Average Lap Decaying Breeze

"However we don't necessarily finish the lead boat first, rather we choose a point between groups of boats to hoist the blue flag and begin finishing as boats cross the club line on their laps (it's in the SI). This way the slow boats often finish before the faster ones and there is rarely more than 10 minutes between first finish and last finish."

That is the way to do it.

Thanks for all replies.  The surprising thing seems to be that there doesn't seem to be anything written down on this by RYA/Sailwave/Clubs etc given the widespread use of Average lap.  Agree that it needs to be part of SIs and with clear guidelines for ROs 

I would say that for club sailing, counting back to the previous lap is justified if there has been a significant change of conditions that grossly penalise a particular group of boats I.e the wind disappearing and boats being sent on a last lap that takes much longer than anticipated.

Well, to my mind you're either doing average lap racing or you aren't. If you are then you need to accept that sometimes you'll get funny looking anomalies. If you don't then you need to accept that you'll get even worse anomalies, but they don't look so obvious.

But having the race committee going back and picking and choosing different methods of calculating results for what they think looks right seems like a can of worms no wise person should open. Most of all they should do exactly and only what the NOR and Sailing instructions say.

The most important things with getting average lap racing right is to pick your stopping point well, and make sure there are enough laps. 2 and 3 aren't really enough. With say 6 laps the effects of one slow lap are normally much smaller.