Asymmetrical gennaker in cruising: better stocking or whisker?

Having an asymmetrical gennaker on board armed with a sock or on a frull is very different, and the two setups affect maneuvers, management of critical situations, and the overall work of the crew. Here are some technical tips from the experience of Luca Sabiu, navigator and sailing coach.

Asymmetric gennaker cruising, the choices to make

For sailing at load-bearing gaits, asymmetric gennakers have spread like wildfire in recent years on both planing racing cabin cruisers and cruising boats. It is in fact a viable alternative to the traditional spinnaker, more practical, versatile and equally effective.

When it comes to asymmetric gennakers however, there is one decision that divides sailors and forms two real “schools of thought” is: stocking or whipping? In general, the sock allows even sails designed with a very pronounced leading edge to be hauled down, but the maneuver in a taut wind is not the easiest and the sail is heavier and bulkier to stow. The use of the whisker is more convenient and practical, but in order for the gennaker to furl the leading edge of the sail will need to be a little straighter and less “round.” It therefore proves more complex to furl a gennaker designed for “sailing low,” while a sail with a more narrow luff cut has no contraindications.

So let’s try in this article to shed some light on the use of the stocking or shake to sail with an asymmetric gennaker and give some useful advice to those who want to buy an asymmetric gennaker without incurring erroneous purchases.

Sock or whip: the 5 technical aspects that make a difference

Let us begin by saying that both options have merits and demerits with substantial differences at the practical level. So let’s go over them together highlighting also some tricks based on my real experiences and how I personally work on these sails in my onboard workshops with students. Let’s start with the 5 main differences between the two weapons, coiled and stocking.

1. “Working” range of the asymmetric gennaker

An asymmetrical gennaker on stocking has the great advantage of having a more pronounced and more powerful “shoulder.” This allows for “lower” leaning and sailing, i.e., with about 15-20 degrees more than a sail rigged on whisker, which because of its shape characteristics (it must be able to furl) cannot have a pronounced shoulder and therefore its range is in a narrower swath. Also remember that the furling sail is an “all in/all out” sail, that is, either all in or all out.

2. Adjusting the leading edge with tack

Another major difference between the two weapons lies in the ability in the one with the sock to adjust the tack by “twisting” the sail, thus accompanying upwind the shoulder. Let’s make it clearer. The gennaker is a sail for carrying swells that over time, because of ease of use compared to the spinnaker, has become more widely used by boaters. It is clear, however, that with this sail you cannot sail leaning like a symmetrical Spi. To be able to get downwind more we need to carry as much “shoulder as possible upwind.” How then to do it?

By letting go of the tack, the sail rises and with it the center of pressure getting a twist of the top and middle of the sail that will allow us to let go more sheet and make our sail deeper and more powerful. This maneuver with the furling sail (except in rare technological cases) is not possible, because the sail is tacked to the mast at a fixed point.

3. Size and ease of stowage on board

Today, unfortunately, fewer and fewer cruising boats have a sail cove like the boats of yesteryear, and so these devices often on board are quite a bit of “baggage” to be moved under beds, or worse, in lockers. Once in the bag, the two sails, furling and stocking, have a similar footprint. The difference is that the furling one will be a long “biscuit” and the other a large canvas tube containing the sail. An important clarification concerns the fact that the furling sail cannot be furled and left furled like the genoa: because it does not have the anti-UV band, the sun would destroy the fabric; moreover, above a certain wind strength, it could be opened and destroyed. Above 17-18 knots my advice is always to haul it down.

In case we should have other furling sails on board, such as Zero tails and foresails, the whisker (without sail) can remain rigged on deck, as on the Class40s, Imocas, etc. Otherwise, it will follow the sail in the bag.

4. Crew present on board

This is for ma the real big difference between the two sails on which I invite my students to reflect. Let’s take two typical crews as examples. The first consists of husband wife and two young children. In this case, a stocking sail in the presence of a gust of wind, perhaps at night, forces the skipper to go to the mast to close the stocking circuit in “solo sailor” mode. Under the same conditions with a furling sail you would do everything from the cockpit, without having to go to the bow.

On the other hand, the other typical crew consists of group of friends who also do offshore racing, so they have no problem covering the various working positions. In this case a stocking sail, having a more powerful entry shoulder, will make them lean much more than the previous crew with obvious course advantages. Let’s say then that a furling sail is easier to manage but is less performant. Although in a situation with so many lumps everyone would want it precisely because of how quickly it can close, then get back on course as soon as the critical moment has passed.

5. Operation of asymmetric gennaker lowering

“Take care more of how to bring it down than how to bring it up.” In my work this is a sacrosanct rule. A sail somehow always goes up, whether by flawless maneuvering or sloppy work. Simply at some point the sail inflates and away it goes. Working with many students, I often see big messes, especially for those who are just starting out or otherwise have little experience. The real problem lies in the lowering: if we lower poorly, confusingly, skipping steps in the procedure, we only do damage, or worse, we also risk injury. So the lowering has to be done following a strict procedure, and the higher the wind intensity goes, the more we have to stay centered on the correct maneuver.

I like to liken the stocking down with a fresh wind to the freediver who ascends short of air and would like to accelerate his finning to resurface, but instead has to stay calm so as not to expend more energy than necessary and make it to the surface. With the blender this turns out to be easier, just let it scald and wrap.

Choose according to your browsing needs

As can be seen, therefore, for the handling of the asymmetric gennaker, choosing one type of rigging, stocking or swash, is very different on a practical level and substantially affects life on board, maneuvering, and in general the approach of the skipper and crew. Knowing and carefully evaluating these differences is the starting point that when purchasing this type of sail allows you to avoid gross errors. After that, it is all a matter of experience, mode and navigational trim. Good load-bearing gaits to all!

Luca Sabiu

If you want to learn more about this topic:

The use of the stocking or shake for sailing with an asymmetric gennaker is one of the topics explored in depth during the Uisp Instructor Training Tour of Sardinia, a long itinerant training organized by Uisp Vela from September 23-30, 2023 and aimed at its instructors. Keeping him aboard his Class 40 “Flow” is Luca Sabiu, ocean navigator and sailing coach, who has developed a great deal of practical experience on this subject. If you want to learn more go to the page
https://lucasabiu.com
.