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View Full Version : Neutral Point Location for Martin P6M-2


David F. Plummer
May 26, 2003, 06:42 PM
Hi!

I'm building a 1/16th scale model of the Martin P6M-2 4-jet flying boat; the wing is swept 40 degrees (referenced to the 1/4 chord line); span is 102.3 ft (77.2" on the model); wing area is 7.42 ft-sq on the model. The T-tail horiz. stab. is also swept at 40 degrees (ref. to 1/4 chord), and has a span of 30 ft (22.5" on the model). Is the geometric method described by Martin Simons (Figure 12.13 of his Model Aircraft Aerodynamics, fourth edition) a reasonably acceptable method for locating the neutral point for the model; would a static margin of 0.15-0.2 be a reasonable starting point for CG location?

Any comments/help/suggestions would be appreciated.

Dave Plummer

John Boren
Jun 03, 2003, 01:39 AM
It's a good book and that method will get you ver close to the proper CG. I would make a small hand launch glider to scale and balance it until it glides nicely. Compare the two and see how close they are. I would move the CG up a little from this just to be on the safe side for the first flight. Good Luck