A guide for teachers.
Why include kites in the curriculum, and where do they fit?
"Why should we teach students about kites and kite flying? Kites have nothing to do with the real world, and they aren't going to help students with their real work."
"We tried to make kites last year, but they didn't work."
"How do you know how to make a kite? Where did you learn how to make them?"
I have heard these questions and statements often while conducting kite workshops. Many teachers see kites as toys, with no legitimate reason for being included in the curriculum and being more trouble than they are worth. Nothing could be further from the truth. Kites are very much a part of the "real world". They form a part of our culture that we seem to have ignored in educational fields. It seems amazing to me that any child still knows how to build a kite when one considers how haphazard is the transmission of this knowledge from one generation to the next. Kites used to be made for and with children by grandparents, parents, uncles and aunts. This practice seems to be falling by the wayside, and kites are increasingly becoming the domain of toy manufacturers. I know, because I run a small business that makes and sells kites. A common occurrence is conversation with adults who remember their parents or grandparents making kites for them. They now want to do the same for their children or grandchildren, but the kites they have made have not worked, and so they've decided to buy one instead. Yet kites are not hard to design or construct. There are several excellent books readily available that contain foolproof plans for a number of kites that may be made from materials that you can find in a school art room, or a hardware store. All it takes is attention to details, and a willingness to learn from your mistakes.
By using kites for a particular purpose within the curriculum, we could expand the view and knowledge of students today. By presenting practical problems to be solved, we could make the knowledge the students use, and gain, much more meaningful. We could for example, set up a project that would require students to use a kite to lift a camera to take a photograph of their school from a height of 200 feet above ground level. In order to do this, the students would need to determine the best sort and size of kite to lift the weight of a camera in the prevailing wind for their school. They would also need to arrange for a release mechanism to take the photograph, and would need to work out how they were going to determine the height of their kite. By using a kite as an example of a design problem, students could come to understand particular concepts by relating them to meaningful situations, rather than simply "knowing" about them as abstractions. For example, the formula for determining catenary (the bowing of a line between two points) becomes important when you want to know exactly how high your kite is and you find that you can not simply measure the length of the line. For a start, the kite is not flying at 90 degrees, and furthermore, the flying line bows because of the wind and its own weight.
Even today kites retain a fascination and the ability to build a good kite is a skill that is prized by many, yet seemingly possessed by few. Making a kite requires a combination of several skills. The maker must display a great deal of manual dexterity, must be able to read a scale plan and follow instructions if making a kite from a book, and most importantly, must be able to identify and solve the many problems that can prevent a kite from flying well. These skills are relatively easy to acquire, and can lead to many hours of enjoyment. They can also be applied to many aspects of the curriculum of upper primary and junior secondary classes.
For a number of years I have been conducting kite making workshops in classrooms across Victoria, using kite designs that are simple and almost foolproof. The enthusiasm and interest displayed by the students I have taught leads me to believe that kites could be used within a classroom as a method of stimulating interest in a wide range of subjects. In these workshops the students have learnt much more than simply how to make and fly a kite. They have also made practical use of mathematics and science. They make use of measuring skills as well as perhaps finding out how to use a protractor and read a scale plan. They could well have made discoveries about symmetry and how in particular shapes the angles add up to either 180 (triangles), or 360 degrees (quadrilaterals). Students may have learnt through experience several important principles about graphic design; a design that looks great from less than a metre probably won't look so good from 50 metres. They will have discovered the necessity of cooperation and communication between members of their group if they wish to produce their kites efficiently. When the finished product takes to the sky, the boost in confidence for some children is phenomenal. The thrill of watching the kites that they made fly provides positive reinforcement and motivates them to take their investigation of and experiments with, kites much further.
Kites can be used as a method of promoting linkages between subjects. By making use of kites in a manner that stresses topics of interest relevant to several different areas of the curriculum, they could be used in schools to promote interdisciplinary study. There are many topics where ideas overlap more than one subject area. Computer Science students could well find themselves studying information more common in the Geography classroom, in order to develop the apparatus to be used in telemetry experiments involving kites. Science students might make use of skills more often found in the carpentry workshop in order to build the kites required for their experiments. Kite making is a very practical activity that emphasizes the need for problem solving skills. By making use of the enthusiasm many students have for building and flying kites it is possible to learn a great deal about other subjects as well. The following information is merely an overview, and a suggestion of possible uses. An approach which makes use of information from several branches of study, but which concentrates on science, is suggested later in this teachers' guide and in the accompanying worksheets.
