Brother dustin and 3were talking tonight about airflow at the driver in his z car, and the MoCAR. I remembered that in the 70 trans am series there was a duct that picked air up from the windshield and tunneled it around the a pillar at the driver. Its circled in this picture
Where can we get them? Seems like the solution were looking for.
Most of them back then were fabricated by the teams.
What I see in most of the cars I rent seats in these days are NACA ducts, which work well if in a high pressure area.
In reply to racerfink :
Problem is theres no good place to mount a naca duct. At least not yet.
How would someone fab this?
Iffen yu can fab a foot pedal space outta a biscuit pan .....I'm thinkin' you got this 
I used a white plastic gutter downspout elbow (about 60 degrees) and a bungee cord to hold it around the rearview mirror. Worked great to duct air into the cabin and could be adjusted on long straights. It was big enough to occasionally catch a tire marble and bounce it into my chest.
On our lemons car we used a dryer vent duct on the roof to accomplish the same thing. Easy button. But looks ridiculous of course.
For what you show there I imagine 3d print, fiberglass, or both.
So, how would i design this to be printed? And would it hold up in the sun?
I can also do fiberglass, but not sure how to make a mold for this.
Clear naca ducts are pretty common for placement in windows:
NASCAR likes to put them into the rear quarter window:
I'd just use sheet metal. Make a mock-up out of construction paper, then use it as a pattern.
How about an under hood air intake? They can be found fairly wide and slim. May fit the A pillar nicely. At the junkyard, it would come with the hose and clamps. Or on Amazon: RCRBT 2720903582 & 2720903682 Air Intake Inlet Duct Hose Left Right Compatible with Mercedes W204 W212 C300 C350 E350
You may find something similar.
Sorry about the picture size
A lot depends on whether the look or function is more important.
In reply to Dusterbd13-michael :
As others said, depends how important looks are. If they are important, you can print in ABS and then glass over it to make a hybrid part. Or use the 3D printed part to make the mold. Or print the mold directly. Lots of options.
I like the clear naca ducts. If you want to enhance them you could always print a scoop that goes on the outside, assuming that isn't already available for sale.
The nice thing about naca ducts is that you can put eyeball vents in them to direct/block airflow as needed. They're great.
The problem with the NACA duct is it there's no wing Windows to mount them in in either of our cars. Otherwise that would be the Easy Button
Re NACA duct location and debris protection
WonkoTheSane said:The nice thing about naca ducts is that you can put eyeball vents in them to direct/block airflow as needed. They're great.
Link to the eyeball vents?
In reply to kevinatfms :
I got them from Jegs about 5 years ago.
Looks like they're out of stock, but that'll get you the part number and brand.
I used a heat gun on the duct to be able to press the vent in.
Dusterbd13-michael said:The problem with the NACA duct is it there's no wing Windows to mount them in in either of our cars. Otherwise that would be the Easy Button
Pics of the cars in question?
Dusterbd13-michael said:The problem with the NACA duct is it there's no wing Windows to mount them in in either of our cars. Otherwise that would be the Easy Button
Fair enough. The picture makes it look like that flat HVAC ducting that RWGBY linked to.
WonkoTheSane said:In reply to kevinatfms :
I got them from Jegs about 5 years ago.
Looks like they're out of stock, but that'll get you the part number and brand.
I used a heat gun on the duct to be able to press the vent in.
I suspect a stock Miata eyeball vent would work, which means there's an Eclipse part that would also do the trick. You can also stick the top of an aerosol can (like brake cleaner) into the duct from the outside to easily block it off.
I've run that exact duct location and boy, if you ever want a dramatic illustration of how well a "submerged duct" works, they throw an amazing amount of air at you.
ProDarwin said:Dusterbd13-michael said:The problem with the NACA duct is it there's no wing Windows to mount them in in either of our cars. Otherwise that would be the Easy Button
Pics of the cars in question?
WonkoTheSane said:Dusterbd13-michael said:The problem with the NACA duct is it there's no wing Windows to mount them in in either of our cars. Otherwise that would be the Easy Button
Fair enough. The picture makes it look like that flat HVAC ducting that RWGBY linked to.
Agreed. Need to order some to experiment with.
Is there a Website that shows what you need in a NACA duct ?
I see them in many sizes but also depths and am wondering what works at what speed.....
I can post the original NACA Technical Report, if you want some interesting original research on submerged duct. It was published in the 30s.
It includes some basic definitions on how to size the ducts. The short answer is the ones typically available are not great, but they mostly work.
Sizing is a function of how much flow rate you need. Its not uncommon to get about 30% of car speed at the exit of the duct.
The original report has dimensions for making your own which is pretty cool. From my understanding, the big flaw in most commercial ones is the lack of a sharp edge on the sides (which is what drives the thing) and they're usually too wide for their length. A proper one can be hard to package and harder to pop out of a mold.
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