I learned not to do that many years ago when I reached over a running Cox .049 to switch on the radio. Still have a small scar on the fleshy underside of my forearm from that one. Amazingly, except for occasionally getting a knuckle "buzzed" by the backside of a prop, I've been quite lucky.

About 20 years ago a buddy of mine and I went out to fly a C/L Ringmaster with a Fox 35. After a couple of flights, he asked if he could start the engine. I said, "OK, but be careful of the prop." Sure enough, after a couple of timid flips, the Fox roars to life. He hesitates for a second then procedes to put his hand directly through the prop (a black plastic Master Airscrew) to detach the battery lead. He did get some cuts on his palm but was upset at himself for his brain lapse. He said he was OK and wanted to continue to fly but I said we were done and needed to get his hand cleaned up. Fortunately, he didn't require any stitches.

Control line precision aerobatics used to score starting points where you had to signal the judges then had 60 seconds to start your engine by hand and get airborne. With so many top fliers going to the carbon fiber "meat cleavers" the frequency and seriousnous of the injuries prompted a rule change to eliminate the starting points and allow the use of electric starters.