Please Note: Access to the Excel Software is via DropBox.
If users would prefer to use the Software directly on their PC just create an account and request it it via comments
and we will forward it directly.
| For most RC Aeromodellers, stability in the pitch or lateral axis is taken care of in the design stage of the models they fly. |
| Typically the design work is done well and the critical positioning on the plan of the center of gravity will give adequate static margin, or degree of stability in the pitch axis. |
| This situation comes into doubt however when the following things occur. |
| 1. The C of G is not where it is indicated on the plan and the needed ballast is greater than expected. So the question comes will the aeroplane still fly well with a more rearward C of G? |
| 2. Significant rework is carried out which again moves the C of G, and so the same question: will the aeroplane still fly well with a more rearward C of G? |
| 3. An own design is attempted and so the question comes, where should we put C of G if the aeroplane is to fly well. |
| In all these case the easy answer is somewhere between 25 and 30 % of wing chord but what if we could improve on that ? |
| Typically our aeroplanes will fly well with a Static Margin, (SM) of 10 per cent. The percentage referred to is percentage of Mean Aerodynamic Chord of the aircraft's wing. |
| The easy way to measure this is by using computer programming to measure the SM for the model concerned. The spreadsheet attached to this RC Aerobase article aloows that measurement. |
| For those who are not familiar with aerodynamics and who want to be able to make such checks, we would recommend Martin Simons book Model Aircraft Aerodynamics. |
| Worksheet 1. of the Spreadsheet Includes a simpler approach which was derived by Gordon Whitehead from the full aerodynamic formula and is significantly easier to handle. This approach has the well deserved title, "The Winning formula." |
| Worksheet 2. of the Spreadsheet uses full Neutral Point theory. |
| The software has logical limits. To understand the limits of use the spreadsheet is annotated, e.g. what to do about biplane stagger, or sweepback or taper etc. |
| To see a brief account of the fundamentals of Neutral Point theory, search "Understanding Neutral Point Theory" on this website. |
| In both these cases it is planned to convert the programming to Visual Basic which should make operation easier for the user. |
Related Articles:
Neutral Point and Static Margin. 1. Visualisation.
Neutral Point and Static Margin. 2. The Winning Formula.
Neutral Point and Static Margin. 3. Software.
Neutral Point and Static Margin 4. Tucking In
Neutral Point and Static Margin. 5. Stall On Landing Approach
Neutral Point and Static Margin. 6. Aircraft unstable about the Pitch, or lateral Axis.
