Top Down furler sets

Operating a Top Down Furler is straightforward – a tug on the control line sets the torque cable in motion, providing uniform gennaker furling from head to tack. Even when sailing solo, the integrated swivel retains the tack position until the final moments, streamlining the process. The Top Down Furling System system offers more than just ease of use; it simplifies hoisting and lowering your asymmetric spinnaker from the comfort of your cockpit. When it's time to furl, the sail depowers from the top down, enhancing safety and reducing stress during maneuvers. Top Down Furling is a game-changer for modern sailors who demand precision and convenience in spinnaker handling

What is Top-down furling, how does it work and can I convert an old asymmetric spinnaker to furling

Top-down furling is used to furl loose luffed, downwind asymmetric spinnakers and gennakers around a torsional cable. The benefits of this system over a traditional snuffer is that the whole operation can be managed from the safety of the cockpit

How does top-down furling work?

• The key to top-down furling is an independent, free-flying swivel, either directly on the drum or using a top-down adapter
• The tack of the asymmetric spinnaker is attached to this swivel, not the cable or the drum
• Therefore, when the drum starts to furl, the cable is turned but not the sail
• The torque from the drum is transmitted the full length of the cable to the head of the sail where the furl starts
• The furl starts working its way down the cable/sail => top-down furling

Can I convert my old asymmetric to top-down furling?

If you are fed up with man-handling a gennaker in a snuffer – can you simply convert to top down furling? This all depends on the shape and age of the sail. Sailmakers design sails specifically for top-down furling. Generally, they make then flatter with a narrower head angle. Therefore, if you have a reaching cruising gennaker it may convert well, however, an old, deep running asymmetric spinnaker may not necessarily convert to top down very well. There is a lot of technique involved in getting a good consistent top down furl even with a sail specifically designed for top down. You might find that with an old, deep sail you get disappointing results

Is it better to have a dedicated top-down drum or a Top-down adapter and how do top-down adapters work?

There two key benefits to a dedicated top-down furling drum. This solution is generally lighter. The overall height of the drum is smaller compared to a drum plus top-down adapter, and therefore there is more available space for the torsional cable and sail luff. However, the ease of use of the top-down adapter plus the fact that you can use the same furler for multiple sails has led to widespread adoption of top-down adapters – even in grand prix racing circles.

How does the top-down adapter work?

• The top-down adapter creates a link between the furling drum and torsional cable with a free flying swivel mounted on it
• The tack of the asymmetric spinnaker is attached to the swivel so that when the drum furls, the torsional cable furls, transmitting the torque to the top of the cable, but the tack of the sail is not affected
• The top-down adapter lives with the sail, in the sailbag, when not in use
• You will therefore need one top-down adapter for each asymmetric spinnaker

What are the key elements of a top-down furling system and whats included in a Top down furling set on the Upffront site

Furling drum - either with integrated tack swivel or the additional of a to-down adapter. A furling line for the furling drum – NOT usually included with the furling drum. Double fairleads - to run the furling line back to the cockpit. A top swivel which connects the top of the torsional cable to the halyard. A torsional cable - needs to be specifically designed for top-down furling.

What’s included in a top-down furling set?

Our standard top-down furling sets can be either a dedicated top-down drum plus swivel OR a furling drum, top-down adapter and swivel. Some sort of attachment for the drum and swivel are “usually” included but check product text for confirmation. We also have some complete furling systems including a torsional cable / stay which offers a cost effective complete solution.

What different top-down furling setups can I have and what length torsional cable do I need

Loads for top-down furling are relatively low. In fact, the torsional cable only needs to be properly tensioned during the furling / unfurling operation. When the sail is flying the cable is often eased off. Therefore, the simplest and best setup is to have the drum attached to the bowsprit with a snap shackle and the cable/sail hoisted on a 1:1 halyard. When using a top-down adapter it is more likely that the overall furling system is set up for higher loads on code zeros and so may include either a 2:1 halyard or 3:1 purchase system under the drum.

What length torsional cable do I need

• For code zeros it is important that the cable is made to fit the luff of the sail
• However, for top down furling, at Upffront we always look to maximise available max hoist (read this blog article on How to measure max hoist)
• For an approximate length use ISP (height of halyard exit above deck) plus the distance from the base of the mast to the tack point of the furling drum to get the hypotenuse length then deduct 500mm for furler/swivel deductions

What size furler do I need for my boat and what do I need to look for in in my equipment in terms of good torsional furling performance

Top down furling loads are low compared to bottom up furling and all manufacturers recommend larger boat sizes and sail areas for their units when used for top down furling. Generally you could come down x1 SWL size compared to your code zero furler. However, obviously if you are using the same drum for your code zero you have to size for the code zero. And, in addition, top down torsional cables are always a bigger diameter than bottom up cables because top down torsional loads are significantly higher. This can lead to problems with interfacing the correct top down cable with the jaw width of the furler. Therefore, at Upffront we normally start with specifying the correct cable and then look for an appropriate furler to fit the cable

What do I need to look for in terms of good torsional furling performance?

• With top down furling “speed is your friend”
• It is large sail area to wrap around a small diameter torsional cable and so furling speed is critical to good furling performance
• Like the gears on a bike a small drum delivers the fastest furl for the same furling line speed, therefore, a small drum diameter is preferable for top down furling
• Having said that, if you are using the same drum for your code zero yo have to accept a compromise because a larger drum is preferable for code zero furling as that delivers more power for the start of the furl on a code zero