Burj Al Arab Richard Hammond's Engineering Connections


Burj Al Arab

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It's one of the most striking buildings in the world.

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In its short life, its distinctive shape

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has made it an icon for Dubai...

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..recognised the world over.

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It's the Burj Al Arab, or Arabian Tower.

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This is the tallest atrium in the world, 182 metres high.

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And that's just the beginning of the superlatives

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in one of THE most opulent hotels in the universe.

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There's enough gold and marble in here to make a rapper look dowdy.

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But behind the bling are some truly remarkable engineering achievements.

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They wouldn't have been possible without...

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..the children's game of jacks...

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..an engine cam...

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..the pages of a phone book...

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Ha-ha!

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..a revolution in fire hose design...

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Look at that!

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..and a camera flash.

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-I see your point. That is a potential problem.

-Yeah.

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Cor blimey!

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Obviously, you don't usually see this bit

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but this is how I start every day's work, this is how we do things.

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Arriving by helicopter is par for the course here.

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Thank you.

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'I'm only doing it to blend in as I'm about to check in...'

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Thank you.

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'..to check out one of the most distinctive architectural achievements in the world.'

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-Thank you.

-Would you like some Arabic coffee?

-I'd love some, thank you.

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Cheers!

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Inside, the suites really are luxurious cocoons,

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sheltering you from the desert outside.

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There really is no sand in here.

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Unless you really want it, I'm sure room service could oblige.

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And then, while your bags are being unpacked for you,

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somewhere in your vast suite,

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you can stride around and look out over the whole of Dubai.

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But perhaps, as importantly, the whole of Dubai

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can look back at the hotel.

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Because this place was designed right from the start to be an icon.

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In the last 20 years, Dubai has shot upwards and outwards,

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looking to find its fortune through business and tourism.

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Oil was discovered in the early '60's

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but people here know it won't last forever.

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The iconic Burj Al Arab is part of Dubai's planned future...

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after oil.

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The architects on the project, however,

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were inspired by Dubai's past.

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Once upon a time, Dubai's wealth came from the sea,

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where they harvested pearls.

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And this building's distinctive shape recalls that history.

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That curve is inspired by dhows, the traditional sailing boats

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that have plied these waters since ancient times.

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Making an iconic building look like a ship

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was only part of the challenge.

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The architects wanted something more.

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They needed a statement.

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The solution, well, put your building 300 metres out to sea

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on its own tailor-made private island.

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Of course it's not going to be cheap or easy.

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Engineers had to make an island

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big and solid enough to hold a quarter of a million-ton tower.

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Most of all, they had to protect it from the sea

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and the power of the waves.

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Even this placid-looking gulf can have a dangerous temper

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which could easily wash away a man-made island.

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Back in the UK, I'm going to attempt

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to show how even a relatively small amount of water

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can do a surprising amount of damage.

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I'm going to create an artificial wave.

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'The man in charge of sea defences at the Burj Al Arab was Mike McNichols.'

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And these things can be pretty powerful?

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In the right circumstances, at the right speed,

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they can act like a solid, smashing into whatever's there.

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This plate glass will test the destructive power of our wave.

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And don't think that this glass is a pushover.

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It's ten mil thick.

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It's the safety stuff they use in tall buildings to stop people falling out.

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It's more than twice as thick as normal window glass.

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This is going to represent our wave - it's a ton of water.

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But it needs one more thing to be like a true wave.

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You need a bit of speed to get this thing going,

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just like a wave pushing through the air.

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Our wave will be set in motion by gravity and explosives.

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You'll like this, it's very subtle.

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At the bottom of the bag is a loop of det-cord, explosive,

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which will explode immediately

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and there will be no bottom on the bag so all this water,

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the whole lot, will fall out in a big solid lump.

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-And that's more like a wave?

-Yes.

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Well, to complete this demonstration of the power of a lump of water,

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I've got this, it's a sort of industrial dining table,

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with a glass top, to give it its full title.

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We will position the bag above there on the crane, fire the explosives, bang, no bottom on the bag,

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all the water comes down in one go on to there.

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And we'll see what happens.

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Part of me thinks even in a solid lump,

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the water will pour round the sides and the biggest problem we'll have is a puddle.

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You'll see, it's going to puncture that glass.

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I'm going to make a suggestion. Whatever happens, let's watch it from over there.

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Now, I have always thought of water as kind of soft stuff,

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which flows around things.

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Sure, in a high-pressure jet, it's good for cleaning the car,

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but a cubic metre of it falling on to thick plate glass?

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Ah, the box.

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I really can't hear a thing now!

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-A nice loud countdown.

-Sorry?

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-A nice loud countdown and press the button.

-Right, this is it for real,

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here is comes, a wave - stand by in five, four,

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three, two, one...

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GLASS SHATTERS

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Well, that was quite a big bang. Thank you for the big bang.

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Yup, too much explosive.

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That's really...

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You can see the thickness of the glass now - ten mil thick, you could stand on that!

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Our ton of water only fell a couple of metres

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and it still had huge destructive power.

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Compared to the power of the waves in the gulf, however, it is a drop in the ocean.

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The biggest waves that batter the artificial island can deliver hundreds of tons of force.

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Each wave can be the equivalent of 130 small cars crashing into it.

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So how do you protect your island from the extreme forces of the waves?

