GENNAKERS MADE EASY
By Julian Plante
The development of dousing sleeves and improvements in sail shape has combined to make gennakers a much more attractive option for the cruising sailor.
For cruising sailors looking to enhance their boat’s performance, recent developments in sail design and handling have made gennakers (also commonly known as multi purpose spinnakers or MPS’) easier to use and great way to increase downwind speed.
Spinnakers have commonly been associated with race boats and shunned by most cruising sailors as unnecessary awkward and potentially dangerous to use. Certainly most of us will have watched with a sense of amusement and sympathy as a crew passes by wrestling a wayward spinnaker that has twisted around the rig or is dragging in the water “prawning”! The spinnakers of days gone by were also difficult to set up and required constant re-trimming, certainly not the user friendly experience that most cruising sailors are looking for.
Developments in sail shapes to improve flying manners and dousing sleeves (also commonly known as snuffers) to aid launch and retrieval have significantly improved the user friendliness of gennakers, making them more attractive and accessible for the cruising sailor. Most good gennakers will feature a tri radial construction for a smooth, stable, easy to trim sail and the mould (design shape) will be optimized for your specific aspect ratio and forertriangle. The measurements required to assist with designing a well fitting gennaker are simple and essential to ensure best performance. Sail shapes have also developed to such an extent that using a gennaker with autopilot is possible with boats that track well and have a powerful pilot to help keep a reasonably steady course.
A valuable addition to any gennaker is a snuffer dousing sleeve, which makes hoisting and dousing the sail a breeze, by gathering an encasing the sail in a nylon tube. Rather than wrestling with arms full of sailcloth blowing over the rail into the water, you just deal with an easy to handle tube with minimized windage. A simple control line quickly pulls the snuffer up or down the gennaker and enables just one person to hoist, set and lower such a sail. If you have an autopilot or device to lock off your helm, then the solo sailor can use the assistance of the snuffer to make using a gennaker relatively easy.
Setting up your boat
Setting up your boat for a gennaker is relatively easy, and there are a few simple pieces of equipment that you need and may have already fitted.
Firstly you need a spare halyard above or outside of your forestay attachment point at the mast to hoist the sail on. The gennaker tack may be attached to the stem of the boat wither with a short, fixed length strop (usually allowing the tack to fly at rail height) or you can set up an adjustable tack line with block at the stem and line leading back to clutch/cleat in the cockpit.
Adjusting the tack will allow for a little more range and performance from the sail by lowering the tack a little when reaching and raising for running squarer. However, it is by no means a necessity. Many gennakers feature a fixed tack strop, which might simply loop around a bow roller, or snap onto the stem fitting.
The final step is providing sheeting arrangements with block and line for sheets. Ideally your sheeting blocks should be positioned close to the stern (at least 80% of the way aft of the bow) to provide a good wide sheeting position and also correct lead to a winch for winding the sheet on.
In regards to your line for sheets, these can be just a simple double braid or equivalent and as a quick rule of thumb the length of the sheets should be around 2.5 times the length of the boat (if you are planning to gybe the sail and have sheets run on both sides of the boat).
Tips for easy sail handling
As always, there are a couple of traps to avoid and tips to consider. Always ensure the tack, clew and foot of the gennaker are pulled out of the bottom of the sleeve otherwise the collar may catch on these points.
Never keep the snuffer control/pulling line under tension when the gennaker is full and sailing. Tie it loosely to the lifelines or cleat to the mast.
Avoid snuffer burn, where the collar on the snuffer rises too quickly and can burn the cloth. On large boats or in windy conditions, keep tension on the control line when hoisting to control snuffer speed.
Up to 18 knots
Enjoy the easy performance that the gennaker brings to your boat and extra miles that you will eat up. Remember; don’t use the gennaker beyond its design range. The recommended apparent wind range for 0.75oz nylon is 18 knots apparent. It is better to snuff than be sorry!