My questions are......

How do you work out the wing loading on an new model? And what does it mean?

What is the difference....... of Aspec ratio and what does it mean e.g a 6/1 how will an aircraft wit his type of aspect fly?

Regards

Vicking_erick!

There are participants on this forum who can give you more detailed answers, but as for some rough estimates:

A good rule of thumb is to provide about 100 square inches of lifting area per pound of weight. Naturally, there are other considerations, such as the airfoils used, drag of the airplane, power used, lift increase provided by flaps, etc., but planning for a reasonable amount of wing area and wing loading can be used to get a rough idea of the airplane's performance. Scale affects this, too. A wing loading of 24 oz./sq ft. would be rather high for a small sport model, but would be quite low for a large model. (Search this forum for much more info)

Aspect Ratio:
This is the ratio of the wing's chord to it's span. For example, an aspect ratio of 6 would exist if the wing chord was 10 inches, and the span was 60 inches. (60/10=6) An AR of 5 or 6 is typical for sport planes. Jets and other "hot" planes tend to have lower ARs and higher loadings, where gliders have much higher ARs and lower loadings.

Wing loading:
It's the weight of the airplane divided by the wing area. For example, use a 6 pound plane (72 oz.) with 600 square inches of area. 72 ounces divided by 600 square inches = 0.12 ounces per square inch loading. Multiply it by 144 to get the more often used figure of 17.28 oz/sq. ft.

Good luck.

In straight, level flight at a constant air speed the four forces: lift, weight, thrust and drag are in balance. Lift is equal and opposite to weight and thrust is equal to drag. A wing produces lift by flying at an angle of attack. The greater the angle of attack, the greater the lift. So, the wing loading will determine how high the angle of attack has to be to produce lift equal to weight for level flight at a particular air speed. The higher the wing loading, the higher the angle of attack for lift equal to weight at a particular air speed. Because wing stall at a particular angle of attack, increasing the wing loading increases the airspeed at which the wing will stall. because the take off and landing speeds must be somewhat higher than the stalling speed, higher wing loadings also result in the need for higher speed to takeoff and land. The higher the wing loading the larger the radius of turn for a given angle of bank so, high wing loading limits maneuverability too.

Induced drag is the drag that results from the wing tip vortices which result from the high pressure on the bottom of the wing and the lower pressure on the top of the wing. The difference in pressure results in a mini tornado of flow at each wing tip. At low speed, somewhat above stall, where the thrust is minimum, the induced drag is equal to half the total drag of the whole aircraft. Since thrust is equal to drag in level flight, the induced drag in low speed flight has a major impact on how much thrust is required to fly slowly. The induced drag is inversely proportional to aspect ratio. A wing with an aspect ratio of six will have twice the induced drag of a wing with an aspect ratio of 12. Therefore, in low speed flight the plane with the aspect ratio 12 wing will only require about 75% of the thrust required by the same plane equipped with an aspect ratio 6 wing of the same area. Because most models are equipped with engines sized for other purposes than level flight at slow speeds, low aspect ratio wings do not present much of a problem in that case. Planes that are intended for long duration, fuel economy or, low glide angle can take advantage of high aspect ratio to improve those aspects of their performance. Sailplanes and the Voyager that flew around the world nonstop without refueling, have high aspect ratio wings.

Vicking_erick,

Ollie points out one of the primary effects of aspect ratio, which is its effect on induced drag. The other main effect is the "lift-curve slope", or how fast the lift increases as the angle of attack is increased. The higher the aspect ratio, the more increase in lift you will see for a given increase in angle of attack. My guess is that for most models, this effect will likely be more noticeable than the reduction in induced drag, unless you are flying a sailplane pretty seriously.

