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Wing Loading

Old 02-25-2005, 01:20 AM
  #1  
lester65
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Default Wing Loading

Does anyone know the formula to figure out wing loading? I have a 120 size Seagull Laser 200 and I want to find what the max wing load where the plane can fly safely. I have a few things I would like to add to the plane while building it, but don't want to overload the wing.

Thanks,
Les
Old 02-25-2005, 03:15 AM
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Default RE: Wing Loading

It's the Weight in ounces divided by the Area in sq feet. The area is the average Chord times the Span divided by 144 sq in/sq ft. So....

W/(Chord x Span/144) = WL

With the answer in this case as ounces per sq foot.

The wing loading for flying is largely a subjective matter. The plane will fly with a VERY wide range of wing loadings but for something like a Laser light is right. Adding much more will adversley affect the aerobatic performace. How much you add before it gets beyond YOUR tolerance and goes from being a fun model to fly to one that's just an accident looking for a place to occur is up to you. I'm sure you could stick an extra 5 lbs of gear in it and it would still be safe to fly but it would not be FUN anymore because it would need to fly so much faster for takeoff and landing to prevent stalling.
Old 02-25-2005, 05:27 AM
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Default RE: Wing Loading

An indicative that is not dependent on the model's size is the cubic wing loading, which may be calculated by dividing the weight in oz by the wing area in sq.ft raised to power of 1.5

Different types of model aircraft may have different cubic wing loadings (oz/cu.ft) as shown below:

Sail and Park Flyer: 4 to 7
Sport and Trainer: 7 to 9
Pylon and Scale: up to 13
Electric Ducted Fan: up to 25

To calculate the cubic wing loading click [link=http://adamone.rchomepage.com/calc_cubicload.htm]here[/link]

The recommended max conventional wing loading is much dependent on airplane’s size.
For instance, a full scale Cessna 152 has a wing loading of about 167oz/sq.ft, a model airplane with such a wing loading could hardly be able to fly.
However, the full scale Cessna has a cubic loading of about 13 oz/cu.ft, which puts it at the high end of a scale model category regardless of size.
Old 02-25-2005, 08:58 AM
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rmh
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Default RE: Wing Loading

interesting-
I took a 1780 sq in CAP aerobatic model - which weighs 22 lbs , which calculates (according to the cubic ft calc) at 8.1.
You say that is good for a trainer .
That specific model actual practice-it is really an average aerobatic model, the wing loading being aprox., 28.5 oz/sq ft
To get into the "sport model " catagory (13--)as you noted, -it would have to weigh 37 lbs . I used the calc you furnished.
What did I do incorrectly?
Old 02-25-2005, 10:13 AM
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Default RE: Wing Loading

You know Dick, even a sailplane can do aerobatics…
What you consider a "sport model" must not weight at least 37lb, it doesn't harm at all if you can do it much lighter, of course.
My figures above are what I think being "typical" for those categories, it is not the same as to say it must be so.
So, I don't think you did anything wrong if your aerobatic model is lighter than my typical "sport model".
Old 02-25-2005, 11:50 AM
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Pathous
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Default RE: Wing Loading

It seems my q500 pylon racer weighing 56 oz. comes out at 8.66. If it was to be at 20 it would have to weigh over 8lbs.

Scott
Old 02-25-2005, 12:04 PM
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Default RE: Wing Loading

It seems my q500 pylon racer weighing 56 oz. comes out at 8.66. If it was to be at 20 it would have to weigh over 8lbs.
It seems you are interpreting my table as showing the minimum cubic load values.
- they are not the minimum values.
The lighter you can build your model the better, no matter which category it belongs to.
[8D]
Old 02-25-2005, 12:21 PM
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Pathous
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Default RE: Wing Loading

Your table is showing typical wing loadings. It seems that your table is not very typical of most pylon racers. Even Q40 racers at max weight will be lighter than your table.

