Why are some AC shrouds facing the wrong way?

[robwok]

I would expect most AC shrouds to face with the sloping part in the wind, and the thickest part toward the rear, so that when you drive down the road, you get less wind resistance. However, I see them facing the other way all the time. Are there that many that are installed wrong, or is there a reason for this? (airplane wings have the thicker portion facing into the wind and tapers to the back)

[vswingfield]

Originally Posted by robwok

I would expect most AC shrouds to face with the sloping part in the wind, and the thickest part toward the rear, so that when you drive down the road, you get less wind resistance. However, I see them facing the other way all the time. Are there that many that are installed wrong, or is there a reason for this? (airplane wings have the thicker portion facing into the wind and tapers to the back)

They are installed wrong. The installer was a(n) [insert your own insult here]!

Not only does it present the blunt end aerodynamically, it exposes the condenser's fins to damage from anything that might come down the top of the trailer. Including hail, gravel, birds, etc...

And you're right, it does seem like there are a lot of them.

[perryg114]

I have seen air scoops on the top of some trailers that look like air conditioners. I can't imagine anyone being so stupid as to install one backwards.

Perry

[barts]

The principle source of air resistance at trailering speed is form drag, caused by an uneven pressure distribution around the object. The shape with the lowest air drag (at least not near other surfaces) is the tear drop; the blunt leading edge and long tapered tail are typical. The tail is important as it helps reduce the formation of a low pressure zone to the rear.

How much practical effect this has on the roof of a trailer is a matter of debate; the airflow is hardly undisturbed by that point.

The shroud on our AC is pretty blunt at both ends.

- Bart