In the right conditions, a spinnaker staysail will increase your speed up to three quarters of a knot, without changing your rating one bit. Staysails are free sail area. The spinnaker staysail, also called the Dazy Staysail, is a tall, narrow, high-clewed very light sail used under a spinnaker, symmetrical or asymmetrical.
The sail is intended to have its tack set on the center-line of the foredeck about one quarter to one third of the way back from the headstay to the mast. Its luff length is as great as will fit between that tack position and top of the foretriangle. Its width, or LP, is about 80% or 85% of J. A wider sail would have greater area, but would not be as effective over as great a wind speed range or within as large a range of apparent wind angles.
The Staysail’s effective range is when the apparent wind direction is between 5 or 10 degrees forward of the beam to 20 or 25 degrees behind the beam.
The spinnaker staysail is effective not only because of the area it adds to the sail plan, but also because it increases the air flow along the leeward side of the main, thus improving the efficiency of that sail as well.
A stay sail can hurt your boatspeed just as easily as it can help. If the wind gets light the staysail will hinder more than help. That’s why most boats have their staysail’s set up with small furlers. With a furler, it is easy to watch the speedo as you roll out and roll in the staysail. Also, you need to roll up the staysail when gybing so that the spinnaker will fill easier without the staysail.
The final pro tip: it is always faster to have the staysail under trimmed. Over trimming will stall the wind flow across the leeward side of the main; therefore, keep those windward telltales on the staysail flying straight up.
This staysail is set flying, meaning that it is not attached to or supported by any stay. Consequently, its luff rope must be made of a low-stretch rope or wire.
A bit of trivia: The Dazy Staysail is named after the IOR Two-Tonner GOLDEN DAZY, which used a tall narrow staysail in her 1975 Canada’s Cup match racing victory.