home-brew overhead console: air vents

Those of you who rolled your own - what did you use for vents? I think I'm going to control overall airflow with the AeroSport butterfly valve, and save some shekels on the air vents by not getting the machined aluminum aircraft grade vents.

Miata dash vents seem popular on eBay, and there is a ragtag assortment of very used aircraft eyeball vents for sale there as well. Curious what others have gone with.

Bill Boyd said:

Those of you who rolled your own - what did you use for vents? I think I'm going to control overall airflow with the AeroSport butterfly valve, and save some shekels on the air vents by not getting the machined aluminum aircraft grade vents.

Miata dash vents seem popular on eBay, and there is a ragtag assortment of very used aircraft eyeball vents for sale there as well. Curious what others have gone with.

Click to expand...

I would still go with either the Aerosport Products or the SteinAir vents. I've seen too many qualities issues to trust just any aluminum valve. At least with these two vendors, you know you're getting a quality product.

Even with the Aerosport Products NACA valve, you still want to ensure that the vents close, especially in the winter.

Bob - do you see this as a belt-and-suspenders thing where both turn out to be necessary?

I was hoping the butterfly valve would mitigate both leaky eyeball vents of the cheap/automotive surplus variety, and the inevitable leaks in the switches, lights and panels in the overhead that everyone says are quite noticeable in the winter.

I dislike the thought of having to pay a premium for both the NACA butterfly controller and top-tier eyeball vents to be comfortable in cold air, but I want to be realistic about what's needed for a satisfactory solution to cold air ingress.

There is a $498 difference between 4 vents from SteinAir and 4 used Miata eyeball vents from Ebay.

The only way I can answer your question is that I purchased the Stein vents for the overhead and the two front vents. I would probably buy the Aerosport Product vents if I were to purchase today, but I have a little bias towards Aerosport Products. I felt it was worth the expense to me.

Only you can make that determination for you. It's all about risk management. If you install the less expensive vents and they work, you managed the risk well. If they don't, you'll have to replace them with the more expensive vents costing the sum of both. There's no right answer.

I was in Japan for a couple of weeks last December, and in several vehicles there I saw these neat air vents that are like an eyeball, with a dial in the center that opens and closes a set of radial vanes to control air flow. I wasn't sure where to find them until I rented a Chevy Sonic during a trip last month. Very similar to what I saw in Japan. I think the vehicles in Japan where I saw them were a Mazda and a BMW. Anyway, I think I have found them here: https://www.ebay.com/p/?iid=251988775072&&&dispItem=1&chn=ps



Now, they are rather large in diameter, and possibly too deep for an overhead console, but I am still considering them for the foward and rear fresh air vents. Bonus: They're pretty inexpensive, and probably available at an auto wrecking yard. I may pick one up just to see where I could make it fit.

Edited: Now that I look at these pictures, I see these are different than the ones I saw in Japan in that they have a folding butterfly behind the vanes to regulate airflow rather than the radial "petals" that rotate on their individual axes like I saw over there. I will now have to find those. I bet the "petal" ones aren't as deep, since the split butterfly has to have at least a depth equal to one radius of the opening...


Edited: Here's an Audi air vent that looks like the ones I am thinking of:


Edited: Are these the Mazda air vents the OP was referring to?

Thanks, Bob

The message I'm getting is that the AeroSport valve does not shut off the airflow enough to obviate the need for good butterfly eyeball vents (and presumably extra attention to sealing switches and panels and lights) to control cold drafts from the overhead.

This is disappointing info from the field, but it's what I need in order to over-think this

Maybe someone who sealed things well and used the expensive vents but not the AeroSport valve will share their impressions of how well their set-up mitigates the cold draft issue and any other drawbacks.

1001001 said:

"Now, they are rather large in diameter, and possibly too deep for an overhead console, but I am still considering them for the foward and rear fresh air vents. Bonus: They're pretty inexpensive, and probably available at an auto wrecking yard. I may pick one up just to see where I could make it fit."

I agree they look big and deep on the Ebay photos - one more reason I was asking what's been tried successfully.

If you get one, please let me know what you think of it!

Bill Boyd said:

The message I'm getting is that the AeroSport valve does not shut off the airflow enough to obviate the need for good butterfly eyeball vents (and presumably extra attention to sealing switches and panels and lights) to control cold drafts from the overhead.

This is disappointing info from the field, but it's what I need in order to over-think this

Maybe someone who sealed things well and used the expensive vents but not the AeroSport valve will share their impressions of how well their set-up mitigates the cold draft issue and any other drawbacks.

Click to expand...

I have looked at pictures of the Aerosport valve (I have not seen one up close) and think it could be made to seal better if a half-ring of felt were bonded to the inside of the valve body, on opposite sides of the butterfly such that when closed, the butterfly would rest against the felt edge.

