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06-28-2014, 05:06 PM
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Join Date: Jan 2005
Location: Peoria, AZ
Posts: 1,053
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Vortex generators for Naca vents for RV-4
In my never ending quest to get the cockpit cooler (not to mention CHTs but thats another story), I made and temporary stuck a set in front of each naca vent on the rv-4 canopy. The vents are in the location called out for in the plans. However, air flows out of the front vent instead of in and the rear vent doesnt have a large volume of air flow. Hopefully these will help reverse that. If they dont work, I will make different ones that have a lot more acute angle on them. Has anyone did this with success?
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Regards,
Thomas Velvick
Goodyear, AZ (KGYR)
2020 Donation sent.
N53KT RV-6a finished 2018, Flying
N7053L RV-4 Wife's RV
N56KT RV-4 Finishing
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06-28-2014, 05:53 PM
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Join Date: Mar 2010
Location: KSGJ / TJBQ
Posts: 2,039
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Quote:
Originally Posted by rvator51
In my never ending quest to get the cockpit cooler (not to mention CHTs but thats another story), I made and temporary stuck a set in front of each naca vent on the rv-4 canopy. The vents are in the location called out for in the plans. However, air flows out of the front vent instead of in and the rear vent doesnt have a large volume of air flow. Hopefully these will help reverse that. If they dont work, I will make different ones that have a lot more acute angle on them. Has anyone did this with success?
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Interesting idea, let us know it works out.

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06-28-2014, 09:35 PM
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Join Date: Jan 2005
Location: Peoria, AZ
Posts: 1,053
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Heres a picture of the first trial set:

__________________
Regards,
Thomas Velvick
Goodyear, AZ (KGYR)
2020 Donation sent.
N53KT RV-6a finished 2018, Flying
N7053L RV-4 Wife's RV
N56KT RV-4 Finishing
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06-29-2014, 01:37 PM
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Join Date: Mar 2009
Location: Somerset UK
Posts: 15
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Cockpit airflow - RV4
Have you read this interesting article regarding airflow? (scroll half way down to NACA section).
http://www.vincesrocket.com/finishing.htm
The positive pressure emanating from the tail could be your problem.
Hope it helps...
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06-29-2014, 05:59 PM
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Join Date: Feb 2010
Location: Vancouver, BC, Canada
Posts: 860
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NACA Vent
The NACA submerged duct works by generating a vortex off the ogival shaped sidewall intersections with the body surface, in this case the airplane fuselage. By doing this the two opposing vorticies draw air down from the freestream and into the duct entrance.
Therefore, adding an additional vortex generator in front of the duct is counterproductive.
One way to increase duct performance with thick boundary layers is by adding deflectors to the sidewalls.
Have a look here for the document NACA RM No. A7I30 figure 6
http://naca.central.cranfield.ac.uk/...a-rm-a7i30.pdf
I agree with the previous poster: if the pressure inside the cockpit is higher than the pressure at the NACA duct inlet, air will flow forward out of the duct.
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Terry Edwards
RV-9A (Fuselage)
2020/2021 VAF Contribution Sent
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06-29-2014, 06:37 PM
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Join Date: Jan 2005
Location: Peoria, AZ
Posts: 1,053
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I flew first test flight this morning. The vortex generator is letting air flow into the cockpit now. Still feels like air is also going out at the same time. So is an improvement as only air flowed out before. Going to test a different vortex generator with more acute angles next. Thanks Terry and Lotuswheelnut. Seems like a good point about positive pressure causing reverse airflow and also using deflectors that follow the naca shape instead of vortex generators. Will keep trying different shapes/things to see if the unusable vent can be made to work. I do not want to cut any more holes in fuselage for more vents.
__________________
Regards,
Thomas Velvick
Goodyear, AZ (KGYR)
2020 Donation sent.
N53KT RV-6a finished 2018, Flying
N7053L RV-4 Wife's RV
N56KT RV-4 Finishing
Last edited by rvator51 : 06-29-2014 at 06:48 PM.
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06-29-2014, 09:21 PM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435
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Quote:
Originally Posted by rvator51
....Will keep trying different shapes/things to see if the unusable vent can be made to work....
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Also VG positions.
And it might be helpful to tuft the area and have it photographed.
Dave
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06-30-2014, 09:07 PM
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Join Date: Nov 2012
Location: Gilbert, AZ
Posts: 124
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Gave up on canopy scoop
I gave up on those worthless side scoops. I cut a vent hole on the lower right below the cheek cowl. Used a naca scoop, hose and eye ball vent. Works great only needed one, idle prop blast will send air into cockpit. Plus very quiet.
Wish I would have done it 25 years ago!
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07-01-2014, 07:11 AM
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Join Date: Dec 2009
Location: St Louis, MO
Posts: 957
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RV-4 Vents
On the way back from the KC Formation Clinic we were down low VFR and I realized in the summer in Missouri I like to be up a little higher. It was quite warm so I turned on the autopilot and started playing around with the NACA vents I have. Not to worry, I had a wingman keeping an eye on me. What I found was all I needed was some deflectors on the inside attached to the back of the NACA vents to direct air towards me. The vents as they are right now seem to just dump the air to the back behind me which is of no use to me.
I think I have a solution in some cheap easy to make sheet metal deflectors that I will RTV to the inside of the canopy at the back of the vent. I will post some pics after I test them out to see if they work.
Oly
__________________
RV-8, Flying
Previous airplanes: Corby Starlet, Citabria, Cessna 140, Vari-Viggen, RV-3, RV-4
RV grin every flight
"Sure is nice to have smart friends"
2018 dues paid
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07-01-2014, 08:05 AM
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Join Date: Jan 2005
Location: Peoria, AZ
Posts: 1,053
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Thanks Oly,
At least you are getting air in through yours! I wonder why you are getting flow in while my flow is out? I am investigating on how to lower the pressure in the cockpit so air flows in more easily. I wonder if anyone has ever put louvers on the bell-crank access panels in the wing?
I dont think I am getting high pressure air from the tail as the fuselage is sealed off completely at the back of the baggage compartment. That leaves the wing, flap holes, naca vents and canopy as the only areas for air to come in/go out of.
__________________
Regards,
Thomas Velvick
Goodyear, AZ (KGYR)
2020 Donation sent.
N53KT RV-6a finished 2018, Flying
N7053L RV-4 Wife's RV
N56KT RV-4 Finishing
Last edited by rvator51 : 07-01-2014 at 09:37 AM.
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