I just want to know the most important equations and guidlines used while designing a wing. Can anyone help me out?

Well the first thing is what kind of plane is it? Do you want something easy to build & fly? Something that will do aerobatics? Or maybe a super-efficient sailplane. The wings for all of those will be quite different.

lots of us don't bother with much of the math when designing models... the "TLAR" method generally works after you've built 3 or 4 kits. (and you need to build at least 3 kits before trying to design one...) You'll get a "feel" for how the structure should look, and what shapes make decent airfoils. Also after flying a few planes of differing design, you'll get an idea of what wing planforms (the shape when looking straight down on the aircraft) are best for which purpose.

The biggest exception... I think Curmudgeon Paul has all the equations memorized. [img]i/expressions/face-icon-small-happy.gif[/img]

The only thing that I have ever worried about when designing a wing is that the Spar supports the wing at the apex of the airfoil (the fattest part). The spar (The fattest part of the wing) should be at 25%-30% of the total chord of the wing, measured from the leading edge. The ailerons ARE included in the wing chord measurement. I've built and flown over 300 wings using this simple guide, and they have all flown. Fat ones, skinny ones, flat bottomed, symetrical, simisymetrical...you name it.

I also try to keep my wing loading down to less than 20 ounces/square foot for good solid performance. good dead stick glide, and better stall charicteristics. This is the size of your wing as it compares to the weight of your airplane.

Wing loading is the weight of your plane in ounces, divided by the area of your wing in square feet.

Ok, thanks for all your advice.

A question...FHHuber, what is the TLAR method?

To answer 00hez, I didn't really have any plane type in mind. I was just curious what equations are most important while designing a wing for certain flying characteristics.

That Looks About Right

If something doesn't look right...it probably isn't. If something looks about right, it probably is. This goes a LOOOOOOOOONG way when building model airplanes.

Ok new question, but it goes along with my first post.

I have a sort of experimental wing design in my head. I would like to test it out, but I don't want to build the whole thing just to find out its crap when it crashes. Is there any way I can go about getting a rough idea of its performance without actually building/flying it?

I'm thinking along the lines of software, or like I mentioned before formulas I can run through myself.

I've been experimenting with wings for several years, but with actual experience. Once you learn how to work with the materials, a wing can be ready to go fly in less than an hour. I've gone to the field with one fuselage, and a pile of wings to try out. If your interested check out
The Spad web site

Unfortunately there are no simple equations to design a wing. The TLAR approach with a generous amount of "cut and try" is the method used by all model designers whether they admit it or not. (After years spent as an engineer in flight test at a major manufacturer, I can assure you that a bit of that goes into full scale design as well)

There are some rules of thumb that will help keep you from making major goofs. Some of these can be found at http://webpages.charter.net/rcfu/HelpsHints/ModDgn.html

A few hints are:

A straight wing is easier to build, but a tapered wing is more efficient.

Use a thinner airfoil for speed, and a thicker for better maneuverablilty

Use a symetrical airfoil if you want to fly inverted a lot ( i.e aerobatic aircraft). A more cambered airfoil is more efficient in normal flight (and would be better for a pylon racer for instance).

Twist is sometimes used to prevent tip stall when landing, however don't use twist for aerobatic aircraft as it aggravates tip stall when flying inverted.

Full span ailerons are easier to build, but conventional ailerons give better control.

Dihedral is used to provide lateral stability but makes knife edge flight more difficult. Use no dihedral for aerobatic aircraft, and a little for other types.

Some sweepback has a similar effect as dihedral. Since our models don't approach sonic speeds, it is primarily an appearance thing. (forward sweep is pretty unstable and dosen't perform well)

I hope this helps in evaluating the experimental wing you have in your head. If it departs too much from conventional, the characteristics will be hard to predict, but go for it and see what happens.

Well...if you are interested in working with some of the latest AND best softaware for building model aircraft go to this site. http://groups.yahoo.com/group/xfoil Mark Drela is one of the best. the software is specifically for the Low RE numbers. I have observed his work and his assistance with the general public. He is constantly giving assistance to us(those who are not aerospace engineers). You can't go wrong with this site. If you stay with it and read, read, read. You will understand theories applying to Reynolds Numbers and why a thin strip of tape close to the leading edge (turbulator affecting the separation of the boundary layer) can decrease drag by a huge amount. His current construction techniques account for the sag between the ribs. He has a paper about that somewhere on the web. There is also a planform spreadsheet out there somewhere also.

Have fun!

KonstantKrash

Great, Thanks for all the info guys.

Couple questions for Lou:
1) Out of curiosity what makes a tapered wing more efficient, and are they always more efficient?

2) How come thicker wings provide more maneuverability?

Rockazella, The most efficient wing planform (all else being equal) is an ellipse, like the supermarine spitfire. This is because an elliptical lift distribution across the span results in minimum induced drag for a finite span wing. The elliptical planform is hard to construct and a tapered wing is almost the same, especially if the tips are rounded. This is why most full scale aircraft have either a single tapered wing (like the Mooney) or a combination of straight center section with tapered tips (like the many cessna models). I own and fly a Piper Cherokee which has the rectangular ("hershey bar") wing and also have considerable time flying the Piper Archer, which is essentially the same aircraft with a tapered outboard wing section. At lower altitudes the difference is not a lot, but at higher altitudes, the efficiency of the Archer is obvious. The efficiency shows up as a better rate of climb at equal power settings, a higher service ceiling, and increased cruise range.

Our radio controlled models are so grossly over powered that the difference in efficiency would probably never be noticed, but it is there.

Generally a thicker wing section will operate at a higher angle of attack before stalling. Since the tightest radius of turn occurs when operating at maximum lift coeficient (max angle of attack) the higher the angle of attack a wing can achieve before stalling, the more "maneuverable" it will be. As matter of fact, if the wing is given a little camber (so called semi-symetrical, or even the old flat bottom type) it will turn even tighter. However when performing inverted or negative maneuvers, it would stall at a lower angle and would not turn as tight. It is this requirement for inverted flight, and negative g maneuvers that dictate a symetrical airfoil for aerobatic aircraft.

I looked up the xfoil site and find it interesting. However the design of an actual wing involves a lot of tradeoffs and compromises in addition to airfoil section. In spite of an AE degree and many years experience in the field, when I sit down to design a model I still use a lot of TLAR. If you are interested I can send you pictures of my latest designed from scratch models. If you want to pursue the technical route a little more you might check the library for "Principles of Aerodynamics" by James H. Dwinnell, and "Airplane Performance Stability and Control" by Courtland D Perkins and Robert E Hage.

I hope this helps. Keep us posted.

Lou,

Excellent information. I like your examples also.
<blockquote>Quote
<hr> looked up the xfoil site and find it interesting. However the design of an actual wing involves a lot of tradeoffs and compromises in addition to airfoil section.<hr></blockquote>
Mark Drela himself has several papers on that site that deal specifically with the tradeoffs of design. A single point airflow (xfoil) is really only an indicator. A wind tunnel may be somewhat better but we seldom find air flowing in such a laminar pattern when we fly. Another situation arises when we build. How close can the average builder come to the actual airfoil plots, consistantly, over the span of the wing.

But...understanding theory that comes from this data allows us to utilize the TLAR method successfully. Your TLAR involves a lot of backgraound and experience. I contend that in order to be successful in TLAR one should really understand the basics otherwise it becomes a hit or miss experiment.

I applaud Rockazella for asking the question and you for supplying an accurate and concise response.

konstantkrash