chuckbdc

Everyone with a 991 coupe knows that over about 60 with one or both windows down (and sunroof closed), there is a very loud, very annoying harmonic, a “thrumming noise” that is unbearable without a helmet. It is caused by the wind flow past the mirrors entering the low pressure area cockpit and then fighting to get out as the pressure rises. The rapidly fluctuating pressure is what creates the harmonic. The new “sport” mirrors don’t fix the problem. Glue-on fins are being offered as fix, but I personally don’t like the idea of gluing anything onto my 991.

So this morning watching a couple of front wings disintegrating at Monaco, I came up with an alternative, bent from heavy stock paper (recycled premium birthday card stock). Then off to cars and coffee. I tried it with one and then with both windows down, one installed one installed each window- the noise was GONE! Then I tried with both windows down and just one installed (drivers side). STILL NO NOISE! Just enough interrupted airflow to defeat the low pressure inside.

It works perfectly. It worked even with the paper version flic bent back a bit at high speed by the airstream - no noise at 60, no noise at about twice the speed limit. Folds over the door plastic and stays on with door closed or open.

I then worked out a version in plastic that deforms not at all at that speed. Should be waterproof and track worthy. Recycled milk bottle plastic cut to flat and then formed to match the paper version (well almost, cut too fast). Stays bent in the same shape as the paper version and stays firmly in place as long as the door is closed. Will fix after drinking the next milk bottle.

I admit toying with the idea of a patent, or at least market advantage by making a mold and casting them in plastic, or getting my kid to manufacture then with his 3-D printer, and flogging them here. The kid drives a hard bargain, so I am doing the right thing and contributing the design to humanity…well at least to 991 coupe drivers who like fresh air or are forced to run with windows down and sunroof not popped. Here it is: (please excuse the weird rotations I have no idea why it did that)

petee1997

deleted....too obnoxious!

chuckbdc

Try w upright photos. (V3 prototype Guards Red w deviated stitching (sorry bout bar code- was the back of the birthday card) .

rustish

Thanks for this! I'll be trying it at the track this weekend. No closed windows and A/C there, so this is much appreciated.

chuckbdc

Enjoy your windows down, or the $300 solution being offered elsewhere.

Zohan

It is pathetic that we need something like this 100-200k car

chuckbdc

Especially given how simple a fix is.

John's 991

Nice job Chuck! I will be at the track next Sunday, and I will give it a try. Agreed that it is silly we need such a thing, but I imagine in the next few months there will be several people coming out with solutions. Not too late if you want to commercialize the solution though!

I appreciate that a company did the work to come up with a solution, even if the price is a bit steep. That and I am not excited about gluing things to the car either. A clip-on style solution for track use would be ideal. Somewhere between $300 and a piece of card stock lies the ideal solution!

porsche518

I'll take mine in alcantara with deviated guards red stitching, I am guessing this will cost about $3500.

fbroen

Bingo! Snaps in -- and just as importantly, is removable.

Will fabricate.

(Although when you said flicks, I thought of GT3 RS 4.0 dive planes, and that was an exciting solution, too).

Thanks for sharing.

chuck911

What? No carbon fiber?!

Milk bottle plastic is cloudy, but the plastic used for packaging things like blow driers is clear and only slightly thicker. I've used it to fashion vanes to keep cold AC air directed away from my wife and towards me. The real fix though would be to change the shape of that trim piece to incorporate a half inch vane or tail. If you have mad skills (skillz? skeels? never mind) you could cover the trim with carbon fiber incorporating the vane shape. But this calls for mad, uh, extensive fabrication expertise. I just thought I would mention that because chicks dig guys with extensive fabrication expertise.

chuckbdc

And a molded in Porsche crest for an added bit of legal turbulence?

chuckbdc

True all Chuck, but here's the deal. I get birthday cards only once a year; its less expensive to use milk bottles for oragami prototypes and the cereal is good for you. I tried blow dryer packaging, but the blow dryers add up fast and they draw stares hanging in the powder room, kitchen and garage already, so have sworn that off.

Agreed re the permanent install solution assuming that wouldn't affect the warranty. I hope whoever molds it will send one to me when, between the increased time spend in car and bed, time permits.

chuck911

Ahh! I was looking at your photo's again and I got it! Go back to the place that did your film install and ask for a scrap of film. Attach it to the trailing edge of that trim piece, fold it back on itself and attach the other end as well. Should be near invisible and semi-permanent! Now whaddaya think a that?

chuckbdc

The heavy paper vane sags in the wind at around 100 mph, but it still works. The plastic doesn't deflect at that speed. I don't know how much either would deflect at track straight speeds, but I am guessing that laminating a second paper or plastic layer would be good. The films for protection are likely too flexible.

Anyway, the more I use it, the more I like the "open door, hang over the plastic triangle, close door" install procedure. I will leave it to the forum to work out the uninstall.

I have decided that the market is really the serious technical/competition enthusiast, so won't be offering in paint to sample or with deviated stitching (right away). In addition to basic black, they will come in red for S owners, yellow for big spenders, and white for those with sponsors.

Off for a ride to test the laminated prototype.