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Aerodynamic design

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Old 07-30-2016, 04:04 AM
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Arthur89777
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Default Aerodynamic design

Hello everyone!
I would like to ask you about the aerodynamics of rc plane.
How to calculate the aerodynamics' forces center of plane?
I have little difficulties with this
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Old 07-30-2016, 10:29 AM
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BMatthews
 
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This is a topic that to cover it correctly would require that we type you out a whole book worth of reply.

What I will suggest you start with is to look at the CG calculator at http://adamone.rchomepage.com/cg_calc.htm .

The key product of the calculations for your needs for the "aerodynamic center of forces" is the box labeled "Stability Margin". If you set this value at 0 the point it says to put the CG on the MAC will be the overall airplane's Neutral Point NP.

Now you can play with entering numbers that alter the size of the wing, the aspect ratio, the tail size and tail moment arm and see how each affects the overall airplane's NP.

Note that there is no "right" or "wrong" to this other than for normal flying that you usually want the balance point or Center of Gravity (CG) to be slightly ahead of the NP. Depending on the design the NP might be as far forward as 20% or as far back as the trailing edge. Yep, that's right. There are a sizable number of vintage free flight models that run with the NP back at or even behind the trailing edge in some cases and put the balance point just a hair in front of the NP.

You can also help yourself somewhat. Do a web search for "model airplane aerodynamics" and read through the various link pages. None of them is truly complete because, as I posted above, it would require a full length text book worth of writing. But you can get enough from each one that after a while it will all start to make more sense.
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