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I think we will take our inspiration, Richard,

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from this little group of jacks here.

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So these are jacks... Forgive me, it seems like quite a leap

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because, how do they take the energy out of the wave?

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This is more a modern version of the jack -

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these things interlock together.

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So the principle is these shapes interlock.

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And the space between them, the water swirls within them,

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and loses its energy.

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-So it's these holes that are doing the work?

-Yeah, the holes.

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It's nothing creates something.

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Holes are the answer, well, sort of.

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Holes were first used in revolutionary jack-shaped sea defences

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created by South African harbour engineers.

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They saw a local version of jacks being played

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and, fascinated by how the jacks interlocked,

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successfully redesigned the harbour defences for East London.

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Almost all coastal defences still rely on this idea of holes,

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including the Burj Al Arab.

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I'm creating a furniture protection system inspired by the sea defences

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used to protect the hotel...

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..in which spaces are the secret ingredient.

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Instead of trying to stop waves dead with a wall,

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the idea was to create a series of spaces -

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holes - that absorb the energy of the sea.

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And we are going to see if the same principle will protect my spare dining table.

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It will be the holes doing the work, I hope.

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We need to clear off out of the way, and let's do it again,

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only this time my table will survive. Probably. ..It's your theory.

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I know!

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Our homemade defences will use the holes in the tyres to redirect the water.

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It will swish around and SHOULD fall harmlessly out the bottom.

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-I have every faith.

-Let's give it a go.

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If we have done our homework right this will save the glass...

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just as it saves the Burj Al Arab's man-made island.

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If we're ready? In five, four,

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three, two, one...

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This is one of those occasions where from seeing something,

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you suddenly really understand it.

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You can see the breakwater break that big lump of water up

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into eddies and swirls and bits.

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-It really was the holes doing the work?

-The holes did all the work.

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Net effect, a protected table, a protected island, a protected hotel.

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Not that my table isn't important.

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In Dubai, the Burj Al Arab engineers used exactly the same principle

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for breaking up waves, except they used concrete, not old tyres.

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Their defences create a smooth, elegant and uniform shape -

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suitable for keeping a world-class hotel's head above water.

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The holes are so good at taking the energy out of waves

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that the island could be built at just seven and a half metres above sea level.

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Keeping the island relatively low allows the architects to continue the illusion

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of a boat on the water.

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But what I think is fascinating is how the architects completed

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the boat itself, inside the sea defences.

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Those are just the outer shell of the island.

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They needed to fill the middle in with something, and they chose... sand.

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I guess it is not in short supply around here, but call me old fashioned...

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I've never thought of sand as the ideal material to make firm foundations for a building...

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especially one that size.

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The Burj Al Arab is 321 metres high -

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slightly taller than the Eiffel Tower.

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How does it possibly stand on sand

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without keeling over in the first stiff breeze?

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Through a remarkably simple scientific principle, in fact.

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Skin friction is exactly what it sounds like -

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it's the friction between the skin, the surfaces of objects.

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If I rub my hands together, friction generates heat, I can feel it.

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Now ordinarily, skin friction is there

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but it's pretty easily overcome.

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So, two pages together, I can feel the friction between them

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but there's not a lot of it.

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However, if I multiply that effect by as many times

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as there are pages in these directories,

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well, let's see what happens.

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I'm going to interleave them page by page. One, two...

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Skin friction is one of the factors

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that keep the Burj Al Arab standing tall.

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'Mind you, I think they built the hotel in less time

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'than it's taking me to do this.'

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1,407...1,408.

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There we go, all done.

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Now, according to the theory, the effects of skin friction

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should have been magnified by as many times

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as there are interfaces between the pages I have interleaved.

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It took a while, but I didn't have much else on this afternoon.

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Knowing how long it took, I'm reluctant to test it, but I'm going to.

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How tough is it?

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HE GRUNTS

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I'm pulling as hard as I possibly can. There is no glue, that is just skin friction.

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There's no way can I pull those apart,

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honestly, I'm trying as hard as I can.

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HE GRUNTS

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No, I need to try harder.

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OK. This should be more like it.

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Obviously skin friction already doing well just to hold this shackle on.

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Remember, nothing holding these together, just the friction between the pages.

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Right, lift it, please.

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How good is skin friction? I mean, really, how good?

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Up!

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OK. Time to demonstrate, if nothing else, my faith in science.

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HE CLEARS THROAT

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Um, yeah, skin friction...

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HE CHUCKLES

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That's all that's holding me up, and the weight of that shackle.

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Remember, no pins in there,

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no tape, no nails, nothing.

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Just friction.

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And friction is also one of the answers to building on unstable material, even sand.

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Otherwise the enormous tower would just topple over.

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The secret was to use reinforced concrete pile foundations,

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which are like long nails driven into the ground.

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They work using skin friction to keep the building in place,

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even in loose sand.

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To show how strong pile foundations can be, a simple demonstration.

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Jar of uncooked rice and a knife.

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Put knife into rice...

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..that's something called skin friction in action.

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Skin friction is strong enough to support a 320 metre tall tower...

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on sand.

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There are six miles of concrete piles bored 43 metres into the sand

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under the hotel to keep it upright and safe.

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Think of each pile as a page in the directory -

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every one makes the bond stronger.

