Why do some boats have a mizzen mast?
So that they can fly their Mizzen Spinnaker!
The mizzen spinnaker is a spinnaker sail that attaches to the mizzen mast and adds more sail area when cruising off the wind.
While this sail requires a significant amount of work to set, and you can’t change tacks with it up (because the main boom is in the way) it does provide a significant amount of speed, power, and stability to the ride. The boat becomes more balanced as the headsail is not the only sail in operation.
While you could get a sail in that space aft of the mast by setting your mainsail, the mizzen spinnaker sail is far enough aft that it doesn’t block the wind from reaching the headsail, meaning you can sail on a deep broad reach without any sail loosing its wind.
This allows you to carry more sail on a broad reach while still having a more balanced helm and plenty of power as you sail towards your destination.
The mizzen spinnaker is a great sail, but it is not a sail to set if you are in close quarters or going to be jibing anytime soon. It takes a fair amount of effort to set and douse the sail, making it ideal on a long passage where the sail will be up for hours (if not days)!
