At first, Red and Green were clear astern and had to keep clear of Blue. When Blue slowed down by rolling, she became windward boat and had to keep clear in accordance with rule 11. Because it was her own action that changed the right of way, Blue had to keep clear at the moment the overlap began without protection from rule 15 (see last sentence in rule 15). Red and Green had to take avoiding action before Blue's masthead was in the water. Therefore Blue has infringed rule 11 and will be penalized. After Blue has capsized (masthead is in the water - see rule 23) Red and Green keept clear. Red's fouling of Green was forced by Blue's infringement of rule 11 and Red will be exonerated under rule 64.1(a).