Where to begin....
 

Hi All,

I've built a couple of boxed models and am fairly familiar with building techniques and I'm getting the bug to design and build my own plane.

One problem....I know nothing about aerodynamics and haven't a clue as to where I start my research. Any good books or on-line resources you can suggest?

Spads are definitely appealing, but at the same time I want to understand a little bit of the theory of model aerodynamics before I start.

Any help you can offer would be greatly appreciated.

Thanks

Slehmann

Yep
 

Because there have been some very bright contributors on this forum, I would recommend the simplest answer...

Just search right here in the "Aerodynamics" forum, and you'll find a wealth of information on almost every aerodynamic issue that applies to models, as well as suggestions for study materials, lots of links to various web sites, and plenty of photos and drawings. (and some heated debates!)

"Ollie" (Oliver Wilson) has been an especially great contributor, and there's a virtual "library" of information here posted by him.

Where to begin....
 

slehman,

I think that the best approach for you depends on your background and how much effort you are willing to put in. One book that I think is really good is "Model Aircraft Aerodynamics", by Martin Simons. There is a web page called "Practical R/C Model Design", which is very light on theory, but gives some ranges for dimensions & proportions. The URL is www.uoguelph.ca/~antoon/hobby/pmdesign.htm. There are lots of web sites that have pretty good stuff on aerodynamics, but you may find that they are better suited for finding answers to specific questions than giving an overall understanding. You may want to do a bunch of Google searches. I have found lots of good sites that way.

Good luck,

banktoturn

Hey THANKS!!
 

Both very helpful suggestions, but I think you're right Bank, This forum and others like it on Scratch building are more places to find answers to specific questions....

Having said that Mike, I have found a couple of wonderful rules of thumb after digging around a bit.

The U of G site looks like it's a good starting point.

Slehmann

Where to begin....
 

Hi ya'all,
This will relate to all other posts that we have had discussion
with, save me the effort to do more than once, OK?
To begin anything you need to understand the medium with which you are working with aircraft of course it is air.
Air is a fluid. Fluids vary from extremely gaseous to almost solid
grease being an example. other end example would be Helium.
Fluids have density and it is that which relegates their position
in the spectrum. Helium being the least dense. Air and water are
near the least.
Fluids are composed of molecules whose composure relates to
the nature of the substance.
Easy to say the molecules are suspended, that is for the most
part they do not touch each other, there is space between them.
The greater the spacing the "lighter" the fluid. The spacing can be
reduced by applying pressure, compressed?
If compressed a force is created, example>compressed air in
your auto tires. Force is great enough to raise the car?
Knowing the above we can relate to an aircraft's use of air.
We need to go to Webster for a diffinition of two common nouns.
First Aerodynamics> This is a branch of physics which is concerned with objects MOVING THROUGH air. Note not with air
moving past the object (wind?)
There are four major forces which effect and/or create flight.
They are> gravity; drag; lift and thrust. The first two are negative
forces, the others are positive. We need to understand them all.
Second> Gravity, no one seems to know it's exact nature but
for aircraft purposes it is a strong force that acts on everything on
or near earth. The force is always perpindicular to the earth's
surface, this never changes.
Thirdly> Drag. this is a force created by some other force. Example; anything moving through a fluid does the moving by
application apllication of force. Drag is the equal and opposite
resultent of that force.
Fourth> Lift is a force which opposes Gravity basically but it can
also be applied otherwise.
Fifth> Thrust; this is a force applied to anything with the intention
of moving it. Can be applied in any direction.
example> airplane; propeller or turbine> helicoptor, rotor>
Auto gyro; propeller and rotor.
Thrust is normally created by a mechanizm but it also can be
created by lift as with rotorary wiings or a lifting device facing the
line of flight,
So, the average modeler is not a professional engineer but can
be an amatuer one if he understands the medium and forces he
is working with, the presented information was done in the realm
of the average modeler and for his benefit only.
Now that the forces envolved are understood one really needs
to know how they are created and used.
That will be explained on a seperate post in this forum to avoid
confusion, see you there?
Others additions and/or discussion of this info is welcome of course!

Hal [email protected]

Where to begin....
 

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]

Thanks Hal...
 

That was extremely informative and exactly what I was looking for. I kind of have a sense of where to look next.

Thank you.

Stefan

Where to begin....
 

Wonderful Hal. Clear and concise.

Slehmann I have not seen it suggested above but I will suggest it now. I have to say I learned more about flight from flying sailplanes, discussing the different designs with others and hard core experimenting than from any other combination. With sailplanes you do not have the luxury of increasing the throttle ... you are 'stuck' with the launch mechanism, gravity, slope wind and thermals to supply the energy. So I became very sensitive to where energy is coming from, how to tap into it and how it is being dissipated. After that an engine was a 'nice addition' if I wanted it. The 'wing' became the focal point. So if you have reached a stage where you really want to LEARN about flight, airfoils, proper dimensions, etc. please try sailplanes for a while. It is addictive. You can still have power planes but there will be no substitute for the feeling of pure flight like sailplanes. And I do not mean just thermal duration (TD) sailplanes. Slope soarers are just as intense. In sports I would associate sailplane flying to fly fishing. You have limited resources and generally light tackle and you are attempting to get maximum results. If you think you have no interest in sailplanes I would suggest you try it first (just do it) or you will be overlooking one of the most gratifying branches of R/C. It has been proven over and over to me that those who try it find something completely unexpected and it is a brand new learning experience because they are finding out all about what it really takes to makes a vehicle 'fly' well.

It has always been wonderful to fly in the late evening when the thermal activity settles down and the air becomes cooler, the wind is gone and the air is stable. At that time, after launch, I can just stare at the plane and see the most subtle changes it makes to my very, very slight changes in controls. It drives home exactly what the plane is going through and just where stall is approached and reached. Recovery from stall is also very evident. Making a slight change in the center of gravity or the installation of a 'trip strip' on the wing becomes a very simple but very interesting experiment because one can 'see' the change in flight behavior or duration of flight changes.

Maybe you have already tried sailplanes but if you have not then give them a try as you make your journey into the study of aeronautics.

An article of interest....
 

I just found this....sorry I can't rememeber who passed me this link, but the article is brilliant and very in depth about designging and building. Although addressed specifically at electric builds, I'm sure there's something here for everyone.

http://members.aol.com/KMyersEFO/shaw1.pdf

Slehmann

Where to begin....
 

Hi Keith,
Your discussion and experience with sailplanes rings a bell so
will add 2 cents worth, OK?
Of course I have gone the sailplane route and our experiences
paralell.
Would like to note a similiar finding>
Electric powered Enduros, powered sailplanes. difference being
they make the launch and desired altitude so simplistic..
A while back I wished to investigate some Aerodynamic items
that were "those gotta do that someday" dreams.
I was into EP and found the Enduros ideal for comparison of
different styles. Spent quite a bit of time and learned much.
With a rather easy way!
Good luck,

Hal [email protected]

Where to begin....
 

Gliders, especially slopers will teach everything anyone could need to know about airplanes.
The experience of almost limitless flying time.. not dependent on the fuel supply, just Ma Nature's wind lets flight past hours happen. One takeoff, one landing, hours in between.
You really get to feel the airplane, and learn how to fly it in all orientations.
And you get to re-experience the innards... fly, repair, fly, repair..... :)
Adjustments are easily done. Toss, evaluate, land, change, toss, evaluate, land... and repair... :)
If it can't fly on the slope, it can't fly!