Every year before the NHL All-Star game, players compete for the title of fastest slapshot in the league. This year's winner: Boston Bruins' mammoth defenseman, Zdeno Chara, with a 105.4 mph shot, a skills competition all-time record. (However, hockey great Bobby Hull's slapshot was once recorded at 118.3 mph - and Hull is almost a foot shorter than Chara.)
The power of the slapshot comes from the weight transfer from the back legs through his hands to the stick. The stick hits the ice about a foot before the puck, causing the stick to bend or "bow" - some sticks have a lot more flex (see the "bow" of Hull's stick, left). When the stick hits the puck, the potential energy from the bent stick is transfered to the puck, and combined with a snap of the wrists in a gyroscope motion leads to a rocket shot.The greater the bend, the more the recoil, so the higher the potential energy release. This also leads to a longer stick/puck contact time, increasing acceleration.
Another version of the slapshot is the classic 1977 Paul Newman movie, which allegedly is being remade. Not sure how I feel about that - how can you improve on the original Hanson brothers? For an in-depth look at the slapshot from a current pro, check out this link: an explanation of the force of a slapshot (and even a brief cameo by a lightsaber!) courtesy of Washington Capitals winger Matt Bradley (known as Professor Bradley on the Caps' Red Line Monday program).
I will see if I can find that pic and scan it in. I am 6'2 and 190# and the man dwarfed me. I look silly in it, mostly because I felt silly standing next to him.
(*) Otherwise known as Stanley Cup winners, 2009 - my prediction.