Our amazing crew at Royal City Science has been brainstorming ideas for travelling exhibits that we can take to schools, festivals, Farmers’ Markets, etc. to share our passion for all things STEAM (science, technology, engineering, arts, and mathematics), while we fundraise to build a permanent home in Guelph. A blog post from the NFB recently caught my eye and sparked a little bit of an obsession with the idea of reproducing our own replica iglu/igloo because, as I dug into the details, I was truly blown away by the incredible brilliance of the design. As June is National Indigenous History Month, it seems timely to share what I’ve learned so far.
Can’t you just picture it? We arrive at a school gymnasium and throw 70-100 perfectly shaped pre-cut plastic blocks on the floor for the students to puzzle over and work together to assemble just so. And then they take turns to climb inside, to marvel at the stable and aesthetically beautiful structure Inuit are masters at assembling with nothing more than snow and a knife. The Arctic is an unforgiving landscape, with no trees to provide timber for the typical structures built in warmer regions. Shelter is essential for survival and Inuit succeed in this harsh landscape through their ingenuity, patience, and understanding of the natural world around them, collaborating with nature rather than trying to conquer.
If you live in a region that regularly gets snow in the winter, then you have possibly tried to assemble your own iglu at some point. Naively you cut rectangular blocks and position them in a ring, but it probably isn’t long before you realize that this simple approach isn’t going to work. First of all, you need the walls to slope inwards to form that classic dome shape, so your blocks need to be shorter on the inside edge than on the outside to a precise degree, as shown in the sketch I’ve made below from the NFB summary of their project.
The next thing to notice is that, starting at Block #1 in this sketch, the first layer of blocks is actually cut to form a ramp or slope that is maintained all the way up to the top of the structure in a continuous spiral. Picture a screw thread superimposed on the dome. Why? When you place the next block up the ramp, part of its weight is supported by the block beside it that you just positioned, giving it more stability. This is particularly important as you near the top where the blocks are angled quite significantly inwards. I mean the genius of this design is truly breathtaking.
The dome, as well as the related arch, have been used in building structures for thousands of years. A domed roof is a fantastic way to enclose a relatively big area without any internal supports – the curved shape does a great job of spreading forces applied at the top all around to the whole structure, making it incredibly stable. This is also why an egg is so strong, even when mumma hen is sitting on it!
So maybe now you can see why I want to make this happen and I reached out to some brilliant colleagues in the Department of Physics at the University of Guelph to explore the idea further. My first stop was Steve Wilson, our fabulous machine shop supervisor. He was (understandably) a little worried about the NFB blog description that “it was too complicated to pre-plan all the angles”; they measured and cut each piece by hand to fit for their exhibit. Fair enough, so my next stop was Bernie Nickel, a retired faculty member in our department who loves a puzzle, and in no time at all he came back with a mathematical model that seems to work remarkably well.
The images below compare Bernie’s models with the shape of the iglu shown in the NFB documentary, traced out on the screen and assuming that camera and screen capture distortions aren’t a big issue here. The blue symbols are the tracing marks from the film. The red curve in the first image is a catenary arch; the black is a catenoid iglu. Bernie wasn’t satisfied with either of these, so the second image shows his refined model of a catenoid iglu at the base, with a spherical cap placed on top. He is now working on a scale model with cardboard to see how it works and I am so excited to see the end product! Stay tuned!
UPDATE! (July 27, 2022)
Bernie is working away on the smaller scale prototype and I got to see it today …. IT. IS. AWESOME!!
- opening image of part of an igloo with the Northern Lights dancing overhead – by Ross Burgener, originally posted to Flickr, licensed under the Creative Commons Attribution 2.0 Generic license
- Child inside a homemade snow structure – from Shutterstock (ID #1917164666)
- Sketch of blocks used to assemble an igloo, created by the author based on the documentary footage from the NFB
- The interior of the Pantheon in Rome, Italy – from Shutterstock (ID # 190788227)
- Images provided by Bernie Nickel, personal communication, comparing his mathematical models with the shape of the igloo featured in the NFB documentary cited here
- Image taken by me in Bernie’s office – 39 of the full 80 blocks have been made by hand out of cardboard by Bernie and he is working away on completing the set. Then we talk to Steve about scaling it up! (The red string is to mark where the door is)
- How to build an igloo by Laurence Desrosiers-Guité and Dan Thornhill, NFB Education.
- How to build an igloo – Documentary film by Douglas Wilkinson, filmed in 1949 with support of the NFB. Please note this message from the NFB before viewing: this is an archival film that makes use of the word “Eskimo,” an outdated and offensive term. While the origin of the word is a matter of some contention, it is no longer used in Canada. The term was formally rejected by the Inuit Circumpolar Council in 1980 and has subsequently not been in use at the NFB for decades. This film is therefore a time-capsule of a bygone era, presented in its original version. The NFB apologizes for the offence caused.
- Mathematics of Igloo Design – by Bernie Nickel, personal communication
- The Igloo, by Charlotte and David Yue, Houghton Mifflin Company, Boston, USA, 1988