What do Bigger Ailerons and Rudder do?

[mars01]

I have a question for the experts.

Take a Christian Eagle for example.

If someone increases the Ailerons by 20% and squares off the tail giving it a larger Rudder, what are the pros and cons?

[Karnak]

Off hand I'd guess better low speed control at the sacrifice of high speed control.  Fly the A6M5b in AH for a prime example of an aircraft that has overly larger ailerons.

[hitech]

Cons:
On larger rudder: Drag and tail needs to be more riged to to posible increase in force.

Ail: Stiffinece of wing, and posible overstress of wing. Fludder problems. Increased control force.


Pros: More control at slow speeds.

[mars01]

Excellent!  Thanks!!!

[Hyrax81st]

Another good example would be JU-87, Stuka... which had to fly around with a small elephant strapped to its belly.

[Karnak]

Originally posted by Hyrax81st
Another good example would be JU-87, Stuka... which had to fly around with a small elephant strapped to its belly.

Denser than the small elephant so it produces less drag and the center of gravity doesn't shift around as it struggles to get free or panics.  It also lacks the trunk with which to begin the disassembly of the aircraft in it's rage/panic.

[mars01]

LOL,

Could you guys see any benefit in regards to Compettion Aerobatics to a Christen Eagle that had 20% larger Ailerons and a bigger Rudder?

[aSTAR]

NADA: Bigger throw will give snappier performance. I increaced the throw on my elevators and ailerons and performed spectacular snaps plus sharper point rolls, was done on my Pitts1.
Personnaly I would not enlarge the surfaces, DRAG.
My 2c worht. Dale knows about this, ED.
aSTAR

[Kevin14]

Originally posted by aSTAR
NADA: Bigger throw will give snappier performance. I increaced the throw on my elevators and ailerons and performed spectacular snaps plus sharper point rolls, was done on my Pitts1.
Personnaly I would not enlarge the surfaces, DRAG.
My 2c worht. Dale knows about this, ED.
aSTAR

By surfaces do you mean the wings?  What was the point of leading edge slats in the 109s for example?  Did they create more lift for the aircraft?  

PS, can someone post a screenie of these slats?

[mars01]

NADA: Bigger throw will give snappier performance. I increaced the throw on my elevators and ailerons and performed spectacular snaps plus sharper point rolls, was done on my Pitts1.
Personnaly I would not enlarge the surfaces, DRAG.
My 2c worht. Dale knows about this, ED.
aSTAR

Nice exactly what I was looking for you guys.

Thanks for the Help.

[Blue Mako]

Originally posted by hitech
Cons:
On larger rudder: Drag and tail needs to be more riged to to posible increase in force.

Ail: Stiffinece of wing, and posible overstress of wing. Fludder problems. Increased control force.


Pros: More control at slow speeds.

Fludder = flutter.  

Larger control surfaces give increased control authority (ie. the ability to generate higher forces to make the plane go where you want it to quicker) but this has the down sides that HT mentioned.

[Simaril]

Originally posted by Karnak
Denser than the small elephant so it produces less drag and the center of gravity doesn't shift around as it struggles to get free or panics.  It also lacks the trunk with which to begin the disassembly of the aircraft in it's rage/panic.

For crying out loud, Karnak, you completely overlooked the effects of tusk goring damage on the craft's ventral aspect!!


On the plus side, you have to consider that the elephant's panicked loss of bowel control has enormous morale effect on targeted troops.

HT, could we model this payload?

[mars01]

Larger control surfaces give increased control authority (ie. the ability to generate higher forces to make the plane go where you want it to quicker) but this has the down sides that HT mentioned.

So are you saying that,

for example:

A Christen Eagle's roll rate is 2 seconds, if I increase the size of the Aileron I could increase my roll rate to faster than 2 seconds?

[SlapShot]

I think that aStar recommendation would be the way to go.

He simply increased the throw/travel of the ailerons which I would think gives him MORE bite into the air. Wouldn't this give you a quciker rollrate than what you have now, and without the increased drag factor that larger surfaces would provide.

[Blue Mako]

When you move your controls you are changing the profile of your wing at the location of the controls.  By deflecting the control you change the amount of curvature of the profile.  Larger control size means that you get a greater change in the curvature of the profile for a given control deflection.  (Basically you are using two different approaches to do the same thing.)  This change in profile has the effect of changing the amount of lift that section of wing is trying to produce.

The problem with increasing the curvature of the wing (by either extra control deflection or increased control size) is that you run the risk of asking too much lift from that section of the wing, causing it to stall.  This is the phenomenom (sp?) that leads to aileron "reversal" at low speeds.  In addition, the change in controls leads to changes in the wing properties which are related to flutter (a problem related to wing elasticity and aerodynamic effects).  Flutter usually results in sudden departure of wings from airframes and begins so quickly that there is usually little chance for the pilot to react.  The weight and balancing of the controls is also effected which has bearing on flutter and also control forces that the pilot has to deal with.

Also, when you work the wing too hard by increasing the aileron deflections you run the risk of stalling the wing at higher speeds than normal and overloading the wing at speeds which are below the max maneuver speeds.  Both of these things are not good.

In reality the design of control surfaces is a very complex task and is an artform on performance aircraft.  Many aircraft were lost trying to perfect it.

My advice to anyone is not to stuff around with the rigging or sizes of control surfaces on a plane if anyone is going to put their butt in it.  It isn't something to be done lightly, I've already seen the aftermath of an accident where someone changed the skins on a glider's ailerons from fabric to aluminium.  This changed the weight and balance of the aileron and caused flutter which took both wingtips (and most of the rest of each wing) off.  Not pretty.  Fortunately (in a way) it was the owner/pilot who had made the change and was flying at the time, no one else was killed (natural selection?).

WRT changing the throw range of a control: this also increases the drag that you get when you make a control input.  More deflection = greater drag.

Manufacturer's put limits on things for a reason.  If you want to exceed them, seek expert help...

btw sorry for the wall of text.  I hope it's informative.