The Parachute Sail

Parachute Sail A parachute sail is a type of downwind sail^[1] [2]that can be rigged at the bow of a sailing yacht and are similar to the kite sails being developed for larger vessels. They are generally made by converting a standard aircraft parachute. This is different from a traditional spinnaker ^[3] or the more modern parasailor^[4] The Advantages of such a sail are that it is self-stabilizing and can be flown in a wide range of wind conditions for downwind sailing. Such sails may be used between 15 and 40 knots of wind. Parachute sails are manufactured commercially ^[5] but may also be easily constructed from military surplus 'chutes. In this case it is essential to obtain a parachute with its line uncut.

Using a parachute sail in the Caribbean.

The Parachute sail is rigged at the bow between a spinnaker halyard and a power line conected via the boaw roller

Construction The Parachute sail is constructed by taking the lines of a standard parachute which are gathered into two groups. One group becomes the top of the sail and is linked by a Spinnaker halyard to the top of the mast. The other set is connected to the bow of the boat, usually by a line run through the bow roller or via a block attached to it. This lower line is known as the power line and is the main one through which thrust is provided to the vessel. The two sets of lines are connected by a linking line which allows stable operation by maintaining tension in the halyard.

High wind adjustment for the parachute sail

Operation To fly the sail it is first linked to the halyard and the power line run through the bow roller or block. the yacht must be oriented so that the wind is around 165 degrees off the bow The sail is launched over the leeward side of the bow. The sail should be hoisted on the halyard until it is possible to hang it over the rail without entering the water. It is generally advisable to determine the position of the halyard in this condition before it is to be used and mark it. Set the Halyard to this point when launching.

The power line is connected to the lower set of parachute lines and its free end can be tied to the mooring cleat. In use the power line is not adjusted after launch but can be released when recovering the sail. Recovery is facilitated by a third line connected to the center of the parachute which can be used to 'trip' the 'chute pulling it inside out.

When flying the sail it may be adjusted by lengthening the halyard allowing the sail to fly progressively lower as wind strength increases. This risks the sail entering the water if wind strength decreases but this is not a huge problem as long as the halyard is not lengthed so much that the sail can be drawn under the boat.

Parachute sails are considered to be self stabilising with the boat's tiller locked in the mid position. The tendency of the sail to fly directly away from the wind means that the vessel will naturally stay on a downwind course.