Anyone using Flow-Viz paint?

[manta22]

We analyzed the airflow over Bob's McLaren M8C in a somewhat similar way. After a Can-Am race the car would be covered with oil & rubber streaks extending from the nose on back. By looking at the streak pattern, we saw that the airflow wasn't all continuing straight back over the front fenders but a significant portion was spilling over the sides. This reduced front down force and also reduced the air flow over the rear wing.

To keep the air flowing straight back, I fabricated a pair of "air dams" out of scrap aluminum by hammering them against the paddock garage concrete floor and pop riveted one on the outside of each fender. Subsequent airflow patterns showed that this channeled the flow where it was needed. In the army, we called this "field expediency" 

Regards, Neil  Tucson, AZ

[Tman]

We analyzed the airflow over Bob's McLaren M8C in a somewhat similar way. After a Can-Am race the car would be covered with oil & rubber streaks extending from the nose on back. By looking at the streak pattern, we saw that the airflow wasn't all continuing straight back over the front fenders but a significant portion was spilling over the sides. This reduced front down force and also reduced the air flow over the rear wing.

To keep the air flowing straight back, I fabricated a pair of "air dams" out of scrap aluminum by hammering them against the paddock garage concrete floor and pop riveted one on the outside of each fender. Subsequent airflow patterns showed that this channeled the flow where it was needed. In the army, we called this "field expediency" 

Regards, Neil  Tucson, AZ

Good save.

[Bratfink]

At work we have a number of different techniques ranging from Laser Doppler wizardry or Air Bubbles (really!!!) to Kiddy paint and oil.

The F1 technique mentioned here is called Fluorescein http://en.wikipedia.org/wiki/Fluorescein You can buy it but I doubt it would work that well an the salt since the sun is way too bright.

some of you might have seen me out there "oil dotting" a couple of different cars. The technique I use is childs powder paint (cheap) and 3 in 1 oil. I grind it all together in a mortar and pestle and then use large cake batter style plunger/needles to apply small dots. Because of the heat out there you have to experiment with the mixture a bit but it works pretty well. The real trick is to get to the car and photograph the results as soon as possible after it gets off the track otherwise it runs off and you can't really figure out what happened when the "wind was on".

If anyone wants a hands on lesson I'll be only too happy to help out on the salt, pm me and we can set up a meet.

[manta22]

I think I've mentioned this before but the Porsche 917 high speed handling problems were solved at a practice session at Zeltweg by John Horsman's noticing that the pattern of smashed gnats on the car showed that there was no airflow over the tail; some sheet aluminum & pop rivets and the car went out again for another practice lap. The driver pulled into the pit and announced "Now it is a real racing car!" Thus, the 917K was born.

Careful observation of the pattern of dirt, oil streaks, rubber dust, or even bugs can tell you a lot about what is happening to the airflow.

Regards, Neil  Tucson, AZ