CHAPTER 9 Downwind
This is the most dangerous state of sea for a power boat. She is vulnerable to a breaking wave crest giving her rudder nothing to bite on, leaving her wide open to a broach. She may also lose control by digging her nose into the back of a wave she is overtaking. In either case, knock-down is a real possibility. The best response to these perils is to adjust your speed positively to be slower or faster than the waves, and to overtake them where appropriate with circumspection. Trim up (leg out) to raise the bow and keep it from ploughing into the trough, and watch out at the crest for foaming water if the wave is breaking. Avoid these wherever you can. If a breaker looks like catching you up, power on and accelerate away ahead of it. Not only does the rudder become inefficient in the breaking water of the crest, the propeller may cavitate and deliver less drive. Be prepared to throttle back smartly if the engine starts racing. This will give the screw a better grip than letting it thrash around in the air bubbles. If things get too ‘hairy’ for comfort, don’t forget there are always other options, such as choosing a different destination or turning up into the wind and dodging.
Handling sailing craft on passage in heavy weather
The techniques of storm survival at sea for sailing boats are dealt with later, but there is much that can be done to help a boat perform while still on passage.
Weatherliness
It has been said with some justification that a well-handled bath tub will sail downwind. The issues arise when the wind is forward of the beam. A boat that can work to windward in hard going is called ‘weatherly’. It is possible to say without risk of generalisation that larger craft perform better in this respect than equivalent smaller ones. A long waterline handles waves with greater readiness, while additional ballast and displacement render a rig more powerful. All sailing craft have a frontier beyond which they cannot be driven to windward and an extreme limit at which they can no longer maintain even their weather gauge. It’s not easy to predict what these parameters might be, but skippers should take every opportunity to expand their knowledge of their boats.
Sail combinations
A poorly set-up rig with a roller reefing genoa furled in to 10 rolls or more will not perform nearly as well as a tautly prepared smaller boat whose headsails are setting properly. The roller-reefing compromise that is so attractive in moderate conditions becomes a nightmare when you really need the sail to perform.
Some serious cruisers and short-handed race boats use a choice of permanently hoisted headsails — generally two. On a typical 40-footer, one might be a full genoa that sets adequately with some rolls in up to force 5. The second is a ‘yankee’ – a full-hoist jib with a high-cut clew of less than 100% of the area of the fore triangle, usually set up close abaft the genoa. Its luff may well have an area of foam sewn into it. All these things militate towards satisfactory reefing of a sail designed for maximum efficiency fully unfurled upwind in force 5. At near-gale and beyond, even the yankee will have run out of steam upwind. It is replaced by a traditional storm sail hanked onto a stay which may need to be set up for the occasion (see page 94).
In more moderate going, the yankee is chosen for any short-tacking, because the genoa is too much like hard work and struggles to pass between its own stay and the yankee’s.
MANUAL OF SEAMANSHIP | 91
Heavy Weather
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