Top down Furling Systems provide an easy option for asymmetric spinnaker handling.
Once you are on a downwind course, the sail can be easily unfurled by releasing the drum and pulling on the sheet without leaving the cockpit. When you furl up the sail, the anti-torsion stay transfers the rotation of the drum to the the head of the sail. Furling from the top depowers the most powerful part of the sail first which makes for a safer, less stressful manouevre.
Top down furling Systems facilitate slick asymmetric sail handling and provide the opportunity to optimise downwind sailing angles. Gennakers and asymmetric spinnakers are generally produced from lighter weight sail cloth with a fuller cut than Straight Luff Reaching Sails. Downwind sailing angles for Genoa, Code Zero, Gennaker and Asymmetric Spinnaker:
A Free Flying Luff independent from the furling cable is therefore required for Top Down Furling:
- Promoting a windward projection in the luff shape (positive luff curve) will be advantageous when sailing deep (low) downwind.
- Rotating the asymmetric around the luff and/or the forestay will be central to completion of a gybe manoeuvre.
- The Top Down method is superior to snuffing because it starts the furl at the top and continues down the luff progressively squeezing the air out of the most powerful part of the sail.
The tack is lashed to the furling wheel and the head is attached to the swivel at the top. The luff is flying free of the anti torsion cable.
Top Down Anti Torsion Cables:
- Should theoretically only be fully loaded during furling and unfurling
- Will be under less load when the sail is out and full because of the luff curve
- The furl begins at the top so the torque has to be transmitted from the drum up the full length of the cable without any assistance from the sail
- Speed is crucial to the successful completion of a top down reef
- High torque loading during a top down furl means that anti torsional performance is the most important characteristic for the cable
- The core fibre needs to be light, but fat to provide support for the cable covers which are doing all the work
- Dyneema® is an excellent choice for the fibre core because it is extremely light and strong
The Jimmy Green Rigging Team are happy to guide you through the options from leading manufacturers - Karver, Selden and Profurl.