Making a more efficient, aerodynamic soapbox gravity race car

[orengomotors]

can you give me some advice about the body shape?
aerohead said to do a flat floor with a 2.5 degree diffuser.
will a naca 0015 be a good shape for the body?
thankyou

[freebeard]

Any advice I can give comes from listening to aerohead.

Originally Posted by Google

NACA airfoil - Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/NACA_airfoil
Wikipedia
The NACA 0015 airfoil is symmetrical, the 00 indicating that it has no camber. The 15 indicates that the airfoil has a 15% thickness to chord length ratio: it is 15% ...

So, no. The paradigm is a half body of revolution with a fineness ratio of 1.78-2.5:1. 15% is 6.666:1. Here is an example of The Template:



...with the open wheels and a rolled edge at the bottom:



The fourth wheel is a racing class requirement. Do your rules require four wheels?

[aerohead]

Originally Posted by orengomotors

can you give me some advice about the body shape?
aerohead said to do a flat floor with a 2.5 degree diffuser.
will a naca 0015 be a good shape for the body?
thankyou

If you're going to do an exposed-wheel car,an 'automotive' application of the NACA 0015 won't have any remarkable benefit for you.
The center airfoil section in the table below is the lowest drag.It's right in the pressure/friction bucket.

It's like the section at the bottom here.Very good flow.

Just turn the section on it's side like Soapbox Derby cars have done,then treat the top of the body as a wingtip.
Enclosing the suspension system inside struts as the Edison-2 X-Prize winner has done would be great.
Also,the wheel fairings,just as Edison-2.

[Xist]

If you rotate the vertical bar 45° and recline the driver, you can see how much your frontal area decreases, and the system becomes more aerodynamic. However, I wonder if that would still provide 10mm of clearance for the head in the case of a rollover:


However, can anyone else see a problem?

[Xist]

I did a quick search to see if anyone ever calculated the cD of a soapbox derby car. I just found this page, which talks about racers achieving 25-35 MPH.

Apparently, the United States does not have hills like Spain does!

[darcane]

Originally Posted by Xist

If you rotate the vertical bar 45° and recline the driver, you can see how much your frontal area decreases, and the system becomes more aerodynamic. However, I wonder if that would still provide 10mm of clearance for the head in the case of a rollover:


However, can anyone else see a problem?

Ignore the rollbar....

(it will be streamlined separately)

[Xist]

Originally Posted by darcane

Ignore the rollbar....

(it will be streamlined separately)

Will the driver be streamlined, too?


Have we gone full grasshopper? I feel like we have gone full grasshopper.

Also, I would like to see a tuft test.

[freebeard]

This is for a racing class, so it will have to pass tech inspection. You can't win if they don't let you start. Xist's redraw has the roll bar rotated 45°.



Someone charged with enforcing this could demand the main hoop be vertical, with the Alt 5 bracing. Also notice the arco de feurezo para los pies. There may be some advantage to raising that.

Originally Posted by aerohead

Sort of this with exposed wheels.

[Xist]

Originally Posted by freebeard

There's a minimum wheelbase but no maximum. A longer wheelbase would allow a recumbent position and better fineness ratio.

Just as long as you have the hoop vertical, maybe? Fine, have it vertical, with the driver reclined, as we have been discussing.

Am I the only one to take his image and try to show him what we are saying?

[aerohead]

Originally Posted by Xist

Just as long as you have the hoop vertical, maybe? Fine, have it vertical, with the driver reclined, as we have been discussing.

Am I the only one to take his image and try to show him what we are saying?

I think that Joan is committed to the rear driver layout which makes use of the AST problematic.It would really require a head first,supine driver orientation to allow the major thickness at 33% body length.
With the existing chassis,I think we're looking at a Granville Brother's Gee Bee R-2 fuselage to wrap the body/driver.
https://s-media-cache-ak0.pinimg.com...efb3379679.jpg