Furling Systems for Headsails and Mainsails

by Simon Boyde, Technical Director, Storm Force Marine


We all know about roller furling genoas: that they are cruising items, and that they are not used for racing, and in the end you end up with a compromise sail. Well this is simply not the case anymore.

IRC gives you about a 1% difference in your rating between using a roller furling genoa and having three separate gennies for use in different wind conditions. This is not a lot and, of course, if you are racing IRC, the difference is taken care of while racing by the handicap. I mean, if its good enough for Ellen MacArthur on B&Q - as well as a whole host of the Open 60 racers, it should be good enough for me!

Additionally, it is obvious that for going from A to B, unless you have a crew which is well trained for quickly changing headsails, you go faster on a boat with a furling genoa. There is a lot more about furling systems which most people don't know about and have not yet seen how they can re-vitalise their boat and their sailing techniques while hugely reducing the work involved in reducing sails or flying downwind sails. I hope in this article to illustrate some of these options for you.

Boom Furling Systems

Profurl Boom Furler from Storm Force Marine, Hong KongNow these are not new: in fact boom furling systems of one kind or another have been in use for over a hundred years. In the old days the entire boom used to rotate, the middle of the boom having been constructed to be wider than each end in order to take up the curve in the middle of the sail while it was being rolled in. The big issue with these systems was the lack of a viable vang.

More recently boom furlers where the main furls round a mandrel which rotates inside the boom (thus you still have a vang) have been tried and from some manufacturers such as Profurl have been put into standard production. Boom furlers were brought in in the modern era as an alternate method of easily reefing a mainsail without the inherent issues that you face with in-mast furling systems.

With a mast furling mainsail what do you do if the system breaks? You can't get the main down! Meanwhile you have a main with no battens in it, which, when all is said and done, is not good, however you look at it. On top of that you have massive excess weight high in the boat due to the vertical mandrel in the mast.

A modern boom furling system does not have these attendant problems: the mandrel in the boom is of course lower in the boat than a mandrel running up the mast. if the system breaks down you can of course still lower the main. and of course you can pretty much run a fully battened main. Racing wise, well, yes, you have a flatter sail, especially in the bottom third, but again IRC will deal with this as you declare such systems on your application. However, and as you can see from the photos attached to this article, you still end up with a pretty handsome mainsail shape, and one which you can reef from the cockpit without the risk of someone being bashed around up near the mast in thirty knots of wind trying to get a slab in.

Profurl Boom Furler from Storm Force Marine, Hong Kong Mast-Furling System

Profurl In-Boom System

Fully-Battened Mainsail

Maximum Sail Area

Efficient mainsail shape

In-Mast or Behind-Mast Furling

No Battens

Negative curved leach

Flat mainsail - poor performace

Flying Sail Systems

Here is where furlers start to get sexy. Imagine a flat-ish asymmetric spinnaker which you hoist furled around its own luff cord. Once it is hoisted, simply unroll it and voila! you have your downwind sail up and flying.

Flying Sail Section

Profurl FLyig Sail Furler from Storm Force Marine in Hong KongThis is essentially what a code-zero sail is: a roller furling spinnaker/gennaker which rolls round a stay not permanently fixed to the boat, but instead fixed to the sail. This stay, once the sail has been recovered and rolled round its (special, anti-twist) luff cord/stay again, can simply be lowered to the deck and coiled, getting rid of that extra windage and creating an ease of handling for a downwind sail which would have been unthinkable only a few years ago. Those of you who saw B&Q in Hong Kong while she was here would have seen exactly that system, but without the flying sail in view, running down from the top of her mast to her bowsprit.

Sail DiagramOf course, because the entire stay is lowerable with its attendant sail wrapped round it, peeling to a smaller kite is simply a question of raising the new one, unrolling it, flying the sheet on the old one and rolling it up. Simple!

New on the block is the Karver Top-Down Spinnaker Furler which offers greater control. The asymmetrical spinnaker is fixed to the anti-twist cable only at the head of the sail, the foot is attached to a swivel within which the cable twists. The sail can be deployed in seconds and furled even in strong winds in less than a minute, single-handed.

The same furler can be used for all suitable sails. Most sails will not require retro-fitting.

Stay Furlers

Of course, once these systems were built, it became obvious that something similar could be done with staysails. The difference here is of course that the stay that a staysail flies on has an additional job of helping to support the mast. However an inner forestay or baby stay is of course a real pain when tacking a genoa, expecially an overlapping genoa.

So, lets not only make it removable, lets make it lowerable as well! Easy: a 2:1 block arrangement at the top of the mast allows us to lower this special anti-twist stay constructed from Technora or PBO using the staysail halyard. In terms of hoisting the staysail, the issue is now one of opening the staysail bag on deck , attaching the 2:1 halyard arrangement, hoisting it, unrolling it - hey presto our staysail is set.

Wind come up? No problem, hoist the staysail and roll up the genoa. We have massively reduced sail area while also moving the centre of effort back towards the centre of the boat. Naturally at the same time we have rolled up part of the main using our boom furler thereby doing the same thing at the aft end of the boat. There is better news as well: this removable staysail stay will be nearly twice as strong but about a quarter of the weight of the stay it replaces.

All these furling systems are available now, in various sizes (Geronimo has one designed to take a 40 tonne load, and HK's own Maiden has one designed for 30 tonnes!), to suit different boats. The different sail makers in HK are all aware of the systems and can provide you with the appropriate furling systems. And are they reliable? Ask Ellen!

Profurl furling systems and Karver Top-Down Furling Systems are available from Storm Force Marine - www.stormforcemarine.com or +852 2866-0114. Storm Force also provides leading boatyards in HK and China with the same systems.

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