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  #1  
Old 10-08-2018, 11:31 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Default Naca Vent: Which Side

I am planning only one naca vent for my overhead console. I am installing a second 2" flange fitting for easy install later, if necessary.

I am curious which side of the fuselage would pick up more prop wash on the ground and therefore, the preferred side for one Naca scoop.

Thanks,

Larry
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  #2  
Old 10-09-2018, 01:26 AM
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az_gila az_gila is offline
 
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Standard diagrams would imply the left side, but why not put them in on both sides? It's not that much extra work "while you are in there"

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  #3  
Old 10-09-2018, 04:12 AM
GregMac GregMac is offline
 
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Location: Albany Western Australia
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We Only put one on the Port (left) side, just behind the baggage door and a little higher, works a treat plenty of air to feed the four overhead vents, even on the ground. Others have said that it doesn’t matter which side you put it on, both work, I used Gills theory and certainly didn’t need two.
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Old 10-09-2018, 06:23 AM
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rleffler rleffler is online now
 
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I prefer them on both sides.

In the air, it doesn't really matter. But when on the ground on a hot summer day, the more air the better.

It doesn't really add to the cost and there's no real negative impact.

bob
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Old 10-09-2018, 06:52 AM
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Jesse Jesse is online now
 
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Prop wash may be better on one side, but it would also be worth considering the possibility of exhaust on the same side. In flight I donít think it would matter, but following the diagram posted, I would expect the chance of exhaust fumes getting into the vent on the left side more than the right side.
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  #6  
Old 10-09-2018, 08:35 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rleffler View Post
I prefer them on both sides.

In the air, it doesn't really matter. But when on the ground on a hot summer day, the more air the better.

It doesn't really add to the cost and there's no real negative impact.

bob
I am not concerned with the cost or effort, but was concerned about drag. It is hard to believe that each Naca is drag free. Does anyone know what the drag penalty is for these?

Larry
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  #7  
Old 10-09-2018, 08:37 AM
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Default Right side

I had the same concerns as Jesse mentioned about the exhaust getting in on the ground, so I put mine on the right side. Plenty of air volume with just one and no exhaust fumes, although those who put theirs on the left don't seem to have any problems either. I still use a butterfly valve to throttle the air with the one NACA vent in flight, so there's certainly plenty of volume to work with.
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  #8  
Old 10-09-2018, 08:57 AM
Marc Bourget Marc Bourget is offline
 
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Location: Stockton, California
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Quote:
Originally Posted by lr172 View Post
I am not concerned with the cost or effort, but was concerned about drag. It is hard to believe that each Naca is drag free. Does anyone know what the drag penalty is for these?

Larry
To obtain the design benefit of a NACA scoop you should put it in an area where the fuselage cross-section is increasing. Also pay attention to the "bar" across the aft end of the opening. Proper design requires a substantial radius (compared to most installations seen).

FWIW
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  #9  
Old 10-09-2018, 09:17 AM
rocketman1988 rocketman1988 is offline
 
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Location: Sunman, IN
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Default NACA

Naca vents are definitely NOT drag free. There have been studies that show them to have 75% - 85% efficiency, though. As previously posted, the location and the surrounding structural environment affects the ducts efficiency...
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  #10  
Old 10-09-2018, 09:39 AM
Volumex Volumex is offline
 
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Location: Sarnia, ON
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Quote:
Originally Posted by lr172 View Post
I am not concerned with the cost or effort, but was concerned about drag. It is hard to believe that each Naca is drag free. Does anyone know what the drag penalty is for these?

Larry
Some light reading from the NACA report that NACA scoops are based on: http://naca.central.cranfield.ac.uk/...a-acr-5i20.pdf

Note that the report states:
Quote:
The data obtained indicate that submerged entrances are most suitable for use with internal-flow systems which diffuse the air only a small amount: for example, those used with jet motors which have axial-flow compressors.
Where complete diffusion of the air is required, fuselage-nose or wing-leading-edge inlets may prove to be superior.
So to paraphrase, they are great for air-breathing engines but don't use them for vents.

This should get some robust discussion going
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