Flying Contraptions

Mathematically speaking, this particular flying object shouldn’t be able to fly.  What do you think about that?


Why can this thing fly? It doesn’t even LOOK like a plane! When I teach at the university, this is the plane that mathematically isn’t supposed to be able to fly! There are endless variations to this project—you can change the number of loops and the size of loops, you can tape two of these together, or you can make a whole pyramid of them. Just be sure to have fun!



It’s actually a bit complicated to explain how this thing flies when “mathematically” it isn’t supposed to, but here goes: there are FOUR forces at work with your flying machine. Gravity is always pulling it down, but air pressure keeps it up (called lift). The way real airplane wings generate lift is by having a curved surface on the top which decreases the air pressure, and since higher pressure pushes, the wing generates lift by moving through the air. (If this idea doesn’t make sense, be sure to watch this video first!)


Ok, but what about a flat wing?


If you drop a regular sheet of paper, it flutters to the ground. If you wad it up first, you’ll find it falls much faster. The air under the falling paper needs to get out of the way as gravity pulls the paper, which is a lot easier when the paper is wadded into a ball.


For a flat wing (like on a paper airplane) to glide through the air, it needs to be balanced between gravity and the air resistance holding it up. In order for a glider to fly, the center of pressure needs to be behind the center of gravity (learn more about center of pressure and center of gravity in the third video below). By adding paper clips to your paper airplane, you move the center of gravity and center of pressure around to find the perfect balance.


When designing airplanes, engineers pay attention to details, such as the position of two important points: the center of gravity and the center of pressure (also called the center of lift). On an airplane, if the center of gravity and center of pressure points are reversed, the aircraft’s flight is unstable and it will somersault into chaos. The same is true for rockets and missiles!


Let’s find the center of gravity on your airplane. Grab your flying machine and sharpened pencil. You can find the ‘center of gravity’ by balancing your airplane on the tip of a pencil. Label this point “CG” for Center of Gravity.


Materials:


  • sheet of paper
  • hair dryer
  • pencil with a sharp tip

We’re going to make a paper airplane first, and then do a couple of wind tunnel tests on it.


For the project, all you need is a sheet of paper and five minutes… this is one my favorite fliers that we make with our students!



Find the Center of Pressure (CP) by doing the opposite: Using a blow-dryer set to low-heat so you don’t scorch your airplane, blast a jet of air up toward the ceiling. Put your airplane in the air jet and, using a pencil tip on the top side of your plane, find the point at which the airplane balances while in the airstream. Label this point “CP” for Center of Pressure. (Which one is closest to the nose?)



Besides paying attention to the CG and CP points, aeronautical engineers need to figure out the static and dynamic stability of an airplane, which is a complicated way of determining whether it will fly straight or oscillate out of control during flight. Think of a real airplane and pretend you’ve got one balanced on your finger. Where does it balance? Airplanes typically balance around the wings (the CG point). Ever wonder why the engines are at the front of small airplanes? The engine is the heaviest part of the plane, and engineers use this weight for balance, because the tail (elevator) is actually an upside-down wing that pushes the tail section down during flight.


When we use math to add up the forces (the pull of gravity would be the weight, for example), it works out that there isn’t enough lift generated by thrust to overcome the weight and drag. When I say, “mathematically speaking…” I mean that the numbers don’t work out quite right. When this happens in science for real scientists, it usually means that they don’t fully understand something yet. There are a number of ‘unsolved’ mysteries still in science.. maybe you’ll be able to help us figure them out?


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Comments

127 Responses to “Flying Contraptions”
  1. Aurora says:

    Most folks can start with the appropriate grade level for their students, and after you’ve completed those, you can dig it more by subject (that way you won’t miss anything!). And remember, you don’t need to do all the experiments to get a great science education – there’s a lot of overlap so you don’t have to commit to each one. Just pick and choose the experiment lessons you’d like to do and progress from there. You’ll find assessments you can use at the end of each section within each grade level.

    Personally, before I get started on a big endeavor like planning what to learn or teach for the year, I first write out what my educational goals are for the year. What do I want them to know, understand, and be able to do by the end of the year? (it’s kind of like planning out your weekly meals before you start shopping, so I can feel great walking out of that store with things I really need, instead of what’s most enticing when I walk by).

