Hi ya'll, again!
The following will refer, be a c


ontinuation, of my post #51.
#51 described the basic forces envolved with an aircraft,
This post will describe how the forces are applied.
To begin one must understand that an aircraft flys because the
resultent lift it creates is greater than gravity,
Secondly that most all portions of an aircraft create lift when in
motion> major lift and miniscule.
The total of all lift is said to terminate at the neutral point.
A comparison could be a ceiling light fixture which may have a
complex make up. The ceiling represents lift. the fixture is attached to it, where the attachment occurs on the fixture would
be the fixture's neutral point.
How is lift created? One common sense explaination is as follows.
Recall> air molecules have space between them and a force can
cause the molecules to move closer together and in doing so a
resultent force is created.
So. as an airfoil moves through air it must displace the air and as
a result compresses it creating force.
To produce lift the airfoil must have an angle of attack to the line
of flight.
Thus the moving airfoil compresses the air it meets and then
splits it. Some passing under the foil and some over it. Both air
passages contain kenetic energy produced by the compression.
The lower passage expends the stored energy by pushing against
the foil's lower side. an upward force.
The passage over the upper side is further compressed by the
upwards curve of the airfoil in it's forward portion.
The upper foil curve changes from an upward direction to downward. ( foil high point?)
When the kenetic force loaded airflow reachs the high point that
energy tends to carry the air in a straight line. In effect the air
leaves the upper surface, so to speak. When the K energy dissapates the air wishes to return to its origional location so in
doing that it drops back down.
This action creates low pressure on the airfoil upper side and high pressure on the lower side. the combo of the two represents
the foil's lift.
Should also say an aircraft in flight is there because lift is greater
than gravity, Gravity is overcome at the lift neutral point. The craft
could be considered suspended at the neutral point.
So then it muist be that ALL forces created aerodynamically must
have their resultent at the neutral point
Another consideration is that an airfoil creates work by moving
through air. The air does not move, craft and foil does.
In that respect it does not matter the craft's attitude. What ever
it may be the aerodynamic forces remain the same
Gravity>Being constantly vertical to earth it is the only force which has any change with craft attitude.
Say in level flight the gravity force is at 90 degrees to the line of
flight. The craft enters a 45 degree climb angle. The gravity force
is always at the craft's center of gravity but before it was applied
at a 90 deg. angle to L of F, now the application is at 45 deg. So
with craft attitude changes the gravity force is constantly changing application angle./
Drag> It is a negative force which can be reduced but not eliminated. The lower this force the greater is the craft efficency.
The drag force is the result of the effort used to move the craft.
at a stand still there is no drag.
The drag force changes with flying speed. it requires energy to
increase flying speed, more force, drag force increase is the equal
and opposite of the force used to create the change.
Drag is created by the air's resistance (compression?) to anything moving through it.
Thus every portion of the moving craft disturbs the air which
results in drag. Thus anything which protrudes the slightest from
the craft's surface is a detriment.
Drag is also produced as the lift is produced. Recall in the lift
discussion the air was compressed? The opposite of that force is
drag. Other lift factors enter in but that gets unnecessarily complex.
Thrust> this causes craft to move. It is created by compressing
and accelerating air. When air is accelerated it is compressed and
a opposite force results, jet propulsion.
Propeller> A propeller creates thrust in two manners.
First it has an airfoil which acts as if it were a wing, creates lift
in a forward direction.
Secondly, especially when pitch is more than craft flying speed the rear of the prop acts as a shovel, moving air back from it and
in turn compressing it. The compression force tends to react on the prop pushing it forward, the total of the two represents the
amount of thrust.
Hopefully with the facts from #51 plus this at may be much easier
to understand your aircraft and even diagnois it's actions, this is
presented as being helpful and nothing else.
Know that the information is from Hal deBolt's knowledge gained
from reasearch, developemnt and experience. it comes from no
where else. It also is intended for modeler's education and nothing more.
If this has raised questions understand that I am available to
at least attempt to resolve them. just contact me. OK?
Good luck!

Hal [email protected]