Kites could be used as apparatus in the study of aerodynamic forces. Kites can also be used as a context for teaching principles of scientific research design such as the careful control of experimental variables. Using one kite of a particular design as a control, students could change the dimensions and weight of this style of kite in order to discover the optimum size and weight for this sort of kite. Students could be asked to find the "ideal" kite style. This is a very open ended task, without one correct conclusion, and depends very much upon the strength of wind the kite is to fly in, and its intended purpose. This task would allow the teacher to see what ideas students have about what it is that makes a kite fly, and what conceptions and misconceptions the students hold about the physics involved. Experiments would have to be performed to determine the relationship between weight, lift, thrust and drag. This could be done by designing a number of kites with wings of differing weight and surface area and then conducting experiments to determine the lift that is generated by each design. The simplest method of measuring the lift would be to use a spring balance to determine the amount of tension on the flying line, but other methods are possible, such as measuring the amount of bowing in the flying line. The tauter the line the more pull is being exerted by the kite. The effect of including a tail and altering its length and shape could also be investigated. Kite performance in varying wind conditions could be looked at as well. The results of these observations could be collated, graphed, and compared. Conclusions about kite performance drawn from these results would have to be tested for validity, which would entail a further series of experiments. Students could also compare the suitability of different materials for making kites. This might prompt some students to investigate what sorts of materials were used for kite making in the past, which could lead into research about the part kites played in the development of powered flight.
As a result of flying kites, students may express interest in finding out more about the wind and the weather. Weather patterns can be studied, and experience gained about how wind speed varies with altitude. To follow this up, students could consider the use of kites in the development of meteorology, and this could perhaps lead into making weather stations and predicting the weather.
Basic concepts that may be illustrated with kites include matching, halving, and symmetry.
Practical work could be done on surface area, perimeter, shape recognition, and angles. Work could also be done on decimals, diagrams, graphs, equations, ratios and scales.
Whilst flying a kite, students could measure flying angles, distances and altitudes, making use of clinometers, range finders, and Pythagoras' Theorem and trigonometry.
By flying a kite in a variety of winds and recording the wind speed and the amount of tension on the line, students could generate the data necessary to create tables that could predict the weight the kite could lift in a given wind.
Kites could be used in passive, non intrusive photography of habitats. Their possible use as a bird scaring device could be studied as an alternative to devices relying upon noise or chemicals.
Geography and History.
Students could study the historical development of the kite and how kites spread through Asia to the rest of the world. They could look at the purposes (games, scientific, military, etc.) for which kites have been developed in different periods and countries, and attention could be drawn to the religious and cultural significance of kites in some cultures.
Kites could be used in Art to study designs and materials used throughout the world, as well as methods of construction and decoration. They could be used as a project in the study of form, colour, and two and three dimensional design. Time could be devoted to experimenting with different ways of decorating the sails, using batik, tie-dyeing and screen printing as well as appliqué and painting. Three dimensional kites can be used as a novel form of sculpture, and the work of people like Peter Travis and Peter Malinski could be examined in light of this. Peter Travis is an Australian artist who progressed from pottery to kites, whilst experimenting with sculpture. His kites/sculptures have been exhibited in many galleries, including the National Gallery in Canberra, and several of his works hang in the lobbies of public buildings and international hotels. Peter Malinski is a German graphic designer whose work in kites is synonymous with perfection. His kites are flown and admired around the world.
As part of a project, plans for the kites could be drawn to scale and models could be made of the kites and the components that might need to be built. A step by step guide to building a kite could be made, either as a series of drawings, or perhaps as a flowchart. Graphics programs such as Corel Draw, Harvard Graphics, and Micrographix Draw could be used to produce working drawings of the kites to be produced.
Manual skills / home economics.
There are several skills that anyone must possess when making a kite. If the kite is to be made of fabric, then the maker should be able to use a sewing machine. Making a kite is a good way of gaining proficiency in these skills. Basic carpentry skills are also useful, and manual skills projects could include making winders and kite frames. A number of kites require specialized fittings to hold the frame at the correct angle, giving the kite dihedral, meaning that the wing tips are located somewhat behind the centre of the kite, giving considerable stability to the kite when it is flying. These could be turned on a lathe by the students.
Class work on kites could include written descriptions of kites, and instructions for making and flying them safely. There are a number of stories that could be read, including stories such as "The seventh Mandarin", by Jane Yolen, and "The Kite", by Somerset Maugham. A suggested reading list is included in the bibliography. Students could write an account of their experiments. They may also like to write their own scripts and perhaps make a video documentary of their experiences, or make their own video on how to build a kite.
Physical / Outdoor Education.
Making and flying kites could be used to teach about kite safety, how to tie a variety of knots. They could be used as the basis of a number of competitions. Kite flying can make use of both gross and fine motor control, and flying manoeuvrable kites develops excellent eye - hand coordination.
Computer programs to design kites can be written, based on the information collected by flying a style of kite in a range of winds and recording pertinent data. A program of this nature could be used to determine the necessary size of a kite to lift a payload in a given wind, and then print a plan of the required kite. Similar programs could be written to predict possible heights attainable by a kite. Senior students might like to try developing an airborne meteorological platform for instruments and experiment with telemetry.
The Asialink Foundation kite project.
A commission received by me from the Asialink Foundation may be used as an example of how kites could be used to integrate several subjects. The Foundation was launched in 1992 and their first major project was a school day in Queen Victoria Hall, located in the Parliament House of Victoria. Students from several schools came to Parliament House for the day and were exposed to many aspects of Asian culture. My commission was to work with students from the school of art and design at Melbourne University and produce as many kites as possible to hang in Queen Victoria Hall. The kite designs were to be drawn from as many different Asian countries as possible, and were to be built by second and third year students from Melbourne University in the months before the display.
