Air Vent Noise

[Chris B]

Anybody have a link for sailplane tape that has worked well for you?

Hi Rick -

Check the first post in this related thread:
http://www.diamondaviators.net/forum/sa ... t4783.html

Chris

[waynemcc999]

After some experimentation, I also implemented the "glider tape over NACA inlet fix" to our super loud DA40 air vent noise problem. Here's a write-up on my results:
https://docs.google.com/document/d/1TcM ... sp=sharing

Bottom line... taping the bottom inlet on both sides decreases vent full open sound levels by about 6 dB, or subjectively cuts the noise in half, with a flow reduction of maybe 25%. Happy camper.

[Steve]

Holy thread resurrection!

Wayne: I did a number of experiments on this (see early posts in this thread) and found that taping the upper inlet provided the same noise reduction, but an increase in airflow. You may want to try that...

Steve

[waynemcc999]

Yes, Steve, I did see your posting and nicely documented experiments on this. At this point I'm stoked with the improvement... but once that becomes the "new normal" I'll most likely try your upper inlet approach. I still have 98% remaining on the 2" roll of (awesome) glider tape .

[smoss]

While taping my top half definitely increased the airflow, it was so much so that I was worried the increased pressure would blow off the hoses or something when closed. I went with the taping the bottom and have been happy for the past several years with such.

[MarkA]

Photos of the nose wheel fin and lower vent plugs on my 2010 DA40 XLS are included below. Mercedes-Benz - Arctic White 147/9147 paint with clear coat from amazon.com was used on all these parts.

https://www.amazon.com/gp/product/B00GV ... UTF8&psc=1.

The color is not an exact match in that it is a bit darker than the rest of the plane but I found the color of the Lowe's Krylon Fusion gloss white paint recommended earlier in this thread for the fin to be too light.

I used M5 stainless steel button head screws to match the other screws on the wheel pant. The vent plugs are held in place with Velcro so they can be easily removed. They look a little better than the duct tape that was previously used to reduce the air vent noise.

[Steve]

Mark:

The vent plugs look nice - where did you get them? I have had my lower vents covered with sailplane tape for years without any need to replace it, but the (I assume 3D-printed) plugs look more "finished". One suggestion - use white velcro on the fuselage - if you elect to leave the plug out (I don't know why you would) the white tape will be less noticeable.

Steve

[chili4way]

I'm confused as to which of the naca vent openings (top or bottom) is the better one to cover/plug to reduce the amount of cockpit noise. The vent plug shown by MarkA plugs the bottom one. The newest version of the DA40NG has only one opening, but it appears to be the bottom one (effectively blocking the top one.

vent-plug.jpg (11.25 KiB) Viewed 1131 times

vent plug

new-naca-vent.png (72.25 KiB) Viewed 1131 times

new DA40NG single vent

[AndrewM]

Paul, not sure if you have flown the av gas DA40? If you have, how would you compare the noise from the vents when opened, between the two planes? When I flew the NG, the weather was cold so there was no need to open the vents but I should have... was having too much fun at the time doing other stuff with the plane!

[MarkA]

I did some experiments with 100 mph duct tape early on and at least for my 2010 XLS, covering the bottom NACA vent seemed to be a bit quieter and still produced a high volume of air. Experiments by others have shown covering the top vent works better on some planes.

My first attempt at producing the plugs was to scan the NACA vent to create a 3D model so the plugs could be printed out on a 3D printer. I messed around with with this quite a bit but could never get an accurate enough scan of the vent. Ultimately I used modeling clay to created a silicon mold to cast vent plugs using liquid plastic.

I was surprised that the shape of the pilot side vent is slightly different than the passenger side vent. The shape of the vents also changed between the 2007 DA40 XL and the 2010 DA40 XLS and obviously again for the NG. I assume the NG change was an attempt to address the design problem causing the vent noise.