Tuft testing: how to

[nwbabybronco]

I'd like to gather how to info here for tuft testing.

• Tuft testing is an easy way to watch the air flow around your car. I have been using it to test prototype parts for my truck.
• I used duct tape and cheap yarn from Fred Meyer, which seems to do the trick.
• Autospeed's advice to keep the strands far enough apart not to touch each other worked well.
• 4-6" long seems to work well
• To be continued...

Question: How much wiggle is expected? The ends of my tufts had a 1-2" oscillation, but they generally lined up nicely. Is that too much turbulence or I have I got it right?

[Cd]

I found that actual yarn has a tendency to stick to itself. I tested both yarn and string side by side and the yarn would twirl around and stick to itself or the yarn above it, ruining the test.

As I have mentioned in other places on this forum, it seems that an easy way to test hard to reach areas such as inside wheelwells and under bumpers would be to purchase a small web cam and run a wire to a laptop within the car.
You could then save a video of the test. The best thing about this method would be that you do not need a chase car.

Any longer than 3" and the yarn seems to flutter due to the turbulence of the yarn itself.
Also it might be a good idea to plan out the layout of the yarn since you don't want the turbulence of a fluttering piece of yarn distorting an area that is smooth.

Edit : I meant any longer than three inches on the length.

[nwbabybronco]

So if I cut off the part that was fluttering I may get clearer results? I put all the pieces far enough apart not to stick to other pieces.

[millenniumtree]

Sailors sometimes use audio tape instead of yarn for "telltales" (to see if the sail is sheeted in correctly).
Might be worth a try.

[Cd]

Originally Posted by millenniumtree

Sailors sometimes use audio tape instead of yarn for "telltales" (to see if the sail is sheeted in correctly).
Might be worth a try.

That seems like a really clever idea. Thank you for suggesting that - I never even thought of that.

Since the audio tape lies flush with the curve of the body, it would seem like there would be less far less turbulence caused by it versus yarn.

[Cd]

Originally Posted by nwbabybronco

So if I cut off the part that was fluttering I may get clearer results? I put all the pieces far enough apart not to stick to other pieces.

It seemed to work for me .
Better to ask the experts on the matter.
I also edited the previous post. Any longer than three inches and I started to see fluttering.