controll surface question
05-12-2009, 03:23 PM
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controll surface question
Hey I was tempted to ask this in the aerodynamics forum, but thought this would be a better place.
I searched the net for about an hour today, and need to know if a beveled LE on a control surface (rudder, elevator) is better than a rounded one. The reason I ask is: Im building a stand off scale bellanca scout, and i just so happen to have acess to 2 of them in the hangar at the flying club. I noticed that it, and other aircraft use a rounded edge, where most models use a beveled edge.
Which one is better?
I searched the net for about an hour today, and need to know if a beveled LE on a control surface (rudder, elevator) is better than a rounded one. The reason I ask is: Im building a stand off scale bellanca scout, and i just so happen to have acess to 2 of them in the hangar at the flying club. I noticed that it, and other aircraft use a rounded edge, where most models use a beveled edge.
Which one is better?
05-12-2009, 03:29 PM
#2
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RE: controll surface question
Either are acceptable. Perhaps it is easier to identify the center of a beveled leading edge when installing hinges. Beveled might also make it easier to attain more control throw. A flat/squared trailing edge has been shown to be less susceptible to flutter.
05-12-2009, 03:50 PM
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RE: controll surface question
thanks for the quick reply! I think i will use the tapered method. Just to make things easier on myself. As per the square TE thing, I looked up diagrams of airflow over certain objects, and you wouldnt think that setup would be more efficient, but it is. I might still taper the surfaces a bit, just for cosmetics more than anything.
Once again, thanks.
Once again, thanks.
05-12-2009, 10:04 PM
#4
RE: controll surface question
You need to taper the LE!
A rounded surface will need to hinge in the center of the radius or it could make your hinges fail! (or you will need a very large gap to prevent hinge failure)
I would draw a diagram, but I'm at Joe nall right now and don't have access to my Photoshop.
A rounded surface will need to hinge in the center of the radius or it could make your hinges fail! (or you will need a very large gap to prevent hinge failure)
I would draw a diagram, but I'm at Joe nall right now and don't have access to my Photoshop.
05-12-2009, 10:17 PM
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RE: controll surface question
Ya im going to go that route. Dont worry about the diagram, although you're famous for diagrams that make even the most complicated things seem simple. This is a 80" span plane, so i would hate to have a hinge fail. If you still want to post a diagram, by all means go ahead. Maybe someone with a similar question will need an answer down the road.
Oh, and i am using robart hinge points, I dont know if that makes a difference, but i used them once, and now im hooked
Oh, and i am using robart hinge points, I dont know if that makes a difference, but i used them once, and now im hooked
05-12-2009, 10:43 PM
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RE: controll surface question
Flat square trailing edge - While I have no scientific test data and only empirical evidence, it is fairly well accepted in the circles of pattern pilots I've been known to hang out with, that blunt (squared) and often thick trailing edges help tracking. Razor sharp trailing edges seem to cause tracking issues. Some pilots have even been known to apply triangle stock to the TE of control surfaces to make them really thick. With a thick blunt TE, it seems the control surface is being stabilized or dampened, which would maybe imply less chance for flutter.
05-12-2009, 10:56 PM
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RE: controll surface question
ORIGINAL: JohnW
Flat square trailing edge - While I have no scientific test data and only empirical evidence, it is fairly well accepted in the circles of pattern pilots I've been known to hang out with, that blunt (squared) and often thick trailing edges help tracking. Razor sharp trailing edges seem to cause tracking issues. Some pilots have even been known to apply triangle stock to the TE of control surfaces to make them really thick. With a thick blunt TE, it seems the control surface is being stabilized or dampened, which would maybe imply less chance for flutter.
Flat square trailing edge - While I have no scientific test data and only empirical evidence, it is fairly well accepted in the circles of pattern pilots I've been known to hang out with, that blunt (squared) and often thick trailing edges help tracking. Razor sharp trailing edges seem to cause tracking issues. Some pilots have even been known to apply triangle stock to the TE of control surfaces to make them really thick. With a thick blunt TE, it seems the control surface is being stabilized or dampened, which would maybe imply less chance for flutter.
I would buy the tracking concept (or "drag" concept). Just look at most of the indoor pattern planes. But I don't agree with the idea that "stabilized or dampened, which would maybe imply less chance of flutter." Totally different animals.
Kurt
05-12-2009, 11:13 PM
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RE: controll surface question
http://www.f1technical.net/articles/...mages/drag.gif
this is probably why it doesnt cause flutter and helps with maneuvers. It doesnt show the general airflow, but it shows the drag coefficient. (lower drag, means less turbulent air)
this is probably why it doesnt cause flutter and helps with maneuvers. It doesnt show the general airflow, but it shows the drag coefficient. (lower drag, means less turbulent air)
05-13-2009, 12:52 AM
#10
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RE: controll surface question
So much to learn....too little time. The internet has definitely allowed a plethora of information to flow within reach and I am amazed at the gigantic amount of information or the size of my ignorance of model flight..............considering I can take-off, fly and land. Gentlemen....thanks for good info.
larry
larry