This is a common way to seal large butterfly valves and could be adapted to these valves, I believe. If the felt were cut to a cross section of about 3/8" x 1/4" (with the 3/8" being the bonding surface to the valve body), I think it would hold up. The small dimension might even be as small as 1/8". It just needs to create a seal between the butterfly and valve body tube.

another idea

The overhead and its fitments leak because of high-pressure/low volume air making its way through the butterfly even when closed. I wonder if a small, always-open overboard scoop (cabin top facing aft, perhaps) could be designed to bleed-off this "leakage current" air in the "high-impedance"/low-flow scenario of a closed valve, yet have negligible % loss in the low-impedance, valve-open, high-flow scenario where you want as much vent air as possible blowing on you.

Trade-offs abound, like in everything engineering.

With any luck our guru DanH will pop in here with some graphs from the 1930's showing that this question was answered long ago I'm sure it was; just not willing to dig out the answer for myself.

Bill Boyd said:

The message I'm getting is that the AeroSport valve does not shut off the airflow enough to obviate the need for good butterfly eyeball vents (and presumably extra attention to sealing switches and panels and lights) to control cold drafts from the overhead.

This is disappointing info from the field, but it's what I need in order to over-think this

Maybe someone who sealed things well and used the expensive vents but not the AeroSport valve will share their impressions of how well their set-up mitigates the cold draft issue and any other drawbacks.

Click to expand...

I don't think Geoff has indicated that the valve was 100% effective. Just like the similar valves used in hvac, it cuts off most of the airflow. It's really a necessity if you pressurize the overhead plenum. You would be surprised how much air will leak through switches and some types of lighting.

I fly when it's below zero, so I want to ensure the entire solution can prevent any cold air blowing into the cabin.

rleffler said:

I don't think Geoff has indicated that the valve was 100% effective. Just like the similar valves used in hvac, it cuts off most of the airflow. It's really a necessity if you pressurize the overhead plenum. You would be surprised how much air will leak through switches and some types of lighting.

I fly when it's below zero, so I want to ensure the entire solution can prevent any cold air blowing into the cabin.

Click to expand...

I wouldn't necessarily expect it to be 100% effective at closing off flow entirely. Its purpose is to control flow, not necessarily serve as a shutoff valve. In industrial situations it is common to have an isolation valve ahead of the control valve to ensure proper shutoff.

It might be possible to modify the valve as I described above to get a better seal and possibly achieve better shutoff characteristics.

did something similar years ago

to the cheapie plastic eyeball vents from Vans. RTV with release agent to serve the same function as the felt gasket you describe. Works pretty well until it starts peeling away and flapping in the airstream

I'm betting the AeroSport butterfly could be "tightened" a bit as you describe.

The Aerosport NACA control valve will shut off the airflow Over 90%. This valve was designed to control the flow of air in the winter and keep the overhead console from filling up with cold air the valve also helps control the flow of air and reduce the air to a more pleasant flow rather Than a hard high speed flow. Today I was out doing approaches and it was around 88f and I had the vents wide open and the valve adjusted so I had a real nice HVLP flow coming in from the overhead vents. Very comfortable. You can have the vents wide open and control the air flow from the valve. Having both a quality vent and the valve makes the overhead console work very nice. I have no noticeable leakage around the overhead anywhere in the winter when the valve and vents are closed. There is a very very little flow when the valve is closed and the aircraft is at cruise speed but when the vents are closed it is a non-issue. With the Aerosport AeroVents installed they shut off the air almost 100% and this combination makes for a really nice system. I have been flying mine for 7 years and would not change anything.

FWIW

Question about the NACA controller

If mounted as Ed and others have done, just behind the baggage bulkhead, is there potential for EMI to the ADAHRS units that will be mounted on a tray jsut below the top skin, ahead of the next bulkhead to the rear?

Not so much worried about brief EMI emissions during changes in the valve position, but whether the servo draws significant idle current or emits significant RF when it's awaiting the next position command (i.e. 99.99% of flight time). It will be only about 15" or so from the ADAHARS units, with its control wiring routed forward into the overhead console.

Bill Boyd said:

If mounted as Ed and others have done, just behind the baggage bulkhead, is there potential for EMI to the ADAHRS units that will be mounted on a tray jsut below the top skin, ahead of the next bulkhead to the rear?

Not so much worried about brief EMI emissions during changes in the valve position, but whether the servo draws significant idle current or emits significant RF when it's awaiting the next position command (i.e. 99.99% of flight time). It will be only about 15" or so from the ADAHARS units, with its control wiring routed forward into the overhead console.

Click to expand...

I have mine mounted about 12" or so from my ADAHRS and have not noticed any issues whatsoever.

I Think

I think a lot of people have mounted it there with no issues.

If you follow the location specs for the ADAHRS unit, the best place to mount it is about 10 feet outside of the wingtip, flying in close formation with the airplane...

good to know

just thinking ahead.