Scott
Old 02-25-2005, 12:30 PM
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Default RE: Wing Loading

Maybe, so I changed it to: up to 30
Is still too much?[8D]
Old 02-25-2005, 01:38 PM
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Default RE: Wing Loading


ORIGINAL: adam_one

Maybe, so I changed it to: up to 30
Is still too much?[8D]
The problem is the methodology. Usually these handy dandy correlations originate from someone who goes through a whole bunch of model designs, plots them on a graph, determines some simplified correlation or trend through the buckshot data & then reports the findings as though that is a design parameter.

The problem is, it ignores many significant & fundamental parameters of which loading is only one. For example, I could take a lightly loaded nice trainer with a forgiving semisym 15% airfoil & stick on a 5% thick sym airfoil with an aft placed high point position & make the same trainer a very nasty model in terms of stall characteristics, takeoff & landing speeds because the airfoil polar sare completely different. Yet the thin winged version satisfies the same weight/wing area loading as the thick winged version.

By the same token, pylon racers have rules governing many aspects depending on the class, the wing dimensions, nominal area, planforms, nominal loading (such as in FAI rules). The airfoils they use are
a result of optimization withinthese boundaries to be legal. But the speed by & large comes from the available thrust. A typical Q500 model is reallly a very tame plane at 1/2 throttle.
Old 02-25-2005, 02:14 PM
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rmh
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Default RE: Wing Loading

In a nutshell - your chart is not very representative of any models we have ever seen.
discuss this info with guys who actually fly various types of models.
Then plug in some numbers --and catagories.
As you have already guessed - I am just a plain ol country boy - --so I am more influenced by results
Calculations are fine but should be representative of real world data -
I thought that was the reason for the "cubic " scaling---
So far I don't see the correlation.
BTW - the 37 lb setup would hardly fly .
Old 02-25-2005, 04:07 PM
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Default RE: Wing Loading

The problem is, it ignores many significant & fundamental parameters of which loading is only one.
I never said that wing loading was the only parameter needed to determine flight characteristics...
The initial question above was about wing loading and as you may know the max recommended value depends on the airplane's size.
By calculating the cubic loading you get a figure that is not dependent on the plane's size and thereby easier to refer to model categories only.
Even if my max figures to pylon race category seem to be on the high side for the actual average and will need adjustment, I think it doesn't make the whole concept worthless as a guideline.


Calculations are fine but should be representative of real world data -
I thought that was the reason for the "cubic " scaling---
So far I don't see the correlation.
BTW - the 37 lb setup would hardly fly .
Dick, with 37lb your giant model would have a wingloading of about 48oz/sq.ft, which is 9oz more than the [link=http://www.rcuniverse.com/product_guide/newproduct.cfm?product_id=378]Matt Chapman's Cap 580 giant[/link] which has 39oz/sq.ft and weights 32lb.
Surely your plane would be on the heavy side, but with that big size, I think it still would be flyable.
Anyways, I did some adjustments to the table above.[8D]
Thank you guys for your inputs.
Old 02-25-2005, 05:40 PM
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rmh
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Default RE: Wing Loading

And that particular example --IS quite heavy---
you should fly something like that --you would see what i mean
A good wingloading for that would be 32-- for sea level -
I am not calculating- or guessing -
I am going from experience .
You have to get out and do some flying - really - besides being fun - it is a damn good teacher.
Old 02-25-2005, 07:07 PM
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Default RE: Wing Loading