The first step was to meet the students involved. They were given information about the history of kites and they watched video footage on some of the best kite festivals in the world. This showed them what was currently being done with kite designs, and gave them a starting point for their own designs. I then taught the students how to build a simple kite using modern materials. The skills that they acquired whilst making this first kite were necessary for the students to be able to successfully complete their own kites later on in the project..
Once these skills were acquired the students were ready for the next stage in the project. At a group meeting the students were shown a variety of kite designs from countries in Asia, and the merits of many of these designs were discussed. Most of these kites were painted in one way or another, and emphasis was given to a discussion of the themes commonly used on kites from a range of countries. The students were then asked to do some research and decide what style of kite they wanted to build. Once that was done they were to draw a full scale mock up of the design they wished to paint on their kite. The design had to be consistent with the themes normally used on that style of kite. When they had done this they were to submit their work to their supervisor for approval.
The next stage was to actually make the kites. We did not have to time to acquire the skills necessary for working with bamboo and rice paper or tissue paper, so we substituted fibreglass and a material called tyvek. Tyvek is a synthetic fabric which has several attractive qualities for kitemakers. Easy to work with and to decorate, it has uses as diverse as surgery gowns and waterproof books. The kite skins were cut from the tyvek, and the spars were cut from a variety of diameters of fibreglass. The spars were then fitted to the kite skins. This work was done by the students, with assistance from me when they needed help in learning particular techniques. This work took several sessions to complete. One student decided to build a carp windsock, using appliqué techniques, and in doing so had to develop strategies for using a sewing machine on very fine materials in awkward proximity to other pieces of her design. A number of kites were built as a group effort as well, to be strung together into one long kite when everything else had been completed.
When the kites were completed the students started to decorate them. The more meticulous students spent some time perfecting the style of brush stroke traditionally used on Japanese kites, whereas others simply attempted to produce a finished product that approximated designs they had copied from books and the examples I had provided.
In completing this project, the students had learnt about the importance of symmetry of weight and surface area in kite design. They had developed some of the construction skills and techniques commonly used to build Asian kites, and had modified these techniques so that construction was possible using more readily available, modern materials. They had spent some time researching traditional Asian kite designs and their decoration, and made use of this information when they were building and decorating their kites.
The hanging of their kites in Queen Victoria Hall was seen as the culmination of the project, and a great deal of time was spent by the students determining how the kites were to be suspended, as well as their placement throughout the hall. The project was judged a great success by the directors of the Asialink Foundation, but it was evident that they had no real appreciation of how much effort the students had put into their work, or how much the students had learnt in the process.
Kites as a technology.
Kites can be used by teachers in a number of diverse subject areas. Uses in the science and art curriculum are fairly obvious, and there is much that kites could be used for in history, geography, manual skills, as well as a number of other subjects. However, I would like to advocate a more integrated approach. Kites could be used within the framework of a subject such a Technology Studies. This approach would allow teachers from several subjects to work together, and show how a technology is not developed purely by scientists for scientific purposes. For a technology is not based purely on science, although it is often considered so, and science should not be taught simply as an historical progression of inventions and technologies. A technology can be looked at in terms of the scientific principles behind it, but it may also be considered from an aesthetic and functional point of view. Geographical factors, such as materials, climate, and need, will also have played a part in determining how a technology developed. Even religious and philosophical considerations might have some influence on the development of a technology.
A study of the technology commonly known as the kite could be developed into such a unit of work. The information that is provided in this kit will be sufficient for you to explore the history of kites with your students, to make and fly your own kites, and to explore the aerodynamic principles involved in flight.
How do you teach about kites?
Kites are very much a part of the real world, and as such may be used by teachers as an aid in teaching about that world. One theory of how humans learn, concerned with what it is that we know, and how we know it, is called constructivism. It is based on the idea that everyone constructs a view of the world and the rules by which the world functions. This view is developed and supported by all our experiences in the world. If events occur that cannot be explained by our current understanding of "the rules" we modify our view of the world so that the new set of "rules" can explain these new and until now inexplicable events. We only change our view of the world when things happen that our current ideas cannot explain. Obviously, this view of how we learn about the world has implications for the teaching style we employ in classrooms. If we subscribe to the idea that our students learn from being exposed to new experiences and then attempting to develop their own explanations about what happened and why, more time must be spent setting up new learning experiences for them. The emphasis on textbooks would have to be reduced, and more importance placed on actual events inside and outside the classroom.
Constructivism recognizes that information is not simply passively accepted by the learner, rather that the learner is actively trying to build up a set of rules that can explain every event that happens in their world. That is, knowledge should not simply poured into students in the expectation that once students have been given the information they will accept it as being true. Rote learning may produce the correct response on cue, but students will not necessarily understand or believe the information they have been "taught". In order for students to accept something as being true, they need to see that it fits into their perception of reality. If the new information doesn't match their experience and their current view of the rules that govern the world, students need to consider two options; firstly, that the new information is incorrect, or secondly, that there is something wrong with their view of the world. If several events occur that cannot be explained by the first alternative, then it is normal to try to find a new rule or a variation of an existing rule to explain why. This new explanation will in all probability change their view of the world and how it "works".
