How different yacht types change sailing characteristics

Most of Britain’s yacht owners, both now and in the future, will be sailing boats built in the 1960s to 1980s, that are highly durable, structurally sound and capable of being restored and maintained to a high standard at a fraction of the cost of buying a new boat.

And because there is a wide choice, potential buyers can take their time to choose a design that handles well – a quality greatly influenced by the hull shape. Amongst older craft, hundreds of Sabre 27s, Alacrity 18s and Hurley 22s are still afloat and capable of taking their owners to Cornwall, France, the Azores or beyond – safely and economically.

Looking back over the last 50 years, I’ve done most of my sailing in those three small yachts.

Comparing their lines plans, you can see that the subtleties in their handling characteristics were directly linked to their underwater shapes.

Back in the 1970s, any review of a new yacht was likely to include a lines plan, and the reviewer would comment on its probable behaviour in the open sea. Nowadays, few lines plans are published and many hull shapes are dictated by the need to incorporate two double cabins aft.

Reviews may record boat speed at varying wind strengths and wind angles but this is generally on flat-ish water and does not tell us how the craft will behave when a Force 5 is fighting a strong tidal stream in the Bristol Channel – especially if the skipper needs to carry out an emergency gybe. All three of our boats had twin keels, because we enjoy cruising between drying harbours and anchorages.

The diagram right shows simplified lines plans, each with one longitudinal buttock line and two transverse sections, one through the forefoot (in the right-hand half of the sections) and one through the quarters (in the left-hand half).

Alacrity 18

I had chartered a Corribee and found it rather tender. The next boat along from its mooring, an Alacrity 18, was noticeably stiffer, so I ordered one. After it was delivered, we spent several weekends adding fittings and then, over a fortnight, the Alacrity took us down to Cornwall and back. Two years later she did it again, comfortably and safely despite strong winds. Excellent!

The transverse sections in the lines plan show why the boat was stiff, because the hull flattened out towards the wide stern, although the transom shape was pleasantly softened at the quarters so that it didn’t dig in when heeled.

The transom left a clean wake until close to hull speed, when the stern wave began to detach, hinting that she might plane if pushed really hard. We achieved that once, in a memorable race. In a SW wind, one leg took us across the Western Solent to the Saltmead Buoy and we were at the tail of the fleet when we noticed the leaders being swept downstream of the buoy by the powerful spring flood.

We hardened up smartly and enjoyed the unusual experience of being first around, as the others tried to claw up to the mark against wind and tide.

We were still leading the pack on the final leg, a broad reach, with a She 31 coming up fast. The wind increased, and I hung onto the tiller. The Alacrity hissed towards the finish with a rooster tail astern. The She’s skipper finally lost his nerve and gave up the chase, luffing to reef in a violent rattle of canvas, with lots of shouting, leaving our little cruiser to finish in glorious isolation.

More a ‘U’ than a ‘V’

On that screaming broad reach, heeling would have encouraged a broach. When a hull with wide, flat aft sections is heeled, the hull’s immersed shape is likely to become asymmetrical, which may induce eccentric handling characteristics. Also, when the windward quarter lifts, the rudder can lose grip.

As dinghy sailors, we compensated by instinctively using our weight on the windward side, but large yachts cannot rely upon crew weight and some modern designs with wide sterns require twin rudders so that one will remain fully immersed.

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The design of a small cruiser is usually a compromise. The Alacrity’s forward hull section – more a ‘U’ than a ‘V’ – indicates a relatively blunt bow, and when close-hauled in a short chop she was inclined to head-butt the crests and lose momentum. She was happier on the open sea, sailing up and over the longer waves, and the generous width at the bow did provide comfortable foot room at the forward end of the V-berth.

The flat-ish after sections and absence of a rudder skeg allowed her to perform an interesting low-speed manoeuvre when berthing at a pontoon, under sail. With care, she could be inserted into a space hardly longer than her hull.

