Recordbreaker
07-31-2002, 03:01 AM
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Recordbreaker
There are other CG calculators around. I have seen this one posted in other threads here on RCU.
http://www.palosrc.com/instructors/cg.htm
Hope it helps.
Russ.
http://www.palosrc.com/instructors/cg.htm
Hope it helps.
Russ.
07-31-2002, 10:34 AM
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CG
The proper CG depends on the degree of pitch stability desired. The degree of pitch stability depends on the purpose of the aircraft and the flying skill of the pilot.
The stability is determined by the static margin which is the distance the CG is ahead of the neutral point. When the neutral point and CG coinside the aircraft is neutrally stable, goes where you point it and has no tendency to diverge or correct after a control input or gust. (It's much easier to find the neutral point by experiment than to calculate it accurately.) The location of the neutral point is determined by the tail moment arm and tail area. The larger the product of the moment arm (in multiples of MAC) and tail area (as a % of wing area), the farther aft the neutral point. Because the tail operates in the wake of the wing and fuselage, its effectiveness is diminished. The slower and more turbulent the flow over the tail the less effective it is. That's why unstreamlined or fat fuselages need more tail area for a given stability and CG location.
Simple formulas for locating CG only work well for aircraft of very similar configurations, proportions and purposes flown by pilots of similar skills.
You can calculate a CG that is a safe starting point for flight testing but, the best CG for a particular pilot must be determined by adjustment.
The stability is determined by the static margin which is the distance the CG is ahead of the neutral point. When the neutral point and CG coinside the aircraft is neutrally stable, goes where you point it and has no tendency to diverge or correct after a control input or gust. (It's much easier to find the neutral point by experiment than to calculate it accurately.) The location of the neutral point is determined by the tail moment arm and tail area. The larger the product of the moment arm (in multiples of MAC) and tail area (as a % of wing area), the farther aft the neutral point. Because the tail operates in the wake of the wing and fuselage, its effectiveness is diminished. The slower and more turbulent the flow over the tail the less effective it is. That's why unstreamlined or fat fuselages need more tail area for a given stability and CG location.
Simple formulas for locating CG only work well for aircraft of very similar configurations, proportions and purposes flown by pilots of similar skills.
You can calculate a CG that is a safe starting point for flight testing but, the best CG for a particular pilot must be determined by adjustment.
