If it is not prominently on your calendar already, mark September 18 as the start of the 2015 Rugby World Cup—the 44-day international competition showcasing a full contact sport that cannot be bothered with cumbersome helmets or protective pads—and whose fan base tends to be equally uninhibited. This year, 20 countries will take the field across 14 cities in England, with each nation vying for the coveted Webb Ellis Cup trophy. While the majority of supporters in the United States are still arden…