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Combined, they make the sand as solid as a rock,

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and keep the building standing tall.

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In Dubai, temperatures can reach a blistering 49 degrees Celsius.

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And that heat posed a challenge for engineers and architects

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working with steel.

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Metal, like most materials, expands when you heat it up.

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Think about it, if you've got the lid stuck on a jar,

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warm it up and the metal lid will expand and you can free it, that's a good thing.

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But if you're working on giant metal trusses,

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and they're expanding and contracting according to the temperature

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at different times of day and you're trying to fit them together

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in a very precise way, it's going to be tricky.

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The Burj Al Arab was constructed using a steel exoskeleton,

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and external frame.

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The six steel trusses that support the building's weight

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are up to 85 metres long.

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That's longer than a Jumbo Jet.

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In the desert heat, the lengths of steel could expand by 5cm,

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which was critical during construction,

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when everything had to come together exactly.

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These two steel triangles will represent

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the huge steel trusses on the Burj -

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and they really are huge, 80 metres long,

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but the principles will be the same, even at this scale.

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So they've been machined very accurately

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so they can be fixed together using these fixings...

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That goes in there, that mounts in the hole...

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..and one here...

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So that's my steel structure firmly fixed together.

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Fine, but it hasn't yet had to cope with the problems of desert heat

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and the problems of heat expansion associated with it.

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Could be waiting a while here for some desert heat,

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but that's OK, we can bring our own.

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Gas axe, please. Thank you.

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While he's firing that up, I'm going to remove one of these fixings,

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because I want to see the effect of that thermal expansion.

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Right...

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Well, that was, I think we can agree, a hot day.

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But, if I try and put my original fixing back in...

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..and line it up - remember this is machined so the holes should align -

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and...oh, surprise, surprise, they don't,

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there's absolutely no way is that going to go through there.

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Because the metal's expanded, the hole's ended up in the wrong place.

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When the top metal bar undergoes thermal expansion,

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it becomes longer,

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but the bottom one stays the same.

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This means that the holes in each no longer align.

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If this were 80 times bigger,

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imagine the effect it would have then.

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But what can you do about it?

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The steel trusses ARE going to grow and shrink depending upon the time of day and temperature,

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that will happen.

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It could be disastrous, you could end up with a crooked tower.

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The engineers found an ingenious solution,

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thanks to the cam of an engine.

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Cams are used, of course, in car engines, you've probably heard of a camshaft.

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Well, here is one.

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This is the top of the engine,

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this assembly here is to operate the valves,

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which would be in the cylinder bores below.

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They have to open and close very quickly to let fuel and air in,

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and exhaust gases out, that's where the cams come in,

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so I'm going to be the engine turning here,

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and as I rotate the camshaft you can see the cams move eccentrically,

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these lobes where they bulge and stick out push down on this assembly here,

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open the valve and then shut it.

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It's a clever principle

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and one that's been used for a long, long time.

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The off-centre bulge of a cam allows it

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to open and close engine valves on each rotation of the camshaft.

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The builders of the Burj Al Arab borrowed from that idea

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to overcome the problems caused by extreme desert heat.

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This fixing is called an eccentric fixing.

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It's been designed using the same sort of principle -

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this is like a cam inside this hole here.

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And that gives us the flexibility we need

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to cope with this heat expansion.

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So let's put it in, line it up roughly, in the big hole there...

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and if I drop that in,

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we can manoeuvre it around, and there it is -

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that lines up perfectly.

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That's the connection between the engine's cam

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and our fixings for building in the desert.

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The eccentric fixing allows the top hole to be moved,

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so that no matter how much the steel expands,

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it can still be aligned to the bottom hole.

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Engineers at the hotel, taking their inspiration from engine cams,

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designed bespoke moveable fixings that allowed them

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to install the massive trusses accurately,

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despite the thermal expansion.

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Once installed, everything was welded firmly in place.

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Now the building expands and contracts as a whole,

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keeping it in shape.

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In the baking heat of the desert,

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one of the ultimate luxuries

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must be a cool, air-conditioned room.

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Even when temperatures approach 50 Celsius outside,

0:22:570:23:01

the interior of the Burj Al Arab maintains a balmy 23 degrees.

0:23:010:23:07

But keeping it this way isn't as simple as you might think.

0:23:070:23:12

Creating and maintaining an oasis in the desert presented the engineers

0:23:140:23:18

with a series of challenges, right from the very beginning.

0:23:180:23:21

The real problem is managing the big difference

0:23:230:23:26

between temperatures inside and outside the hotel.

0:23:260:23:29

On a hot day, the difference between the two can be 20 degrees Celsius.

0:23:310:23:36

Temperature differences create pressure differences.

0:23:370:23:41

In nature, big pressure differences create violent winds,

0:23:410:23:44

even hurricanes.

0:23:440:23:46

Pressure differences affect all skyscrapers.

0:23:480:23:51

They're especially bad in a structure the size of the Burj Al Arab, in the desert.

0:23:510:23:56

It could literally stop people getting in and out of the building.

0:23:560:24:02

'Back on home soil, Professor of Building Engineering Physics

0:24:030:24:07

'Doug King explains why combining air conditioning,

0:24:070:24:10

'a tall building and a scorching desert can stack up big trouble.'

