frontal area questions

[johnneilson]

Tony,
I just received my latest issue of "Bernoulli" last week, 2 1/2 years after my first issue. Now that The Automotive Book Store in Burbank is closed you can probably only get it by subscription.

Rex

Rex,

I believe the store just moved down the street a couple blocks. They had a nice little "Grand re-opening" about 2 months ago.

John

[interested bystander]

Just checked Autobooks Aerobooks website . Looks like they're still in the same location as last time I was there. (Date on home page was today's.)

Address : 2900 W Magnolia , Burbank Ca.  Phone 818 8450707

If you get there today (Sat) around noon you'll likely see Jay Leno hanging out.

[tortoise]

Fa is a much easier concept for the non aero professional to understand and how affect its influence (make is smaller).
Fa does have an effect...maybe not as much as separated flow...but...ya know.

Or, you could conceptualize your design around the goal of lowering the surface area to a minimum while avoiding separation. Surface area may be harder to calculate, but minimizing it is pretty straightforward even if you don't figure out exactly what it is.

The necked down fuselages in Costella's machines don't lower the frontal area, but they do drastically reduce the skin surface, as well as moving the center of pressure rearward.

[Jonny Hotnuts]

Woody ... interesting perspective ... frontal area / coefficient of drag / different design arguments and then an open wheel roadster goes 304 ...

Joe

With enough horsepower anything is possible.

Unfortunately this also is a reason that just because a streamliner went fast, doesn't automatically mean it was the best....or....even a GOOD design.

Consider factors like handling, visibility or what COULD of been (*speed).

It would be very interesting to see a group of dissimilar designs with the same power. I will bet peoples opinions would be different by the end of the test.

~JH

[joea]

Joe ..."""interesting perspective ... frontal area / coefficient of drag / different design arguments and then an open wheel roadster goes 304 ... """

now take that hp from roadster and speed and you get the drag number...

take the same from something streamlined such as any of the 300 to 400 mph streamliners...

then substitute back in the roadster hp....and see what mph pops up......

[SPARKY]

I wonder how much having the rear tire in the middle of the nice curved shape like Ack's as opposed to on each side  like a lakester would affect the seperation and how far out one would have to move the tires to lessen the tires influnce 

[A2WindTunnel]

I think you guys need to put this in two categories.  Bluff bodied and streamliners.  A car/motorcycle (bluff bodied) is dominated by Invicid flow (pressure drag) and viscid flow (skin friction) accounts for very small percent of the overall drag (less than 10%).  A streamliner will be affected by a much higher percentage of skin friction than a car, and wetted area is something to take into account.  There might be some confusion about the two styles of cars and looking at FA or wetted area and who is right.  

-A production based car is not a streamliner and vise versa so they might need to be approached 2 different ways.  Also a production car is almost impossible to make smaller physically (see attached image).  You’re kinda stuck with what you got so you can really only improve drag by improving how the air gets around it.  Where a streamliner you can design how ever big or small you can.

I don’t know if that helps or not?  A roadster is not the Ack or #7 and it seems like people are dumping all cars in the same category in this post and then there is confusion about who is right.  My 2ct.

[jl222]

  Lots of hp doesn't help if you can't hook it up, thats why two streamliners that I know of that are being built will have wings.

                   JL222

[Rex Schimmer]

I think A2 has hit it on the head. Streamliners and roadsters, or Cameros in John's case, are completely different from an aero analysis stand point. A properly designed streamliner should have very little "pressure drag" and that would only be from the area of the boundary layer as it thickens to the back of the body and then recombines at the rear of the body. The rest of the drag for a streamliner would then be skin friction which should be the dominate drag on a streamliner. On a roadster or sedan, which is, as A2 has said, a bluff body the aero calculations depend on the frontal area and the Cd. The long runs of flat sides that many of the present streamliners is not as efficient at maintainling attached flow as the rounded shape that you see in Robs design.

Rex

[John Burk]

Low drag wings need to be long and slender , tapered , accurate , well mounted and at least 2 feet above the ground . Good downforce with slenderness requires an aggressive profile . NACA 63-021 (21% thickness) has good performance up to 12 deg and low drag . A long slender wing needs to be strong . The simplest wing is cnc milled aluminum . The 63-021 is symmetrical so only one setup is necessary . Anybody interested in making low drag wings can contact me , joyseydevil@comcast.net .

John Burk