# Building a Pinewood Derby car

1. Dec 27, 2008

### Cosmology101

I am building a Pinewood Derby car (Just for fun) and I want to make my car REALY areodynamic, but I dont really know the basics of areodynamics. Please help!

2. Dec 27, 2008

### Cosmology101

Re: Areodynamics

I know it has something to do with the wind and how something "cuts" through it, but how and why?

3. Dec 27, 2008

### Burningmace

Re: Areodynamics

Aerodynamics is about the flow of air around an object. Imagine you drop 50 golf balls onto a big sheet of paper. Most will hit the paper. If you turn that paper so that the balls fall towards the edge of the paper (instead of the front of it) it is likely that none will hit it.
It's all to do with momentum. Each particle of air and dust hitting your vehicle transfers momentum to it. As each particle has very little mass, and your car has a lot of mass, the effect of each particle is very very small. However, when you have millions upon millions of particles hitting your car every second, the effect becomes very noticeable. The fewer particles that hit your car, the better. If you make the car very flat it will dramatically cut down on the frontal surface area, and therefore the number of particles of air that hit your car every second.
The other thing you need to remember is that air flows like water. Turn on a tap full blast and put a spoon underneath it so the face of the spoon is being hit by the water. Then rotate it 90 degrees so that the edge of the spoon is being hit by the water. Notice how much easier it is to hold the spoon in place? That's because the water just flows around the curve of the spoon instead of hitting it face on. If you make your car pointy and sharp at the front like the end of a bullet, it passes through the air much more easily.

4. Dec 27, 2008

### Phrak

Last edited by a moderator: Apr 24, 2017
5. Dec 28, 2008

### Ranger Mike

Re: Areodynamics

i spent a lot of time on this one..as Waddel Wilson said ( famous Nascar crew chief)

i recommend yo uget a shop vacuum cleaner, the kind that blows as well as sucks, build your self a cardboard box big enuff to put the pinewood entry into, if possible use as much clear plastic, plexiglass or even window glass for the top. fabricate an opening at one end for the vacuum hose ( in blow mode) leave the exit end of the box open..go get some yarn ( the kind grand mother used to knit with) and duct tape tufts (about an inch long piece of yarn) all ovet the car.. turn on the vac and you now have your wind tunnel..
a stiff wire about two feet long with a piece of yarn attached will permit you to see the air action in front and in back of the car..
note dead zone in back of the car..this is drag...the less dead space and drag , the better aero
good luck

6. Dec 28, 2008

### PhanthomJay

Re: Areodynamics

You might find some additional help or pointers at the Aptera 2 website www.aptera.com , one of the most aerodynamically efficient proposed autos (I guess technically it's a motorcycle) in the world.

7. Dec 31, 2008