violets in most cases shouldn't be run over 700mA absolute max! due to higher heat at the junction of those chips.
With the heatsink you linked fans will temendously increase thermal load capacity as they are ribbed fins, which with forced air flow give a large increase in cooling power. The downside is the base of the heatsink is thin which doesn't spread the individual led's heat out as efficiently as a thicker base heatsink so the fans and fins can't remove the heat as fast.
without getting into technical calculations if you can maintain a heatsink temp that allows you to keep your finger on it near the edge of the led star chip where it meets the heatsink for a long time without pain you are in a good place and way under what the led can tolerate long term.......violets often being the exception but Cree can run at temps that would burn you and have no issue. Just better to err on the side of caution and run some fans knowing that the Crees at least will be able to tolerate it for some time should the fans ever fail...
With the heatsink you linked fans will temendously increase thermal load capacity as they are ribbed fins, which with forced air flow give a large increase in cooling power. The downside is the base of the heatsink is thin which doesn't spread the individual led's heat out as efficiently as a thicker base heatsink so the fans and fins can't remove the heat as fast.
without getting into technical calculations if you can maintain a heatsink temp that allows you to keep your finger on it near the edge of the led star chip where it meets the heatsink for a long time without pain you are in a good place and way under what the led can tolerate long term.......violets often being the exception but Cree can run at temps that would burn you and have no issue. Just better to err on the side of caution and run some fans knowing that the Crees at least will be able to tolerate it for some time should the fans ever fail...
