This Activity is meant for Boy Scouts.

Per patrol: 
3 6ft or longer staffs or posts 
3 10ft ropes

Each patrol lashes the poles to form a tripod with 1st rope.
Tie a bowline knot in the second rope and loop it over the top of the tripod.
Tie a bowline knot in the end of the 3rd rope.
Tie the 2nd and 3rd ropes together with a square knot or sheetbend.
Have a scout sit in the bottom bowline loop and not touch the ground while the patrol gives their patrol yell.

Alternatives: Instead of tying a bowline in the second rope, just throw it over the top of the tripod and have all the patrol pull on it to pull the swinging scout up and keep him up for 10 seconds.