Air Vent Noise

[Antoine]

BTW, I used the 1" sailplane tape to cover seams on the wing tips, around the landing lights, and a few places on the tail. Definitely increased TAS by 5 knots.
Chris

Chris ( this IS a serious request). Would you mind documenting this in a separate thread or alternatively PM me some info? I am especially interested in the mods of the tail / Thank you

[Chris B]

BTW, I used the 1" sailplane tape to cover seams on the wing tips, around the landing lights, and a few places on the tail. Definitely increased TAS by 5 knots.
Chris

Chris ( this IS a serious request). Would you mind documenting this in a separate thread or alternatively PM me some info? I am especially interested in the mods of the tail / Thank you

Hi Antoine -

Sure. No problem. I'll take some pics tomorrow and start a different thread.

But you do realize that I am being completely facetious about the speed increase? Any change is probably negligible. Cleaning-up the gear/wing interface & getting a decent nose wheel fairing would probably be measurable improvements. Sealing a few small gaps, not-so-much.

Chris

[Antoine]

Haha, well much to my embarrassment NO I did not realize you were facetious. I am so focused on performance gains these days that I thought you had done the gap sealing better than I did - just did not buy the 5 knots though.

If you have done something interesting in the tail area, please do pass the info a long. I can use ANY improvement... It takes a lot of small details to get where I want to...

[smoss]

WOW! Just completed my first warm weather trip with half the inlets taped, and what a joy. Nothing short of magic! Fully open vents and barely any increased noise over closed, yet still with great airflow. Needless to say I'm thrilled that I started this topic 8 pages ago. Thanks for everyone's help.

[Charles]

smoss, that's great, but which half?

I second Chris B when he says taping various areas on the tail and wings has very little impact TAS.

[smoss]

I ended up taping off the bottom half. When I taped off the top half, I as well did get a significant increase in airflow (overwhelming, actually), but the noise did not diminish for me nearly as much as taping off the bottom half.

[Steve]

I found that taping the top half gave the greatest reduction in measured noise level, and actually increased the air flow. See my earlier posts in this thread for specifics…

Steve

[Antoine]

FWIW I blocked the upper part, it IS less noisy and the pressure is enormous. Air leaks from all over the instrument panel. I suppose the differences in our experience have to do with the smoothness of airflow inside the duct.
it is very roughly finished and therefore probably different from plane to plane.

To Robert: If Diamond could make a *real* NACA inlet with a diffuser it could be made much smaller which would result in less drag and noise.
The key is controlled diffusion because once the air has slowed down enough, aerodynamic noise will no longer be a problem. We don't need the air blasted in our face at 140 knots, do we?

[Chris B]

FWIW, I've tried taping both the bottom and top of the vents for extended trips. I don't doubt other results, but for my aircraft the hands-down winner is taping the bottom half. The noise is essentially gone (with a noise-canceling headset), but the airflow is still excellent.

I have no idea why the results would vary from plane-to-plane, but apparently this really is one of those YMMV deals. If you don't like the results from your first attempt, try taping the other half!

As Antoine suggests, a much smaller NACA vent would probably be perfect, but in the meantime sailplane tape is a very cost-effective solution.

Chris

[rwtucker]

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