Why there are weight rules

Rafts and loops are designed for a certain weight. Too light and the raft might stop on a hill. Too heavy and it could jump. So there are rules, and lifeguards weigh the raft!Water is the lubricant between skin (or tube) and gelcoat; without it friction would stop or burn a rider within metres. It also carries the rider like a current. Gravity supplies the energy, friction and drag remove it, and banked walls supply the centripetal force that keeps a rider turning instead of flying straight - which is why a curve's wall rises higher the faster the design speed.