More streamlined than a barn door?

I'm just curious about automobile aerodynamics and, as the owner of a chopped model A sedan, wondering if the aerodynamics are changed if I prop open the windshield. Better or worse aerodynamically? Wonder what a Model A's number would be. Anybody know? I imagine it's pretty bad.
Recently I read that a Humber H2 has a drag coefficient of .52, a Dodge charger .33, and a 1986 Ferrari Testarosa, .36, a Prius .26.
Interestingly, a 1935 Tatra, which had a big flat pretty vertical windshield had a drag coef. of only .212! (source:Hemmings Sports & Exotic Car Mag, Aug.2009)

 

I remember reading an article about aerodynamics in some mag. They took a brick and shaped one end like a bullet. When they tested it in the wind tunnel, the brick actually had much better aerodynamic properties when they turned it BACKWARDS, so the bullet shaped end was in the back. I don't get it...but then again, I don't drive a brick.

 

A good place to start is this, as you double wind speed you quadruple the resistance ( double the flow resistance, double the pressure).

 

Think of an airplane wing . Big end is forward . As far as the model a goes , it's hard to say; wind does some strange things . The one that cracks me up is people driving pickup trucks with the tailgate down to get better mileage . That one has been tested over and over and they're more aerodynamic with the tailgate closed !

 

Your windshield is actually a dead zone. If you look at a thermal image of a car in a wind tunnel, you'd see that hardly any wind is 'pressing' against it. Weird, but true.

 

Yep the tailgate thing and those damn range and yellow mesh things for a tailgate , these dumb asses really think they are saving gas . The only ones making out are the people selling this shit !
Well if the windshield is open a little , then the air is coming in and has to go out somewhere but I really don't think it really makes a difference . Might be a little better due to the air not hitting something flat nd just flowing straight through !

 

What if you drive a 55 Olds I know a 57 Chev had enough space in front of the radiator in the winter you could keep a case of your favorite cold Remember those days, Aerodynamics ??? just add more gas & oil as the old saying goes G.G.A No body rides for free

 

From my years building and racing streamliners at Bonneville, I can tell you that total frontal area is more important than CD (coefficient of drag) There was a couple guys who mounted '27 roadster bodies backwards back in the 50's thinking the rounded deck was more aerodynamic the the flat radiator.

The photo above in Hail Satin's avatar is a common racers attempt to lessen the CD of an early body. While it does help the CD minimally, the body will still have the same amount of frontal area, as measured in square inches, with or without the pointed nose.

 

Hahaha. That just made me laugh. The brick part.

 

I found out that in the rain, my Model A windshield gets wet but after that there is virtually no rain on the glass. I've been driving it for 12 or 13 years now with no windshield wiper.
Dont need one

 

So if Hail Satan's streamliner had a perfectly flat front, but with the same amount of frontal area, it would be just as fast as with a pointed front?
And if the brick theory is correct, as I have no doubt it is, how come lakes modifieds, which are built for speed, don't usually have boat tails?
Just wondering.

 

I have made many dragstrip passes with the windshield open and closed, and it makes no diffrence whatsoever.



BUT. There are so many variables in a 1/4 mile pass that it is really hard to tell...

To make up for any aerodynamic losses, you should just put a bigger engine in it....

-Abone.

 

if you are concerned about aerodynamics why in hell did you by a model A?I'm not finding fault with A's I'm working on one too!

 

A raindrop falling through the air will give the perfect aerodynamic shape. Big in the front (bottom) tapering to nothing at the back (top). The pointy noses etc. are a result of having to package things in specific places and needing air for specific purposes - engine cooling, engine intake, brake cooling.

Formula 1 cars used to spend countess hours in the wind tunnel perfecting the aerodynamics. All sorts of little add ons - barge boards, winglets, wing ends, diffuser. Then someone crashes int o the car, breaks off the barge board, and the car gets faster.

Look at some of the LeMans racers back when the Mulsanne straight was 5 miles long and the fast cars could touch 240 mph. The Porsches all had long tails.

 

The Chrysler Airflow was based on the observation that a Chrysler sedan of the early 30's flowed air MUCH better when turned backwards. I think they're kinda pretty.

 

The long tail is important as it lets the air that's going around the body rejoin itself without turbulence. Cars with chopped off rears get "pulled back" by the air turbulence caused by the airflows crashing into each other.

Or something like that.

 

Quite a few years ago, the SCCA had a mini-truck road racing class (sorry NASCAR fans, they had them first!). Anyway, the story goes the Archer Bros tested their trucks and found that the tail gate position made no difference. It was the nose / windshield / roof angle that mattered. So give your ride a little more front rake to improve mileage! And roll up the windows, of course, if you have a top. Gary

 

Years ago I had a buddy who drag raced a hoopty muscle car and he ductaped all of the body seams for the fun of it. Hood to grill, hood to fender, fender to door etc etc.... He gaines 2/10 of a second on his 12 second car. Took the tape off and gained the 2/10's back.

For what its worth...

 

Hans Ledwinka was ahead of his time, the type 77 was a seventeen foot long tear drop with a central tail fin, windscreen large but is not vertical, 46 degrees of tilt, which is steeper than most modern 'sportscars'.
Independent springing on all four corners and an OHV V8.

Poster child for low CD odd to say is GM's EV1.

Reducing frontal area makes for bigger gains than minor tweaks of CD, so a serious roof chop, section and channel is all going the right way.

 

Wasn't it Smokey Yunick that said aerodynamics are for people who couldn't build motors?

 

Wasn't it also Smokey who built a Chevelle that was smaller, ie less frontal area? He also had a car with holes in the tops of the fenders to allow the air being pushed up by the tires to escape, in theory allowing the car to ride lower.
Even the man who could build pretty damn good motors was thinking about air flow.

 

F1 aerodynamics are all about downforce. In terms of aerodynamic drag the cars are probably as bad as a stock Model A. Of course they go faster when the add-ons break off - until they inexplicably run off the track!

 

Just a thought, I believe that drag increases as it passes over an object, so it is not necessarily the front that is so important, however, hold your hand out the window and blade it. You'll see that it takes far less energy to hold it when it is bladed as opposed to holding the fist open. But, stability is far more sensitative when it is bladed. I would guess that the front is just as important as the other lines on the vehicle.

 

1950 SAAB 92 CD .30 or less, they built aircraft, too.

 

I was traveling down the highway at 65 mph in my 29 model A with a 2 inch chopped top ,stock visor and a fluffy piece of cotton from a cotton wood tree came up and started to swirl up and down in a circular motion front of my windshield.It kept doing it for about 3 or 4 minutes.I was amazed how the air must of been flowing over the visor creating a vortex.Wife wasn't impressed but I was.LOL

 

Heres my barn door,we just keep adding motor to make it quicker,and ballast to give some traction and stability.I will be adding a spoiler to the back of the body inline with the roof to create some downforce,hope to have some hoodsides on it for speedweek,going to try and get a few more miles per hour out of it

 

One of the worse things is a flat back on a vehicle. Like Semi trucks for example. The air passing around and over the truck creates a vacuum behind the trailer thus pulling the truck backwards. Kind of like when you open your hand up and shove it through water. There is a small spot behind your hand where there is no water. What me and my friends would do in his Volkswagon Bug was to get right up beind a truck like almost touching it and shut the car off. The vacuum behind the trailer would just pull his car along.

 

Most modern cars have moderate positive pressure at the windshield base (that's where the fresh air to the heater comes from); above that the air is deflected from the nose and passes over it.

 

Always thought it was Enzo Ferrari.....?