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Author Topic: Aerodynamics question  (Read 193 times)
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bendds
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« on: January 25, 2020, 03:47:20 PM »

When I was building free flight in the 1960s, the center-of-gravity was always supposed to be 50-75% of the wing chord, if my memory serves.  I've built two EZBs in the past two months, and have put the CG at about 60% for stability  I know that the rules for F1L have changed considerably in 50 years.  Elsewhere on this forum, people are talking about putting their wings in front of CG.  Has something in aerodynamics changed, or has something been done to increase stability?  Thanks
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Tapio Linkosalo
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« Reply #1 on: January 26, 2020, 02:49:45 AM »

Those models with high aspect ratio tails are rather tandems, where the tailplane carries a fair share of the model weight. To load the tail enough, the CG must move back. Tandem models typically have minimal decalage so that the tailplane works on almost similar angle as the wing, and they also compromise some of the longitudinal stability to achieve the efficiency (but then again, conditions indoors are stable, so you do not need much stability anyway). The sufficient stability comes from the models having large tailplanes and long tail moments.
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bendds
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« Reply #2 on: January 26, 2020, 02:40:15 PM »

Thanks; this is a great, understandable answer.  And makes a lot of sense when I see giant stabs on plans...
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