The mizzen on modern boats is not really thought of as a “power producer” but more of as a balancer. The mizzen mast is often jokingly referred to as the “radar mount” or “wind gen mount”.
While the mizzen sail itself isn’t often thought of as a powerful sail, it does lend itself to the availability of adding power in a little know form: the mizzen headsail.
Mizzen headsails are attached at three points and provide lots of power when sailing off the wind. The head is attached to the mizzen, the tack is attached to the aft bast of the main mast, and the clew is sheeted through the end of the mizzen boom.
The sail is set flying, with no stay supporting its luff. As a result, easing the halyard will allow the sail to billow and generate a lot more power!
The Center of Effort (CE) will be moved aft with the mizzen staysail, so it is important to make sure that the geometric center (where the CE is found) is as far forward as possible. This is why yawls perform better than ketches with mizzen headsails; the mizzen is very small and set far aft, meaning the the majority of the sail will be found forward on its way to the mast.
Another important point with the mizzen staysail is that by easing the mizzen sheet to the mizzen boom, the clew of the mizzen staysail will move forward which will also help to move the CE forward and help fight weather helm.
Mizzen staysails are incredible power generators but care must be taken with them to ensure that they do not cause too much weather helm and thus disrupt the balance of the sailplan. It is important to always couple the mizzen staysail with a very large and far forward headsail that will induce a healthy amount of lee helm into the equation, helping to cancel out any weather helm generated by the mizzen staysail. A large genoa may seem like a good idea for this task, but if the genoa is sheeted too far aft, the CE will be brought back behind the mast and actually induce weather helm which would then compliment the weather helm of the mizzen staysail, causing the yacht to “Round Up” into the wind.
Additional sails should always be flown cautiously and judiciously. They can both create a lot of power, as well as a lot of problems.