Control surface alignment

I'm hoping the home built community can assist me with a small problem.
I own a glider that does not fly straight without applying a little
constant cross control (L stick and R rudder). If hands are removed
from the controls, it slips (or yaws?) to the left, and then the nose
gently swings around to the right. If allowed to continue, the
aircraft begins to dive to the right and rapidly builds up airspeed.

The aircraft was never damaged but may have had control rods for the
ailerons replaced putting the control surfaces out of alignment. The
maintance manual gives the proper aileron and flap deflection angles.
The angle is measured from a reference point on the bottom surface of
the wing 100mm forward of the aileron-wing junction to the trailing
edge of the aileron.

My question is how do you measure the angles of the control surfaces to
see if they are within tolerance of their deflection angles?

wrote
My question is how do you measure the angles of the control surfaces to
see if they are within tolerance of their deflection angles?

The easy way is to find someone with, or buy, a "smart level" that
electronicaly reads out the degrees of the surface it is set upon. A real
handy tool to have around, for many other purposes. I would get one that
has a small removable core with the guts, that can be put into different
levels of many different lengths. You can also make a widget using a
protractor and a plumb bob hanging down from it's center pivot point. Make
sure the aircraft has been blocked up level, and stationary.

Check that the wings themselves were rigged correctly, with the same angle
of incidence, if it has removable wings, and that the trim tabs are where
they are all supposed to be.
--
Jim in NC

wrote:

My question is how do you measure the angles of the control surfaces to
see if they are within tolerance of their deflection angles?


One of these cost about $2 at Harbor Freight. (The tool, not the elevon).

http://ernest.isa-geek.org/Delta/Pic...DownTravel.jpg

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

"Ernest Christley" wrote \\

One of these cost about $2 at Harbor Freight. (The tool, not the elevon).

http://ernest.isa-geek.org/Delta/Pic...DownTravel.jpg

How accurate and reliable are those things? I'll bet they are not accurate
to more than 2 degrees, and reliable?

Good for guesses, but I wouldn't even want to build a house with one, let
alone an airplane.

Sorry if I step on any toes with this.
--
Jim in NC

Morgans wrote:
"Ernest Christley" wrote \\

One of these cost about $2 at Harbor Freight. (The tool, not the elevon).

http://ernest.isa-geek.org/Delta/Pic...DownTravel.jpg


How accurate and reliable are those things? I'll bet they are not accurate
to more than 2 degrees, and reliable?

Good for guesses, but I wouldn't even want to build a house with one, let
alone an airplane.

Sorry if I step on any toes with this.

Guess you would never ride with me in my RV-6 then because that is what
I used. On July 14 I will have been flying it for 16 years so I guess
they must work. You are right I would never build a house with one.:-)

Jerry

wrote in message ups.com...
I'm hoping the home built community can assist me with a small problem.
I own a glider that does not fly straight without applying a little
constant cross control (L stick and R rudder). If hands are removed
from the controls, it slips (or yaws?) to the left, and then the nose
gently swings around to the right. If allowed to continue, the
aircraft begins to dive to the right and rapidly builds up airspeed.

The aircraft was never damaged but may have had control rods for the
ailerons replaced putting the control surfaces out of alignment. The
maintance manual gives the proper aileron and flap deflection angles.
The angle is measured from a reference point on the bottom surface of
the wing 100mm forward of the aileron-wing junction to the trailing
edge of the aileron.

My question is how do you measure the angles of the control surfaces to
see if they are within tolerance of their deflection angles?



Sounds like more a matter of where the neutral points are rigged, not what the deflection is at the stops. Maybe a warp
in the left wing; less washout? Does the rudder have centering springs? If so an imbalance there...

Morgans wrote:
"Ernest Christley" wrote \\

One of these cost about $2 at Harbor Freight. (The tool, not the elevon).

http://ernest.isa-geek.org/Delta/Pic...DownTravel.jpg


How accurate and reliable are those things? I'll bet they are not accurate
to more than 2 degrees, and reliable?

Good for guesses, but I wouldn't even want to build a house with one, let
alone an airplane.

Sorry if I step on any toes with this.

How accurate is a plumb bob?

All this is, is a weight on a pivot. The accuracy is wholy dependant
upon the radius of the scale. I'll leave the envisioning of the
geometry as an exercise.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

"Ernest Christley" wrote

All this is, is a weight on a pivot. The accuracy is wholy dependant
upon the radius of the scale. I'll leave the envisioning of the
geometry as an exercise.

My reasons for doubting its accuracy are two. One, is the closeness
together of the degree markings. No doubt, they are very small distances
between the degrees. Could you see if it was reading 11.3, or 11.8, or even
if it was 11 or 13? Two, if there is any friction or binding, the weight
would not allow the mechanism to be pointing to the true number that it
should be. In a cheap plastic mechanism, I think the chances of a non
binding system is pretty low.
--
Jim in NC

Morgans wrote:
"Ernest Christley" wrote


All this is, is a weight on a pivot. The accuracy is wholy dependant
upon the radius of the scale. I'll leave the envisioning of the
geometry as an exercise.


My reasons for doubting its accuracy are two. One, is the closeness
together of the degree markings. No doubt, they are very small distances
between the degrees. Could you see if it was reading 11.3, or 11.8, or even
if it was 11 or 13? Two, if there is any friction or binding, the weight
would not allow the mechanism to be pointing to the true number that it
should be. In a cheap plastic mechanism, I think the chances of a non
binding system is pretty low.

You are correct, but...

-a plastic housing doesn't necessarily imply plastic movements
-only a very small amount of weight hangs on that movement
-you can only guess between 11.3 and 11.8, but who cares?! It's control
surfaces, not wings. I use a water level for that, because being off by
..1 degree will show up as a very noticeable 1/16" difference over 8ft.
With control surfaces, you adjust them centered with the stick centered
and then verify that the movements are withing a degree or two. You
never see where they're actually at in a light plane, just how they
'feel' and 'react'. (I think I've stated this last sentiment poorly.)

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

In article ,
Ernest Christley wrote:
Morgans wrote:
"Ernest Christley" wrote \\

One of these cost about $2 at Harbor Freight. (The tool, not the elevon).

http://ernest.isa-geek.org/Delta/Pic...DownTravel.jpg


How accurate and reliable are those things? I'll bet they are not accurate
to more than 2 degrees, and reliable?

Good for guesses, but I wouldn't even want to build a house with one, let
alone an airplane.

Sorry if I step on any toes with this.

How accurate is a plumb bob?

4.271839526+ times more accurate than a Billy-Bob. *snicker*