On Feb 1, 5:50*am, (Michel Talon) wrote:

There is not a single proof that this is true...

Any of several public domain wing weight estimators will show you
nearly exactly what the difference in structural weight is between 14m
and 15m. It's not to be sneezed at.

The difference of cost between 14 m span and 15 m is
presumably totally insignificant....

No, not true. As I've written elsewhere the manufacturing cost seems
to scale exponentially with span. A lot of that is due to the larger
tools required to make larger wings, the larger buildings required to
store and use the tools, the greater amount of energy and other area
and volume costs and business expenses associated with larger
buildings. It goes to worms in a right hurry, it does.

One has to chase economies elsewhere.

One must chase economies everywhere.

Thanks, Bob K.