be done by an adult. Only a few millimeters of the blade must be exposed).
To cut the balsa wood, first draw the cutting lines and then trace the lines with a utility knife.
Draw the cutting lines similar to the one shown in the image and then start to cut. Note that you also need to cut two slits. One to hold the wings and the other to hold the horizontal stabilizer.
Cut the second piece of balsa wood to two pieces. One 18″ x 3″ to form the wings and another 6″ x 3″. This last piece must be cut in half again to make two 6″ x 1.5″ pieces. One of these 6″ x 1.5″ pieces is being used as the horizontal stabilizer.Finally cut some 1″ x 2″ pieces that will be used to connect the two sides of fuselage together.
Note: You could use one piece of balsa wood with a higher thickness (1/8″) to make the fuselage. Here we used two pieces, because the wood that we used was too thin to be used as fuselage and as a support for other parts.
When you have all the pieces, use wood glue to connect the pieces together.
In connecting the pieces you must make sure that the wings and horizontal stabilizer are centered in relation to fuselage. Also note that wood glue takes about 30 minutes to one hour to dry. You have to do the final assembly in two or three steps. After each step you must wait for the glues to dry.
Use different objects around your model to hold it securely while the glue is drying.
The final model will certainly look like an airplane, but it will neither glide nor fly. It will not fly because it does not have a propeller and an engine (such as rubber band). It will not glide because the front of airplane is too heavy. There might be other aerodynamic problems as well. Aerodynamic objects must have rounded edges so as to reduce wind drag.
Another problem that may exist in your new airplane model is imbalance. For a flying airplane, the center of the gravity of the plane must be the same as the center of gravity of the wings.
Center of gravity test:
Find the center of the wings. Insert a small pin or eye screw in the center of the wings and use it to hang the airplane with a string. At this time the airplane must stand horizontally. If it is nose down, it means that the front of airplane is too heavy. If it is nose up, it means that the tail of the airplane is too heavy. You may create the balance by connecting the wooden or metal objects to the front or back of the airplane.
For very small airplanes such as paper airplanes, a paperclip may create the balance. For this model, a wood block can be good. Another option is changing the location of the wings to create the balance. In the above picture, I used a rubber band to hold the wings. In this way I was able to move the wings enough to create the balance.
The model airplane that you see it’s picture on the top, can fly good but it can not glide. To convert it to a glider, I placed the wings in the back and stabilizer in the front.
Now it glides perfectly.
All other experiments that you may do, will use similar steps in making model.
Experiment 2:
How does the wingspan of the airplane wings affect the distance that it can glide?
Procedure:
Make a working model of a glider airplane. As seen in the previous experiment, you can use a kit or cut your own balsa and assemble a model.
After you have a working glider, record its wing span. Wing span is the distance between the edges of the wings. That is the same as the width of the airplane.
Throw the airplane and let it glide to the ground. Measure and record the distance that it glide. Repeat this three times from the same height and with the same force. each time measure and record the distance. Make sure that there is no wind to affect your results.
Cut about 1/2″ from both wings and repeat the previous step.
Continue cutting from the wings and testing the gliding distance for different wing spans until the wing span is less than half of what you started with. So if your starting wingspan was 16″, you will need to cut and test about 8 to 9 times.
Record your results in a table like this:
| Wing span | Glide distance 1 | Glide distance 2 | Glide distance 3 | Glide distance Average |
| 16″ | ||||
| 15″ | ||||
| 14″ | ||||
| 13″ | ||||
| 12″ | ||||
| 11″ |
If you have learned how to make a graph, use the wingspan and glide distance to make a graph.
Experiment 3:
How does the position of airplane wings affect the distance that it can glide?
Procedure:
After you have a balanced airplane that flies well, move the wings about 1/2″ toward the back or toward the front and test its gliding capability. Repeat this with about 3 backward disposition and 3 forward disposition.
To move the wings, either the wings must be attached by a robber band or they can move in a slit. In either case, you must secure the wings using a pin or any other method while you do your tests.
Results table will look like the results table of experiment 2. You substitute wingspan with wing disposition. Values for wing disposition can be -1.5, -1, -0.5, 0, 0.5, 1, 1.5.
Negative numbers mean disposition toward the back of the airplane.
Experiment 4:
How does the surface area of the wings affect the distance that an airplane can fly?
Procedure:
Make a working model of a glider airplane. As seen in experiment number 2.
After you have a working glider, record its wing surface area. Wing area is the area of the rectangle that forms the wings.
Throw the airplane and let it glide to the ground. Measure and record the distance that it glide. Repeat this three times from the same height and with the same force. each time measure and record the distance. Make sure that there is no wind to affect your results.
Cut about 1/4″ from both front and back of the wings and repeat the previous step. Note that cutting from the front and back of the wings, does not reduce the wing span.
Continue cutting from the wings and testing the gliding distance for different wing surface areas until the wing surface area is less than half of what you started with. So if your starting wings surface area was 48 square inches (3″ x 18″), you will need to cut and test about 3 to 4 times to reduce the wing width from 3″ to 1.5″ or 1″.
Record your results in a table like this:
| Wing area Square Inches |
Glide distance 1 | Glide distance 2 | Glide distance 3 | Glide distance Average |
| 54 | ||||
| 45 | ||||
| 36 | ||||
| 27 |
Additional experiments:
You may also choose to see how does the wing design affect the way an airplane can fly or glide.
Below I am suggesting some wing designs that you may test.
Materials and Equipment:
List of material can be extracted from the experiment section. You may substitute the material as needed.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
Description
Summery of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
References:
List of References
