calculating wing area
 

I, for the life of me, cant remember how to figure out the area of a wing... or anything for that matter, if its not a perfect square or rectangle....

the wing's chord by the fuse is 15.25" and at the tip is 7.25". The LE is 31.75" and the TE is 33.5"

also, whats the formula to figure out wing loading again? ARGG!!!!

any help would be appreciated!

RE: calculating wing area
 

nevermind on the wing loading... a simple google gave me this.....

How to Calculate Wing Loading
In this example, we will use an aircraft weighing 5-1/2 lbs (5 lbs 8 oz.) with 600 square inches of wing area. Calculating the wing loading requires that the wing area be converted to square feet (ft2) and pounds to ounces.

1) Convert the area to square feet. There are 144 (12 x 12) square inches in a square foot.

600 in2 / 144 = 4.17 ft2

2) Convert the total empty weight (ready-to-fly with no fuel) to ounces. There are 16 ounces in a pound.

5.5 lbs x 16 = 88 oz.

3) Divide the weight by the area:

88 oz. / 4.17 ft2 = 21.1 oz / ft2

Using round numbers, this gives the aircraft a wing-loading of 21 oz / ft2 or

You can perform the entire calculation in one shot using simple substitution:

(Weight x 2304) / Wing Area

Where weight is in pounds and wing area is in square inches

Plugging the numbers from this example into the above formula gives us this:

( 5.5 x 2304 ) / 600 = 21.1 oz / ft2

RE: calculating wing area
 

Area = Length * Width

However, the surface of an airplane's wing isn't flat. This will require a little more. The easiest way I can think of to figure it would be to use a piece of string. Hold one end of the string on the leading edge. Pull the other end to the trailing edge. Mark each end. Measure the distance between the marks. Use this as the width. Measure the length. WingArea = 4 * (width * length) - assuming a symetrical airfoil.

If it's a tapered wing with a symetrical airfoil:
Use string method at the tip and the root. This is a trapezoid. Area = [(TipWidth + RootWidth) / 2] * length
WingArea = 2 * (TipWidth + RootWidth) * length

A flat-bottom or semi-symetrical airfoil will require a top wing measurement and a bottom wing measurement.
WingArea = 2 * (TopArea + BottomArea)

RE: calculating wing area
 

my 17 year old says its 734 sq inches... I think thats way too low.

RE: calculating wing area
 

RichD wrote:
As a matter of fact its even less:

Average chord = (15.25"+7.25")/2 = 11.25"
Average span = (31.75"+33.5")/2 = 32.625"
Wing area = 11.25" x 32.625" = 367 sq.in.

/Red B.

RE: calculating wing area
 

sdavied wrote: Its common practice to use the wing chord to calculate wing area, NOT the length of the curved surface.

/Red B.

RE: calculating wing area
 

thats just one wing... total, with both wings attached, would be 367 x 2 = 734

maybe it is that low... hrmmmmm

RE: calculating wing area
 

Sounds about right for a 65" span wing to me. ;)

And yes, we typically use the flat measurement, not the measurement of the curved surface.
Dennis-

RE: calculating wing area
 

oh, add another 9 inches to the wingspan, as I totally forgot the fuse section. Its on an extra 260, plug in wings that mate to the fuse.

Tip to tip is 72"... making total around 810.

RE: calculating wing area
 

You wouldn't count the fuse section as part of the wing area. Although it technically does provide a small amount of lift, it isn't considered part of the wing.
So the formula is:

WingArea = ([(RootChord + TipChord) / 2] * Length) * 2

Which simplifies to:

WingArea = Length * (RootChord + TipChord)


Note:
Length = distance perpendicular to fuse to tip. NOT (trailing edge length + leading edge length) / 2

RE: calculating wing area
 

Go to this web page and download the free calculator that will let you find wing loading, thrust for various props, etc. by just plugging in some numbers. - Quicker than all the math calcs...

http://www.bmaps.net/

click on the Goodies button and get it.

quin

RE: calculating wing area
 

Rather than just putting blind faith in a calculator, wouldn't you like to know where the number are coming from? Believe it or not, calculators have been know to lie from time to time.

RE: calculating wing area
 

Not a case of 'blind faith' just that the program has the same formulas that we used and gives the info without going through all the math work. I guess if he wanted to learn the formulas then a calculator would take out all the fun, then again if he only wanted the info it would work out OK. I'm an engineer and welcomed the use of slide rules (remember those?) and later calculators and computers to solve my design parameters. Never had one lie, but I did punch the wrong button from time to time. :eek: I do apologize for trying to help, thinking he only wanted the data.

quint

RE: calculating wing area
 

I was always taught to INCLUDE the fuse dimensions when computing wing area. I've often wordered how the amount of the fuse's lift would or wouldn't effect wing loading - but without the fuse, I guess the wing wouldn't be doing much lifting :)

Jerry

RE: calculating wing area
 

Well the Horten bros. and Jack Northrop showed some flying wings without a fuse. :D

If we assume that an airfoil gets its lift from the pressure diferential between the upper and lower surface, then the fuse would only be included if it was shaped like a lifting body. If we use the lower surface at a high alpha, then we might get some 'lift' from it. However most model wing areas are given using the tip to tip wingspan. Interesting isn't it?