Some of Piaget's ideas about learning can be used when discussing constructivism, and some proponents of constructivism use Piagetian terms when explaining what happens in the learning process. Piaget formulated the idea that if people are given new information a number of outcomes are possible. If the new information is not at odds with the person's existing concepts, a state of equilibrium will exist, and the new information will be accepted as correct and will be assimilated into the current view of the world held by that person. But if this new information does not match what this person already "knows" then a state of disequilibrium will exist. The new information will either be rejected as incorrect, or the previous views will be modified to explain the new information. If this modification takes place then the person is said to be accommodating the new information. Although some of the language has been adopted, there are differences between Piaget's ideas and constructivist theory. One major variation between Piaget's views and those of a constructivist relates to the development of theories by the learner. Constructivists argue that people, regardless of their age, develop theories to explain any new situation. Piaget maintained that people were only capable of theorizing once they were in the formal operational stage of development, that is, only once they were around eleven years old. Many constructivists would argue that a major flaw in Piaget's theory is the view that we are governed by biologically determined stages of thinking and that until a student is of a particular age they cannot be expected to think in a particular manner. There is ample evidence to suggest that this is not the case and that students do develop ideas to explain what they have experienced, whether they have reached the age of eleven or not.
New experiences, which cannot be explained by previously held views or beliefs, form the basis of learning. As teachers, we should place in the way of our students new experiences that cannot be explained with their current understanding of a topic. It is our job to ensure that these new experiences are not so far outside the scope of their present knowledge that they are in fact inexplicable, yet for there to be enough variation between their existing ideas and what is presented to them for there to be a need for the disequilibrium to be resolved. We can present material about kites in this way. Students could learn a great deal about aerodynamics from kites, in such a way that they actually "know" it, rather than simply having been "taught" the information.
Appleton (1990) has proposed a learning model for science education based on Piaget's ideas of equilibrium, assimilation, disequilibrium and accommodation. He sees every learning situation as having four possible outcomes, or exits.
Exit 1. Assimilation. Students will have their existing ideas reinforced (right or wrong).
Exit 2. Accommodation. The previous ideas will be replaced with a better understanding of the concept.
Exit 3. False accommodation. Existing ideas will be unchanged, but there will be a "correct" answer to be used in school situations.
Exit 4. Existing ideas will remain unchanged because the student opts out of the learning process.
He suggested that this model could serve as a basis for developing teaching strategies ideally suited to science education. He calls these 9 strategies "teacher interventions". Listed below are the 9 steps or interventions identified by him as being necessary in ensuring that a concept or task is adequately covered.
1. Identify preconceptions.
The teacher needs to identify the preconceptions the students hold about the chosen topic. This may be done either by questioning the children directly, or from the literature already published on the subject.
2. New encounter
The teacher must then provide a new encounter that will provide a link to past experiences, which will not be explicable by their present understanding of the topic. This needs to be both interesting and challenging, and allow for first hand investigation of the problem. If students can use their present understanding of the topic to explain the results of the investigation without revising any of their ideas then they are simply reinforcing their current set of ideas (whether they are correct or incorrect).
3. Identifying the ideas that links are being made to.
By discussion with individual students or the group, the teacher should find out what aspects of the encounter the students are focusing on and what ideas the students are linking to. For example, if the teacher was trying to teach that kites are more stable when they are bowed, then concentrating on the materials used in the skin of the kite would not be beneficial.
4. Challenging incorrect ideas.
If some or all of the students appear to have simply reinforced incorrect concepts it is necessary for the teacher to challenge these incorrect ideas. Students may have focused on an inappropriate aspect of the encounter because of a previously held idea, or they may not have observed some important part of encounter. The teacher needs to identify these problems in step 3, and then present a situation where it is obvious to the student that their current ideas cannot explain what is happening. This may be done by challenging their ideas directly, getting the students to test their ideas, asking for other ideas and testing them, and by drawing attention to the important aspects of the encounter. This needs to be done until all misconceptions are dealt with.
5. Avoiding false accommodation.
It is important that every student be asked to provide their own hypothesis to explain what happened in the encounter. This is necessary to prevent students being able to sit back and wait for another student or the teacher to provide the correct answer. This is important as it stops students being able to give the "right" answer, whilst still maintaining their own erroneous views. This isn't something that happens only in primary or secondary schools. White (1988) conducted a study that showed that some medical students who had been taught about natural selection still believed that the skin colour of a family would change in a few generations if they moved to another climate. A student can be said to falsely accommodating an idea if they regard it simply as the "right" answer for the task, without actually changing their own conceptions.
6. Preventing students from opting out.
Appleton also stresses the importance of knowing the students well enough to be able to recognize when particular students are losing interest or are frustrated enough to opt out of the learning situation. The teacher should be ready to encourage and provide more structure or other form of help in order to bring students back on task. If this does not happen, students will exit with the same set of ideas as they held at the start, and possibly with a negative attitude towards science as a subject because it is "too hard".