Yes Dick, I know that low wing loading improves the flight characteristics, especially when landing, as it lowers the stall speed.
But I just can't afford to fly all model categories myself, so I have to refer to some data I found by other ways:
Following is a result of some search:
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXVU18&P=0]Great Planes Fundango Aerobatic Park Flyer [/link]- cubic loading: 4.2
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJA53&P=0]Tower Hobbies Uproar 60 [/link]- cubic loading: 6.5
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKF82&P=7#tech]Thunder Tiger Trainer 60 [/link]- cubic loading: 8
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXFF96&P=0]Sig Piper J-3 Cub [/link]- cubic loading: 8.2
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJ576&P=0]Great Planes Super Sportster 60 [/link]- cubic loading: 11
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAP68&P=0]Midwest Little Cap 232 61 [/link]- cubic loading: 12
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJ571&P=0]Great Planes P-51D Mustang [/link] - cubic loading: 12
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLP44&P=0]Great Planes Giles G-202 46 [/link]cubic loading: 12.6
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHU97&P=0]Top Flite Douglas DC-3 [/link]- cubic loading: 13.5
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXM398&P=0]House Of Balsa P-51D Mustang [/link]- cubic loading: 13.6
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCNL6&P=0]Kyosho F-16 Fighting Falcon DF [/link]- cubic loading: 15.5
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJRX7&P=0]Ultrafly Model F-16 electric[/link]- cubic loading: 22
Old 02-25-2005, 07:43 PM
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rmh
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Default RE: Wing Loading

Now I understand how you got your "catagories "
some of those cubic listings are VERY odd----------------
We do fly quite a bit of stuff as well as build 50% scale models down to teensy weensy electric aerobats.
Also having done more than a little designing and building of models -for fun/ contests (at all levels) - professionally for many years .-I was rather mystified by your catagories.
still am ---
Old 02-25-2005, 08:22 PM
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Default RE: Wing Loading

My conclusion so far is that most models have cubic loadings between 7 and 13 while Park Flyers may have less than 5, and EDFs plus some jet electric pushers may exceed 22.
If you have other way to categorise them, just enlighten me. [8D]
Old 02-25-2005, 09:10 PM
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rmh
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Default RE: Wing Loading

why?
Apparantly you are content with simply catagorizing models according to some kit info - (some of these kits are really not good performers - some are )
Kits are sold into a market -typically based on eye appeal - not performance - just like cars and clothing .
To find out how they actually perform -- you have to become involved.
Then you will get an informed viewpoint of them.
I honestly see little practical value in the "cubic loading formula".
Does it assist in determining performance?
How can it ?
small models which are radio controlled almost all have to operate in the same parameters - except for competition racers /speed gliders .

The reason?
they must be kept in close enough and in a speed envelope which can be seen and controlled.
It matters not if they are models of a B29 or an x-1- loadings have to be similar-or you cant fly em.
you have about 1/4 mile range to use for any maneuvering control and the runways are typically quite short.s
the size dictates the basic wing loading parameters .
What models DO you fly?
Old 02-25-2005, 09:38 PM
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Default RE: Wing Loading

...To find out how they actually perform -- you have to become involved.
Then you will get an informed viewpoint of them.
Maybe for you Dick, but not everybody can afford to test every model type...
If I tell you that a model has a wingloading of 28oz/sq ft, it won't tell you much until you know the actual size.
But if I tell you that model's cubic loading is 7, then you'll get a better idea whether it is capable to slow landings without needing to know the model's actual size.

For instance, if the Thunder Tiger trainer had 28.5 oz/sq ft wingloading it would fly like a brick, while your 1780 sq.in CAP flies like a feather despite same wingloading.
However, the Thunder Tiger has only 17 oz/sq ft wingloading, which is the same cubic wingloading 8 as your 1780 sq.in CAP.
I've flown several models since I begun for a decade ago, some were kits, other scratch build, some survived other didn't, but what does it matter, the question is often how heavy it is related to wing area and model's size.
Using cubic wing loading you don't need to bother about the actual size of the model.
Old 02-25-2005, 11:04 PM
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rmh
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Default RE: Wing Loading

keep working on it
Old 02-26-2005, 01:06 AM
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Default RE: Wing Loading

I've seen that cubic loading idea show up in other spots and while the idea is good I think you're working with too small a database of model designs to accuratley set the guides for the categories at this point. That's where the downfall is. It's not the idea but rather just that you don't have enough data and reports of what the models in each category are actually LIKE to fly.

