Making a more efficient, aerodynamic soapbox gravity race car

[orengomotors]

some sketches:


wich do you prefer?

[orengomotors]

Originally Posted by aerohead

We need to include your body with helmet in the equation,including a top view if possible.
The body width is very important as well as the final roll bar height,and whether or not you can recline even lower inside the chassis.

top and front view:

[aerohead]

Originally Posted by orengomotors

some sketches:


wich do you prefer?

*You want 'fish' proportions with the body,with the overall body width within the first 1/3rd of body length,so I'd lean towards the lower image.But drop the nose down to level with an airdam.(I have an image I'll try and get scanned into Photobucket today and post for you).
*The diffuser should begin as forward on the body as you can make it.You don't have an axle inside there,so you may have an advantage there.
*Looking from above,the nose should be a semi-circle.
*Looking from above,the headrest/rollbar should be wing-shaped,and as long as the rule book will allow.
*If you can't enclose the cockpit,do a half-bubble canopy as close to your head as you can get.Integrate it into the roll bar as best you can

[orengomotors]

Originally Posted by aerohead

*You want 'fish' proportions with the body,with the overall body width within the first 1/3rd of body length,so I'd lean towards the lower image.But drop the nose down to level with an airdam.(I have an image I'll try and get scanned into Photobucket today and post for you).
*The diffuser should begin as forward on the body as you can make it.You don't have an axle inside there,so you may have an advantage there.
*Looking from above,the nose should be a semi-circle.
*Looking from above,the headrest/rollbar should be wing-shaped,and as long as the rule book will allow.
*If you can't enclose the cockpit,do a half-bubble canopy as close to your head as you can get.Integrate it into the roll bar as best you can

Hi aerohead!

looking forward to seeing that image,
ok, so the bottom will be flat until the tube chasis ends, and from there it will be a diffuser, is that what you meant?
I will close the cockpit.

[orengomotors]

I want to start making the mold this week.
I need your advice:
- what would be better: make the mold as a separate piece or make the mold on the actual car?
-how would you make the mold?
-the shape can be drawn and sculpted by hand, or has to be precise and is better to cut it with the laser machine? in this case,How can I draw it this way with the software?

thank you,

[aerohead]

Originally Posted by orengomotors

Hi aerohead!

looking forward to seeing that image,
ok, so the bottom will be flat until the tube chasis ends, and from there it will be a diffuser, is that what you meant?
I will close the cockpit.

*Yes,perfect!
*And it's good news on the canopy.Here's some data which might help

*And here's the table for the different nose configurations.I'm using the #5 type nose on my truck.It's only 30-pounds of down force at 130-miles per hour,so not much induced drag.

[orengomotors]

Originally Posted by aerohead

*Yes,perfect!
*And it's good news on the canopy.Here's some data which might help

*And here's the table for the different nose configurations.I'm using the #5 type nose on my truck.It's only 30-pounds of down force at 130-miles per hour,so not much induced drag.

-what angle has to be the diffuser?
-I think that i will do the 3 o 2 figure canopy.
-sorry but i don't understand that:

*You want 'fish' proportions with the body,with the overall body width within the first 1/3rd of body length,so I'd lean towards the lower image.But drop the nose down to level with an airdam.

-so the nose has to be near ground?

like this image cd-14?

[aerohead]

Originally Posted by orengomotors

I want to start making the mold this week.
I need your advice:
- what would be better: make the mold as a separate piece or make the mold on the actual car?
-how would you make the mold?
-the shape can be drawn and sculpted by hand, or has to be precise and is better to cut it with the laser machine? in this case,How can I draw it this way with the software?

thank you,

*The official way is to make a plaster ( Portland cement-based) male mold off the car from which molds can be made,in which the actual body parts are created with wet layups of some sort of composite,or a pre-preg fiber/epoxy fabric (whatever fits your budget).Pre-preg usually requires a post cure in a vacuum autoclave.
*For a lower-cost alternative:
*put a protective barrier film on your car chassis
*fabricate your shell from cardboard and masking tape armature as best you can
*fiberglass directly over the cardboard armature (wet layups of Polyester resin with fiberglass cloth/mat)
*when the resin is cured,pry off the shell and throw it in a tank/pool of water to dissolve away the cardboard, leaving you the fiberglass shell.
I did my Honda CRX this way.
*

[aerohead]

Originally Posted by orengomotors

-what angle has to be the diffuser?
-I think that i will do the 3 o 2 figure canopy.
-sorry but i don't understand that:

-so the nose has to be near ground?

like this image cd-14?

out of time,will catch up Monday!

[freebeard]

Well, it will be a couple of days.

-sorry but i don't understand that:

The teardrop shape has it's widest section ahead of the midpoint. It's generally a 30/70 split. That means you can sort of bury the front suspension, but the body needs to taper before it gets to the rear wheels, which is a problem.

The cardboard armature works. You could also fill the frame with blocks of foam and carve the final shape out of it and leave the foam buried in the body. Big blocks of foam outside the frame with a thin fiberglass skin could make a crushable or ablative safety feature.

You need to decide how many sections the body will be in and how they will attach to the frame. These will determine the details of the form work. Also provisions for repair and maintenance.