7. Helping towards accommodation.
Whilst some students will not have any problems grasping the new concepts, many students may need help. The teacher could provide this help in a number of ways, such as helping students to plan activities, finding resources, or providing a forum for discussion and exchange of ideas. Accommodation occurs when students restructure their existing ideas, discard some old ones and make use of some new or improved ideas in order to achieve a more correct explanation of the observations they have made.
8. Applying new ideas.
In order to reinforce the accommodation of the new ideas it is important that opportunities be provided for the students to use them in practical, real life situations. Appleton feels that this practice should be in the form of problem solving that has relevance to the students. In this case, students could be asked to build kites for specific situations, such as very light winds, carrying payloads, reaching a given height, and so on. Given the current popularity of manoeuvrable, two string kites, this could be another option, or a separate project in itself.
9. Diagnosis and remediation.
Before closure, the teacher should investigate the ideas that students have formed, in order to determine whether any remediation is necessary and if so, what sort of situation or encounter would be most beneficial.
Using this model, the teaching of a new concept, or group of new concepts may be described as a process running through a number of steps. The teacher should monitor the progress of each student and present opportunities to correct any misconceptions the student holds or might acquire along the way. This can be represented as a flow chart, with satisfactory progress being shown as a straight line progression through each step. When the student does not hold the appropriate concept or ideas it is necessary for the student to be placed back at that point in the process where this false concept may be reexamined and discarded in favour of one that better matches the observations of the encounter.
Appleton's 9 teacher interventions.
An example. Designing a kite and lifting a camera.
Appleton's teacher interventions may be used to describe what should happen when students are introduced to kites as a topic in the science curriculum. This process described below could be used in the task of building a kite suitable for taking a photograph of their school. The task could be given as a research project, where the process of developing their lifting kite would have to be fully documented by the students.
Before the start of the project the teacher should find out what the students know about kites. Questions could be designed to find out what the students "know" about what makes a kite fly, what is the best shape for a kite, what are the best materials, and so on. I have frequently found that students in primary grades concentrate on two factors when I have talked to them about what it is that makes a kite fly. It is common for them to feel that a kite must have a tail if it is to fly, and that the lighter the kite is, the better it will work. When students are launching their kites they frequently exhibit no understanding about the effect that wind has on a kite; at least half a dozen students from each class try to launch their kites by running with the wind rather than into the wind. A number of techniques could be used to find out what your students know about kites and kite flying. The more questions you ask your students, the better picture you will build up of their understanding about how kites fly. Examples such as the questions below might be of use;
"Why do you think a kite can fly?"
"What shape is a kite?"
"Name some other shapes that are used as kites?"
"What do you think might happen if we took the tail off the kite?"
"What might happen if we made the tail longer?"
"What would happen if the tail was shorter?"
"What is the best material to make a kite from?"
"Could a kite fly on the moon?"
"What keeps a kite up?"
From questions like these you should be able to build up information about what your students know about kites. Many children think that kites get "pushed" into the sky by a wind blowing the kite straight up, as if the wind blew at a right angle to the ground. Others concentrate on the weight of the kite and assume that the lighter the kite the better it will fly. Asking them to predict outcomes to a change in a kite, such as the length of its tail, allows us to set up a new encounter where they can test their prediction and explain why the prediction did or did not fit their observations. Give them a sheet with a drawing of a person and an arrow showing which way the wind is blowing.
Ask students to add a kite to the drawing, with the kite line being held by the person in the drawing. You will be surprised by the number of responses that show the kite either directly above, or even upwind of the kite flier. You may even find a number of your students don't think that a kite needs a line attached to it.
It may be that all students in your group say that kites have tails, or that kites are a particular shape. Students could be introduced to a variety of kites that are of different shapes, and which do not need tails in order to be stable. Students could investigate exactly how much tail is necessary for a kite such as a diamond. The traditional rule of thumb is that a single strand tail needs to be 7 times the length of the spine of a diamond kite, yet there are diamond shaped kites that need no tail at all, because they are not flat kites, rather they are bowed to make them stable. Use a "predict, observe, explain" strategy with your students. Ask questions that require them to give an opinion rather than questions that look for a yes/no response. Get them to give reasons for their answers. The following scenario more fully explains the "predict, observe, explain" technique. Ask your students to predict what would happen if the tail of a particular kite were taken off. Some students may say that it won't fly, while others might say that the kite will fly better because it will be lighter. Once they have made clear their views, get them to try flying the kite without a tail. If the kite they are using is a flat, diamond shaped kite it will probably not fly without a tail. Get your students to explain to you what happened when they tried to fly the kite, and to explain why it happened. You might like to try the same experiment with a bowed diamond kite, which will fly without the need for a tail. See if your students can explain why a bowed kite will fly without a tail, while a flat kite won't. Having done this, you could present the students with a number of different styles of kites, and ask them to predict which of them would fly without a tail. After they have tried flying them, ask your students to explain which flew without a tail, and why. It is likely that the students will build a rule to explain which sorts of kite need tails and which don't. Tails are generally needed on flat kites. Kites that allow the wind to make the sail billow, or form a pronounced upwards curve from the spine out to the wingtips will usually not need tails. A tail produces large amounts of wind resistance, or drag, and this drag holds a flat kite facing into the wind at the correct angle. A kite with a sail which bows in the wind normally doesn't need any extra drag in order to face into the wind
By comparing these two styles of kites students normally make the discovery that it is only flat, or planar, kites that need tails in order to fly well. If the kite is bowed in some way it is possible for the kite to fly without a tail.