0:24:100:24:15

Big temperature differences, although they make life nicer inside,

0:24:170:24:21

-they can bring big problems.

-Absolutely. We're going to demonstrate that with this model,

0:24:210:24:25

which is a scale model of the atrium at the Burj.

0:24:250:24:28

I did wonder. It's not as big, is it?

0:24:280:24:30

No, unfortunately, we couldn't get one that big in here,

0:24:300:24:34

so we've had to scale things down. We've got a light bulb at the bottom,

0:24:340:24:37

representing the heat gains from people and the sun shining in the windows.

0:24:370:24:41

And we've got about a kilogram of dry ice on a tray at the top,

0:24:410:24:45

representing the cooling effect of the air conditioning.

0:24:450:24:48

'And the problem is all to do with airflow.

0:24:500:24:53

'An air pellet will show how the air circulates.

0:24:530:24:56

'Heat from people and the sun through the windows on the ground floor cause the air to rise.

0:24:560:25:03

'The air conditioning cools it down, making it more dense, and the air falls...'

0:25:030:25:08

So we've got up-flow on the one side and down-flow on the other side.

0:25:080:25:12

'..leaving you with a tall column of cold, heavy air surrounded by the hot desert,

0:25:120:25:18

'which doesn't sound like a problem.'

0:25:180:25:21

-I still don't see - why the big problem?

-If the building stays closed, it's not a problem.

0:25:210:25:25

The problem happens when we've got this big stack of cold air inside.

0:25:250:25:29

We've got warm air outside, and it's all being held back by the front door.

0:25:290:25:33

-So why don't you open the door and see what happens?

-This door down there?

0:25:330:25:36

-That's the one.

-So I'll open the door...

0:25:360:25:38

-Wooh! Yes!

-What's happening now... See how quickly it's clearing down?

-Yes.

0:25:380:25:42

You've got this big column of cold air inside, much heavier than the air outside,

0:25:420:25:47

-and it's being forced out through that little opening.

-You can see it's rushing out -

0:25:470:25:51

that's not just tumbling out because I've opened the door, that's being pushed out...

0:25:510:25:56

-Right.

-..by this pressure difference.

-See how quickly all that air inside the model

0:25:560:26:00

-has fallen down and pushed the air out.

-So if that's how it works on this scale,

0:26:000:26:04

how big a problem does it represent

0:26:040:26:06

for something the size of Burj Al Arab?

0:26:060:26:08

Well, for something as big as that atrium - it's 180 metres high -

0:26:080:26:11

that's an enormous stack of cold air. Very, very dense at the bottom.

0:26:110:26:15

Opening that door against that pressure is like trying to lift a sack of potatoes.

0:26:150:26:20

To be more precise, the vast atrium at the Burj Al Arab,

0:26:200:26:23

combined with the heat of the desert outside,

0:26:230:26:27

could create the equivalent of 21 bags of sugar pressing against the door.

0:26:270:26:33

So, a 21-kilo weight suspended from a pulley.

0:26:330:26:37

This, then, is about as tough as it would be to open the door at the Burj Al Arab.

0:26:370:26:41

I mean, it's not impossible, but it is a bit of a workout.

0:26:410:26:44

I don't think you want a work out every time you open the door,

0:26:440:26:47

especially if you've saved up to book a suite.

0:26:470:26:50

With the largest atrium in the world,

0:26:510:26:54

this problem is especially acute for the Burj Al Arab.

0:26:540:26:57

The unwanted stack effect was first noticed

0:27:010:27:04

with the rise of the skyscraper.

0:27:040:27:07

Workers in New York and Chicago complained not only of draughts,

0:27:070:27:10

but that they couldn't even open the doors of their buildings

0:27:100:27:14

because of pressure differences inside and outside.

0:27:140:27:17

One solution to the problem is to equalise the pressure inside the building

0:27:190:27:23

with the pressure outside the building.

0:27:230:27:25

But that would mean you'd need to equalise

0:27:250:27:28

the temperature in here with the temperature out there...

0:27:280:27:31

in the desert.

0:27:310:27:32

You wouldn't be able to heat or cool the building.

0:27:320:27:35

And I think having the temperature in here hover around the 40-degree mark

0:27:350:27:39

does rather spoil the whole idea of an oasis in the desert.

0:27:390:27:43

The hotel might lose a star or two for that.

0:27:430:27:46

What you need is a means of getting between two areas of different pressure -

0:27:460:27:51

outside on the street and inside the hotel -

0:27:510:27:54

without allowing the pressures to equalise.

0:27:540:27:57

There was a different solution

0:27:570:28:00

and it came from something inspired by a 19th-century French coal mine.

0:28:000:28:05

In 1839, French mining engineer Jacques Triger overcame the problem

0:28:060:28:11

of moving between two areas of different pressure

0:28:110:28:14

in waterlogged coal mines.

0:28:140:28:16

He created the world's first airlock.

0:28:160:28:19

This is how Triger's system worked. This is my waterlogged ground.

0:28:210:28:24

Well, it's a glass, but you know what I mean.

0:28:240:28:27

Here's my mine shaft.

0:28:270:28:29

If I just sink a mine shaft into waterlogged ground like this,

0:28:290:28:32

it's just full of water at the bottom,

0:28:320:28:34

nobody can work down there.

