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I was just looking at this site:

http://www.cptips.com/energy.htm

It is a cycling site, but since the IMAS is all about bikes, it's a perfect fit.

They mention that race drivers wax their cars to keep wind resistance lower. I wonder if anyone has ever noticed differences from wax on their Insights?

Interesting reading and here is their formula for wind resistance:

BEGIN QUOTE
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Let's review the factors in air resistance again:

Air resistance =.5*(rho/g)*Area*Cd*V^2

rho=air density
g=gravity
area= frontal area of the rider and bike (scrunch down, less area, faster ride)
Cd=coefficient of friction (smoother rider and helmet, and less protrusions from the bike, the lower the Cd. This also refers to the shape of the frame, wheels, etc. A tube, spoke, fork shaped like a wing has a lower Cd than round spokes, tubes,or forks.)
V=air speed - which is squared (ie going from V=7mph to 21mph is a 3x increase in speed which is then squared and the force required is now 9
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END QUOTE
 

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That page is a good summary of bike "physics", but I couldn't find anything about waxing in there.... I appreciate how they point out that the rotating pieces are much more important than the stationary frame in the overall weight saving scheme of things. People look at me funny when I give the advice to save their dough on the astronaut frame--get a good one but it doesn't need to cost 1000 bucks--and spend the money on the wheels, and drivetrain for that very reason. Too many posers.... but I digress..

I may be wrong, but I can't see how a coat of wax will help the aerodynamics any, other than you have to wash the crud off before you wax it. And you have to factor in all that extra energy spent in rubbing and buffing :wink:
 

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rotating pieces are much more important than the stationary frame in the overall weight saving scheme
True...I have seen estimates that unsprung rotating mass is eqivalent to anywhere from 2 to 4 times its mass in suspended (sprung) weight. Having switched my CRX from 18 lb stock wheels to 11.5 lb aftermarket wheels, I can say the difference is noticeable.

I have also seen stories about the waxing...I don't know about it's true effect, though. In theory, there should be a stationary "boundry layer" of air right next to the surface (I was told this is how moving fan blades still accumulate dust) so no (or very minimal) moving air would actually contact the wax surface.

I have always told friends (who still disbelieve me) that "black cars go faster" The idea is that black absorbs visible light and re-radiates it as heat. This infra-red energy warms the air immediately surrounding the car (which you can actually see if you look across the top or hood of a car sitting in a parking lot!) and we all know that hot air is thinner than cold air (and since someone will probably catch me on this, I am talking about thinner based on static volume and pressure) So when you put all that together, the black car is traveling through a slightly hotter (thinner) pocket of air...hence less air resistance!
 

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Discussion Starter #4
I must have read the waxing in a different article. It was claiming that for cars used in racing they waxed them to reduce drag. I don't recall the correct link.
 

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Here are my observations from a pilots point of view. After waxing my Ercoupe, a 110 mph airplane, I noticed no speed increase. After waxing the Citation, a 400+ mph jet, I noticed no speed increase. After waxing My SeaBee, a 105 mph large, heavy, low power, dragy, small amphibian, I noticed no speed increase but it did climb better. The prop on the Ercoupe was rough,( several coats of paint, rock nicks etc). I stripped, smoothed, and repainted it. The speed had increased 6 mph. Some air racers rough up the leading edges of there airplane so that there will be a better laminer flow of air over the airframe. They claim it makes them go faster.
Louis
 

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1. There should be no "g" in that formula.

2. Roughening the leading edge will trip the flow over the wing and cause it to become turbulent. This is desired to prevent stalling, as it will take a higher angle of attack for a turbulent airflow to separate.
 

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Vortex generators are used like stated above. This is why spheres have much less drag when they are rough (golf balls). I've done research on this myself and have proved the roughness principles. There's even Lexus who puts roughness on the bottom underbody of their cars which improves airflow. I'm not sure the effects of roughness on cars, though but I do know sharks body's are rough which helps them glide through the water.
 

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Waxing the hull of a boat helps quite a bit. It brought the speed of my fathers boat up from 43 to 47 (speedometer pinned). Hmmmm, don't recall seeing many rough torpedoes or submarines and the body of a Lancair VI 365 MPH homebuilt aircraft is definately smooth. As for an
Insight.......shiny paint definately looks slicker. Perhaps roughness under the car helps.
 

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Vortex generators are used like stated above. This is why spheres have much less drag when they are rough (golf balls). I've done research on this myself and have proved the roughness principles.
From what I have seen, there is some benefit to a rough surface. So, who will be the first to take a ball-peen hammer to their Insight? Anyone? A bunch of uniform dimples across car may just wring out a few more MPG :lol:

Anyone with a hail damaged Insight that has seen a mileage increase?
 

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[quote="Anyone with a hail damaged Insight that has seen a mileage increase?[/quote]

lol...ouch
 

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Two things
1. vortex generators DON'T INCREASE max speed but they do LOWER stall speed.
2.with a fresh wax job on the bottom of the SeaBee it will take off from the water somewhat quicker and it has less tendency to pitch nose down on a high speed step taxi (say 60 mph on the water).
Louis
 

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"Riblets" reduce drag in the water

I was a rower in college, and remember discussions of a 3M product which could be applied to the surface of a racing shell to reduce drag and increase speed. It was a plastic film with little wavy lines in it. The US team used it in the '84 Olympics.

A little googling, and I found a reference to NASA's involvement in the 1987 "Stars and Stripes" bid for the America's Cup.

http://oea.larc.nasa.gov/PAIS/Riblets.html

MF
 

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Turbulent flows exert more shear drag, so they are undesirable unless you are trying to prevent flow separation and the associated pressure drag. Airflow over the Insight body should remain unseparated until it reaches the Kamm back. Making the flow more turbulent will not change the separation point at the back of the Insight, and thus it will only be undesirable. So, the Insight is designed to keep the flow over the car as laminar as possible.
 

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Tim Maddux said:
Turbulent flows exert more shear drag, so they are undesirable unless you are trying to prevent flow separation and the associated pressure drag. Airflow over the Insight body should remain unseparated until it reaches the Kamm back. Making the flow more turbulent will not change the separation point at the back of the Insight, and thus it will only be undesirable. So, the Insight is designed to keep the flow over the car as laminar as possible.
Thank you! Since the insight has little form (pressure) drag, roughening the surface to increase the shear drag will just increase the total drag on the car.

Off topic, I remember that new swimsuits for Olympic swimmers have roughness on them that is supposed to make the swimmer faster.
 

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I believe the swimsuit material creates a layer of air (if my memory isn't going). :)
 

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b1shmu63 said:
I believe the swimsuit material creates a layer of air
The suits have little features on their surface that are designed to reduce drag. For example, "riblets" are small longitudinal grooves like those found on sharks (~0.1mm wide). The features are designed to prevent the turbulence from developing or from mixing. It's the churning and mixing of the turbulent flow that makes it exert greater shear forces than a laminar flow.

This isn't related to separation... for example it's been studied in flows over flat surfaces. You could do something like this on a car, but think of the car you'd have to take with the surface and the tuning required, and the cost.
 

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All this roughness talk has certainly settled my concerns over the multiple scratches that seem to be accumulating on the front of my insight.
 
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