[Xist]

Originally Posted by Massimo Tava

You could always buy some Flow-vis (short for Flow Visualisation) is a paint-like substance used for aerodynamic testing during practice sessions in Formula One. A high-contrast luminous colour, it is applied to an area of the car – e.g. one side of the front wing.

Originally Posted by Gungan Works

Flow vis paint is just Mineral oil and fluorescent dye.

Okay, but what do you do with it?

Originally Posted by Leo Jackouski

You could use a pressure sensor to measure your air pressure in the tail section. Then pressure drag is equal to this multiplied by the area of your truncated cross section.

Originally Posted by drippingwax

When I was in Afghanistan many semis had cloth over their grills.
What about a dust filter with vertical pleats?

Originally Posted by Leo Jackouski

A good starting point is 13° on the top, maybe the same 13° on the sides, and 7° on the bottom. Take it down to at least 30% of the maximum cross section. But the more the better. Then having a really sharp, crisp, trailing edge is super important to get clean flow separation.

This guy again?!

Originally Posted by Excalibur John Deere

You’re a roof rack on top of the roof is like fins they are actually a bonus the way you have them now. Your boattail needs to also have that same affect upper and lower Slope. And don’t forget to give Wire mesh a try

I don't have any idea what he thinks he is saying.

Someone mentioned variance in accelerating and I remembered people here adding hand throttles, then wondered about adding a servo or something so that it accelerates up to speed the same way every time, then you can use cruise control.

You would just need an immediate way to deactivate it.

Originally Posted by olsonspeed

Reel to reel recording tape is now the preferred material for tuff tests.

Originally Posted by Alan John

I've seen people use choroplast (plastic cardboard) to smooth out the underside of their cars. Lots of info on Ecomodder

Get our name out of your mouth! The last thing we need over here is activity!

Originally Posted by Samuel Hopely

Filling in the rear of the tail surely hurt you a bit. The plate cover is a large surface for the low pressure wake to act upon. Remember that it's pressure region's acting on a moving body itself that contribute to drag! Having the tail hollow the first time around meant that realistically only the edges of the foam were subject to wake forces, with the gradient increasing to probably around atmospheric when you reach the body. With such a better optimized curve on the tail, you had way higher velocities at the bluff cutoff, so every square cm had an even more severe pressure drop to contend with vs the former. If you cant get a point (which you probably can't achieve efficiently anyways) find a way to leave her hollow!

In reply:

Originally Posted by Lumber Jack

Well, the old design created a large cavity, and there is no way to tell what the internal cavity pressure was without some further analysis. Sometimes it can result in higher pressure when you create desirable recirculation inside the cavity, but in this case I suspect recirculation was minimal. So it was probably transmitting the wake recovery pressure, or a lower pressure, up against the hatchback and bumper inside the cavity. Which means not much of a reduction in base drag. The new closed boattail shape is probably better.

Excalibur John Deere pointed out that you get better fuel economy at slower speeds.

Originally Posted by Mijc Osis

Its a pity that an overhang like that on the back of a vehicle is illegal. You are only allowed to overhang by so much of the wheelbase.

This says that is for cargo, but I am sure that is open to interpretation.

Originally Posted by turbogto

First

I finished reading the comments?!

Many comments recommended installing a separate gas tank and weighing it before and after.

How did they do that on the Centurion?