At this point the challenge could be made to design a kite to lift a given weight. The teacher could impose certain design criteria such as a maximum size, or that the kite must not use a tail, the maximum or minimum wind the kite is to be used in, and the materials that could be used, etc. Once the students had shown that their design could lift the required weight, the students could be given the task of using their kite design in a project to take an aerial photograph of their school. This project would require them to develop a safe method of lifting a camera with their kite, as well as finding ways of aiming the camera and taking the photograph. This idea is developed further in the next few pages.
Identifying ideas that links are being made to.
You should be aware of what information students are using in designing their kites. Students may consider ideas about bird wings, sails, aeroplane wings, and how they could be applied to their task. Ask students to explain to you what they are doing, and why. Careful questioning will help you discover more about how students think kites fly. It is important that you ask for the students to explain their reasoning to you, rather than for you to simply show them "the right way" to perform the task. Some students may well make a kite according to a design taught to them by a parent or other relative, Ask them about the design, and why they think it works. Try to get them to look at the design critically, and to see if there are ways of making the design better.
Challenging incorrect ideas.
Some students may be focusing purely on increasing surface area, or on reducing the weight of the kite. Others may concentrate only on the materials the kite is made of, or on making the frame as rigid as possible. Examples could be given in which simply increasing the surface area would not help, e.g. by doubling the surface area of a kite, much more stress is placed on the spars and fabric used. Therefore larger, and heavier, spars and stronger material would have to be used, reducing the supposed gain in efficiency. This would be a good place to explore the concept of scaling. Doubling the dimensions of the kite will increase the surface area fourfold, requiring much stronger spars. A similar situation occurs with the spars, except that the increase in weight is proportional to the cube of the diameter of the spar, rather than squared, as is the case with surface area. Because of this, a point can be reached where the benefits of an increase in surface area will be offset by the increase in weight. Many students will need to think carefully about how and why a kite flies, and you may need to present more information or additional resources for this purpose. Going back to the "predict, observe, explain" technique could be useful at this point.
Avoiding false accommodation.
It will be important to remember that there will be more than just one solution to the task. In a situation like this there could be several designs that could achieve the results required. It is most important that students are not given the chance to sit back and wait for the "right" answer to be given to them. Every student should make a contribution and form their own views on which design would be best. It is then up to them to prove it.
Preventing opting out, and helping towards accommodation.
Kites are difficult to design and build if one has little or no experience. It may be that you will need to provide additional information about kite designs, and possibly plans, for the students to consider. This would allow the students to examine a number of options without having to proceed on a hit and miss basis. The kite plans and the instructional video included with this kit would help considerably in this regard, but beware of "giving" the student all the answers. The video footage could be used as a way of finding out about construction techniques and design tips rather than just as a way of making the kite shown in the video. Also included on the video is a segment about how to fly a kite, which might be worthwhile watching before you venture outside to fly your kite.
Applying new ideas.
As suggested above, once the students had developed their prototype, and proven that it could lift the required weight, work could commence on building a bigger kite of the same design, suitable for lifting a camera. This project would entail solving the construction problems inherent in enlarging the existing design. Students would need to look at whether the materials that they used in the prototype would be strong enough to be used in the final kite. Once the kite had been constructed it would need to be tested to ascertain that it would lift the required weight. Students would also need to develop ways of aiming the camera and exposing the film whilst the camera was in the air. The solution to this may be as simple as a bracket on which the camera could be swiveled and using the automatic timer function on the camera. Other possibilities could include a spring loaded release mechanism, clockwork devices, fuses, or a string from the ground. It could also be more complicated, involving the construction of radio controlled or infrared equipment. The solution to the problem would depend on the "mission" the students had been given; whether the aim was to simply take one photo with the camera aimed straight down at the school or to take several photos, to get a panoramic view. Other tasks could also be suggested, such as raising banners, towing vehicles across an oval, and so on.
Diagnosis and remediation.
It may be that some students are unable to complete the task. This could be for a number of reasons, including poor understanding of how kites work, or difficulty with construction techniques. Throughout the task it would be important to watch for students who were experiencing difficulties. The sooner these difficulties were resolved for or by the student the less likely are they to opt out. A poor understanding of why a kite flies, or why one flies better than another could be dealt with by giving examples about lift; the simplest being to blow over the top of a sheet of paper with two adjacent corners held between your hands with the edge of the paper between those two corners placed directly underneath your lower lip. Students normally expect the paper to be pushed down when they blow over and towards the top of the sheet, yet the reverse happens because of the lift generated by air flowing over the upper surface of the paper.