0:28:340:28:36

The answer to that is

0:28:360:28:37

fairly simple - seal it at the top.

0:28:370:28:39

That stops the air getting out,

0:28:390:28:40

which means the water can't get in.

0:28:400:28:43

That's all well and good until you need to open the top

0:28:430:28:45

to let your workers go down the mine,

0:28:450:28:47

then it flows with water again.

0:28:470:28:51

That answer to that one - establish your dry mine shaft,

0:28:510:28:56

fit an airlock at the top,

0:28:560:28:58

let your workers in.

0:28:580:28:59

Then once they're safely in,

0:28:590:29:00

seal it behind them - everything stays dry, everybody's happy.

0:29:000:29:05

What they needed at the Burj Al Arab was some sort of airlock

0:29:050:29:08

so they could separate the pressure inside the hotel

0:29:080:29:11

from the pressure outside.

0:29:110:29:13

Sounds complicated, like something off a space station.

0:29:130:29:16

But in fact, I've just been through it -

0:29:160:29:18

it's a revolving door.

0:29:180:29:21

Revolving doors are designed in such a way

0:29:220:29:24

that there's never a direct opening to the street.

0:29:240:29:28

The inside is sealed from the outside,

0:29:280:29:30

even when the door is spinning.

0:29:300:29:33

First used in Rector's Restaurant in Times Square in New York in 1899,

0:29:340:29:39

its tagline was, "Always open, always closed",

0:29:390:29:41

because the door keeps a seal, even when you go through it.

0:29:410:29:46

This makes the sort of airlock that's needed

0:29:480:29:51

to stop the big out-rush of air that would happen

0:29:510:29:53

because of the stack effect.

0:29:530:29:55

Now, everyone who can afford it can come and go in comfort.

0:29:550:30:01

But comfort can bring its own difficulties.

0:30:010:30:04

It's probably not surprising

0:30:050:30:07

that pretty much every electronic gizmo conceivable

0:30:070:30:10

has been incorporated into these rooms,

0:30:100:30:12

all operated by remote control.

0:30:120:30:14

At the touch of a button, televisions drop from the ceiling,

0:30:140:30:17

or pop up out of pieces of furniture.

0:30:170:30:19

You can change the temperature, open and close the doors,

0:30:190:30:22

change the mood, adjust the lighting, dim it, make it romantic.

0:30:220:30:26

Let's leave it bright.

0:30:260:30:27

So, whilst all of this is great for the guests,

0:30:270:30:30

it can be bit of a headache for an electrical engineer.

0:30:300:30:33

Luxury calls for a lot of energy.

0:30:350:30:38

Just the lights in one suite can draw more power

0:30:380:30:41

than all the appliances in a British home burn in a whole day.

0:30:410:30:46

And making the mood romantic could have shocking consequences.

0:30:460:30:51

So, to dim the lights, simply press a button.

0:30:510:30:54

Not complicated - we're all familiar with dimmers.

0:30:540:30:56

But simply pressing that button could have had a catastrophic effect.

0:30:560:31:01

The origin of the potential problem lies

0:31:010:31:04

in what happens to an electrical current when you dim the bulb.

0:31:040:31:08

It can heat the wires to abnormal levels and start a fire.

0:31:080:31:13

To show what can go wrong when you're adjusting the ambience,

0:31:160:31:19

we're going to check in to my own replica of a luxury hotel room.

0:31:190:31:23

I've brought electrical expert Paul Mitcheson along

0:31:300:31:35

to create a sophisticated lighting system.

0:31:350:31:37

Oh, yeah, home from home.

0:31:410:31:42

No, I'm not back in the Burj Al Arab, this is my replica.

0:31:420:31:46

There's no en suite yet or Jacuzzi or under-floor heating,

0:31:460:31:49

but it's got a bedside table and plastic roses.

0:31:490:31:52

Everything the modern luxury bedroom needs, including lights.

0:31:520:31:56

They don't really come on and off when you do that,

0:31:560:31:59

that's just Paul out there operating them.

0:31:590:32:02

Still, thank you! There it is, all working perfectly.

0:32:020:32:06

My shed may not be a fully authentic replica,

0:32:090:32:12

but it has two crucial similarities.

0:32:120:32:14

It has a high voltage power supply for the electrical systems

0:32:150:32:19

and it has a dimming system.

0:32:190:32:22

Paul, in addition to providing adult supervision,

0:32:250:32:28

has set up a high-tech monitoring station

0:32:280:32:30

complete with a complicated array of gauges and test equipment.

0:32:300:32:35

Paul, to me as a customer, staying in my luxury hotel room

0:32:350:32:39

the lights are on, that's it. What is going on in there? What's happening?

0:32:390:32:43

So, what we're doing is we have a wave form, which we can see on the oscilloscope,

0:32:430:32:47

and this is electric current which is powering the lights.

0:32:470:32:50

And at the moment, the key thing to note here is that this is a very smooth wave form.

0:32:500:32:54

So, this is what a normal current looks like on an oscilloscope.

0:32:540:32:59

It's regular and safe.

0:32:590:33:02

So, a smooth wave form there. What if I change things a bit?

0:33:020:33:05

This is what I want to change.

0:33:050:33:07

It's a luxury bedroom, but that light is a bit harsh.

0:33:070:33:10

You want something a bit more cosy?

