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

Question about rudder angles

Reply

Old 05-15-2008, 03:42 AM
  #1  
golf_lake
Member
Thread Starter
 
Join Date: Sep 2002
Location: Adelaide
Posts: 78
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Question about rudder angles


Being new to this and trying to learn to fly on my own I have an annoying problem with my XP electrafun.

When turning it drops it nose and will go into a dive unless its turned really slow.

I have already moved the push rods for both the rudder and elevator to the most outside holes to reduce movement so I don’t over control it.

Looking at the rudder it slopes back at a fair angle, I cant help thinking that this angle is giving the tail end some lift as it turns.

Would cutting the tail fin so the rudder section is more upright, would this reduce this effect?

What other effects would this have?
golf_lake is offline  
Reply With Quote
Old 05-15-2008, 06:40 AM
  #2  
LouW
Senior Member
 
LouW's Avatar
 
Join Date: Dec 2002
Location: Moreland, GA
Posts: 809
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

My guess is that you are turning using rudder only. The action you describe is perfectly normal. The rudder causes the wing to bank, which causes the airplane to turn. However the wing is no longer lifting straight up but is tilted also. The amount of lift lifting upward is less so the airplane begins to descend.

The solution is to simply apply a little up elevator to increase lift on the wing during the turn. It may help to think of the rudder as the “bank” control and the elevator as the “turn” control.

(Changing the slope of the rudder would have very little effect either way.)
LouW is offline  
Reply With Quote
Old 05-15-2008, 06:44 AM
  #3  
wellss
Senior Member
 
Join Date: Jun 2002
Location: St. Catharines, ON, CANADA
Posts: 145
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

Not likely, if anything it would cause the nose to pitch up, right?

It could be gyroscopic effect of the prop. The faster it yaws, the more it will pitch. Depending on the direction of rotation of the propeller, it will be worse in one direction. Not much you can do about it, except what you've done and apply more elevator in the turn.
wellss is offline  
Reply With Quote
Old 05-15-2008, 07:04 AM
  #4  
golf_lake
Member
Thread Starter
 
Join Date: Sep 2002
Location: Adelaide
Posts: 78
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

Thanks for the input
golf_lake is offline  
Reply With Quote
Old 05-15-2008, 12:07 PM
  #5  
R8893
My Feedback: (20)
 
Join Date: Oct 2002
Location: Cincinnati, OH,
Posts: 894
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

Being nose heavy will also cause the nose to drop in a turn even with some up elevator input.
R8893 is offline  
Reply With Quote
Old 05-15-2008, 12:58 PM
  #6  
crasherboy
Senior Member
 
Join Date: Oct 2006
Location: Bryant Pond, ME
Posts: 113
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

Here is 2 cents. Being nose heavy could cause you some problems,aside from that I don't think rudder would have much to do with that. In a full scale airplane,one has to give it a certain amount of up elevator when making a turn .The steeper the turn [bank] the more up elevator you have to apply. The same goes for our models to. I training for a pilots licence they have you do what they call a 720 in which you do a very steep turn so as to keep your wing tip on a point on the ground[by sight that is]. Believe me it takes plenty of up elevator to keep the plane from falling off into a dive. Same thing as us modelers have to face. I have a full scale licence,but I won't be getting a medical anymore,so now I am stuck with the models. Do you have a computer radio where you could program in some up elevator in a turn? This would help you a lot if you could. If you don't then it is up to you to so it.
crasherboy is offline  
Reply With Quote
Old 05-15-2008, 01:24 PM
  #7  
Sport_Pilot
 
Sport_Pilot's Avatar
 
Join Date: Jan 2002
Location: Acworth, GA
Posts: 16,916
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Question about rudder angles

Crusherboy is correct. You have to add up elevator in turns. Even with aeileron's. This is from the fact that a banked wing is creating its lift at an angle to the earth, this angle means part of the lift is now turning the aircraft, and there is less lift keeping it in the air. You have to add up elevator to add lift, this speeds up the turn as well as to keep it level.
Sport_Pilot is offline  
Reply With Quote

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