Saturday, 7 July 2012

Bamboo Hyperbolic Paraboloid

On Thursday night I needed something to occupy my mind and keep myself awake while I waited for David to come home so I decided to make this…


It’s a hyperbolic paraboloid, which is a surface shaped like a saddle made from perfectly straight bamboo skewers. This is known as a doubly ruled surface since it is created from two families of rulings (straight edges).

Mathematically it is given by the Cartesian equation   z=(y^2)/(b^2)-(x^2)/(a^2)

Structurally it is created by forming a tetrahedral frame and gluing bamboo skewers from one side to another in one direction and then again in the opposite direction. Finally (and preferably once completely dry and solid) you remove the two unused skewers to leave you with the saddle or giant pringle! It looks amazing if you hang it and allow it to spin on an axis.

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Unfortunately, this story has a sad end. I took my work into school on Friday to share my creation with fellow appreciators of geometry but Yavuz dropped it. This knocked some of the skewers off and compromised the structural integrity of the surface. It is now back in the form of 24 individual sticks and is waiting to be reconstructed using a stronger glue before it can take its place in my classroom.


  1. Thank you so much for the shout out, FINALLY. I've been waiting for it :) But I thought you were going to use my Mashed Potato code name? I love the saddle thing, please do hang it up in the classroom!

  2. I just couldn't remember the code name Mashed Potato! Hope you're having a good break.


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