So I've finally arrived at a time all aircraft engineers hope to get... Maiden flight. But I've had too many experiences where the maiden flight is all but over in a matter of seconds becauseI was too eager to "free the bird". The end result... A disgruntled soul wishing it had been more patient.
I've learnt my lesson (with my wife's mentoring) to be more methodical and pragmatic about my approach to the maiden flight. Since I don't have the luxury of wind tunnel testing of the wing and the airframe, the only reliable weapon in my arsenal was... Calculations. To be more specific, weight and balance calculations and measurements.
After using AutoCAD, a weight balance spreadsheet to calculate the estimated (emphasis on "estimated") center of gravity in relation to the wing mac (mean aerodynamic chord), measuring the actual cg will all electronics included was the next (and hopefully) final step.
It must be said that prior to this step I realised that packaging tape on the wing will not be enough for a 2.4m - 800g foam glider. Reinforcing with carbon tube over 85% of wing span should increase the rigidity of the wing. I had also reinforced the nose as the glide speed could reach 9m/s (36 km/h). Landing nose first at that would surely break the fuselage in half. I had made provision for a "tweeking" the c.g. by having a long enough battery bay (the battery weights about 1/4 of the total mass) to shift the c.g. quite drastically.
Based on some research including this intuitive document on weigh balance, it was quite clear that doing a hand toss launch for this size of glider was not a good idea. It was recommended that if the glider was powered, rather use that option so you have more control while you try and find the optimum weight balance point for the plane for smooth flying at all air speeds.
So currently the c.g. sits at 30% (57mm) from the leading edge of the main wing. This should be a good starting point for the maiden flight (I so hope).
I've learnt my lesson (with my wife's mentoring) to be more methodical and pragmatic about my approach to the maiden flight. Since I don't have the luxury of wind tunnel testing of the wing and the airframe, the only reliable weapon in my arsenal was... Calculations. To be more specific, weight and balance calculations and measurements.
After using AutoCAD, a weight balance spreadsheet to calculate the estimated (emphasis on "estimated") center of gravity in relation to the wing mac (mean aerodynamic chord), measuring the actual cg will all electronics included was the next (and hopefully) final step.
It must be said that prior to this step I realised that packaging tape on the wing will not be enough for a 2.4m - 800g foam glider. Reinforcing with carbon tube over 85% of wing span should increase the rigidity of the wing. I had also reinforced the nose as the glide speed could reach 9m/s (36 km/h). Landing nose first at that would surely break the fuselage in half. I had made provision for a "tweeking" the c.g. by having a long enough battery bay (the battery weights about 1/4 of the total mass) to shift the c.g. quite drastically.
Based on some research including this intuitive document on weigh balance, it was quite clear that doing a hand toss launch for this size of glider was not a good idea. It was recommended that if the glider was powered, rather use that option so you have more control while you try and find the optimum weight balance point for the plane for smooth flying at all air speeds.
So currently the c.g. sits at 30% (57mm) from the leading edge of the main wing. This should be a good starting point for the maiden flight (I so hope).
Comments
Post a Comment