Cardboard Cubbyhouse: 2. Design

This is just a quick overview of everything I planned to do.

sketch.jpgThe basic, “typographic arrow” shape we’ve covered. In fact I think I got that from another impromptu box cubby put together by my good lady other half. You get an entrance tunnel and windows looking out in two directions.

Drawing it

AI printout of plan viewPencil and paper handled the initial ideas, then gave way to Illustrator, which made all the angles and measuring much simpler. Turning that into 3d was not so easy, and I was doing quite a lot of pythagoras. version-in-sketchup.pngThere it would have stayed, had I not stumbled across Google Sketchup while just fooling with Google stuff as you do.

As you can see, sketchup’s little measuring doodad was invaluable. With this, I had everything.

Above

The roof obviously couldn’t be cardboard, but it pretty much cried out from my first sketch that this modernist aussie installation had to have a corrugated iron roof. I then discovered CGI mini (not to be confused with any lightweight web-scripting you might be doing). It seemed perfect, small corrugated iron for a small edifice. Ultimately, this choice caused a few problems.

drip-test.jpgI realised I’d need something to stop water running back down the inside of the roof from the front, and came up with a garden hose slit along its ‘belly’ and glued. This was unexpectedly tested ahead of schedule, and performed very well.

Below

Nor can cardboard just sit on the ground, even if I didn’t live in a termite nexus. It needed to sit up on some kind of piers, and I obviously have some sort of pathological weakness for lightweight, easily worked materials. Hebel (or AAC) is something I’d learned about on those home improving shows that were all the rage for a while there. To simplify slightly, it’s “leavened” cement, like a very solid sponge (or a very gritty Aero bar). It’s very ligh, can be worked with woodworking tools and is pretty cheap (it also has excellent acoustic and thermal properties which we make no use of here). Credit goes to Mr. Peter Collen from work for pointing out that they’d need a waterproof layer to prevent ground water seeping into the cardboard. I eventually settled on a square cut from one of the thousands of PET milk bottles we go through these days.

The floor itself is the hardest-working piece of all and I never really entertained it being cardboard. For a while I planned on masonite, but then realised that plywood would fit in much better. I also decided some of that metal kick-strip stuff they have on stairs would be good at the very entrance.

The meat in the sandwich

edges.jpgLet me try to be brief here. The plan was for 100mmx100mm members for all the formwork, using standard half-lap joints (I call them “rebated”). I decided to laminate with the flutes up/down to prevent crushing. I had a bright idea to run the occasional layer horizontally to add strength in another axis, but once built I could see the opposite would have been better: 3 vertical and 10 horizontal (see construction for more info on that)

Columns benefit from this knowledge and are mostly vertical. For the columns where the “shaft” joins the “head” I came up with a natty way of making an L-shaped piece without wasting any cardboard.

The roof frame is 50×50 – not having to carry children – and the roof ribs are 50×100, so that they line flush with the frame.

Walls I just left vague – they might be single sheets of double-wall, but probably some kind of laminate, with the flute alignment alternated for strength. Again to deal with water, the walls are meant to extend just 1m or so below the floor formwork, so any drips that form will stay on the walls.

Fixings

All laminating was done with PVA glue – this is biodegradable, though it takes a long time. Cardboard itself is held together by a starch, so if you were super keen for degradability and lived in a moisture-free place you could use flour and water.

countersunk screwThe bigger bits are joined to each other via countersunk screws. Cardboard has the nice property of being self-countersinking. I also discovered afterwards that screwing “into the grain” produces a pretty weak result.

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