The trick was to steer towards the middle of the space until half a length from the pontoon, put the helm down a little to get her turning, then apply full lee helm, when the rudder swung 90º to become a water brake and she drifted sideways to lie neatly alongside. I described this as a ‘handbrake turn’ to a petrolhead friend who expressed scorn until we compared the physical forces and agreed on the similarities.

Hurley 22

I grew up beside the Tamar Estuary, where the Royal Navy kept a training flotilla of Hurley 22s and I had always admired this compact, businesslike yacht. It was an unusual design for its time: a small cruiser with very heavy displacement and sailing qualities having priority over accommodation.

In fact, there is a small mystery over the displacement: the designer, Ian Anderson, wrote that she had a 40% ballast ratio, and the original lines plan showed the twin keel variant with a draught of 2ft 6in. However, all the manufacturer’s brochures indicated a ballast ratio of around 59%.

Most or all of the twin-keelers have a 3ft draught, and they appear to float nearly two inches lower in the water than shown on the drawings. It looks as though Hurley Marine judged the design as being too tender, so added deeper keels and extra ballast.

The Hurley 22’s heavy displacement, coupled to a marked deadrise over much of her length, gave her a very steady behaviour and she would happily slice through most sea states. Sometimes she even ‘submarined’ through steep breakers, most memorably at St Albans Head when I tried, and failed, to find a calm passage inshore of the tidal race.

With a large outboard well at the stern, the rudder and cockpit were set well forward, restricting the length of the cabin space. It could have been uncomfortably cramped but the boat’s interior was deep, as observed in a 1968 magazine review: ‘One really does “go below” in this little cruiser.’

The accommodation was very cosy and secure and our Hurley 22 was an early version, with a comprehensive fit-out. There were only four places to sit – no proper settee berths – but the occupants could not be flung around because they were surrounded by a wealth of joinery. The numerous lockers, which even included a small sideboard, provided proper stowage for every piece of loose kit, and there was a sliding chart table.

Family adventures

That snug security was very welcome when it came to sailing with our two small daughters. We enjoyed several cross-Channel cruises, and the size of our boat never restricted the cruise planning. Lee-cloths on the quarter berths gave the girls safe nests for overnight passages and wild weather, which the Hurley coped well with.

Our most memorable day was a long quartering run from Torbay to Poole Bay, when we had been delayed by bad weather and I was running out of holiday time. Forecasts predicted strong SW wind for several days, so we weighed anchor just before first light and the breeze stiffened.

By the middle of Lyme Bay, reefed main and storm jib were working hard and as we passed Portland, spume was blowing in streaks. A cross-Channel ferry from Weymouth was battering south with waves driving over her bridge and a 15° list to port, while our girls were calmly eating lunch, seated comfortably on the cabin sole.

After coming into the lee of Purbeck we decided to spend the night in Studland Bay and we were hailed from an anchored boat: ‘Where have you come from? It’s been pretty windy here.’

Directional stability

The Hurley 22’s rudder skeg helped directional control when travelling fast but made her less agile than the Alacrity in low-speed manoeuvres, when it resisted sideways motion and ‘handbrake turns’ were no longer an option.

She was also untrustworthy when running in big waves with a fading wind, a trait that affects many yachts and demands careful concentration when a steep swell is rolling up astern. As a wave passes, the water undergoes a circular motion: up, forward, down, back and repeat (see diagram above).

At the crest the movement is a forward surge and reduces the influence of the rudder. For instance, on a steep wave with a period of five seconds and a height of three metres the forward surge at the crest is at approximately four knots. If the boat is running at a gentle five knots, then as a crest comes up astern the flow over the rudder is suddenly reduced from five knots to one knot and the helmsman will struggle to maintain control – a common cause of broaching.

The Hurley 22 may have been particularly susceptible because the rudder was set well forward and had a short lever arm in relation to the keels.

I once sailed with a companion who had seen a preliminary version of the design in which the rudder was hung in the conventional fashion, on the trailing edge of a single keel. Several yachts from that period (eg Roundabout & Clarionet) had skeg-hung rudders close to their keels and were notorious for broaching.

I reckon the Hurley 22 would have been even better with a transom-hung rudder.

