- Let's hit it. - ( fans whirring )

Gav: Well, that doesn't mess around!

Dan: That's a full 45 right there.

Why don't we start testing some elements?

( wind blowing, spraying )

Gav: ( laughing ) Look at that liquid!

I brought my own balloon.

It's a condom.

( screaming )

Gav: That is the stupidest thing I've ever recorded

in slow motion in my life.

Well, that was a beastly wind tunnel.

It really was. It was what? 80 miles an hour?

Yeah. The shots of you in the water,

especially 'cause we backlit the water.

It just looked really cool.

Like, it was fascinating to see how the air

was moving around you, but it also just looked wicked.

It was like commercial grade footage.

You look like a certain singer

- from a 90's music video. - ( Dan laughs )

( R&B music plays )

Gav: Oh, that's magic.

♪ Yeah, yeah ♪

I also think that you condom sailing

on a skateboard might be the most bizarre thing we've ever shot.

You know, that will be one of the most fun things I've done this year

- for sure. - ( laughs )

Something about your flat hair,

with your smug face, with that flapping in the wind.

Goodness, gracious me.

I didn't expect it to work

and then it worked

and I was so happy.

It was so much fun.

Well, we thought it'd be a good idea

to learn a little bit about the facility

so we talked to a bloke who works there called Kevin.

Let's kick it to Kev.

- Dan: Kevin. - Hi, Dan.

Hey, so you're one of the aerodynamicists at Mira, right? Have I got that right?

- That's right. - Yeah. That's a cool job title.

Damn good occupation.

So what does that actually mean?

Like what do you do?

So, one of the jobs I have here

is to essentially characterize how vehicles behave

from an aerodynamic point of view

in terms of drag, lift, front lift, rear lift.

So what are some of the fastest speeds of wind you've seen in this tunnel?

Um, so we can-- we usually operate up to about 80 miles an hour.

And that's like equivalent to like a hurricane or something?

- Uh, um-- - Light hurricane?

- Yeah, a light hurricane. - A light hurricane?

- A breezy hurricane. - They can go quite strong.

So, how do you feel about the fact that

you're an aerodynamicist with a PhD,

and does very scientific things,

and we come along, whip out a condom,

and fly along the floor with a skateboard.

You have this huge scientific facility,

you know, do you mind? Is that--

Well, from an engineer's point of view,

I kind of have to be very professional

about everything and that basically makes my day job

a little bit dry,

so to have something interesting happen for once

makes for quite a nice change, so...

And I bet in the-- what? 70, 60 year history of this place...

Kevin: Yup.

Gav: ...It probably not had been done before that.

You may have very well set a record there.

Yes.

It's quite an honor that you lasted in it, to be honest.

That is great.

Thanks very much, Kevin, for letting us mess around in here.

- No, thank you. - It's a real honor.

Thanks a lot. That was really so much fun.

- That was a lot of fun. - Glad you had fun.

All right, back to you, Gav and Dan.

Oh, thanks, us.

It's amazing how many of the things we filmed

is so heavily influenced by aerodynamics.

It's not just things we film though,

I remember I used to ride my bike to school,

one day it was really windy

I was, like, ten minutes late for school,

so as I walked into the class,

and the teacher was like, why are you late?

and I was like, "It was windy."

And she just goes, "Get out."

And the class just laughed at me.

Did you get laughed at a lot as a kid?

Let's-- ( stammers ) Let's leave that, all right?

To find out more about aerodynamics,

and why I was late for school,

we've brought on someone who is clearly never late for school,

Lisa, who's an aerospace engineer.

- Thanks for coming. - Thank for having me.

Hello. Were you ever late to school?

- Oh, no, definitely not. - Gav: Definitely not.

I'd love to get your opinion on some of the aerodynamics

of Dan and I, so why don't we go over to the screen...

- Sounds good. - ...and have a little look.

- Okay, first clip. - The idea behind that was,

it was that I was trying to sit down fully,

90 degrees with my legs,

but I couldn't do it unless I had that little bit extra

where I put my hands out to help me...

- Makes sense. - To get a bit more...

Yeah, just a little bit more track.

It was amazing the difference that this made.

- Mm-hmm. - Gav: Over here what I'm doing is I was holding

my lab coat out, and I was trying to make

forward progress and the more I had it open

I actually couldn't go anywhere. It was like holding--

Oh, that makes sense, you had a parachute behind you...

- Yeah. - ...at that point.

