wing area X % scale =? - RC Groups
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Feb 16, 2013, 12:57 PM
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CoolerByTheLake's Avatar
Discussion

wing area X % scale =?


Maybe I didn't put i down quite right, but what I would like to know is this?

If you are going to increase the overall size of a plane by say 150%, and you have a given wing area (sq in) , how do you figure the new area out? A x 150%, just doesn't seem right.
TIA
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Feb 16, 2013, 01:12 PM
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ShoeDLG's Avatar
If you increase all dimensions by 150%, then you will increase the wing area by: 1.5x1.5 = 2.25, or 225%.
Feb 16, 2013, 01:37 PM
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CoolerByTheLake's Avatar
Thanks,
I was thinking it had something to do with being "squared" , just not sure on what and how. Now I have learned my one new thing for the day!!
Feb 16, 2013, 03:40 PM
Registered User
Your thinking was correct. The increase would be 1.5 squared or 2.3 times the original area. If you wanted to have the new size to have 150% as much area as the original you would increase the linear dimensions by the square root of 1.5 or 1.2247 times.
Last edited by Rodney; Feb 16, 2013 at 03:49 PM.
Apr 15, 2013, 11:59 AM
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CoolerByTheLake's Avatar
OK, here's one more question. I'm trying to find sq.in (wing area) of a model which is 8.79% scale. Full size plane is 202 sq.ft. So do I take 8.79 x 8.79= 77.26/202=2.61 x144=375.84 sq.in.?
Apr 15, 2013, 02:16 PM
B for Bruce
BMatthews's Avatar
You need to convert the % to a decimal. So 8.79% is actually .0879.

So it's the size change squared times the full size area in sq feet times the conversion from sq ft to sq inches. Or;

.0879^2 x 202 sq feet x 144 sqin/sqft = 225 sq inches
May 23, 2013, 07:36 PM
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CoolerByTheLake's Avatar
Thanks for the help guys, but I'm doing something wrong here.

Where I think I'm going wrong is in figuring the scale. The full size plane has a WS of 40ft or 480" and 400sq/ft. . Model has WS of 53" -----sqft?
I took 53/480=9.056
So, using BMatthews formula .0905^2 x 400 sq/ft x 144 sqin/sqft = 471.7sqin

Now if I take 44.5" WS/480 =10.78
then .1078^2 x 400sqft x 144sqin/s1ft =669.3sqin? -shorter wing with more sqin? WRONG.
It has to be something simple I'm missing, HELP Please.
May 24, 2013, 03:02 AM
Registered User
You're calculating the scale factor NOT the percentage change. Effectively your division is upside down which is why the calculations go astray.

Scale factor is Original size / Model size. 480 / 53 = 9.056

Percentage change is Model size/Original size (x 100)
53 / 480 = .1104 (or 11.04 %)
44.5 / 480 = .0927 (or 9.27%)

The percentage change also equals 100 / scale factor. I.e. if scale factor is 4 that's 100/4 or 25%, if scale factor is 8 that's 100/8 or 12.5%. For 53" span you got a scale factor of 9.056, which is a percentage change of 100/9.056 or 11.04

Steve
May 24, 2013, 03:10 AM
Registered User
EDITED - I was being a numbnuts...
Last edited by MCarlton; May 24, 2013 at 03:28 AM.
May 24, 2013, 06:18 AM
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CoolerByTheLake's Avatar
slipstick, Thanks much, I knew something was astry, just could not pin point it.

To some it may seem a "Stupid"question, but I can't be the only one who doesn't/didn't know! It may help others later on, in a their quest for knowledge!

Having gotten the solution,I see where I went wrong-

The dividend is the number that is being divided. The divisor is the number that the dividend will be divided by. Had to look it up, it's been a long time since I have seen the inside of a classroom!!
Last edited by CoolerByTheLake; May 24, 2013 at 06:27 AM.


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