Introduction: Stellated Snowdecahedra

About: NAPA is a multi-disciplinary studio that designs, fabricates, and installs interactive projects.

Snow sculpting is an ancient and honored art, humbly beginning ~16,000 years ago outside the caves of Lascaux, France.  Inside the caves they had fine pigments, powders, brushes, extravagant meals, and fire.   But outside the caves?  Just snow.  

In this Instructable you'll learn to make a beautiful geometric form, the small stellated dodecahedron, out of snow.  Since we don't have to tell YOU that kanevvluk (Eskimo for "fine snow/rain particles") is the supreme material, grab some mittenfulls of the wet white stuff and let's get crackin.  

Well, first we need to make a hollow 5-part mold out of steel, so grab your welding mittens and let's get crackin!

Step 1: Stellated Snowdecahedra - the Pieces

There's a whole internet of geometric info on the stellated dodecahedron.  For now, you need to know that it's made of identical triangles which have a height : base ratio of 1.54 : 1.  For this particular mold, my triangles are about 3-5/16" on the base, 5-3/32" in height.  Like people, they don't have to be perfect.

Cut yourself a pattern, tessellate them out on a strip of steel, and slice them up with your method of choice.  I used the hydraulic shear at my friendly neighborhood makerspace, but jump shear and plasma cutter are fine alternatives. 

In total you'll need 50 triangles, but having extra is always nice.  For this size mold that comes to about 3 sq ft of steel, and I chose a healthy-looking crop of 16-gauge.  

Step 2: Stellated Snowdecahedra - Welding the Cones

Once you've got your triangles cut and ground to remove burrs, tape their edges together and origami that puppy up into a pentagonal cone.  Tack-weld the cone into shape, wearing proper protective gear of course.  

Lather rinse repeat until you've got 5 such cones.  Feel free to weld up the seams for strength and total enclosure, MIGging your way to glory.

Step 3: Stellated Snowdecahedra - the Face

Take your pentagonal cones and weld more triangles to the top edge and bottom two edges, so you end up with an oversized, dangerous-looking Star Trek comm badge.  Like, if it was a Klingon rather than Federation design.  

Step 4: Stellated Snowdecahedra - the Face, Cont'd

Support your new Klingeration comm badge in an upright position, and weld on two more triangles to the bottom as pictured.  Remember, tape first and get them in position before welding.  

These new triangles should be angled so that they meet in the middle, and the new bottom of your badge should now have two sections that looks like 2/5 of the original pentagonal cone.  if you've done everything right they should line up just perfectly.  If you're like everyone else, remember nothing's perfect and love your new-mangled creation.  

Make 5 of these identical pieces, and you're ready to start putting them together.

Step 5: Stellated Snowdecahedra - Putting It Together

Line up your Badges and tack-weld in between the cones just enough so that they hold together.  You'll be removing these welds eventually.

Step 6: Stellated Snowdecahedra - Putting It Together Cont'd

Continue all the way around so that all 5 pieces are tacked in place.  Add some registration marks so you know which sides match each other.  Yes, this is one of those "regular geometric polyhedra" and the faces should be identical, but remember how I've been saying nothing's perfect?

Add in some hardware to help keep it all together when you eventually remove those tack-welds.  I welded some nuts and hastily created an ill-advised "top-bracelet" to guide a fastening rope, but I'm sure you can come up with something better.  

Step 7: Stellated Snowdecahedra - Pack It Up

Untie the rope, grind away those aforementioned tiny tack welds so your 5 sides come apart, and there you have it!  Five "identical" pieces that line up to make your hollow mold.  

Here are some pictures of the mold slightly disassembled, and stacked up for transport.  For lovers and for mold pieces, nesting is always nice.  

Step 8: Stellated Snowdecahedra - UPDATED Assembly Method

After many trials, it was determined that I needed new assembly system (and fewer lawyers).  I cut off the rope guides and welded on these steel tabs, which have handy holes for short 1/4-20 bolts.  

Now the entire thing can be put together very quickly, and is much more rigid and portable when assembled.

Step 9: Stellated Snowdecahedra - Use It!

Here's a view of the hollow form from underneath the mold.  

Time to take it outside, pick a highly-trafficked area, and unleash your Platonic Public Art into the world!

Make sure to pack the snow all the way into the very corners of those cones, or else you'll end up with the "Sphinx effect" of broken noses.  Nobody likes that.

Plop it upside down, loosen the fastening devices, and carefully remove each face, one at a time.  Et voila, a beautiful spiky star for all to enjoy.

Till next time,

New American Public Art

A very special thanks to NextFab Studio and the Philly Sculpture Gym, the makerspaces that enable projects like this.