Aerodynamics - Question about wingtip shapes

[marry del]

Short of picking up an aerospace engineering book and learning a lot of complex math, I figured I'd ask here.

Looking at the wing tips of planes like the Spitfire, P-63 Air Cobra, P-47 Thunderbolt, A6M Zero, etc... you'll notice the wing tips are rounded.

Looking at the wing tips of the P-51, the BF-109, modern Cessnas, FW-190, etc... you'll notice the wing tips are straight.

Does this affect aerodynamics much? Roll rate/roll performance at all? If so, could someone explain why the rounded wings are better/worse?

 

[phinds]

I have no idea but you might also want to note that modern jet airliners all have the wingtips extended slightly and bent upwards.

 

[Lnewqban]

The round shapes of those wings tried to avoid tip stalls.
They were complex to fabricate.
More agile and acrobatic airplanes prefer the stalls beginning by the tips, so they are quick to roll.

Please, see:
https://en.wikipedia.org/wiki/Elliptical_wing

 

[russ_watters]

Welcome to PF!

Looking at the wing tips of planes like the Spitfire, P-63 Air Cobra, P-47 Thunderbolt, A6M Zero, etc... you'll notice the wing tips are rounded.

More specifically, elliptical.

Looking at the wing tips of the P-51, the BF-109, modern Cessnas, FW-190, etc... you'll notice the wing tips are straight.

Does this affect aerodynamics much? Roll rate/roll performance at all? If so, could someone explain why the rounded wings are better/worse?

Elliptical plan wings are most efficient, but there are many factors affecting the choice of plan. Here's a primer on common shapes:
https://www.aircraftcompare.com/blog/types-of-aircraft-wings/

 

[David Lewis]

Elliptical wing planforms were inspired by Ludwig Prandtl's Lifting Line Theory.

The P-51 Mustang was designed with squared off wing tips in order to save time and cut costs. After engineers noticed no apparent loss of efficiency, squared off tips eventually became the norm.

The rationale behind the constant chord (e.g. Piper Cub) or tapered (e.g. P-39) wing with rounded tips is that it was supposed to yield some of the efficiencies but be easier and less expensive to build than pure elliptical. It turned out to be a mistake, and when Aeronca Champ or Piper Super Cub wings are built new, they have square tips. The side benefit is that the ailerons have a longer moment arm and flaps can be longer.

Elliptical wings hung on for a long time because they appealed to intuition. They look beautiful, efficient and graceful. About the only benefit is higher torsional strength-to-weight and torsional rigidity-to-weight ratio.