SonexBuilders.net

It seems there are three types of vents commonly used for cabin air:

• NACA duct
  • Eyeball on instrument panel
  • Eyeball near duct
• Van's rectangular vent
• Snapvents on windshield

I'm hoping to find a solution where I only need one type of vent. The NACA ducts look good, but I get the impression that without adding scoops they don't give great airflow. Plus, I don't like the idea of running tubes to the instrument panel (seems like it could clutter up the space).

I'm leaning towards using the rectangular vents--seems like it would give plenty of air and I doubt I would ever need them fully opened (except maybe idling on the ground). Plus the installation seems simple (although adding a handle to actuate them might complicate it a little).

Has anyone flown with only windshield snapvents? Is that sufficient for 90+ degree days in Alabama? Installation would be extremely simple.

Any thoughts? Or builders who wished they installed something different?

I don't have experience with the snapvents, but can say that the Van's rectangular vents are great. There's a lot of airflow even at idle, they are light (no ducts, etc) and they have very low drag when closed. Though the air "blast" is aimed at the left leg, plenty of air flows up the trunk and across the face. If you use a kneeboard/checklist, you'll probably want to keep it on your other leg in the summer so the pages don't flip in the breeze.
Regarding an objective comparison of the total airflow among the various options, probably the best approach is to compare the actual vent area normal to the airflow/prop blast for the Van's and Snapvent. The stock SONEX NACA duct wouldn't be strictly comparable due to the nature of a submerged duct. I can get a measurement of the Van's duct next time I visit my plane, will post it here.

I've flown in Sonexes that have the Vans style rectangular vents, and my Waiex has the Vans style NACA duct vents with the eyeball vents in my panel. In terms of which offers more air, I do think they're close but I would probably give a slight edge to the rectangular style vents, probably due to the "ram air" nature of how that vent works. That being said, I'm plenty happy with my NACA vents on the side and I really appreciate the ability to aim the airflow all around the cabin. Even though the rectangular vents provide slightly more air, it blows mostly on your thigh and lap.

I'm sure it would be overkill and I haven't done it, but a small part of me actually considers adding the rectangular style vents to my already existing NACA scoops, just so I can get TONS of air in the summertime. I haven't done it, but maybe someday...

Ultimately you'll be fine either way, but if you're looking for maximum airflow, I agree with Mark...the rectangular vents will be hard to beat!

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