Jake -
Most times the Sailing Instructions give a specified period of time for the "First" boat to finish to constitute a race. Only if they have a instruction that states "all other boats must finish within thirty minutes" or whatever time frame, then you must issue a DNF. You could also modify the Sailing Instructions to say "all "DNS" receive points equal to the number of boats registered + 1 and "DNF" to all the boats that started plus 1. That would solve the problem of a boat that broke down, or couldn't complete the course in time, and not get the same points as someone who stayed on the beach.

Paul Nardone