That's pretty much what I did before, just in a different order. I have no idea how you got that answer. I got the exact same result as before when following that guide.
Edit: Read that link. I understand what you did now.
You figure an 8 inch prop at 1/2 it's length and use the hub to tip length of 4 inches. The actual distance of the circle the tip travels in 12.56 inches. That's 1.05 feet.
What's the size of this blade? 8 inch total diameter, 4 inch radius, correct? That's what I got from your first post. If so, here's what you did wrong:
To calculate the circumference (total size of a full revolution) you'd do 2πR, or 2π times 4 inches. this would mean the full revolution draws a circle of 25.13272 inches. Given that you ended up with half of that, I'm going to assume you forgot that pi is the ratio of the diameter to circumference, rather that radius (what you used.)
You then multiplied the (incorrect) circumference by pi again for some reason . I assume you thought the formula wanted circumference, but the correct value would have been the diameter of the blade, or 8 inches/0.6667 feet.