Go Back  RCU Forums > RC Airplanes > Aerodynamics
Reload this Page >

do ailerons provide lift?

Notices
Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

do ailerons provide lift?

Old 02-07-2013, 10:12 AM
  #176  
eddieC
Senior Member
My Feedback: (2)
 
eddieC's Avatar
 
Join Date: Nov 2002
Location: Jackson, MI
Posts: 2,102
Likes: 0
Received 0 Likes on 0 Posts
Default RE: do ailerons provide lift?

As you can see from BMatthews post, you can still get lift at negative A0A. 

I suspected as much, from playing with undercambered airfoils. 
Fortunately, mankind has progressed since the Wright Flyer and its ilk. For more conventional, efficient airfoils, I believe my original statements still are true. My bad, thinking we were talking about present day technology. 
Old 02-07-2013, 01:58 PM
  #177  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,446
Likes: 0
Received 12 Likes on 10 Posts
Default RE: do ailerons provide lift?

ORIGINAL: eddieC
I suspected as much, from playing with undercambered airfoils.
Fortunately, mankind has progressed since the Wright Flyer and its ilk. For more conventional, efficient airfoils, I believe my original statements still are true. My bad, thinking we were talking about present day technology.

Positively cambered airfloils can produce lift at negative angles of attack, they don't necessarily have to be undercambered.
Old 02-07-2013, 02:14 PM
  #178  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 3 Likes on 3 Posts
Default RE: do ailerons provide lift?

There is no lift at zero or negative angles
Old 02-07-2013, 02:58 PM
  #179  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,446
Likes: 0
Received 12 Likes on 10 Posts
Default RE: do ailerons provide lift?


ORIGINAL: rmh

There is no lift at zero or negative angles

Didn't you see BMatthews curves?


Unless you defined angle of attack to be reference to the zero lift line and not the chord line, you still have lift at negative AoA.

Attached Thumbnails Click image for larger version

Name:	Zx71417.jpg
Views:	41
Size:	113.4 KB
ID:	1849328  
Old 02-07-2013, 03:53 PM
  #180  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 3 Likes on 3 Posts
Default RE: do ailerons provide lift?

Yes, I saw that - The definitions of zero lift line and the chord line - are the problem.
You can NOT have lift if the effective AOA is zero or less
The concept of a lifting surface is simple
it is any shape which may develop unequal pressure- Typically higher pressures under the shape - lower pressures above
How efficiently it does this is quite a different matter . The shape may be perfectly flat -and simply forced to hold an angle of attack
OR it may be a flat sheet - curved and forced to move at a given angle of attack
OR it may be a rather involved combination of curves
IF you change the angle it is moving , such that pressure above and below are equal- THAT is a zero lift path draw that line -
it is the zero lift line .
Old 02-07-2013, 04:20 PM
  #181  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,446
Likes: 0
Received 12 Likes on 10 Posts
Default RE: do ailerons provide lift?

Let me see if I understand.

"When an airfoil is set to its zero lift AoA, it creates.....wait for it.....zero lift"


I found this on the internets:

As a wing moves through the air, the wing is inclined to the flight direction at some angle. The angle between the chord line and the flight direction is called the angle of attack and has a large effect on the lift generated by a wing.

And from the same webpage

Notice on this plot that at zero angle a small amount of lift is generated because of the airfoil shape. If the airfoil had been symmetric, the lift would be zero at zero angle of attack.
Old 02-07-2013, 04:36 PM
  #182  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,446
Likes: 0
Received 12 Likes on 10 Posts
Default RE: do ailerons provide lift?

oops almost forgot the website was


www.nasa.gov
Old 02-07-2013, 05:48 PM
  #183  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 3 Likes on 3 Posts
Default RE: do ailerons provide lift?

Good ol NASA
This is simply an exercize in logic
If No lift is produced was by the moving airfoilthere was no effective angle of attack
stated differently - -there was no effective pressure difference top to bottom
- the wing must be held at some angle to acheive an effective AOA
depending on the shape utilized the appearance of the effective AOA can be misleading . as soon as you throw in"chord line ", things get cloudy
If your idea of the chord line is different than someone elses idea of chord line the AOA will be a different number.
wings ar all about getting effective pressure difference - in the most efficient manner .
How can we as poor model builders know when we have selected the optomized shape?
it's tricky as once yo u change weight - speed and load and speed range- the best shape changes - as does the the necessary shape use to prevent the wing from twisting /bending.
It's all a SWAG- and trying for some "perfect" shape is simply a make work project.
Old 02-07-2013, 08:42 PM
  #184  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,057
Received 0 Likes on 0 Posts
Default RE: do ailerons provide lift?

http://en.wikipedia.org/wiki/Angle_of_attack

http://en.wikipedia.org/wiki/Zero_lift_axis
Old 02-08-2013, 06:11 AM
  #185  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 3 Likes on 3 Posts
Default RE: do ailerons provide lift?

paragraph 2 says it

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.