Friday, October 19, 2012

The Perfect Arch; Or Grubbing Around for a Cup of Sand

So, concrete making happened today...hence the grubbing about at the oval behind us, scooping up sand with an empty yoghurt cup and sneaking it home. I probably should have bought sand but hey, it was right there, doing nothing except sitting in a corner by a wall.

We were taking a closer look at arches.

How's this for a Mama Nature made beauty ?

After checking out this most awesome bridge, we got out the clay and made out own, making sure that the ends were thicker than the curve of the arch at the top.

Then we got out a knife and chopped it up into wedges. The challenge was to see if the arch bridge could be rebuilt with the wedges. Yoshi was dubious, but - tah dah! It worked!

Can I digress for a minute to say that I'm relieved that so far, unlike our science experiments, our engineering experiments have actually worked. I know that's because of the laws of physics and stuff, but trust me, we manage to violate many natural laws whilst doing science.

So here's the proof  that arches rock.

Yoshi was kind of impatient at this point to get on with the concrete.

We mixed a cup of sand, 1/2 a cup of cornstarch and 125mL of boiling water in an OLD saucepan I bought yesterday at the op-shop. Then we stirred it over another pan of boiling water until it thickened.

It came out a hot blob like this.

As soon as it was cool enough to handle, we shaped it into two piers, a beam and an arch and popped them into the oven on 130 degrees C to dry.


Whipped them out - a little too soon probably, but we were both losing focus - and tried them out for strength. I was seriously concerned the beam would end up being stronger.

A gentle to medium push with both thumbs and the beam cracked. Yes!

The arch, however, under as much pressure as my two thumbs can muster, was triumphant!

As so ended another Engineering Friday.

Well, almost. We had to put the pier in water and see if it was waterproof. It wasn't. I think it was supposed to be. I think it needed to be baked for longer. I had a lot of sand in the kitchen to clean up at this point, so I decided we were good with just calling it non-waterproof :)


1 comment:

  1. Great job! I love the sand arch especially.

    (and ditto on science experiments)