Let's say I'm rounding a mark and I think I might have hit it, but I'm not sure (I was busy steering and trimming, my crew busy trimming, etc.). Should I circle? Presumably I should if I think there's a 90% chance I hit it. What about 50%? 10%? 1%?
The rules say:
A fundamental principle of sportsmanship is that when competitors break a rule they will promptly take a penalty, which may be to retire.
This doesn't give a lot of leeway -- it doesn't say that if you *know* you broke the rule, you take the penalty. So I suspect the right interpretation is that you must either take a penalty or be very very confident that you didn't break a rule.
But what do others think? Are there any relevant cases?
My interpretation has implications for how you allocate your attention as you round a mark. If I'm right, then it's really important to know for sure whether you hit it, so you should be looking at it if it's nearby -- even if that distracts from trimming and so on, and even if it actually increases the chances you hit it.