Lisa: So this is a great example of the four forces

acting on you all at once.

You are trying to exert thrust on yourself

by moving yourself forward.

You've got the drag of the wind

pushing on you trying to keep you back.

You've got the weight of your body

keeping you on the floor,

and then the lift, you can actually see a little bit

in the parachute from your lab coat

and just that kind of lift and pushing up on your chest as you lean forward, too.

So all of those forces are acting on you at once

even as the wind is blowing in one direction.

I look like I'm totally chilling there.

Gav: You're having the time of your life.

Dan: Usually, it's so much effort to do that,

but it was so easy because the wind.

But now that it takes 80 miles an hour to do that for me.

And now I've gone for a jump here. By me jumping forwards,

I went almost straight up and came back down like this.

Wow, you'd be so late for school.

( laughter )

Gav: If I had a lab coat on

and I walking through that to school,

- I wouldn't get there. - Yeah. ( laughs )

Lisa: Couldn't make it.

Gav: Uh, this was actually the scariest thing that I did.

I was wondering what would happen if I went on the floor.

But as soon as I held up my lab coat like a parachute.

Lisa: Yup.

It just started sucking me along the floor.

And I got some significant distance here.

See, here's me, I've got-- I'm going too fast.

So I've put it down and I'm still,

- the momentum is still-- um, is still-- - ( laughter )

Apologies for that. No one wants to see that.

So why don't we move on to a little table top experiment?

So we've been to a multi-million pound wind tunnel in England

and now for our table top experiment,

we've got a little wind tunnel

that didn't cost millions of pounds.

- Multi-pounds? - Multi-pounds, though.

- Yeah. - Can't get it for a quid.

It's just a normal fan with a tube,

a bunch of tape, and a lovely clear wind tunnel area.

So we can test out these two cars.

We got an old boxy one, and a lovely streamlined one.

Because we can't see air, so we want to know what's gonna happen,

we've got this vaporizer here,

which is gonna create a bit of smoke for us.

I'm gonna shove it in and hopefully we'll see

the smoke going around the cars in different patterns.

Gav: Why don't we start with the boxy one.

What is your prediction for this then?

I'm not thinking it's very aerodynamic.

- ( laughter ) - You're probably just gonna see

smoke going everywhere.

( machine buzzing )

Yeah, you can see it just bashing against

the wind-screen there.

Lisa: Yeah, that blunt front is not doing it any favors.

Gav: Shall we try the second one?

- Yeah. - A little bit bigger.

But we'll pretend that it's the exact same size.

( scoffs )

Gav: All right, I'll give it some action.

( machine buzzing )

Lisa: So for this one you can actually see the smoke

- rising over the top. - Gav: Yeah.

It's coming all the way back here,

and then it's coming down at the end.

Exactly. This car is much better designed

for fuel economy than the old car.

And this way you save drag, and when you save drag,

you save gas, and when you save gas, you save money.

What's the weirdest stuff you've put into a wind tunnel?

Some of the oddest things I've seen

would have to be a trash can.

Why would you need a trash can to be--

Is it to stop from blowing away in the wind?

Exactly, you don't want it rolling down...

Gav: Actually makes total sense.

...once you've put it on the street.

Actually, I've got something I want to put in here.

Thinking about it, hang on.

- Us. - Oh, us from episode one.

Yeah.

Obviously, I assume I'm going to be less aerodynamic.

- ( chuckles ) - Let's put me slightly there

- and you slightly off. - Okay.

( machine buzzing )

Gav: Oh, yeah, it's coming around you,

It's going through your arm holes.

Dan: It just goes like nothing through you.

- ( Gav laughs ) - Dan: It just completely avoids you.

Gav: Do you learn the same information from doing it scaled down

than you do full size?

You can learn most of the information you need

from a scaled test.

Usually it's a much bigger scale than this,

but you definitely can.

I like that. I like it when, just like,

physics and principles just scale up perfectly.

Thank you very much, Lisa, for joining us.

- Yeah, I enjoyed it. - And teaching us about aerodynamics.

Well, hopefully you enjoyed that video.

Feel free to watch other episodes from "Planet Slow Mo."

Make sure you check out Dan's condom sailing,

- that was amazing. - Worth it.

And you can subscribe to the Slow Mo Guys if you'd like.

It would make us a bit happier, wouldn't it?

- Mm-hmm. - You have a smile?

Not quite as happy as when I was using

- the condom as a sail. - Well, obviously not.

That was up there.