This practical example of Bernoulli's law can be used to help explain what causes the lift generated by a kite. Bernoulli's law states that the air pressure in a stream of moving air is lower than the same air when it is either not moving, or moving more slowly than the faster stream of air, and that the faster the flow of air, the lower the air pressure. The flow of air over the top of the paper is moving quite quickly, while there is very little movement in the air below the paper, and so the air pressure above the paper is lower than the air pressure below the sheet of paper. Lift is generated because of the difference in the air pressure above and below the paper, and this amount of lift will continue while the same amount of air flows over the top of the sheet. The faster the flow of air over the upper surface the greater the amount of lift that is generated.
In the case of the sheet of paper the lift is developed only because there is a stream of air moving over the upper surface while there is little movement of air underneath the paper. However, air flows around both sides of a proper aerofoil, and it is worthwhile taking a close look at exactly how the air above an aerofoil finishes up with a lower pressure than the air below the aerofoil.
If an aerofoil is looked at in cross section, it is obvious that the upper surface is curved and the lower surface is more or less flat. The aerofoil acts as a wedge, cutting the airflow into two streams, one passing over the aerofoil, and one passing under it. The streams of air intermingle again after they have passed the aerofoil and reach the back, or trailing edge, of the aerofoil. The curved, upper surface is longer from front to back than the flat, lower surface, so air must move faster over the aerofoil in order to reach the trailing edge of the aerofoil at the same time as the air that has traveled along the lower surface. Tilting an aerofoil so that its leading edge is higher than its trailing edge increases the distance that the upper stream of air has to travel, and as the time taken by the stream of air to travel from leading to trailing edge is not increased, the air pressure is further reduced. This means that more lift is produced when an aerofoil is tilted so that its leading edge is higher than its trailing edge. The angle of this tilt is called the angle of attack. As the angle of attack increases, the air above the upper surface starts to become turbulent, and slows down, which reduces the amount of lift. If the angle of attack becomes excessive, the turbulence becomes severe enough to slow the airflow over the wing to the point where no lift is produced.
An aerofoil has four forces acting on it. They are gravity, lift, thrust and drag. The way these forces interact determines whether a kite, or an aeroplane, flies.
The force of gravity is the force that determines the weight of an object. Weight is not caused by the size of an object, rather the weight of an object is determined by how much mass, or matter, an object has, and the strength of the gravitational field that object is in.
Lift is the upwards force generated when air moves over the upper surface of a wing faster than the air is flowing over the lower surface of the wing. If the amount of lift developed is greater than the weight of the aeroplane, that is, it exceeds the force of gravity, the aeroplane will accelerate upwards.
Thrust is best described as the force that drives the forward motion of the wing through the air. In an aeroplane this force is provided by an engine pushing air backward fast enough to move the whole aeroplane forward through the air. On a kite the thrust is provided by the string holding the kite steady in the wind.
Drag is the wind resistance, or turbulence caused by an object moving through the air. As drag on an aeroplane increases, more thrust is required to maintain a constant speed. Consequently, much research has been undertaken to determine how drag can be minimized, and on developing shapes that allow the air to flow smoothly around an object. This minimization of drag is called streamlining. The results of this research has been applied to cars, and most modern vehicles are heavily streamlined to reduce wind resistance. Spoilers on the back of cars are designed to reduce the amount of turbulence in the wake of a car. The less turbulence there is, the less drag, and so the car becomes that much more efficient. Early aircraft were quite inefficient, and their surfaces produced great amounts of drag. As the shape of aircraft became more streamlined they became more efficient and produced much less drag. Devices called wind tunnels were used to test for optimum shapes. Streams of smoke or steam were played over the surface of an object while the air was being forced over it at great speed. By using smoke or steam the flow of air became visible, and any areas of turbulence would show up.
If an aeroplane wing can move through the air fast enough to develop sufficient lift to counteract both the weight of the aeroplane and the drag, or wind resistance, caused by the aeroplane moving through the air, then the plane will fly. It was discovered that the less the airflow was disturbed by the body it was passing over, the smaller the amount of resultant drag. The research that has been carried out into drag has resulted in greatly increased efficiency in aircraft, with larger payloads being able to be carried by newer aircraft, often using smaller engines.
