Last year I just took a table saw and cut the block in about 2/3 and 1/3 then had my son play with the belt sander and another sander to smooth and shape the body.
This year I want to do a little more. I want to make the car shaped like a tornado on its side. I have some lines drawn.. I just need to get my son to use my dremmel to help cut some sections off and we will need the belt sander again to get that curve.
Anyway my question is about putting a hole through the car from the front to back. It would help make the car lighter but would it hurt the aerodynamics much? I want to break out the drill press to wow my son into the garage to want to help. Plus it will look better and more like a tornado if it is hallowed out.
Thoughts?
Car body question.
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Stan Pope
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Re: Car body question.
A way to evaluate the design is to draw the view as seen from the front of the car. This view shows an area that is called the "frontal cross section." Where you see wood is where the car will have to move air out of the way. That area is one factor in the aerodynamic drag equation. If the area is doubled, drag is doubled.
The second factor in the drag equation is the shape as viewed from the side and top. That shape determines the "drag coefficient," the second factor in the drag equation. The drag coefficient is less intuitive, but you can find the drag coefficient for various shapes posted both on DT and elsewhere on the net. IIRC, they range from 0.04 for an airfoil to more than 1.0 for cross sections which are flat on both front and back.
Aerodynamic drag is the product of the drag coefficient and the frontal cross section.
That said, aerodynamic drag is one of the less important factors in car design, but it will establish a top limit for the performance of your car. That is to say, as you improve all other aspects of your car, ultimately aerodynamic drag will probably separate your car from the winner.
The second factor in the drag equation is the shape as viewed from the side and top. That shape determines the "drag coefficient," the second factor in the drag equation. The drag coefficient is less intuitive, but you can find the drag coefficient for various shapes posted both on DT and elsewhere on the net. IIRC, they range from 0.04 for an airfoil to more than 1.0 for cross sections which are flat on both front and back.
Aerodynamic drag is the product of the drag coefficient and the frontal cross section.
That said, aerodynamic drag is one of the less important factors in car design, but it will establish a top limit for the performance of your car. That is to say, as you improve all other aspects of your car, ultimately aerodynamic drag will probably separate your car from the winner.
Stan
"If it's not for the boys, it's for the birds!"
"If it's not for the boys, it's for the birds!"
Re: Car body question.
We did wind tunnel testing in fall of 2010.
All I can say, is that slick/ smooth, and flat and less is best.
The lower the air stream, the less effect on the car.
You're design would capture allof of air and likely be very hard to make a super fast car with. But could make it fast, but not winning at our council level.
All I can say, is that slick/ smooth, and flat and less is best.
The lower the air stream, the less effect on the car.
You're design would capture allof of air and likely be very hard to make a super fast car with. But could make it fast, but not winning at our council level.
Re: Car body question.
Tornado car on it's side... Sporty & Stan are right, it's not the most aerodynamic profile.
Hole through the car? Tried it this year on the drill press.
If you have a series of Forstner bits, it would be 'fairly easy' to drill from the rear area of the car towards and through the front with the smallets bit (1/4"?), and then do a little bit less farther with a slightly larger bit. Kind of making a series of steps in the inside of the tornado.
It's a fascinating idea... maybe cut the tornado in half lengthwise, put 'debris' around the outside and in side for weights?
It would be fun to try... not sure if it could end up real fast though...
Good luck!
Hole through the car? Tried it this year on the drill press.
If you have a series of Forstner bits, it would be 'fairly easy' to drill from the rear area of the car towards and through the front with the smallets bit (1/4"?), and then do a little bit less farther with a slightly larger bit. Kind of making a series of steps in the inside of the tornado.
It's a fascinating idea... maybe cut the tornado in half lengthwise, put 'debris' around the outside and in side for weights?
It would be fun to try... not sure if it could end up real fast though...
Good luck!
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