Ice Arch - 6' Freestanding




Introduction: Ice Arch - 6' Freestanding

If life makes you freezing cold, make something beautiful.

My goal here is to show you how to make your own 6' ice arch, by showing you what I did.

In a nutshell the process is:

1. Build the wooden arch frame that will support the water while it freezes.

2. Create a plastic sleeve or tube to hold the water on the wooden arch frame.

3. Fill the sleeve/tube with water while it's outside on top of the wooden arch frame.

4. Let the water freeze.

5. Remove the arch frame and cut away the plastic sleeve/tube.

Cool Story Bro: I became interested in ice as building material after reading the Wikipedia entry on Pykrete. Back in World War II, British inventor Geoffrey Pyke proposed creating aircraft carriers out of floating ice bergs. He even came up with a way of strengthening ice using wood shavings. He found the optimal ratio to be 14% sawdust to 86% water by weight. I was tempted to laugh at this idea until I read about a demonstration of Pykrete's strength shown at the First Quebec Conference, a top secret between the UK, Canada, and the United States during WWII. Lord Mountbatten placed a block of ice and a block of Pykrete side by side on the ground. He then fired his pistol at each block. While the block of ice shattered, the Pykrete ricocheted the bullet, making it graze Admiral Ernest King's pants leg before lodging in a wall. (The Wikipedia articles on this are great!)

This arch is designed as a catenary for maximum strength. A catenary is very similar in shape to a parabola, but is slightly stronger. A catenary is the shape rope makes when it hangs between any 2 points. I highly recommend starting down the Wikipedia rabbit hole on this too if you want to know more!


For wooden arch frame:

  • plywood (for laser cutter, and to make 18 gusset plates (aka. rectangles) very roughly 4" x 1.5")
  • 2x4 wood (You'll need 10 pieces, each 20" long)
  • enough wood to make four 3 foot strips (for supports)
  • 4 short pieces of fabric, preferably something thick and tough. I used bits of seat belt.
  • wood screws
  • wood glue
  • filament for printer (I used PETG. PLA or ABS should be fine.)
  • 8 bolts
  • drill bit only SLIGHTLY larger than your bolts

For creating sleeve/tube for the ice:

For filling the sleeve/tube:

  • Don't use water from an outdoor spout. You don't want to risk water freezing in it.
  • portable water pump of some kind - see photo - (enough to easily pump several gallons of water 6 feet in the air)
  • 5 gallon bucket of hot water (may need access to refill)
  • length of hose
  • list of handy swear words

Big Tools Needed

  • laser cutter with at least 20" deck -OR- printer + tape & scissors
  • bandsaw
  • tablesaw
  • 3D Printer
  • drill press
  • drill (hand held)
  • ladder tall enough that you can comfortably reach 6' in the air

Step 1: Create Arch Templates

  • Make physical copies of these SVG files. Each piece should be just a bit less than 20 inches long.
  • If you have access to a laser cutter with at least 20" deck:
    • Make your physical copies out of plywood or cardboard. Use the laser cutter to cut
      out the blue lines, and raster the green lines. (It doesn't matter exactly what material you use, physical copies are just for tracing.)
  • If you DON'T have access to a laser cutter:
    • Make your physical copies out of paper. Have a local printer print out the files on large format paper.
    • OR: I think Adobe Acrobat Reader lets you print out images across
      several pages. Then tape the pages together, the hard part will be taping them together correctly. You may have to fiddle around to make it work.

Step 2: Trace Templates on 2x4 Pieces, Then Cut Out

  • Place each template on the broad side of your 2x4 and trace around it with a pencil. Not every template will completely fit and that's fine, just make sure you trace the outside edge and the dovetail joints. Label each piece with it's template name too. (For example, R1, R2, R3...) This will be surprisingly handy later.
  • Use the bandsaw to carefully cut out each template.
    • Check the dovetail joints after you cut out each new piece. If it doesn't fit with the previous section, use the bandsaw until it does.

Step 3: Attach Arch Pieces L1-L4 and R1-R4 Together

  • Please note that I left out pieces L5 and R5. They form the top of the arch and you'll be gluing those pieces together in the next step. For this step, you're gluing all the rest of the pieces into two arch "legs".
  • Glue them together on a flat table to make sure your arch won't be warped when it stands up.
  • For additional strength, I cut 18 gusset plates, roughly 2" x 4" pieces of plywood, and placed them over the joints, glued them, and finally screwed them in.

