Douglas F4D original wing shape

[hesham]

Hi,

here is the original Douglas F4D wing,and its modification.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930087359_1993087359.pdf

 

[KJ_Lesnick]

Why did the F4D/F-6, and F5D's have those rounded wingtips?