I kept it simple. In a large aircraft at take off the fuel near the tips of the wings ( fuel will rarely fill the wing to tip ) and especially fuel in tip tanks reduce the moment the wing has to carry at the root and if the aircraft doesn't drop weight from the fuselage, typically passenger and cargo aircraft, the loading of the wing root will be worse when the fuel has been burned.
In the F-104 Starfighter the wings were bolted to very heavy fuselage frames and there was not an ordinary wing carry through structure. Those frames were chemically milled from heavy blanks from which IIRC some 95% of the metal was removed. Those wings had a thickness of 6 %, had many spars and for every spar there was a frame.
The BV 144 had a wing carry through structure in the shape of a tube, as had many of the aircraft by its designer Richard Vogt, that contained the fuel and was the shaft for changing the wing incidence.
There are endless possible variations.
In the F-104 Starfighter the wings were bolted to very heavy fuselage frames and there was not an ordinary wing carry through structure. Those frames were chemically milled from heavy blanks from which IIRC some 95% of the metal was removed. Those wings had a thickness of 6 %, had many spars and for every spar there was a frame.
The BV 144 had a wing carry through structure in the shape of a tube, as had many of the aircraft by its designer Richard Vogt, that contained the fuel and was the shaft for changing the wing incidence.
There are endless possible variations.
