wing area X % scale =? - RC Groups
Feb 16, 2013, 12:57 PM
Do it Right, the first time!
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# 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
 Feb 16, 2013, 01:12 PM Registered User 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 Do it Right, the first time! 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 Do it Right, the first time! 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 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 Do it Right, the first time! 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 Do it Right, the first time! 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.