Getting a crapload of lightsharpener traffic from this thread. ;)
Building the 12' mirrored Light Sharpener was pretty easy. Check craigslist for people dumping mirrors from their bathroom remodel and cut them into squares with a $3 glass cutter. Attach with liquid nails. I used about 850 4"x4" squares. Don't worry about the geometry of fitting them together like a puzzle, it works out fine.
I didn't invest the time to make it track the sun because I just wanted to play with it, burning and melting stuff like I had seen with the Solar Death Ray.
Aluminum foil heated stuff up, got wood to smoke but not flame.
Mirrors ignited wood in 15 seconds or so. I dried a soaking wet shirt in 3 minutes, then it burst into flames. Jiffy Pop and the watermelon were my favorite. We were literally too scared to keep the coconut on there for more than 2 minutes. We knew we had a tropical bomb up there. Should have drilled a relief hole and watched the cocomilk steam shoot out of it!
We tried to pump water past the focal point, but it takes a pretty powerful pump to get water 8 feet into the air, and if the water stalls, you get steam shooting out which you cannot turn off. I did not get ahold of a steam engine and I didn't try a Sterling engine, both of which require more engineering and money than the giant mirrored death ray.
No one died.
