Air Dams

NC74392

NC74392

New member
Not into NASCAR or motor sports in general, but the air dams they use on the cars are interesting.
I wonder if a simple air dam could help keep air out of our wheel wells? Something like this:

http://img.photobucket.com/albums/v41/cruisair/NC74392/AirDam.jpg

It seems so simple. No fussy gear doors- or am I just full of it :?: :!: :?:
 
Here's a bigger picture. The air dam is in green for contrast. Only obsticle I can see is the gear leg may impenge on it too much.

http://img.photobucket.com/albums/v41/cruisair/NC74392/AirDam-1.jpg
 
I can't decide if it looks more like a speed brake or a fairing (like the wheel pants some have used). Depends on shape I suppose.
 
We've had this discussion before, in much detail, as no doubt you recall, DD. Despite the aerodynamic arguments that fail to support this notion, and the ones that do, and certain conclusions regarding aesthetics and such, the only real test is the before and after.

Most people who have wheel fairings bought their airplanes with them and, thus, cannot say - based on credible testing - whether they improved performance. Several of us have experimented with the easy stuff, such as wing root fairings, found no speed difference, and made our decisions based on looks. The Viking clam shell fairings are not conclusive either because they tend to suffer problems with sealing properly. I believe it was Andy Vano who told me that the doors became a standard feature at one point, "Because customers believed they made the airplane faster, whether they actually did or not." The demonstrable clean up, that Andy described in an article in the newsletter, involved the cowl and faring of the nose wheel which is not part of the wing structure.

In short, try it and let us know :) Please excuse the unsolicited advice but it makes more sense to me to get the airplane flying first, and work on optimizations later. Trying them now - even though that might seem sensible given that your aircraft is undergoing restoration - means more time and approvals...the last thing I imagine you'd want right now ;)

Jonathan
 
You're right of course. I hope I can try this out one day AFTER getting 392 back in the air.
I just can't keep the idea from popping back up. It seems almost too simple to work, and I find it hard to believe no one else has tried it.
Apologies to everyone for beating a dead horse...
 
Here's two ideas:

http://img.photobucket.com/albums/v41/cruisair/NC74392/AirDams.jpg

Now, problems are:

1) Are they the right height to do anything?
2) Howlong should they be? Should they end at the back of the wheel well or stretch all the way to the flaps?
3) Do I go with a deflector (top) or a true air dam that keeps the relative wind against the bottom of the wing (bottom)?

Anyway, it'll be fun experimenting when the time comes. All thoughts and input appreciated :D
 
As I am no artist, I don't feel badly saying you share my affliction, DD :)

Is your design aimed at faring the junction of the top of the wheel protrusion and the wing? Given that the chief speed cost of the exposed wheel bottoms (halves really) is disruption of the high pressure surface (bottom) of the wing, do you visualize this as creating less disruption there?

I guess what throws me is the use of the word, dam. Dams hold things back. Fairings smooth things over.

Jonathan
 
Two thoughts on yer damn air dam:
1. In cars actually the airdam is keeping the major flow of air out from under the car.....sort of sealing the car off from the road....an airplane we don't have anything solid under the wing to seal against.

2 Having said hat.....I used to do a lot of airdrops out of cessna 206's and Maules as a bush pilot in South America. When you take the back door off a 206 you install a "deflector" ( Air dam if you will) this is a two inch wide metal strip that attaches to the front door post angling into the slipstream .......without it you get the "thud, thud, thud," turbuance sound in cabin....with it the airflow is deflected saround the open door and the turbulence is greatly decreased. I cooked one up for the Maule M-5 and it worked there too.

By makng the air "skip" over the dang landing gear and open wheel well, is there any performance gain? any smoother operation? (we all know how much noisier most planes with completely enclosed retractable landing gear get when we toss out the hardware. planebones
 
Noise is an interesting question. I'm not sure if you were serious or tongue in cheek when you mentioned the noise factor when enclosed gear is changed to open. Are there any 210 drivers who can answer as to whether there is a noise factor?
 