0:33:100:33:12

Yeah, I'd like to change the light setting.

0:33:120:33:14

Instead of three on full, I'd like to put six lights on but dim.

0:33:140:33:19

OK, in that case, what we could do is, we could dim those,

0:33:190:33:23

bring up another three.

0:33:230:33:26

It's a much better ambience in there.

0:33:270:33:29

Am I right? That's the same amount of light.

0:33:290:33:33

We've just got six lights on but lower.

0:33:330:33:35

That's right. The same amount of power into the lights.

0:33:350:33:38

We can see from the oscilloscope that something has changed drastically.

0:33:380:33:42

So, what's different?

0:33:420:33:44

The problem is now that we're delivering power to the lights in short bursts.

0:33:440:33:49

So that's how the power's been halved then?

0:33:490:33:51

That's exactly right, yes.

0:33:510:33:54

Because I always thought a dimmer was like a tap,

0:33:540:33:57

cos if you turn a tap on full and then that's too much

0:33:570:33:59

you turn it down halfway and half the amount of water comes out. I thought a dimmer was the same.

0:33:590:34:04

Turn it down and half the amount of electricity goes to the lights.

0:34:040:34:08

So, it's more like turning the tap on and then off and then on and then off.

0:34:080:34:12

Modern dimmer switches basically shut off the power to the light

0:34:140:34:18

120 times a second.

0:34:180:34:20

It has the effect of not letting the light ever achieve full brightness.

0:34:200:34:25

It also has a side effect.

0:34:250:34:28

So, it's the same amount of electricity

0:34:280:34:30

but being switched on and off.

0:34:300:34:32

-Right.

-Why is that different? Why does that upset things?

0:34:320:34:35

You're only delivering the power for a short period of time.

0:34:350:34:38

And in order to that, you introduce extra heating effects in the wires.

0:34:380:34:41

An electrical current in a wire always creates

0:34:410:34:44

a certain amount of heat.

0:34:440:34:46

But adding a dimmer switch can add extra heat to the wire,

0:34:460:34:50

sometimes dangerously so.

0:34:500:34:53

The on-off action of a dimmer switch creates so-called harmonic distortion,

0:34:530:34:58

a sort of chaotic current in the wires,

0:34:580:35:01

frequencies the system isn't designed to deal with.

0:35:010:35:05

A wire heating up doesn't sound too ominous.

0:35:070:35:10

It might smoulder away but, in the wrong circumstances,

0:35:100:35:13

that wire can ignite flammable items close to it.

0:35:130:35:17

If, for example, someone had carelessly left the exposed wire

0:35:170:35:22

on a waste paper basket full of cotton wool,

0:35:220:35:25

which might happen to be soaked in nail varnish remover.

0:35:250:35:29

It could happen!

0:35:290:35:31

With six lights on dim, let's see what does happen.

0:35:360:35:40

My hotel's on fire, just so they know.

0:35:500:35:53

That's a lot of heating!

0:35:530:35:56

That took less than 20 seconds to catch.

0:35:560:35:59

You really wouldn't want that in a top-class hotel.

0:35:590:36:02

Our shed's on fire. You've ruined my hotel quite badly.

0:36:030:36:07

I see your point. That is a potential problem!

0:36:070:36:11

Cor blimey! Bloody hell.

0:36:130:36:15

Man, that's hot!

0:36:220:36:23

Obviously, this is a very exaggerated scenario.

0:36:260:36:31

Electricians don't generally run exposed wires through flammable bins of cotton wool.

0:36:310:36:37

But if it is a serious threat, how come dimmers are so common?

0:36:370:36:42

Why isn't there a fire every time someone wants to change the ambience?

0:36:420:36:46

That could ruin the mood.

0:36:460:36:47

It's because of electrical defences that include part of a camera's flash.

0:36:480:36:54

Yeah, I do see your point.

0:36:580:37:01

It's not great, is it?

0:37:010:37:02

My hotel's ruined. So clearly that needs to be avoided.

0:37:020:37:05

It is. They have dimmers and that doesn't happen.

0:37:050:37:08

So, what's the solution?

0:37:080:37:09

So, the solution is the capacitor that's in the camera flash.

0:37:090:37:13

We're all familiar with a regular camera.

0:37:130:37:17

Early camera flashes used explosive powder to create the bright light

0:37:190:37:24

but carrying that around was not for the faint-hearted.

0:37:240:37:28

They needed a safe, portable alternative.

0:37:320:37:35

And the solution came in the form of an electrical component,

0:37:380:37:42

known as a capacitor.

0:37:420:37:44

In cameras, the capacitor stores up energy

0:37:440:37:48

and releases it all at once setting off the flash.

0:37:480:37:52

But, in buildings, combined with inductors,

0:37:520:37:55

they act like filters, removing the chaotic currents that can cause fires.

0:37:550:38:01

This is a regular, relatively large capacitor.

0:38:010:38:03

So, this is the thing that allows you to take energy more slowly

0:38:030:38:08

and release it back to the lights.

0:38:080:38:11

All that does is accumulates this energy and releases it at a controllable rate.

0:38:110:38:15

And stops that happening.

0:38:150:38:17

Burning your shed down.

0:38:170:38:19

Wish I'd known that ten minutes ago, I'd still have a shed.