A body will begin to accelerate in a direction only when there is a net force applied to the object, and that once that net force has been applied the object will continue in that direction with a constant speed until its direction or speed is altered by the application of another net force. In order to make the aeroplane move, a net force has to be applied to it. Initially this net force will be thrust, and it will have to be greater than the friction caused by the wheels on the tarmac if the aeroplane is to move. Once it is moving, it will continue moving as long as the amount of thrust is equal to the amount of friction, or drag being exerted on the aeroplane. If the amount of thrust is greater than the friction the aeroplane will accelerate. When it is moving, and air starts flowing over the wing surfaces, lift is being generated. Once the amount of lift is greater than the weight of aeroplane it will start to accelerate up away from the tarmac. In other words, the aeroplane will start to fly. Once the aeroplane is moving in this direction it will continue to do so as long as the four forces are in equilibrium, or in balance. If the amount of lift is greater than the weight of the aeroplane it will continue to climb at an increasing rate. If the amount of lift equals the weight of the aeroplane it will continue to climb at a constant rate. This will continue until another net force is applied to the aeroplane which will make it alter the speed or direction in which it is travelling
Kites fly according to the same aerodynamic principles. Instead of a motor the kite uses a line to the ground to prevent the kite being blown backwards as the wind flows over the surface of the kite. An aeroplane uses an engine to create its own thrust and to move through the air, while a kite uses the existing wind, and the flying line to hold it into that wind, to generate thrust. Consequently, if there is no wind there is no thrust, and the kite will not fly. If there isn't any wind, you can create some for your kite by running with the kite. Running at five kilometers per hour with a kite in still air is the same as standing still with a kite in a five kilometer per hour breeze. In both cases there is a five kilometer per hour movement of air over the surface of the kite. If the wind is strong enough for the kite to generate sufficient lift to overcome the weight of the kite, and the kite is not producing too much drag, then the kite will fly.
A certain amount of drag is necessary in kites in order to hold the kite at the correct angle to catch the wind. This drag is partly provided by a tail, but it is also determined by the angle at which the bridle of the kite is set. Too much drag will make the kite difficult to fly, but too little could result in the kite being impossible to fly. Don't immediately explain all this to your students. Rather, ask them to explain their theories to you, as this will give you further insight into how they see what is happening. Basically, a bridle is used to adjust the angle at which a kite is presented to the wind, in an attempt to make the kite more efficient. A kite that is developing lots of lift and has little drag is said to be operating efficiently, while a kite that is developing only a small amount of lift and has lots of drag is said to be inefficient. By adjusting the point at which the flying line is attached to a kite it is possible to make a kite fly with greater efficiency, or reduced efficiency. Altering the angle at which a kite is presented to the wind is called altering its "angle of attack" and will increase or reduce the amount of drag produced by the surfaces of the kite. The angle of attack is simply the angle at which a kite, or aeroplane wing, is presented to the flow of air through which it is moving. By adjusting this angle, the kite may be made to fly at a higher or lower angle, with more, or less tension on the flying line.
A parallel may be drawn between the bridle on a kite and the elevator on the tail of an aeroplane. An aeroplane has three sets of control surfaces to control its movement in the air. They are the ailerons, the rudder, and the elevator. The ailerons are flaps set into the main wing, and control how much the aeroplane rolls from side to side. The rudder is mounted on the tail of the aeroplane, and is used to turn the aeroplane left and right. The elevator is mounted in the small wing at the tail of the aeroplane, and is used to control attitude, or up how much the aeroplane pitches up or down.
By deflecting the trailing edge of the elevator downwards, the air pressure above the elevator becomes lower. As this happens, lift increases and moves the back of the aeroplane upwards. This pitches the nose of the aeroplane down, reducing the angle of attack of the main wings. This reduces the amount of lift generated above the main wings, so the aeroplane descends.
Deflecting the trailing edge of the elevator up will increase the air pressure above the elevator, reducing lift, and allowing the back of the aeroplane to move down. This pitches the nose of the aeroplane up and increases the angle of attack of the main wings. This increases the amount of lift generated above the main wings and the aeroplane will climb.
A similar set of illustrations may be used to explain what happens when the bridle is adjusted, altering the angle of attack of the kite. If the kite is lying parallel to the flow of the wind, then little lift is generated, but if the kite is held across the flow of the wind at too great an angle, the airflow around the kite becomes turbulent and more drag occurs than lift, preventing the kite from flying. Moving the bridling point of a kite towards the nose of the kite reduces the amount of drag, but also reduces the amount of lift generated by the kite. Moving the bridle towards the base of the kite can produce too much drag. The optimum location for the bridling point is where the maximum amount of lift is produced for the minimum amount of drag.
This can be used to explain why some kites are more efficient than others and generate more lift or fly in lighter winds. Kites with a greater airflow over their uppermost surfaces tend to be more efficient, and therefore generate more lift for a given surface area. Students may need to be directed to references, or to conduct a series of experiments with a particular kite by changing its angle of attack and observing how this changes the flying characteristics of the kite. The most important aspect of the assessment of the unit would be the documentation provided by each student. Teachers could use this to determine what changes have been made to the student's understanding of why kites fly, and could also use it to identify misconceptions that need to be resolved. Whilst evaluating the work, teachers could also identify ways in which concepts could be better covered or explained.
Other tasks could be set which were more specific, such as an investigation on the effect of varying the nose angle on a delta kite, or on what happens when the ratio between the width and height of a diamond kite is altered. Another area which could be studied would be about the technology involved in kite lines. For small, simple kites, lines such as button thread is more than adequate. High performance, dual control kites require much stronger lines, with a minimum of stretch and as thin as possible in order to reduce drag. A new technology develops not only when there is a need, but also only when the necessary materials for that technology exist. The high performance kites flown today could not have been built thirty years ago, because the materials used have been developed as a direct result of the American space programme. Students could be asked to determine what is the best sort of line. "Best" is a subjective term, and the students would need to develop their own criteria as to what are the most important attributes for a flying line.