Question: why are wings wide at their base and short at the end?

Andres Rivero answered on 8 Mar 2017:

Hi Jason_Bourne05,

This is because something called stress and bending moment. Even though the tip of the wing is what achieves the largest displacement when in bending, the base of the wing has to resist all that bending (the base of the wing is called the root). Because of this, the stress at the root of the wing is much higher than at the tip; it actually has its maximum value at the root and its minimum value at the tip.

Stress is what causes structures to break, so a structure needs to be wider and stronger at the location of maximum stress. Because of this, the root of the wing needs to be wide. Remember that I mentioned above that the stress is minimum at the tip and maximum at the root? Because of this, we can gradually decrease the dimensions of the wing as we move closer to the tip, and we do this because airplanes need to be as light as possible. If we do not this, the airplane would become more expensive to manufacture (as more material needs to be used) and it would consume more fuel as it would be heavier.

Just a little extra information: those wings that vary their width along its wingspan are called tapered wings, and the ratio between the width at the root and at the tip is called the taper ratio. So if a wing has a taper ratio of 0.7, it is 30% wider at the root than at the tip.

From the structural point of view, aircraft structures engineers (like myself!) have the mentality that any weight that does not come from passengers, cargo or fuel must not fly unless indispensable. You’d be surprised by how few extra kilograms could increase the fuel consumption by a significant number. This is why carbon fibre is being used in airplanes a lot these days, because they allow us to achieve lighter designs than with metals.

Andres