Physics of Half-Turn in Straps?

its aerodynamics, without the twist the air blows straight across the strap creating wind turbulence which will alternately lift and lower the strap, when this picks up speed you have the vibrating strap. the twist breaks up the straight across force of the wind.

the same sort of thing that causes a airplane to lift off the ground , the plane wings are shaped to do this , but a strap with its flat design will vibrate.

 

It's called Bernoulli's Principle. I learned that back in my ATC days.

Scroll to the bottom.

http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

 

I find it worse when I strap over something in my pickup. I simply MUST put a half or even whole twist. Generally not so much on the trailer, but then I REALLY tighten those up!

 

The physics describing how an airplane (more specificaly: airfoil) creates lift is Bernouli's principle. I don't know for sure if this is the reason for the strap vibration or not. I would think not, because that would need an arc shape across the strap which would need to reverse shape to an arc in the opposite direction in a rapid manner.

I think more likely it's simpler. The air flows across the strap while the strap is not perfectly aligned with the air flow. This slight unalignment or yaw forces a greater yaw in the strap. The wind pushes the rear half of the strap to the opposite side, then repeats this rapid oscilation, or vibration.

The half twist eliminates the reed action because the strap, or reed, is now curved so the oscilation is impossible.

Also, with a half twist, half of the strap segment is facing the air flow; then the other half is a mirror image. So that would create a neutralizing effect in regard to yaw. No vibration.

But, what do we know? We're just dumb truck drivers.

 

hmm why make it so darn complicated.. its how it works.. done

 

Which came first, the chicken or the egg?

 

I think it's like the face in booby effect.