What's the slowest you can drive a convertible...

[Greg_D]

....in the rain and not get wet?

let's assume all rain has the same terminal velocity
let's assume it is really persisting down.
let's assume no weird aero affects at the trailing edge of the windscreen surround.
let's assume that the top of your head is 6" below the top of the windscreen and 12" behind

so in all reality i am asking how quick you would need to go to 'beat' the rain that just skims the top of the windscreen before it hits your head.

Discuss

[Mr Roper]

Absolutely no idea

[andy-xr]

45mph is the slowest I've been in a downpour and not got wet

[ZOLLAR]

I did it couple of months ago, anything below 30 and I was feeling it on my head.
It's quite bizzare driving at 70 on the motorway whilst its raining with the roof down, you know you should be getting wet but you aren't

Edit to add it wasn't a downpour when I did it just "normal" rain.

Edited by ZOLLAR on Monday 6th June 14:12

[Flip Martian]

Its stopping at the traffic lights which is the real bugger...

[AyBee]

Greg_D said:

....in the rain and not get wet?

let's assume all rain has the same terminal velocity
let's assume it is really persisting down.
let's assume no weird aero affects at the trailing edge of the windscreen surround.
let's assume that the top of your head is 6" below the top of the windscreen and 12" behind

so in all reality i am asking how quick you would need to go to 'beat' the rain that just skims the top of the windscreen before it hits your head.

Discuss

Is this not a bit like asking how long's a piece of string? I imagine the aero of the windscreen is a big factor in this question...

[300bhp/ton]

Greg_D said:

....in the rain and not get wet?

let's assume all rain has the same terminal velocity
let's assume it is really persisting down.
let's assume no weird aero affects at the trailing edge of the windscreen surround.
let's assume that the top of your head is 6" below the top of the windscreen and 12" behind

so in all reality i am asking how quick you would need to go to 'beat' the rain that just skims the top of the windscreen before it hits your head.

Discuss

Depends on the rain, wind and vehicle. I've done 70mph on the dual carriage way and still got rain coming in, yet at other times 20mph was fast enough.

[Pints]

They tested this on Fifth Gear a few years ago. I don't remember the answer though. YouTube, anyone?

[Baryonyx]

30mph in my MX5 would see off most light rain. You just had to avoid stopping! 70mph on a dual carriageway kept me dry in a serious downpour!

[Big Rod]

I have T-Tops and can categorically say that anything under 40 MPH will see you wet. Real pisser when the automatic reaction of everyone else on the road is to slow down when there's a cloudburst!!

[MDT]

The Dude's at Mythbusters did this test a few years back.

http://mythbustersresults.com/car-vs-rain

[wombat172a]

In my experience:

• Over 30mph is dry.
• Over 75/80mph and you start suffering from spray problems, where the light stuff is brought back into the cabin
• Hail = bugger, and ouch

[Mars]

Caterham with windscreen (they don't all have one) is ~60mph.

[JonnyFive]

At a certain speed, the rain actually comes back through the car from behind.. So you can't go too quickly either.

[Greg_D]

i've just done the sums based on the measurements i gave and the speed is very slow (6mph).

heavy rain drop = 7.5m/s
travelling 0.1m down whilst the vehicle is travelling 0.3m forward results in

0.13sec=0.3m
0.4s=1m
1s=2.5m
60sec=150m
1hr=9000m
=C.6mph

being realistic, there is an aero effect 'pushing up' on the rain that would counteract the fact that(after looking at real life piccies) the top of most peoples heads when in a convertible are pretty much level with the trailing edge of the windscreen, so we will keep the 0.1m 'drop zone'
the piccies also show people sitting further back, let's say 0.5m.

that means, mathematically that you are looking at C.10mph for rain to just skim your bonce.

Surprisingly slow, isn't it!

[TommyBuoy]

Well, I'm not going to argue with the maths above, but overtaking lorries causes all sorts for problems...

[kambites]

In the Elise, it seems to be just over 30mph.

[garrykiller]

Baryonyx said:

30mph in my MX5 would see off most light rain. You just had to avoid stopping! 70mph on a dual carriageway kept me dry in a serious downpour!

+1

[bigdods]

IME

MX5 25mph
Saab 9-3 30mph but the passengers in the back will get wet whatever speed you do
TVR 30mph

above ~70 In all these cars I noticed I started to get some light spray entering the cabin (as exhibited by spots of water on the rear view mirror) I guess due to the wind curling back around at the higher speed.

All of the above assumes the side windows are up of course.

Its very weird to drive in a torrential downpour and not get wet. Best bit ever was ~40mph in the MX5 I hit a massive area of standing water I looked up as I went through and there was a solid sheet of water above me !

[SSBB]

Greg_D said:

i've just done the sums based on the measurements i gave and the speed is very slow (6mph).

heavy rain drop = 7.5m/s
travelling 0.1m down whilst the vehicle is travelling 0.3m forward results in

0.13sec=0.3m
0.4s=1m
1s=2.5m
60sec=150m
1hr=9000m
=C.6mph

being realistic, there is an aero effect 'pushing up' on the rain that would counteract the fact that(after looking at real life piccies) the top of most peoples heads when in a convertible are pretty much level with the trailing edge of the windscreen, so we will keep the 0.1m 'drop zone'
the piccies also show people sitting further back, let's say 0.5m.

that means, mathematically that you are looking at C.10mph for rain to just skim your bonce.

Surprisingly slow, isn't it!

Not sure I fully follow your maths, but if you are doing 0.1m / 7.5ms-1 that gives 0.013s, not 0.13s.