Increasing A/C Airflow

[TCollins]

Below is a picture of the bottom of one of my a/c vents. The upright collar protrudes about 1/2" above the bottom of the duct into the airflow when the vent is mounted.


I am wondering if I can increase airflow through my MH by cutting off 1/2" of the collar so it is flush with the duct or are they purposely designed this way to "balance" the system?


The airflow at either end of the MH is pretty pathetic. I would like to be able to improve the flow.

[US1]

They are long to allow one to attach flex duct to them. Cut it down till your heart s content

[00 Buckshot]

I completely removed all of those rings from my vents but it didn't seem to help much if any.

[hclarkx]

I gave up on the ceiling ducts formed into the foam. There was only about 3/4" of foam between the top of the duct and the thin plywood roof. I closed all of the vents and removed a panel inside the A/C return-air grille that is there to force air into the ceiling ducts. I then had a massive plume of cold air coming down; far more than the sum of the ducts. The result was noisier and a bit of a nuisance, but at least the RV would get down into the 70's. I lost air in the bedroom, but rarely used it anyway. We've since started avoiding hot months and places and removed the A/C unit to make way for more solar panels. Someday if we want to go to hot places again, I'll mount a 3/4 or one ton mini-split on the back bumper and have quiet, efficient solar powered cooling. I think I'd go mini-split even if I wasn't a committed dry camper.

[Old Scout]

...as a trial--think I would trim down the leading edge facing the AC first--rear edge might act as a foil to divert some air?????