Step 4: Create Your Removeable Keystone

  • Attach pieces L5 and R5 together with glue. (I got lucky because the pieces fit just right after I cut them, so I didn't need gusset plates for mine).
  • Measure about 6" out from either side of the center line between the two pieces, and cut parallel to that line (Please see first picture). Cut all the way through on both sides. You're making a keystone that can be removed by pulling it down.
  • I found it helpful to label the ends of the keystone and their matching sides with A, B, C, & D.
  • Take the two end pieces of L5 and R5, and attach them to L4 and R4 (respectively) like in the previous step, but cut a little triangle out the corner to make room for other stuff. (See the pic with L5 and L4 labeled.)
  • Figure out a way to re-attach that center portion such that you can still remove it. Here's how I did it after much experimentation:
    • I cut 4 thick wood pieces about 1" x 6" and screwed them to the keystone.
    • I then clamped the keystone to the arch leg, and used a drill press to drill a hole through the 1"x 6" wood piece such that I can slide in a bolt to hold it. Do this step to the other side too. (Even with that bolt, there will still be a lot of wiggle between the keystone and leg, to prevent the wiggle do this...)
    • Next I cut two, 2" x 4" rectangles of plywood.
    • With the keystone still clamped to the arch leg, I placed the plywood over the joint, above the 1" x 6" piece.
    • With the drill press, I drilled a hole through the plywood on each side of the joint. Again, make the hole just big enough to slide bolts in and out of it. Do this for the other side as well. (Note: I drilled 3 holes in mine, I think it was overkill. 2 holes should be fine.)

Step 5: Add the Guard Rails

  • With your 3D printer, print off 14 copies of the attached file. (I only printed 10, then wished I put in a few more.) I used PETG filament, but any filament type should work.
  • Position the guard rails as shown in the photos, with...
    • the angled portion extending out from the outside edge of the arch, angling out as well.
    • Guards should come in pairs directly across from each other. (Screw holes are positioned to screws won't hit each other.)
    • Make sure there is a pair of guard rails at the very top. The exact position isn't that important for the rest of them.
  • Screw in the guard rails.

Step 6: Add Support Legs So Your Arch Can Stand Upright

  • Cut four 3' sections of wood board.
  • For each of your 3' boards: take one of your fabric pieces and screw it into the end.
  • Measure a spot about 2' from the bottom of each leg, and screw the other part of the fabric into the leg. Do this for both sides of both legs.

Connecting the support legs with fabric gives them a wide range of motion, which is useful when outside on uneven ground. There are probably more elegant or secure ways of doing this, but this had the added benefit of being cheap.

Step 7: Create the Sleeve/Tube to Hold the Water

  • Cut a piece of your tubing about 15' 6" long.
  • Seal off both ends of the tube. I did this by:
    • Cutting 2 small pieces of parchment paper, and sandwiching one end of the tube between them. Then I quickly went over the end with a hot iron. The plastic melted together to form a seal.
  • Put the 2 sealed ends together, and find the middle of the tube.
  • Mark it with a permanent marker.
  • Use your sharp cutting tool (exacto knife) to make an incision length-wise so that it's just big enough to fit one end of your hose. When you're cutting be careful to only cut 1 side of the plastic. (In other words, make one hole to put water in, don't accidentally make a second hole for it to pour out.)

Step 8: Wait for Temp to Go Below Freezing

  • It's best if there's snow on the ground as well.

Step 9: Put Up Your Wooden Arch Outside

  • Stand the arch up somewhere that both feet are at about the same elevation
  • Put tent stakes around the feet of each arch leg to secure it in place.
  • Make sure the arch is as vertical as possible. Secure the support legs with more tent stakes.

The arch needs to stand perfectly upright on its own. Remember you'll be putting an additional 10 pounds of water on there.

