A curvy, ridged shape a bit like a potato chip

With round folds, you can make flat paper into curvy origami

Folding origami cranes and paper aeroplanes is fun, but they tend to be made of straight lines. So what happens when you fold in curves?

sharp hazard iconSafety: This activity uses a craft knife. Ask an adult to help.

You will need

  • Thin sheet of cardboard
  • Craft knife
  • Pencil
  • Ruler
  • String
  • Pin
  • Eraser
  • Cutting mat
  • Scissors

What to do

  1. someone poking a push pin into some paperCarefully stick the pin through the middle of your sheet of cardboard to make a tiny hole.
  2. someone measuring with a rulerMark points that are 2 cm, 4 cm, 6 cm, 8 cm and 10 cm from the hole.
  3. A pin goes through a piece of paper, and into an eraserPut the eraser underneath the hole in the cardboard, and stick the pin back through the hole and into the eraser.
  4. a piece of string tied around a pencilCut a 30 cm length of string and tie one end around the pencil.
  5. a piece of string is tied to a pencil. The string is attached to a sheet of paper by a push pinPin the other end of the string so the pencil lines up with the 10 cm mark. Keeping the string tight, rotate the pencil around the pin to draw a circle.
  6. several circles drawn on a piece of paper. There's a string attached to the pencil, and it's pinned to the page.Use the same process to draw circles at the other marks.
  7. several circles drawn on a piece of paper. There's a string attached to the pencil, and it's pinned to the page.Turn the cardboard over, then mark 3 cm, 5 cm, 7 cm and 9 cm from the hole. Using the method above, draw circles using each of these points.
  8. someone is running a knife along a circle drawn on paperGet your craft knife and lightly run the blade along each circle you have drawn – this is called ‘scoring’. You don’t want to cut through the cardboard, you just want to make it easier to fold along the lines.
  9. Turn the cardboard over and score the circles on this side too.
  10. someone is cutting a circle out of paper with scissorsUse scissors to cut out the 10 cm circle and discard the rest of the cardboard.
  11. Hold the cardboard circle in both hands, with the 9 cm circle on the far side. Bend the middle of the card toward you.
  12. someone is bending a circle of paper. the rim is creased upwardsAlong the 9 cm circle, fold the cardboard so the edge comes towards you.
  13. someone is bending a circle of paper. The rim is creased up and then down.Turn the circle over, and use the same technique to fold along the 8 cm circle. The fold should be in the opposite direction to the previous fold.
  14. Someone is bending a piece of paper. There are several curved ridges folded into it.Fold the remaining circles, remembering to flip the cardboard over after each fold.


What’s happening?

If you’ve ever made paper planes or folded origami, you might have noticed the creases tend to be in straight lines. When you’re making these things, the paper usually ends up flat at the end of each step, except in the final few stages when the wings fold out, or the box pops up.

A fold must be straight to lie flat. To understand why, imagine folding along a curve. To lie flat, the paper on the inside of the curve will have to match exactly to the paper on the outside of the curve. You would need to stretch the paper on the inside of the curve until it curved the other way! This is why the shape made in this activity pops up as soon as it is folded.

Real-life maths

You can make a lot of different shapes using curved folds in a flat surface. Mathematicians call these shapes ‘developable surfaces’ and they can be beautiful, and also very useful. When manufacturers want to make an object, they often start with a flat sheet of a material, such as steel. It is relatively easy to put curved folds into steel, so designers working with this material try to make as many parts as possible from developable surfaces.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

By submitting this form, you give CSIRO permission to publish your comments on our websites. Please make sure the comments are your own. For more information please see our terms and conditions.

Why choose the Double Helix magazine for your students?

Perfect for ages 8 – 14

Developed by experienced editors

Engaging and motivating

*84% of readers are more interested in science

Engaging students voice