Like I mentioned above a given model will take to the air under a very wide range of wingloading values but the fun aspect vs adequite performace vs pig to fly occur at various points along that scale based not only on the cubic loading but also on the power of the engine used.

I seem to remember that Thunder Tiger made a 40 trainer and if so then I've helped a student fly one. Terrible plane with only a so so glide that didn't seem to uderstand the idea of forward motion too well even with a not 40 up front. I don't know the cubic loading of that one but if it's in the same 8 value or even up to a 10 then the system needs to be fudged some more or reviewed to determine the missing elements.

I also ran through some numbers for my own models and they seem to fit not too badly at all into your current ranges shown in the chart on your site. My 89 inch Flamingo Old Timer comes in at 1180 sq inches and 5.5 lbs for a CWL of 3.74 and it certainly does fly as lightly as this suggests. My old sport power Quickie 500 with the 25 at 52 oz comes in at 8.04 and that fits within your current numbers for a nice sport model. My 1/2A rudder only sport model at 255 sq in and 19 oz hits the scale at 8.31 and I'd say that's not far off. The glide of that one is nice but a trifle quick and that fits with the idea of the range.

A suggestion. Lightweight 3D or the old school boom fuselage fun fly models of all types will obviously fit within the low range and you may want to add them there.

Or better yet, if enough folks provide model data and some accurate feedback on what the models fly like with comparisons to some well known samples as benchmarks then I would suggest you remove the name categories and instead include notes on the type of performance that can be expected for the ranges of cubic loadings. My 89 inch old timer is sure not a parkflyer but it floats as nicely as a Gentle Lady glider. So the numbers suggesting a style of flying may be more accurate than the types of models.
Old 02-26-2005, 05:25 AM
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Default RE: Wing Loading

Or better yet, if enough folks provide model data and some accurate feedback on what the models fly like with comparisons to some well known samples as benchmarks then I would suggest you remove the name categories and instead include notes on the type of performance that can be expected for the ranges of cubic loadings. My 89 inch old timer is sure not a parkflyer but it floats as nicely as a Gentle Lady glider. So the numbers suggesting a style of flying may be more accurate than the types of models.
Yes Bruce, that's it. You guys are welcome with suggestions.
So far one may say that cubic loadings up to 8 are likely to give reasonable low take-off and landing speeds regardless of actual plane's size, provided other conditions are met.
At higher cubic loadings one should expect increased landing and take-off speeds, assuming no special lift devices are used, such as flaps.
Old 02-26-2005, 08:42 AM
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Default RE: Wing Loading

HI,
GO TO THIS
www.lcrcc.net/
you will get all you want , my self found it very practical
Old 02-26-2005, 09:22 AM
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rmh
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Default RE: Wing Loading

Yes -Bruce- one must have some real background in a subject -before you attempting to overhaul it
You already know that from hands on experience.
Many "organizers" have attemted to catagorize /quantify/qualify , ad nauseum , models .
The elusive fact?
Each time I see one of these charts -I am reminded of the 3 blind men describing an elephant.
There is truth and fact - but viewpoints are disparate.

There is NO common thread as to what constitutes performance.
The scale warbirds - typically, were barely flyable (have gotten much better) too heavy---Sport models - "move up to low wing from a high wing" What the hell does that mean?


It is a hobby -- each person has his own parameters for performance(and that is a moving target).
My own criteria? keep it fun and interesting.
Pottering about with numbers and formulas and charts is apparantly fun for some - I guess I should buttout.
Old 02-26-2005, 01:24 PM
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Default RE: Wing Loading

Oh-yes-no Dick,
The categories above don't show what the values must be, but what the values may be, and knowing that low wingloading is good for your toys, then you may strive to get the lowest cubic loading you can. And, if you get it below 8 then you know that you are on the safe side.
That's it.
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