Step 10: Start Filling Your Water Sleeve/Tube

  • Fill your 5 gallon bucket with water. If it's already below freezing outside: fill it with hot water.
  • Set up your ladder under the wooden arch frame. Don't put anything on the arch yet.
  • Set up your pump close to your arch. Connect hoses to the pump and make it draw water from your bucket.
  • With the long plastic tube in your hands, put the end of your hose into the small slit you made in the center.
  • Start pumping water down one leg of the tube. Once that leg is maybe half full, start pumping the water down the other leg of the tube until it is half full as well.
  • Take out the hose. If it's already below freezing outside let the pump keep running so your hose doesn't freeze.
  • With the half full plastic tubing in your hands, climb up the ladder and drape the tubing over the top of your wooden arch. The guide rails should help keep the tubing from slipping off, and the half full legs of the tube should keep it weighted down enough to stay in place. If the tube keeps slipping off, check that your arch is completely vertical.
  • Your tube should be a little longer than your arch. Inspect the foot of each leg. Take the bottoms of the tube and tilt them off to the side a bit. It will create a pinch in the tube. Move it such that the pinch is right at the base of the wooden arch.
  • Climb back on the ladder and keep filling the rest of your tube until no more water can go in. You may have to refill your bucket at some point. Note: I had trouble filling water at the top because my tube wouldn't hold its shape towards the top. You can see in the pictures how it flattens out as it goes up. Eventually I hope to have a fix for this. See photos in next step.

Step 11: Make a Slushy Base for the Arch

  • Pile up snow around each foot of the arch, and then gently splash water from your bucket on it to make slush.
  • Sculpt the slush into a base around each leg. Pile it up against the plastic tubing, don't pile it up between the wooden legs. You'll be removing the legs once everything freezes.

Step 12: Wait Until All the Water Freezes.

  • You can check if it's frozen by squeezing the plastic tubing.

Step 13: Take Down the Framework and Cut Away Tube

  • Cut open the portion of plastic tubing that's over your keystone.
  • Take out your keystone, cut away the rest of the plastic tubing, and inspect how much ice is there.
  • If there isn't enough ice at the top to complete the arch. Get some more water, make some more slush, and use that to fill in the gap.
  • Once the slush is frozen, remove one of the legs of the wooden arch.
  • Using your sharp edge carefully cut away the plastic tubing around the free side of the ice arch. Don't bother trying to remove the plastic buried in the slush at the base. You can leave that there.
  • Remove the final leg of the wooden arch, and cut off the rest of the plastic tubing. Again, don't bother with the part of the plastic under the slush.
  • Stand back and admire your work!

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    4 days ago

    Beautiful! Unfortunately temperatures are up again here (Netherlands). I will try next year.
    As as suggestion: would it be possible to add LED lights at the bottom in the arch? Shining through the ice arch? I think an RGB lighting would give a stunning effect at evening / night :-)


    Reply 1 day ago

    LED strip can be made water proof pretty simply. Could lay strip in the full length of the arch.


    Reply 3 days ago

    That would be stunning, I completely agree!


    Reply 4 days ago

    Great thought!


    2 days ago

    That's really cool! (no pun intended) I actually like the look of the top as it came out of the mold - it almost looks like two stalagmites bending and reaching towards each other.


    Reply 3 days ago

    Those are amazing! I love how with every change the rest of the structure immediately readjusts to new optimal positions. Thank you very much for sharing that link!


    Reply 2 days ago

    One of the most fascinating parts of visiting the church (book tickets early ahead, you're also funding the next part of the building) are the fragile, slightly tilted, almost grown pillars in the nave built from different materials. Have also a look here and the virtual tour of the inside
    if you are also geocaching, you could see this nice description of the column stones and some mor info here


    3 days ago

    Great project! Perhaps you've tried other ways, but I wonder if I could make one more simply (but less elegant). (If it's been tried, failures are interesting to know about, too!) Unfortunately we will be above freezing for the next week or so but it will give me time -- I definitely want to try this! I have done something similar with long balloons before, but it's so tricky not to pop them when filling or moving.
    BTW - the link for the tubing does not currently work (404 not found). It looks like your link was truncated. This one works for me.
    It's available from the same company and others on Amazon as well.
    (Make the wooden arch with guides for the tubing, and maybe parchment paper on one side for easy separation. Lay the arch flat in place and fill tube. Allow to freeze, then stand it up and secure it, then remove the frame. The tube would probably not be perfectly cylindrical but I think it wouldn't be noticed at normal distance.)


    3 days ago

    I have thought of a simpler method:
    Take a large flat board, stand it vertical and hang a rope or chain from the top corners, trace it to make the catenary shape.
    With the board horizontal, add angled (for easy release) tube supports.
    Add the tube and fill it with water.
    When frozen, carefully tilt the board upright and support the arch.
    Tilt the board away from the arch to release it.

    Or, advancing from what others have suggested, hang and fill the tube inverted against the vertical board (with tube supports), and when frozen, rotate the board 180 degrees.
    The board could be centrally pivoted on a mobile frame to ease the process.


