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Old Mar 02, 2012, 11:47 AM
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CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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Problem on Scale drawing.

Where I am running into a problem is in scaling down the wing area on ( full sized palne) to the model size. For example- F-86A, WS (full size) 37.11 ft. 37.11" x12"=445.32" divide by 1/7th scale= 63.62". No problem. There total wing area is 288 sq.ft. You just can't divide by 1/7th. I don't think the model would do to well with over 41 sq. ft. I'm thinking it has to do with the fact of the numbers being squared? I know I'm missing something easy, but could use some help, thanks.
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Old Mar 02, 2012, 01:40 PM
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Maybe I'm missing something here, but I'm guessing the 12 in your equation is the root? Or are you trying to get the # of inches of the span? I'm guessing span in inches.

Since you are interested in the AREA of the wing, so you will need span and tip & root cord. Figure those out for your 1/7th scale, then figure the area based on your "new" wing.

You should also work in the same units as opposed to mixing them. (inch/feet, sq feet/inches)

Well that's how I do it anyway.
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Old Mar 02, 2012, 02:00 PM
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OK, lets make it easy. What I need to find out is, the full size jet has a total wing area of 288 sq. ft. I want to know is, what is the wing area at 1:6.5 scale,? The 12" you refer to , is to convert ft to total inches. Thats for lineal measuremnent.
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Old Mar 02, 2012, 02:10 PM
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As we are dealing with area, you will want to take your scale factor and square it. So 6.5*6.5 is 42.25
Now take your full scale area (288) and divide by your squared factor (42.25)
288/42.25=~6.81 sq Foot or about 981.5 sq Inches. Which is about right for a ~68" wing
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Old Mar 02, 2012, 03:45 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
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rcav8r2, Thank You. That is exactly what I was looking for. I knew it had to be simple. Mark
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Old Mar 02, 2012, 05:08 PM
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By the same token the weight can be sort of scaled using the cube of the scale factor.

I said "sort of" because to allow for the size factor and how the unscaled air works with smaller aircraft you can't really do this. Instead you need to determine what a good target wing loading is for this particular size of model based on studying other designs in the same size and performance class. If scaled directly using the cube of the scale factor then the 30 something lbs/sq foot would result in a totally unflyable model airplane version.
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