philscho

Can anyone direct me where to find the formula for determing the wing loading of a special RC airplane?

Thanks Phil

JetPlaneFlyer

weight divided by wing area... pretty simple

NJSwede

The trick is usually to figure out the wing area...

JetPlaneFlyer

it's often quoted in the manufacturers specifications, failing that (for wings with straight taper or no taper): tip chord plus root chord x half of wing span

Larry3215

I think you mis-typed that final operator. Shouldnt that be a X instead?

JetPlaneFlyer

Good catch Larry.. yes of course i meant x not /.. I'll correct it

Rodneh

A much better indicator for how well a model flys is its "wing volume loading" sometimes called "cubic wing loading". Lots of info on using that measurement in the forums if you do a search.

kyleservicetech

Agreed: Wing cubic loading is much more useful. What would be a decent wing loading on a giant scale model would be so out of line in a back yard flyer, it would not get off the ground.

Rodneh

Here is a chart to see what the wing volume loading is along with wing loading.

FlyWheel

What is "cubic" wing loading? Is this a Bernoulli<Sp?> thing?

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JetPlaneFlyer

No, nothing to do with Bernoulli

Cubic loading takes into consideration the scale effect. 'Normal' wing loading can be confusing. For example a micro model with a wing loading of (say) 12oz/sq ft might fly like a lead brick, whereas a giant scale model with exactly the same wing loading would fly like a feather.

That's because our perception of flying speed is influenced by scale. A giant scale model flying at 20mph looks super slow, but a micro doing the same speed looks fast.

Cubic loading takes into account scale effect so it gives a number that is consistent for planes of any size. For instance if you have a cubic loading of 6 then you know that plane will be capable of slow sedate flying, regardless of size.

Bill G

...which is generally exaggerated with ARFs and RTFs.
The AUWs often are understated also.

BBCorvette18

I'm noticing this now that Im looking into this.

For example the Fun Cub I'm building states that it has

Wingspan: 55 in.
Wing Area: 589 sq. in.
Wing Loading: 9.8 oz./sq. ft.
Fuselage Length: 39 in.
Weight (English): 40 oz.


Now when I measure the wing in real life it's 55x9 which would be 495 sq in. and I would think you would have to subtract the width of the fuselage in the wing area equation.

JetPlaneFlyer

No, convention is that you include the bit of the wing 'inside' of the fuselage. But you would have to make some deduction to allow for the rounding off of the tips on the cub.

BBCorvette18

Thats the part I dont get on how multiplex is coming up with 589 cause I was using the widest part of the wing and the longest. so you would think the actual area would be less?

sometimes I think its better to not worry about all this stuff and just fly LOL

slipstick

It's always possible they're including the tailplane area as well as the wing.

I think there are still a few free flight classes that do that. I guess it's so you can't cheat by building tandem wings and claiming only one of them is the wing and the other doesn't count because it's the tailplane .

Steve

Stevephoon

I've just started down the path of wanting to understand more on aerodynamics as well. I've just come across this summary of wing loading.

http://www.eastbayrc.org/TimTips/Tim...ingLoading.htm

They go thru the numbers on some Slicks. From RC to real size.

Steve

BBCorvette18

That makes alittle sense will have to bust out the tape tomorrow and see if tye numbers add up.

solentlife

So think about this one then ...

Fairly simple on a Cessna / Cub etc. where you have wing + tail area as the total LIFTING SURFACE area supporting a weight ...

What do you do with such as the F16 which has a lifting surface called a FUSELAGE ? in addition to the wing / tail.



Nigel

JetPlaneFlyer

yeah nothing in life is ever that simple!

Also consider that when you talk about 'lifting area' the tail on a most conventional planes 'lifts' downward. So that's why you dont usually include it in the 'wing area' calc. Arguably in fact, as it has 'negative lift' you would be more correct to deduct it from wing area rather than add it

For planes like the F-16 the fact that you project the wings to the centre of the fuselage when working out area takes some account of the lifting area of the fuselage, but it's far from an exact science.

slipstick

Not really a problem....you design modern jet fighters using computational fluid dynamics. Crude measures like "wing loading" really don't come into it .

Steve

kyleservicetech

A while back, someone calculated the wing loading of a fully loaded full size jet fighter. The wing loading was something like making a frisbee out of a cast iron manhole cover!

BBCorvette18

anything will "fly" if it has enough thrust