Feb 16, 2013, 11:57 AM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 4,125 Posts 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, 12:12 PM Registered User Germany, BW, Stuttgart Joined Mar 2012 740 Posts 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, 12:37 PM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 4,125 Posts 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, 02:40 PM Registered User Florida Joined Aug 2004 3,945 Posts 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 02:49 PM.
 Apr 15, 2013, 10:59 AM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 4,125 Posts 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, 01:16 PM B for Bruce The 'Wack, BC, Canada Joined Oct 2002 10,703 Posts 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, 06:36 PM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 4,125 Posts 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, 02:02 AM Registered User Staffs, UK Joined Nov 2003 9,706 Posts 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, 02:10 AM Registered User Cromer,Norfolk, UK Joined Nov 2006 2,505 Posts EDITED - I was being a numbnuts... Last edited by MCarlton; May 24, 2013 at 02:28 AM.
 May 24, 2013, 05:18 AM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 4,125 Posts 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 05:27 AM.

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