Air Dams for wheel wells.

I've pursued this with others wise in the ways of aerodynamics and here's the essential problem with what is essentially an urban legend that you can get more speed by faring the gear.

The gear protrude within the high pressure surface (lower wing). Anything the obstructs the low pressure surface prevents laminar flow. Smoothing this can produce modest results, but modest results only because they exist in an area where there'd best be nothing at all. This is why the notions of farings on Bellancas is totally different from the notion of wheel pants on fixed gear aircraft: on the latter, the gear are far away from the wing. I believe this difference bred a misconception that has endured for more than half a century.

One strategy employed by the post Bellanca, Bellanca company in Minnesota was to try to reduce the wetted area in front of the wheel. This was a good idea but, as I noted up-topic, proper rigging without constant vigilence was nearly impossible and, even when rigged properly, the speed gain was modest. Plus, this was done on Vikings - an aircraft where little improvements mean more than they would in an aircraft with fewer horsepower.

The only way to gain SUBSTANTIAL improvement would be to have a bump on top of the wing that would allow the gear to completly retract into the wing. Undoubtedly Giuseppe knew this but found it impractical, as he did the behind the gear farings on the Junior.

Keep in mind that Beech had already introduced fully retractable gear when the 14-19 made its debut, as had North American with the Navion. Thus, you can be reasonably certain that Giuseppe would have made a fully retractable gear if he could of. Problem is, as you all know, his company was not prosperous, and such a major redesign was probably beyond their means.

Cruisairs and Cruisemasters are what they are - the best combination of handling, control harmony, and yet magnificent stability in even rough air, all delivered with defiant excellence of style unmatched in the general aviation fleet.

I'll skip the Henry the 5th St. Crispin's Day speech of "we few, we proud few...." :)

Jonathan
 
hey jonathan!
good observation about surface discontinuities in low/high pressure flow fields. makes sense when you think about other high speed aircraft such as fighters, concorde, etc. all the ordanance, stores and other "sticky-outy-thingies" are slung BELOW the wing and the top is kept very UN-cluttered. and they manage mach speeds (granted, with lots-o-power!)
according to a knowledgable -2 owner i know, one improvement the wheel fairings do give is a marked reduction in rumble and noise in cruise. he reports a modest increase in speed with them, but i'm not sure that there was a careful before/after performance study done.
anyway, it still comes back to the old "stock or customized" question and anyway you slice it, we are still "lucky men, sir!"
blue skies,
vic steelhammer & N522A
 
Drew Peterson said:
NC74392 said:
IS there a good reason why I can't do a little research and develop small air dams in front and to the sides of my wheel wells? Seems to me this is a simple solution to drag created by these huge holes in the wings. :idea:

I currently have a set of molds for the gear fairings on my cruisemaster. I am in the process of lining up a small production run at this time. This has come about due to the help of several Bellanca- type people. I would like to make these as affordable as possible-my cost. These fairings will not have the small doors due to the fact that they can be difficult to keep in rig and their need is questionable.

I have never flown my Cruisemaster with the fairings off, so I am unable to give any info as to their speed value. I simply like the way they clean up the gear. On my airplane I have a small metal fairing that attaches on the under side of the leading edge of the wing just ahead of the top of the landing gear leg. From this a half circle flange protrudes down to smooth the airflow around the top of the landing gear leg when retracted - hence, your air dam.

I do believe that the fixed fairing attached to the underside of the wing just behind the the tire (when the gear is retracted) may produce the greatest drag reduction.

If anyone is interested in the fairings please let me know as I would like to keep the cost as low as possible.
 
That would be great, Mark!

I am sorry if I came across as a kill-joy on this. The last thing I wanted to hear from these experts - including the current incarnation of Bellanca - is the fundamental aerodynamic reasons why I can't get ten more knots with a non intrusive faring, gap seals around the wheels, or the like.

The consensus was the improvement could be in the area of 3-4 mph, IF the faring had a good seal and if the faring extended to the flap. The question then comes down Vic's conclusion.

Where this takes on the proportion of an urban legend is when you go to Columbia (the fly-in in California) and have folks point to their sawed off C152 wheel pants and say, "Got 10 mph from those."

Drew's magnificent flying machine came with farings, thus there is no before and after. It's fast. It also has 110 more horsepower than a 14-13, 70 more horsepower than a 14-19, 30 more mph than a stock 14-19-2, a wonderful paint job, and very smooth wings.

Finally, I'm certain that some owners will see more improvement than others. Vic mentioned the -2 owner that experienced rumbling without the farings. Clearly there's something going on with his airplane that isn't going on in all such airplanes. For example, I don't have that problem. Thus, I'll bet that each Bellanca - given that they're hand made and old - has at least a slightly different wheel to wheel well fit.

In short, wheel well farings, air damns and such are not, by any means, a dead end. It's simply that the magnitude of improvement is limited.

Jonathan
 
First of all, I'd like to thank everybody on this discussion board for adding to my education. I have found your comments most enlightening!

When discussing the value of wheel fairings, maybe it is appropriate to ask what the value would be for climb and descent? Since my Cruisair has the old "armstrong" gear, I concentrate flying the airplane until I'm well above the earth, so my crank-up gear is "down 'n danglin'". Perhaps the gear fairings might increase climb rate when the airplane is dirty?

Despite legend, I guess, Bob Petten is old, but still very alive and well and living near Las Vegas. He is the guy who microballooned his wings, put on smaller stabilizer ends, and made the Drew Peterson type gear fairings. He swears he got 174mph in level flight from them. He also said he had trouble keeping them closed. Who knows, though, what the greatest contributor to his speed was.

