Only when you are willing to bet your life on your instinct or the directions of a friend.
Blind horizons are a pretty big gamble and the stakes are as high as they get.
But I've run blind stuff on the advice and lead of good friends who know the turf. When you are following someone that you trust. Hopefully they have run the rapid before. It is important to have good communication skills with this person. It is also okay not to scout if you are a good boat scouter.