The MythBusters The MythBusters

MythBusters Episode 192: Hail Hijinx

Premier Date: October 21, 2012

It is possible to jump to safety on a collapsing rope bridge.


This myth is based on a scene in the film Cliffhanger in which Sylvester Stallone’s character is able to make a running leap to one end of a rope bridge after the mooring at the opposite end of the bridge is destroyed with explosives.

Adam and Jamie built a small scale bridge and a pneumatic “jumper” to begin their tests. Electronic timers controlled the jumper and controlled a solenoid that dropped one end of the bridge. A control jump (without dropping the bridge) resulted in a jump height of 22 inches (56 cm). With a 50 millisecond delay after dropping the bridge, the jump height was 10 inches (25 cm) and with a 100 millisecond delay the jump height was 4.5 inches (11 cm). With a 150 millisecond delay the jumper was no longer able to jump from the falling bridge.

Adam and Jamie then built a full scale, 1600 lbs (725 kg) bridge with pine boards and steel cables. They strung the bridge across a large dry dock in a ship yard. Quick releases with small explosives (squibs) were used to release one end of the bridge. To test a running leap, Jamie began several strides from the safe side of the bridge as the other end was dropped. The bridge went slack immediately and Jamie fell with it because he had no footing to jump from. Next, Adam attempted to make a smaller, standing jump. He stood at an achievable distance and waited for the sound of the explosion before he jumped. The bridge fell before Adam even had time to react to the sound; he was not able to jump at all.

At this point the myth was busted but Jamie wanted to see if it was possible to hang on to the hand ropes as the bridge fell. He was successful in holding on but was not able to climb all the way back to safety. He suggested he might be able reach the top if his life really depended on it.

A violent hail storm can sink a boat.

plausible (barely)

To begin their tests in the shop, the Build Team fired large, baseball-sized spheres of ice at boat hulls from a compressed-air cannon. They began firing the ice at 80 mph (123 km/h) to simulate terminal velocity. At this speed the ice did not puncture an aluminum, fiberglass, or a wooden hull. At 150 mph (241 km/h) (simulating hail in a hurricane) the ice still did not puncture any of the hulls. At 300 mph (483 km/h) (the fastest recorded tornado speed, even though hail isn’t typical in tornadoes) the ice only penetrated the weakest areas of the wooden hull. At this point the myth was described as busted but the team decided to continue these tests with the boats actually floating on water. On water the ice did not penetrate the fiberglass hull even at 300 mph (483 km/h). With the wooden hull, the ice penetrated at 300 mph (483 km/h) and 150 mph (241 km/h), but not at 80 mph (123 km/h).

The Build Team also reasoned that hail could potentially sink a boat by filling up its volume with enough extra mass. At a port they began filling one of their small boats with ice. The boat only began to sink after 4,000 lb (1,814 kg) of ice was added. The boat did not sink entirely because the ice began floating and supporting its own weight when in the water. Because this myth appeared to be possible in extreme situations, it was deemed plausible.