Aerodynamic drag and why a coupe is better

[Pbondar]

Recent conversations about various owners fuel consumptions got me thinking about aerodynamic drag..as I'm sure you often think about it..

I was discussing some performance profiles in aircraft and recollect that my kit plane I built in the 1990's would do 155 knots (about 178 mph) on a Rotax 921 engine rated at 100 bhp..

Obviously a whole bunch of aerodynamic related factors figure in that equation..

I then pondered about various Z4 fuel consumption figures..about 95%+ of the time I drive with the roof down..whereas..I ususally see most other Z4s with their roofs up!

So I wonder how much extra fuel I'm burning compared to those top up guys and the coupes?

Interesting article here http://sersol.weebly.com/workshop/conve ... rodynamics# about some modelling top up and down and the effect of a rear spoiler on affairs..and also the wind deflector effect..


Since drag force goes up with the square of the speed at 70mph I must be burning quite a bit more fuel?

Enjoy!

[enuff_zed]

Pbondar, you are missing the one vital part though.

Life is a drag with the roof up

[tintoverano]

Life is a drag with the roof up

[Pbondar]

Pbondar, you are missing the one vital part though.

Life is a drag with the roof up

Thank you for that detailed, reflective analysis!

[Chris_D]

Don't even get started on bike-racks!

I'd be interested to see the CFD model of adding my bikerack and sometimes 2 bikes on the back of the zed, top down averaging 100kmh (new Dutch speed limit. s'okay).
I swear I can feel the drag sometimes, especially in a headwind.
What a drag.

IMG_20190920_142122.jpg (205.74 KiB) Viewed 557 times

[enuff_zed]

Pbondar, you are missing the one vital part though.

Life is a drag with the roof up

Thank you for that detailed, reflective analysis!

My pleasure.
Can't just let you get away with slack fact-finding.

[flybobbie]

3 and 4 looks a bit draughty in the back seats.
What kit plane did you get 155kts on 100hp, Pulsar by any chance.

I'm still waiting to try out a Glasair in the hanger.

[Pbondar]

3 and 4 looks a bit draughty in the back seats.
What kit plane did you get 155kts on 100hp, Pulsar by any chance.

I'm still waiting to try out a Glasair in the hanger.

Dyn Aero Banbi MCR01

[Chris_D]

That reg no.

[Pbondar]

That reg no.

I had to formally write to the UK CAA explaining why it was OK, they refused to grant my original application..

I had to explain that Toad of Toad Hall and Pooh Bear where my role models..

Notice the yellow theme there too?

[enuff_zed]

Hell, it's so small it looks like you have spats on your feet!

[Pbondar]

Hell, it's so small it looks like you have spats on your feet!

That's why it was so speedy..0-10,000 ft in 6min 45 secs..not bad for a kit plane..bloody vicous handling..snap roll on stall..roll rate greater than 90 degrees per sec..

The ex Empire Test School check pilot loved it!

Just like a little jet fighter he mused..couldn't get the buggar out of it!

[buzyg]

Pbondar, you are missing the one vital part though.

Life is a drag with the roof up

Spot on, stuff the techno babble.

[buzyg]

Dyn Aero Banbi MCR01

I have shoes bigger than that.

Looks and sounds like amazing fun.

Enjoy play time in your very own PooP.

Oh and if you get the chance, put the roof down.

[MACK]

Getting back on top kinda.
I was always told using the air con had a detrimental effect on fuel economy. Obviously driving top down isn't as efficient as top up, but I do wonder how top down and air con off compares with top up and air con on.