NASA contractors, fighting penguins, killer polar bears, no atmosphere, or super freezing temps are all the excuses I have read regarding why no one has ever explored the edge of the earth. I don't buy it, especially the fighting/killer NASA developed penguin guards, LOL. Lets not mention the moon landing because if you believe the earth is flat, you certainly don't believe the moon landing happened. Instead lets look at Mount Everest, or the deepest parts of the ocean scientists have sent unmanned submarines. If the edge of the edge of the earth is unreachable by any humans then surely people have discovered ways to send unmanned vehicles to the edge. Whether that be drones or any other unmanned remotely controlled vehicles. If you say we don't have the technology to do such a mission then I believe your lack of confidence in the human race is far worse than I originally thought.
Now, I know mathematics can prove the curvature of the earth but I assume you would insist that the calculations are simply wrong. I recently watched a video that claims all photos of space, or from space are all photo shopped. It's a really crazy but with that said, in order for me to be convinced I would like to know two things. 1. Why have we not been to the edge of the earth. 2. Why would the edge of the earth be so secretly protected considering we would have ways to visit because we have the technology to do so.
I will completely dismiss any answers that claim aliens, killer penguins, dragons or any other fairy tales.