Comments?

You guys are great!

Mike
 
Hi Drew,
If I am not on your list for gear doors, would you please put me on it. I just like the way they look, and besides, when I finish installing the JATO unit, I know I will be able to beat everyone off the blocks to FL250. From there on, I will be relying on my new warp drive to leave them behind.
Larry
ps- Randy, whats happening with the ones I sent you?
 
Go to the experamental side and see what they do to make an airplane faster. Small inlets on cowl , good fairings, closed wheel wells, Tight door seals . The list goes on. Every little bit helps. At the races they even tape the gap from the engine cowl to the boot cowl :lol: :lol:
 
It seems to me the greatest drag is not created by the tires hanging out of the wing, but by the big holes they retract into. I'd like to see some data on drag reduction using deflectors to keep the airflow out of the holes.
Air is somewhat like water. If you have a hose and spray high-speed water over a surface with a hole in it, the hole will cause alot of spray (turbulence). If you take a simple air dam and place it infront of and taper down the sides of the hole, it will deflect the water up and over the hole.
This boils down to one glitch- will the air dams around the holes cause too much turbulence under the flaps?

There must be some data out there- possibly from NASCAR? I mean, there's a reason they use fender flares to deflect air from around the tires...
 
Drew.
Have you been able to reproduce any? Please email me at earlar@yahoo.com as I have aquired a rough set similar to yours.

Drew Peterson said:
NC74392 said:
IS there a good reason why I can't do a little research and develop small air dams in front and to the sides of my wheel wells? Seems to me this is a simple solution to drag created by these huge holes in the wings. :idea:

I currently have a set of molds for the gear fairings on my cruisemaster. I am in the process of lining up a small production run at this time. This has come about due to the help of several Bellanca- type people. I would like to make these as affordable as possible-my cost. These fairings will not have the small doors due to the fact that they can be difficult to keep in rig and their need is questionable.

I have never flown my Cruisemaster with the fairings off, so I am unable to give any info as to their speed value. I simply like the way they clean up the gear. On my airplane I have a small metal fairing that attaches on the under side of the leading edge of the wing just ahead of the top of the landing gear leg. From this a half circle flange protrudes down to smooth the airflow around the top of the landing gear leg when retracted - hence, your air dam.

I do believe that the fixed fairing attached to the underside of the wing just behind the the tire (when the gear is retracted) may produce the greatest drag reduction.

If anyone is interested in the fairings please let me know as I would like to keep the cost as low as possible.
 
Wow - looking back, it's hard to believe that Drew's post on this subject was over two and a half years ago. Sometimes, given time acceleration with age, I wonder why I'm not 80 yet :wink:

Yet another thing to consider is the AoA of an aircraft in cruise. Our magnificent machines have a very low AoA in this segment of flight, and this could easily affect how effective gear farings would be. Okay....I ran into another Bellanca nut who chucked his farings after failing to see any speed difference and was given the above thought food by someone he knew. Yes....yes, this is how urban legends are born :lol:

Jonathan
 
Hi Johnathan!

I was reading an article about Ozzie Levy's Cruisair. He mentioned he was not going to make farings or gear doors, but he was a little interested in making a wing hole seal- sort of a gasket that would seal around the tire upon retract.

Ever notice the wind deflectors on a B-17 around the waist gunners' windows? These little sideways "flaps" pop out whenever the window is opened (G model) right in front of the window opening perpendicular to the slipstream. I think they also have one in front of the radio operator's top window.

Question is, how much did they help? Were they put there for crew comfort only or to help reduce drag as well? I remember reading "Half a Wing, Three Engines, and a Prayer" and how the waist gunners were miserable with the relative wind whipping into the open fuselage windows.

Here's a link to a picture of what I had in mind:

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

Something very simple. I have no idea how high to make it however. Sure would be interesting to have access to a wind tunnel :D
 
Hi, Dave. Long time!

I wonder if you could simply make it out of a somwhat thick piece of rubber with a slit in the middle? Too bad our Cruisairs aren't experimental!

Mike
 
Mike:

Just because our triple tails are not in the experimental category doesn't mean you cannot experiment. Just keep in mind that if you do you become a test pilot. With Cruisemasters this is even a more important point as our landing gear system is hydraulic. Should a pump take a nap or dump our fluid, or the power pack fail along with the hand pump backup, our final defense against a gear up landing - using gravity to get the gear to drop - might be gone if the seal holds the gear up. One of those unintended consequences :oops:

Dave:

I understand your speculaton regarding the turret. It would difficult to know what, exactly, the designers had in mind. However, given that the pre-war notion of bombers that could out-run fighters had vanished early in war, clearly the addition of the chin turret after the G model indicates a change in strategy from speed to defense on the B-17. The A26 was a different matter entirely. It was designed for speed and designers kept it very clean. They did a great job; after its bomb load was dropped, it shot down more fighters than it suffered losses from them. Then again the A26 was our only airplane designed and delivered in substantial numbers after we entered the war.

I guess the only way to settle this is to have someone try one of these notions in a rigorous before and after fashion....you look like a fine candidate, Dave :)

Jonathan
 
Hey! I resemble that remark!

Hmmm. yeah, I guess I could make these up without trouble, but I really wonder if it's worth the trouble. Definitely something to do AFTER 392 is back in the air! :D
 
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