Wing loading is probably more noticeable on most models. Many trainers, which are intended to be able to fly quite slowly, have low wing loading, so that they don't need to fly very fast to generate enough lift to support the weight of the aircraft. Many models intended to fly faster will have higher wing loading, and will not be able to fly as slowly without stalling.

banktoturn

Good point, Banktoturn! The tip vortex that produces induced drag also produces induced angle of attack by dumping air on top of the wing. This downwash requires the wing to operate at a higher angle of attack to generate the required lift. The lower the aspect ratio the larger the percentage of the wing that will be in the tip vortex downwash. For very low aspect ratio wings with an aspect ratio somewhere around one or even lower, the whole wing is operating in the down wash. Not only that but as the angle of attack gets larger the downwash angle also gets larger so that it can seem like the wing won't stall even when at an angle of attack of 20 or 30 degrees. The SST lands at such a high angle of attack that the nose section of the fuselage has to be drooped down for landing so that the pilot can see where he is going. The Space Shuttle also lands with an extremely high angle of attack.

Thanks guy's....... this all makes sence now. I will compare my trainer with a low wing aircraft I am currently building ( it is a Chandelle scratch uild from the Airborne mag drawing supplies we have here in Australia) and will do a comparison between the 2 A/C.

Regards

Vicking_Erick

Wing Loading?

Every plane has a Wing Loading but what does this means. If the weight of the airplane is change, the results change, if the stap and elevators size change, the result change and if the wing is shortened or increased in size, the results also changes. Where is the braking point?

Lets consider that I have an airplane with a 14”x87.5” wing and has 12 pounds weight = WL 24.5 oz per sq. foot, what does this mean? Can I lift more weight or do I have to reduce the weight with this result?

To correctly understand the Wing Load total there must be something to witch I can evaluate too and also, to determine witch is my maximum payload capacity.

Roberto Pérez F.

Roberto - there is no limit to the weight - just keep upping the speed -
Some guys will say a plane of that size will fly at 50 oz/ ft.
It actually will fly - like a ballistic pig.
for a model that size - to be a friendly flyer - you can add a few lbs - but where you are - is a good range for nice sport flying.
If you could -thru the miracle of imagination, reshape that wing - whilst still retaining the SAME wingloading - you would see some interesting results -
stretched way out - it would seem to fly
lighter - shortened way down - it would seem to fly "heavier".
The maneuverability tho would change -- A LOT!
Once you got the span down to where it was shorter than the chord, the model would fly " heavy" but odddly enough - would never stall- just mush easily .
If the span got out to say 10 feet - the model would fly lightly - but stalls and turns - especially tight turns, would have you in serious trouble .
Your payload?
it is all relative - to speed and area and wing type.
Again where you are is fine for sport.
A close friend supervises a state school team - in interstate competition for weight carrying electric model competition.
They won outright easily first time and I think have done very well since ( Utah State )
He use simple , model proven techniques -

Dick: It is true that there is no limit to the weight if power and speed is increased however, there must be a math formula that will tell you where is the WL optimum performance and limits without considering the engine, the power and speed. This braking point will enable R/C fans to properly select their engines and to increase the pay-load if necessary for other purposes.

Better ask one of the guys who loves to do math -BUT- first -you should qualify the job intended for the model.
Is it to be a weight lifter - with no other criteria- or a speed plane ?
And/Or is power limited to a specific
The electric powered weight lifters my friend Dave worked with had restrictions on battery used etc..
The competition was nationaland the students -I recall were engineering or aero engineering guys.
Dave is not a graduate engineer - but a graduate musician (fine chello man).
This is a case where CONCEPT played the biggest role - not hours on a slide rule .
My comment was intended to convey that for our uses - a sport wing (such as you used in your example ), is a good all around setup.
Formulas in math are nothing more than numbers used to relate known information to others .
First get the idea working.
Now then -this does not work for quantum mechanics--or does it -who knows?

Roberto,

For full scale aircraft, I would say that there is no such thing as an optimal wing loading. What is more typical is to reduce drag by reducing the wetted area ( total outside surface area ) as much as possible without raising the stall speed too much. For this reason, the wings on most full scale aircraft are small enough that flaps, and sometimes more elaborate high-lift devices, are needed for take-off and landing. Most sport models do not adopt this approach, because fuel economy is not an issue, and our engines are so powerful that there is no strong motivation to reduce wetted area. Moreover, the complexity of flaps is not always welcome. Ironically, many of the models that have flaps are those that need them the least: trainers that already fly very slowly. Having said all that, wing loading is probably a more important design parameter for us than for the full scale guys, because it affects the flight characteristics, and our models have only one purpose: to be enjoyable to fly.

banktoturn

Bank to turn- Well said -

banktoturn & dick Hanson:

Thanks to both however, the point that I’m trying to get across is getting very clear to all of you. It is not the way the wings are shaped nor if there is a bigger engines, or that the plane is fore race, or for acrobat or for what ever, it is about the WL total. WL total comes in all the airplane boxes, airplanes plans that you purchase and also from personal designs, but the total along is not very conclusive; something is missing.