0:38:190:38:24

The Burj al Arab's capacitors are buried deep in the building.

0:38:240:38:28

With the inductors, they are the unsung electrical heroes

0:38:280:38:32

that protect the hotel from itself and its pampered guests.

0:38:320:38:36

I guess it is a relief to know that, when I dim the lights,

0:38:360:38:39

I'm not going to set fire to the Burj al Arab.

0:38:390:38:42

I imagine the bill would be quite big if I did.

0:38:420:38:46

I'd never get that through on expenses.

0:38:460:38:48

The designers of this amazing building

0:38:500:38:54

didn't limit the spectacle just to the structure.

0:38:540:38:57

It is, after all, a hotel.

0:38:570:39:00

And the guests will spend most of their time inside looking around,

0:39:000:39:03

not outside looking in.

0:39:030:39:06

When it comes to earning its keep,

0:39:090:39:11

this building is all about symbolising luxury and opulence

0:39:110:39:15

so what could be the best possible luxury here,

0:39:150:39:19

in a hotel perched in a scorching desert of sand and sea?

0:39:190:39:23

Yep, fountains.

0:39:250:39:28

Think about it, a fountain in the desert is the ultimate in opulence.

0:39:290:39:34

And, not just any old fountains,

0:39:340:39:37

a series of digitally-controlled million-pound masterpieces.

0:39:370:39:41

And, whilst fountains are pretty and all that,

0:39:420:39:45

it takes some surprising engineering to create the flair.

0:39:450:39:48

You need to be seen to do something extravagant

0:39:510:39:54

and opulent with the water.

0:39:540:39:56

And the water features here are an engineering feat

0:39:560:39:59

in their own right. Mesmerising.

0:39:590:40:02

Sometimes the water doesn't even look like water.

0:40:030:40:07

That's because it's not behaving like water,

0:40:110:40:14

normal water that is.

0:40:140:40:16

Normal water can't move like this does.

0:40:160:40:19

To allow it to play these tricks, you need to eliminate turbulence.

0:40:220:40:28

It has to achieve an almost unreal glassy smoothness,

0:40:280:40:31

something called laminar flow.

0:40:310:40:35

Here it comes, if you need it,

0:40:360:40:38

a quick reminder of how water behaves in a flow normally.

0:40:380:40:42

There it goes, that's...

0:40:440:40:47

Well, it's a mess, that's because of turbulence,

0:40:470:40:50

there's lots of eddies and flows and swirls in there,

0:40:500:40:52

which is fine for use here on the farm.

0:40:520:40:56

But if you want to make those beautiful polished glass-like tubes

0:40:570:41:01

in the fountains at the Burj al Arab you need to smooth that flow out.

0:41:010:41:06

You need to make it laminar.

0:41:060:41:09

And to do that engineers turned to a type of hose

0:41:090:41:12

used to help put out fires in sky scrapers.

0:41:120:41:15

The 1930s. Buildings grew taller.

0:41:170:41:22

Fire fighters needed to stream water higher to quench towering infernos.

0:41:220:41:26

A helpful hydraulic engineer realised that turbulence

0:41:260:41:30

reduced the range of fire hoses,

0:41:300:41:32

because the water flow broke up in air.

0:41:320:41:35

His invention to smooth out the flow in fire hoses,

0:41:350:41:38

to make it more laminar,

0:41:380:41:40

was the key to the Burj al Arab's glassy fountains.

0:41:400:41:43

Right, quick quiet minute before we do the next bit

0:41:430:41:46

and we'll be finding out about this laminar flow business.

0:41:460:41:49

Which is far as I understand is doing, well what seems impossible?

0:41:490:41:54

Here is an example, my coffee,

0:41:540:41:56

don't worry, they'll get a coffee too, once they've earned it.

0:41:560:42:00

If I stir in milk, there you go,

0:42:000:42:05

stir it all in, there you go, it's all mixed up thoroughly.

0:42:050:42:08

Wouldn't it be kinda cool if we could un-stir it,

0:42:080:42:12

and we would be left with a blob of milk and black coffee?

0:42:120:42:16

So maybe if I stir the other way?

0:42:160:42:19

Obviously you can't, that would be turning back time.

0:42:190:42:23

We haven't yet conquered time travel and you can't un-stir coffee

0:42:250:42:30

unless you can make water behave in a fully laminar way.

0:42:300:42:34

Amazingly, however you can un-stir some liquids.

0:42:340:42:39

Professor Tom Mullen from Manchester University,

0:42:400:42:43

an expert in fluid dynamics shows me how.

0:42:430:42:46

So Tom, with this device are we about to spin a salad

0:42:470:42:50

or do some painting and what's this got to do with laminar flow,

0:42:500:42:54

whatever that is, and trying to unstir my coffee?

0:42:540:42:57

That's your mission to explain all of that.

0:42:570:43:01

Well, what you have to do is put this colour dye into the fluid

0:43:010:43:04

and we will stir it around and see what happens.

0:43:040:43:08

The liquid inside is thick viscous sugar syrup...

0:43:100:43:13

-A bit further along here. This direction.

-Right.

0:43:130:43:16

..and the coloured blobs are the same stuff with food dye added.

0:43:160:43:21

So three blobs, good, not much flowing,

0:43:230:43:26

laminar or otherwise going on now.

