It's difficult to say as you can't actually get to the edge. As you continue your research you'll find that not every Flat-earther holds the same views about features of the earth (other than, of course, its flatness).
For example, some say the Earth is infinitely wide and so you can never reach the edge.
Others will tell you that the edge is an ice wall patrolled by the US govt which stops intruders.
A third possibility is that
"As it is difficult for proponents of Flat Earth Theory to obtain grant money for scientific research, it is nigh on impossible to determine which of these theories is correct."
NOTE : This funding problem refers specifically to Universal Gravitation, but I assume that similar problems blight all their investigations.