    That said, with the program, if your goal is to interest and excite your kids about science, then it’s ok to hop around to the things that interest them most and you don’t really need as rigorous of a scientific notebook/journal as much as a science scrapbook photo album of their progress (if that suits you). If you’re preparing them to really think like a scientist and learn the process of how to do science itself, that’s going to have a different approach, as will preparing them for high school. What you do with the program is also going to depend on what kind of documentation your local state requires at the end of the year.

    If you need to keep a science journal, you’ll find how to do that here: https://www.sciencelearningspace.com/category/resources/keeping-a-scientific-journal/

    I would first figure out your educational goals and then it will be easier to figure out how to meet that goal – use this approach for any curriculum, not just ours. Hope this helps!

  2. TW says:

    I was inquiring about how to go about using the science with a 5th grader and an 8th grader? Do I start a notebook for them? Will there be worksheets for comprehension? Are there tests or quizzes?

  3. Aurora says:

    That’s an interesting idea… you can try, and then let me know what happens!

  4. Tamara Howard says:

    Are you supposed to put a 3rd circle in the middle?

  5. Lisa Pearson says:

    cool! we built this and it was great.

  6. Wanda Ross says:

    wow its amazing

  7. Aurora says:

    Yes! Take a look at the responses/comments! 🙂

  8. Effath Choudhury says:

    Hi. Can you explain how they are able to fly?

  9. Aurora says:

    Try it! 🙂

  10. Melanie Church says:

    Thanks for teaching me.

  11. Melanie Church says:

    What if you place a third ring in the middle of the stick?

  12. Student Science says:

    Really liked the video! 🙂

  13. Student Science says:

    Really cool! 🙂

  14. Carrie Savino says:

    fun experiment for our 12 & 13 year old girls. though we are not able to explain why they fly. maybe has something to do with the airflow through the circles creating the appropriate draft needed? we did discover that attempting to fly it with the larger circle in the front is unsuccessful.

  15. Lissa Caswell says:

    I think it flies because the bottom half of the circle wing is creating a dihedral shape and dihedral creates lift. Is that right?

  16. Adriana Hall says:

    So simple and fun! We did not have straws lying around, so we used a paper towel roll and cut it and rolled it to make it smaller. We doubled up on the weight of the index cards. It flew so far and my son was thrilled! Cannot wait to get to the store and try it with the straw!

  17. Aurora says:

    That depends on what you want them to get out of the experiment. If it were me, I would point out the 4 forces (lift, weight, thrust and drag), and then show that the lift is coming from the ring surfaces. You can blow over a single sheet of paper and show how the sheet rises up when air goes over it quickly, just like the Ring Thing glides through the air. That might be enough for now. 🙂

  18. Tomczyk Clan says:

    Hi Aurora. How do I explain how this works to my 5 year old?

  19. Shawna Johnson says:

    Who knew a straw and two strips of construction paper could be so fun?! 8 thumbs up! 🙂

  20. Aurora says:

    Here’s a hint: there are four aerodynamic forces: lift, weight, thrust and drag. Can you identify these in your flying machine?

  21. Lee Wells says:

    Well, I was talking with my dad about it, and every time, I developed a theory, he showed me why it was wrong. He says he doesn’t understand, either, but he thinks it has something to do with Bernoulli’s Principle. But I think if it were Bernoulli’s Principle, it would be mathematically able to fly!

  22. Aurora says:

    Great questions! What do YOU think?

  23. Lee Wells says:

    How does this work? How does it glide? Why is it mathematically not supposed to be able to? Why doesn’t it work when you throw the big circle first?

  24. Aurora says:

    Yes they are supposed to. Let me check with my tech team and get right back to you. You’re sure you’re logged in?

  25. Tina Hedberg says:

    The video won’t play on my Samsung tablet. Using Chrome. I thought the videos would play on all devices?

  26. Aurora says:

    What device are you viewing this on, and what type of web browser?

  27. Nosheen Ayyub says:

    This video doesn’t play for me!
    What can i do to fix the problem?

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