Wings
I had been to Croydon Aerodrome and seen the giant Hannibal HP42 and Argosy Airliners in about 1935. But my wood-workings skills would only allow me to make a Monoplane. A flat piece of wood for the wings, set at a slight angle to the fuselage and a tail plane ought to do the trick... But it crashed. A Grown-up told me that the top of the wing needed to be specially shaped, not flat, to give my aeroplane LIFT... That more lift came from above the wing than from below it. It seemed odd to me... But he WAS a Grow-up... And he had been a pilot in the R.F.C... I humoured him... One day I will find out, I expect !