0:43:260:43:28

No, we have to create the flow, so to create the flow

0:43:280:43:31

we have to turn that handle, say five times in that direction.

0:43:310:43:36

-Right, it's quite thick stuff this. One...

-Very sticky.

0:43:360:43:40

Two...

0:43:420:43:43

Keep going.

0:43:430:43:45

Three...

0:43:450:43:46

Four...

0:43:480:43:49

Five. OK, I've done that.

0:43:500:43:52

-Now, it looks like we've created a right mess.

-It's a mess. It's all gone.

0:43:520:43:56

What we need to do is go backwards, the same number of times.

0:43:560:44:00

-So I'm literally un-stirring it?

-Unstir.

0:44:000:44:03

I feel like someone might be having a laugh at my expense.

0:44:030:44:07

One...

0:44:070:44:08

Two...

0:44:100:44:12

Three...

0:44:130:44:16

-Four.

-Slow down a bit, slow, slow, slow.

0:44:180:44:25

There you have your three blobs back again.

0:44:250:44:28

Wow. Look at that! I have literally unstirred it.

0:44:280:44:32

That's a great party trick.

0:44:320:44:33

Thick, viscous liquids like sugar syrup are very smooth.

0:44:370:44:40

It's easy to make them move in a laminar way.

0:44:400:44:44

They don't behave turbulently like water.

0:44:440:44:46

So you can un-stir them and make the blobs re-appear.

0:44:460:44:50

If water behaved like that you could un-stir your coffee.

0:44:500:44:54

To make water flow in a laminar fashion, you need to remove

0:44:580:45:03

the turbulence, with a laminar flow nozzle.

0:45:030:45:06

The good news immediately is, now correct me if I'm wrong,

0:45:060:45:09

is that this appears to be laminar flow in water.

0:45:090:45:12

This is laminar flow coming out of this nozzle here,

0:45:120:45:15

whereas this is turbulent flow. The reason you can tell

0:45:150:45:18

immediately that it's turbulent is that you can see it.

0:45:180:45:22

It scatters the light and in this case it's glassy smooth and laminar.

0:45:220:45:26

Quite a simple difference really, neat tidy and elegant, and scruffy and a mess.

0:45:260:45:30

But to achieve this it needs this device here,

0:45:300:45:33

-that looks like something from a '60s sci-fi movie, what is it?

-You have turbulent flow coming in

0:45:330:45:41

and you have the flow goes through these gauzes and these straws and so the turbulence decays as it comes

0:45:410:45:46

through here and you end up with laminar flow coming out of the nozzle.

0:45:460:45:51

The gauze and straws effectively smooth the water,

0:45:510:45:54

removing the bubbles and swirls that cause turbulence.

0:45:540:45:58

Non-turbulent water can flow quicker and more smoothly.

0:45:580:46:03

So to solve the problem then of fast moving laminar flow in water

0:46:030:46:06

for the Burj al Arab's fountains, what you need is a device like this.

0:46:060:46:10

-To calm the water down.

-Yes.

0:46:100:46:13

And smoothly flowing water also helped fire fighters.

0:46:140:46:19

In the '30s, American engineer Horace Barker had a brainwave.

0:46:210:46:24

He realised that removing turbulence made the water travel further.

0:46:240:46:29

His new fire hose design had metal feathers inside

0:46:290:46:33

that aligned the water as it left, reducing this turbulence.

0:46:330:46:36

Barker's flow-straightener extended the range of fire hoses.

0:46:380:46:41

The smooth water flow travelled further.

0:46:430:46:45

So fire-fighters could tackle blazes on the higher floors

0:46:450:46:48

of sky scrapers more easily.

0:46:480:46:50

Laminar flow nozzles go one step further than Barker's device,

0:46:510:46:55

removing all turbulence

0:46:550:46:56

and smoothing the water to a glassy finish.

0:46:560:46:59

The fountains at the Burj al Arab incorporate 66 laminar flow nozzles,

0:47:040:47:08

I'm pretty sure theirs aren't made from drinking straws though.

0:47:080:47:13

Either way, they allow for breathtaking displays.

0:47:130:47:15

You see, the crucial thing about the Burj al Arab is that

0:47:170:47:20

it's all about the bling. It's engineering to impress...

0:47:200:47:25

not just to survive.

0:47:250:47:28

All these engineering achievements have made

0:47:280:47:31

the Burj al Arab a spectacular feature on Dubai's skyline.

0:47:310:47:35

The Burj al Arab instantly joined the world's list

0:47:370:47:39

of iconic landmarks. Becoming the face of Dubai.

0:47:390:47:42

Synonymous with it's re-invention as a luxury playground.

0:47:420:47:49

Behind the glitz, the glamour and the spectacular show,

0:47:550:47:59

there is some amazing, and solid engineering.

0:47:590:48:03

And none of it would have been possible without...

0:48:050:48:08

..a game of jacks...

0:48:080:48:09

..an engine cam...

0:48:110:48:14

..the pages of a phone book...

0:48:140:48:17

..a revolution in fire-hose design...

0:48:190:48:21

..and a camera flash.

0:48:210:48:25

-You've ruined my hotel, man!

-THEY LAUGH

0:48:250:48:29

Subtitles by Red Bee Media Ltd

0:48:360:48:39

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0:48:390:48:42

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