    Reply 3 days ago

    I think using the large flat board to stand it up once it's frozen would work great! Elsewhere here FilipW suggested something similar, and I recommended including your plywood technique. The next time it goes below freezing here I'll try it as well.


    Question 4 days ago

    I wonder.... Would it be possible to just hang the tube suspended in its ends (exploiting the very definition of the catenary) and then carefully invert it when frozen?


    Answer 3 days ago

    I'm sure it would be. Before I made the arch I used the tubing to make rods of ice. I found they would break when just a little shear force was applied. I think the most difficult part of freezing it upside down would be putting it upright without breaking it. Elsewhere here ElectroFrank suggested using a large plywood board to stand the arch up, I think using your idea with ElectroFrank's would work great!


    3 days ago

    Well done, the arch is absolutely stunning.
    I checked out pykrete on Wikpedia and loved the story of Lord Mountbatten taking a block of it into Churchills's bathtub to demonstrate its strength. Churchill was so impressed he instructed Mountbatten to take a pykrete sample to the Quebec Conference.


    4 days ago

    A possible labour-saving variant: create the catenary upside-down, hanging from its ends. You can then either leave it hanging or carefully try to turn it the other way up!

    I haven't tried this, and Oxford UK is not cold enough to do so right now, but I would think that some procedure like the following could evolve into a usable alternative technique. The transverse strut/plank would not be necessary if you plan to leave it hanging (for hanging catenary you could simply omit plank and screws from my proposed method, and thread a strong thin white string through entire tube before filling and before freezing, hanging it from each end of the string ready for post-freeze skinning ... though you might want to stretch the innertubes a bit to avoid unsightly wrinkles).

    Proposed method: hang a 2m plank horizontally in freezing location, 3m off the ground, with one very long slightly angled screw or stiff wire at each end to connect the frozen catenary to underside of the plank. Then get 2 or 3 large-wheel-diameter bicycle inner tubes and cut and join (use bicycle repair kit glue and a bit of skill - make sure the overlapped joint is waterproof) to make a long open-ended pipe. 26" innertube opens up to be circa 2.07m, so a couple of these might give you a long enough catenary. Position the tube ends so that the tube hangs from the plank, each tube end concentric with a long screw. Fill with water so the water brims up to meet the plank. This needs some care: you want a large contact surface between the water and the plank. Maybe use screws and washers to stretch the mouth of the tube into a large oval around the nail? And somehow fill with water, maybe through hole drilled in plank (you might get some bonus ice-strengthening sawdust in your tube while you are at it! Leave it to freeze, but the sagging tubular bladder might creep and need topping up, or squeezing by wrapping more bicycle innertube spitrally around it mid-span, to ensure that the water stays in contact with the plank. Possible problem: you want mid-span to be thinnest, or at least not thickest, but filling with water may cause some undesirable longitudinal stretch near ends and undesirable radial stretch near midspan. Another possible problem: the overlapped joints might stretch less, causing undesirable local constriction.

    When it is well frozen, skin the innertube off the ice by cutting longitudinbally with scalpel, and maybe have multiple people very carefully (good luck with that!) turn the entire structure over if you want an upside-down (rainbow orientation) catenary.

    If anyone has the cold weather and the will to try this please let me know, as it's just untested fantasy design! :) Dom



    4 days ago

    Very cool! Next time maybe add a strip of LED lights before filling to make a nice effect. Nice job!


    5 days ago

    Can you go into more detail about how how “cut away” at the top?

    If the tube is cut away, how can you add more water and slush to freeze? Do you put the tube back?


    Reply 5 days ago

    Sure! With the keystone out and the plastic in that area unwrapped you’ll have the bare ice exposed. Once you make the slush it will stick nicely to the ice. Then you can sculpt the slush to make it match the curve. Given more time the slush will freeze as well. It won’t be as hard as the ice, but it will be able to keep the arch up.
    I’m working to find a better solution since the slush becomes an Achilles’ heel when the temp goes back above freezing. I’ve done some experiments joining some more plastic tube to the hole in the main tube. That seems to keep the pressure up enough that the tube maintains its shape. The one in this pic developed a leak but you can see the idea.


    Reply 4 days ago

    Just thinking (you can probably hear the cogs whirring from where you are sitting) but if you started the freeze with the arch inverted and then topped up the water at the 2 ends/feet - probably far to complicated.
    Alternatively inject more water into the top of the arch when it is in situ to make sure the full bow will freeze. Big feeding syringe should do it.
    Love it!