Consider my original example: An airplane with a 14” x 87.5” wing with a weight of 12 pounds has a WL of 24.5 oz per sq. foot and suppose that the max weight of that planes is 48.9 lbs with a WL 100 oz per sq. foot, if we plot results the model is place at 25% of that scale, is this good or bad? What is the proper rate?

My intention is very simple, there must be one or more tables for evaluating results for example: A table for acrobatic airplanes, for racers, for beginners, etc. and not just due to experience or because it works for me on this plane it should work for your… Lets be more precise in our evaluations… My recommendations is to make a case study of this issue in order to come out with a more precise formula that will be more meaningful to all of us, lets follow the Center of Gravity example.

Roberto....What you could do is build a common aircraft with a simple airfoil(Ollie has those details)...say a 90-120 size Telemaster.....say a Semi-symmetric airfoil and do your own research.....get a speed gun and add graduated weight and determine ground effect...rotation speeds....AOA....Stall Speeds..wing loading.....etc...might be fun to do....Just my .02 cents worth....Bill.. .

Inasmuch as the CG is not a precise thing -actually can change with airspeed. -it should not be a surprise that a difinative chart on wing loadings is pretty iffy.
Just an example or two -
If one were to watch the new powered (electric) gliders -designed for all out speed - they may be quite astonished at how fast they are - in fact they get out of sight in about 5 seconds.
These models - much like the recent turbine models are in the 200 MPH range-
Once we go much over 100 MPH -the air can react differently- and so --one persons' idea of a speed design -may be much different than anothers concept of "speed".
The wings are quite small in chord on these -but obviously not maximized , as I watched the guys do some simple maneuvers.
Why one would use a semi sym airfoil on one of these is a bit of a puzzle -
If one did do a "test bed model - where just the wing were changed - I don't think there would be a very wide speed envelope to research.
That is - the rest of the design would need some change also - to maximize the wing efficiency- at it's extreme size changes.
Some generalizations can be made now - on good setups for speed and aerobatics and gliders etc.
The BUT is that unless you can grind all of the other pieces of the equasion to a fine point -- you will never find the one perfect "airfoil/wingloading -for that setup-
So back to generalizations - which is where a hell of a lot of the full scale designs start- then the bolt stress engineers come on board - In todays world it has to be that way.
If someone has a chart which works for models -bring it on.

Roberto/Dick/Ollie/BanktoTurn......Points well taken ..This is why when aircraft(Refering to large transport category aircraft) are certified they are done individually due to the uniqueness of all those aerodynamic combinations your speaking of...operating envelopes , T/O and Landing speeds ,Numerous "V" speeds,Max fuel wt,gross wt,Stall Speeds, single engine performance for twins,..Etc...Have made several trips out to Boeing in Seattle and was quite impressed with their flt testing....as well as structural testing..... so in a nut shell each airframe whether a trainer or 777 has its own unique flt characteristics..and by going thru some experimentation those answers can be found....rather than some simple calculation or formula......Bill...

Roberto,
Your assumption that there is such a thing as an optimum wing loading is not a good asumption. If maneuverability is a high priority, then the lower the wing loading the better. If duration or the ability to carry pay loads are priorities then low wing loading is desirable. If the object is to be able to take off and land slowly, then a low wing loading is desirable. If the objective is to be able to fly through turbulence with a minimum of deviation then a high wing loading helps. Almost every type of aircraft benefits from a high strength to weight ratio and the associated low wing loading. In the case of sailplanes it is desirable to have a range of wing loadings available so that the wing loading can be adjusted to the flying conditions. that's why sailplanes use water ballast and model sailplanes use lead ballast at the center of gravity.

Hello Mike James, I believe that 16 oz is = to 1 lb, so 6 lb should't be = to 72 oz.

please let me know if I'm correct.

Iromman210