Wing Loading....
 

Please correct me if Im wrong, but to calculate the wing loading of an airplane...is the following the correct method?

1. Divide the weight of the aircraft by the wing area
2. To get it to oz / inch, multiply your number by 144, as there are 144 square inches to a square foot
3. Multiply that number by 16, because there are 16 oz per pound?

this just doesnt sound right to me, but the numbers look right...as an example on an edge 540 with a 75" wingspan and a 26cc engine...

Weight-Lets say 10 lbs
Wing area-990.7 sq inches

10 / 990.7=.010093873

.010093873 x 144 = 1.453517712

1.453517712 x 16 = 23.25628339

Would this put the wing loading as 23.3 oz/sq inch? I seriously think I am overcomplicating this, but someone here should be able to tell me.

Thanks in advance!

TonyG

RE: Wing Loading....
 

You did it correctly; that is the wing loading of that model.

RE: Wing Loading....
 

Better yet - that is pretty common and flyable loading .
for a typical aerobatic rc model

RE: Wing Loading....
 

Thank both of you for your response....

Given that wing loading....if you had to just guess....do you think that that airframe would be prone to tip stalling, or any other possble bad habits? i know that the info I have provided you is limited, but its worth asking...

thanks again,
TonyG

RE: Wing Loading....
 

Well tip stalling -whatever THAT is - is a description which has a bunch of explanations
Many of em wrong and oft repeated
But let's stick to your particular model The EDGE 540
The model is shaped to give the full routine of areobatics
The wing planform is excellent for this
IF your model is perfectly straight and perfectly trimmed and ideally balanced - it will still - if held off on landing- drop like a rock if speed drops too far.
If you have some rudder in it at slow speeds , it can easily drop a wing- again- that's normal.
I have built and assembled very similar models of the EDGE
Is not to fear tho - just practice flying it to the ground - don't chop the throttle n hope for the best
It can and will land very nicely

Overly harsh application of elevator will snap the model at some speeds - The design should do that .
Really

RE: Wing Loading....
 

Dick Hanson,

Thats along the lines of what I was expecting....I will set up short throws on low rate, get up to a good altitude and see what kind of slow speed charactaristics it has..

Thanks alot!

TonyG

RE: Wing Loading....
 

TonyG,

There is one problem with your calculation. When you multiplied your number by 144 you converted from "per square inch" to "per square foot". The final number is 23.3 oz/sq ft. I'm sure that's what you meant and no one else bothered to mention it. An easy way to do conversions is to think of the units as fractions separate from the numbers. Here is how I would work your problem:

10 (lb) / 991 (in^2) = 0.01 (lb/in^2)

0.01 (lb/in^2) x 144 (in^2/ft^2) = 1.45 [(lb)(in^2)]/[(in^2)(ft^2)] = 1.45 (lb/ft^2) The in^2 terms cancel.

1.45 (lb/ft^2) x 16 (oz/lb) = 23.3 (oz/ft^2) Again, the lb terms cancel one another because lb/lb is 1.

RE: Wing Loading....
 

OH....I see....I new the final figure looked about right, but I thought something was coming out wrong. I was just trying to calculate the wing loading to compare it to other planes that I have looked at...comparing planes to ones that I see for sale.

Guess I had the right number, just had the wrong terminology...

Thanks for the help!

TonyG

RE: Wing Loading....
 

Eventually even the U.S. may go metric, in the meanwhile there is Google. Try entering the following expression in the Google searc field:

10/991 lbs/sq.in in oz/sq.ft

RE: Wing Loading....
 

How would you go about calculating the wing loading on a biplane?

RE: Wing Loading....
 

Same way.
Evan, WB #12

RE: Wing Loading....
 

Yea, I believe it is done the same way. Only difference is that you have to calculate a total wing area from the surface of both wings...then divide that into the weight. Then multiply by 144 and then by 16 to get oz/sq ft....

TonyG

RE: Wing Loading....
 

Try not to complicate the thing too much, you want the answer in ounces per square foot. So calculate the weight of the model in ounces, use an imperial scale and weigh the thing, and convert your answer to ounces if you need to. If you calculate the wing area in inches, then you will need to divide by 144 to find the square foot number, easier to measure the wing in feet, and fractions of a foot. Then divide the weight (ounces) by the area (square feet). The math is essentially simple.
Evan, WB #12.

RE: Wing Loading....
 

Biplanes can be less efficient than monoplanes due to the interference of the air flow caused by two nearby wings. If the wings are spaced at least a chord length apart, it is quite close to the same efficiency as a monoplane but, if they are closer together, the efficiencies can fall as low as 70%.

RE: Wing Loading....
 

They also are less efficient because their wing area is degraded by 4 wingtips instead of 2. And very seldom do you see one without interplane and cabane struts, something seldom seen on monoplanes.

RE: Wing Loading....
 

Another equation...

Wing Loading (in oz per sq ft):

Wt x 2304 / WA

Where:

Wt (weight) is in pounds
WA (wing area is in square inches)

RE: Wing Loading....
 

And since we are not calculating the relative efficiencies between monoplanes and biplanes, we don't worry about any other coefficients in the calculation. Wing loading, by definition, is simply weight divided by wing area.
Evan.