Cutting Rear Naca Vents Today - Tips?

Today will be the first day making a cut into my otherwise unblemished tailcone. I picked up the Vans SV-1 naca vents and their paper templates. I did some reading of where others have placed them and have chosen the first bay of the tailcone section about 4" back from the bulkhead and even top and bottom. Any tips for cutting and shaping before I make a horrible mess of my tailcone?

I cut mine there too. I'm not flying but am concerned about the possibility of the NACA vent causing pressure or turbulence issues at the static ports that are directly behind it.

Perhaps some others who have used this location and comment on static error with this location of the cutouts.

If I were doing it again I'd probably drop them down one bay so they're under the static ports. Or move them further aft so they're behind the ports.

Needless to say though, it's something you need to be thinking about before cutting the skins like I did.

Phil

Vents

Position is OK. Ours works fine.

I put mine in the same position as Geoff Combs's. I first made a template using the front cutout, created a center line to level it and traced the outline onto the skin. I used a dremel with a cutoff wheel and then finished up with a small round file and flat file. I counter sunk holes around the perimeter and used CS rivets along with proseal. It took a couple of hours for both.

No noticable error

I put mine right about where you are planning on. I made the cutout template from the front cut-outs. I have about 16 hours on the plane so far and have no noticable static error. Maybe something will be detected after I get a full pitot static check and can make calibrated comparisons, but I don't forsee any issues.

Eric Kallio
N518RV
14 hours left on phase 1, then paint.

I spoke with Vans Aircraft today...

...and was told that a NACA vent in that location was not recommended since that area of the tailcone has known low pressure (thus the static port being there) and would not provide high pressure to draw good airflow to the overhead console. Does anyone have any thoughts on this? (I was surprised to hear this since it seems like everyone has placed NACA vents in that area)

They work fine in that area. 200hrs and no problems.
Geoff

dhmoose said:

...and was told that a NACA vent in that location was not recommended since that area of the tailcone has known low pressure (thus the static port being there) and would not provide high pressure to draw good airflow to the overhead console. Does anyone have any thoughts on this? (I was surprised to hear this since it seems like everyone has placed NACA vents in that area)

Click to expand...

There is one senior Van's employee that will tell you every mod is bad when you call without spending the time to understand the facts first. Most just hang up when they get him. My experience is that it really depends on who you talk to at Van's to get good feedback.

There are dozens of folks that have installed rear naca vents. Geoff shared his opinion. I'm not flying quite yet, so I can't offer direct experience. However, I can share second hand stories about folks that installed rear naca vents and had too much air, in which their air vents and switches leaked air becuase the pressure was too great. The is why many are purchasing the NACA Air Vent switch/valve from Aerosport Products to actually reduce the air flow.

It seems that real world experience conflicts with the information that you got from Van's. I can share with you that flying in Geoff's RV-10, that there is plenty of overhead air being supplied.

bob

I concur with Bob L. I had close to 200 hours on my first RV-10 before selling it and had aft NACA vents. I was initially concerned about issues with static port pressure but reality didn't bear it out. Specifically, my vents were just a few inches aft of the baggage bulkhead and the top edge was slightly below the level of the static ports. Multiple GPS runs showed airspeed readings to be within 2 kts of calculated which seems to be as good as you can get regardless of having the aft NACA vents.

Airflow is very good, in fact I was a beta tester of Geoff's air controller for the very reason cited - you get too much at cruise speed! The overhead console is pressurized and aside from the mentioned air leaks, you'll get high velocity + high flow through the vents. For comfort you really need lower velocity and the controller allows you to dynamically control that. For winter flying you can close off the air almost entirely. Air leaks around switches/lights can be mostly mitigated with RTV but I was never 100% successful.

Would I do it that way again? I'm now building my second RV-10 and have aft NACA vents in the exact same location and have already purchased on OH vent controller from Geoff.

Bob

Would one of you guys that has the rear naca vents installed mind posting a picture of the location?

civengpe said:

Would one of you guys that has the rear naca vents installed mind posting a picture of the location?

Click to expand...

Here's mine, which are in the same location that Bob Condrey described is were. I know that Geoff and several other's are centered on that panel. It doesn't seem to make a difference, so pick the spot that looks the best to you.

Thanks!

As usual, great feedback from you guys! I'll proceed (as originally planned) with the vents, the flow controller, and the overhead console.

Thanks again!

Here are some pictures of my install. And a link http://combsfamily.phanfare.com/3161550_3627646

Is there any reason that you could not mount them above the main longeron in top skin, just aft of the glass top. This would make for shorter hose runs.

Here's where I put the NACA ducts in my bird. I've had no problems with the static ports. I have a "accuracy avionics" overhead and almost get too much air. I plan to put a vent control in at next annual.







Dr Fred
N515FW
300 hrs