Bones:

Interesting job you had down there :)

I'm curious, even though this is anthing but an apples-to-apples issue: did you note any chang in cruise speed after you added these wind shadow fairings?

Jonathan
 
I have seen this before. I think it was the Navion guys. It was a ramp like deal to deflect the air over the open main wheel wells.

Kevin
 
Ok. We need some aeronautical engineers! Airdams are great for autos. As far as I can see, deflecting air creates drag. Laminar flow reduces drag. Any ideas? Dan Cullman
 
The questions might be
1)is there any reduction in turbulence caused by the wheel wells with these deflectors?
2)Would the drag induced by the holes in the wings be any less with the relative wind deflected around the hole?
I can't believe a deflector would make things worse than an open wheel well with a tire hanging half out of it...
 
Just my opinion, but the Navion - an aircraft I've long admired - is the best example of owners trying to make an aircraft something it never way meant to be. One constant in the aircraft owner universe in the US - aircraft used for pleasure, not working aircraft - is valuing speed so highly that often the chief virtues of an aircraft are overlooked. The Navion is a rugged machine, capable of short and soft field use, with the most comfortable cabin that offers a spectacular view, even for passengers, sitting in seats placed above the two front ones. But soooooo many speed mods have been created for it:

Palo Alto Tail - the angle of incidence of the horizontal stabilizer was such that level trim created drag.

Rear step - the original had a front step...which allegedly created drag.

Flush canopy - not as nifty, IMO, as the original, but smoother.

Wing root fairings - elaborate ones faring mostly aft, mirroring the Bellancas as originally designed.

After market cowl - this is more for changing the cooling from updraft to downdraft cooling, with an eye toward drag reduction.

And the one that works - upgrading the engine to an IO520 or 550. It can actually power through the inherent drag enough to get you more than just greater climb, just as the massive engine added to essentially the same airframe made the Viking a 160kt airplane. The fuel bill, however.... :roll:

Why the heck am I mentioning the Navion in a Bellanca forum? Because it's a great example of folly. Just fly the airplane. It flies as fast as it flies. Some examples of the very same airplane will fly faster, some slower. Unless something is out of rig, or dreadfully wrong structurally, there's no point in worrying about it. Labor, money, and clever design may get you two, three, or perhaps 5mph more, but the cost of even proven mods - Knots2U applied to dirty airplanes that could benefit from cleanup - comes out to $1000.00 per knot. Our triple tails have immense and numerous qualities apart from speed alone.

Jonathan
 
Dan,

You can pass many Navions in a 150HP Bellanca but I guarantee you wont pass everyone. Anyone with 225HP and over will be hard to keep up with.

Kevin
 
My AI talked me out of a 220 hp mod for my Cruisair pointing out I wouldn't gain much speed, but I would increase my climb rate and fuel consumption. Wise advice.
My main focus is elimination of drag. Looking forward to having 392 for various tests :D
 
Lo these many months, Dave, you and I have had this back-and-forth discussion regarding this issue. I, as any person capable of comprehending the written word knows, am firmly in the anti-speed-mod camp. But honestly, I hope you prove me utterly wrong in this "argument." ;) Your ultimately being proven right would be far more interesting and exciting.

Jonathan
 
Above all I intend to enjoy my Cruisair for what it is. The test flights will be secondary.
This whole "speed" thing stems from my idea of what a Cruisair- carefully rigged and cleaned up- can do without major modification; probing the depths of potential I see in this design.
Having yet to actually FLY a Cruisair, I'm really still very excited to see for myself what all the brouhaha is about.
I can't wait to get my hands on that yoke, ease the throttle in, do my little tapdance on the rudder pedals, ease the yoke forward a tad, rotate, and ZOOOOOOMMMMMMM- off into the wild blue yonder! :D
 
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