Calculating wing area

[zbrubaker]

When you calculate wing area, do you carry it to the centerline of the aircraft (like when calculating CG)? Also, do you only calculate the upper surface only?

[Dick Huang]

zbrubaker,
The answer is yes and yes. When the upper and lower areas are calculated togather it is called wetted area.
Dick Huang:)

[zbrubaker]

Originally posted by Dick Huang
zbrubaker,
The answer is yes and yes. When the upper and lower areas are calculated togather it is called wetted area.
Dick Huang:)

Just to make sure I understand this right...if I had a rectangular wing 24" long and 3" chord, I would have a wing area of 144sq.in.?:confused:

If a model weighed 10oz, with the above wing, the wing loading would be 10 oz/sq.ft?

[balsaman]

No,

24x3=72 square inches

72/144= .5 square feet

10 oz./.5=20 oz. per square foot

Eric

www.e-zflight.com

[zbrubaker]

Originally posted by balsaman
No,

24x3=72 square inches

72/144= .5 square feet

10 oz./.5=20 oz. per square foot

Eric

www.e-zflight.com

Thanks Eric...that's what I thought...I was getting some confusing info from other sources so I thought with the Ezone group.

[Speed E Freak]

while on this subject, could anyone please post details on how to do this.

thanks
speed

[wayne]

Hi Eric

How would work it had 8" chord in middle and 4" chord at end like a flying wing lets say 15" wing for each side. Like to build a foam wing.

Thks
Wayne

[DaveSawers]

Then use the average chord. In this case 6" x 30" span = 180 Sq ins.

[mdennis]

Are ailerons counted as wing area? How about full length elevons on a flying wing? Which leads to; Are the full length elevons or ailerons included when measuring the cord? Are they also included when figuring out the CG?

Sorry for the twenty questions - but they are related.

[balsaman]

Yes to everything you asked. :)

Eric

www.e-zflight.com

[mdennis]

Does the thickness of the wing effect the CG? For instance; on a zagi the wing is thinner at the tip than at the base. After taking measurements on the wing it appears thet the recommecded CG is farther forward than the calculated CG, (based on the calculations done on http://www.palosrc.com/instructors/cg.htm at 25% of MAC)

Is there software, (freeware), available that will do more complicated CG calculations based on more airfoil parameters?

[vintage1]

I think you are about to step off the edge of 'here's a simple rule of thumb, use it and then fine tune it by shifting the battery pack' into 'why not do a masters in aeronautics, a few years of wind tunnel resting, and come back and tell us ...:)

[mdennis]

You are right - and I have done exactly what you said, But I thought that if the software was available ... and ... if...

I have the tendency to go from "hobby" to obsession occasionally

Thanks for the reality check

[putt_13]

Originally posted by balsaman 72/144= .5 square feet[/B]

I am confused by the above statement. Where does the 144 come into the picture. I know that 72 is 24x3, but then you divide 72 by 144. Where does the 144 come from? Thanx Patrick

[balsaman]

72 was the square inches. There are 144 square inches in a square foot. Therefor 72/144 = .5 square feet. We needed to know the square feet to determine the wingloading in oz. per square foot.

Eric

www.e-zflight.com

[bosley]

Putt_13
Wing load ing is expressed in Oz per square foot. You typically find the wing area in square inches. So if you have a wing area of 72 square inches you would divide by 144 square inches to determine how many square feet you have.
In short there 144 square inches per square foot.
Hope this helps.

Boz

[bosley]

Eric you beat me to it and you made more sense too.:D

Boz

[putt_13]

Hello,
I see. Thanx. Now what actually does Wing Loading have to do with flying. I mean, like i asked this same question in the Fan Fold thread, but ill ask here too. What does wing loading have to do with motor selection etc. Thanx Patrick

PS- Does the motors thrust have to be less than or equal too the amount of oz. per sq. foot?

[balsaman]

I don't think they are directly related in that way. I know you want the wingloading low and the thrust high.:D A better rule of thumb would be the minimum 50 w per pound rule. Also, around 10 oz. per square foor for parkflyers, and +/- 20 for sport is a good idea.

Just keep it light as practical.

Eric

[vintage1]

There is a bit of a relationship between wing loading and power to fly needed.

Power vcan be anslysed into two parts - overcoming the drag generated by (mostly) the wing and climbing the plane.

I did some rough calcs, and it turned out that well over half the power on a sensible model is used to get a decent rate of climb.

But of the rest, higer wing loding planes need more watts- per-lb to maintain level flight, because (all other things being equal) the same weight on a smaller wing has to fly faster to keep everything in the air, and so the drag is a bit higher, cos the wing is likley to be a bit less efficient.

So a higher wing loading plane needs a few more watts per lb to fly.

BUT watts per lb is a very very good 'rule of thumb'