Sabre 27

We adopted our Sabre 27, London Apprentice, for an unconventional refit project – that was 37 years ago and she’s still one of the family at the age of 53. The designer, Alan Hill, did not publish a lines plan but his general arrangement drawing included several sections and from these it was possible to reconstruct the lines.

His drawing scale was stated as 0.547 inches to 1ft, which looks strange. Maybe he produced a generic lines plan for a medium-sized cruiser and when Marcon, the builders, requested drawings for a 27-footer he simply calculated a scale to make the lines fit that length. The hull form certainly resembled some cruiser-racers of the late 1960s, albeit with fuller bows to accommodate a decent vee-berth.

London Apprentice has several underwater features that could inhibit performance, including relatively shallow twin keels and a GRP shaft log moulding that resembles a second skeg. Twin keels are valuable for intimate exploration of shallow and drying cruising grounds, so we’re happy to have them and accept that the boat is no greyhound. However, she is extremely docile, which compensates for some loss of speed by reducing stress on the crew, particularly on long legs in troublesome conditions, when it is possible to push her hard without inviting trouble.

Strangely enough, those good manners may be partly linked to low initial stability. When at rest she is actually quite tender, like the Corribee, and the lines plan shows that aft of amidships the sections approximate to semi-circular arcs, so there is little form stability.

Also, the ballast is in shallow keels, although the ballast ratio is a respectable 45% and she stiffens up on heeling. In rough water, those semi-circular hull sections are beneficial because, when heeling or rolling, the immersed hull shape will remain more or less symmetrical. That would encourage the user-friendly handling qualities, such as not griping to windward when struck by a gust.

Centre of effort

I have no personal experience of using the Sabre 27 in gales on ocean passages but a couple of single-handed owners who have made a habit of ocean cruises report that it remains relatively placid, whether pressing on or hove-to. One of them, on passage from the Azores, hove to, retired to his bunk and slept for six hours as breaking crests thundered past.

The other was ‘welcomed home’ by Border Force officers who had been tracking him on AIS. They were suspicious about some strange zig-zags off the Spanish coast and were reluctant to accept his explanation that he’d just furled the sails and made a cup of tea.

As most of the hull’s lateral area is well aft, the bow is inclined to fall off the wind after going about, so that she never misses a tack, and close-quarters manoeuvres are possible under sail, although it’s important to maintain steerage way.

Close-hauled and under full canvas, well-heeled in a fresh wind, our Sabre 27 carries a fair bit of weather helm because the rig’s centre of thrust is then somewhere over the lee side, and the forward component of the wind force is trying to make the boat luff.

There’s no point in sailing the boat on her ear; very often a reduction in sail area will produce an increase in speed, especially if we take the area out of the mainsail and shift the centre of thrust forward to achieve a neutral helm, so in a rising wind we usually reef the main first and hang on to full genoa as long as possible.

The diagram above right shows why this tactic works. On elevation drawings it is conventional to show a centre of effort for the sails and a centre of lateral resistance for the hull, but those only relate to lateral components of forces, acting sideways.

The wind thrust and hull resistance vectors actually act obliquely, and when the rig swings out to leeward the wind thrust vector may move outboard of the resistance vector, so that the combination tries to turn the boat to windward. Applying weather helm maintains a straight course but at the cost of extra resistance from rudder drag. If the mainsail is reefed while retaining a full genoa, the centre of thrust moves forward so that thrust and resistance vectors cancel out and the rudder has less work to do.

The result can be gratifying. Even under genoa alone we have maintained a full 6 knots when close hauled, with the dinghy towing astern. That’s close to the boat’s hypothetical ‘maximum hull speed’ of 6.3 knots. It suggests that, for this twin-keeler, the direct effects of hull and keel drag may be less important than rudder drag under weather helm.

Off-wind handling

I value our boat’s off-wind characteristics, because most cruising miles are achieved downwind, and on a fast run a badly behaved yacht can be a menace.

This is where the Sabre’s underwater appendages justify themselves. The rudder is set well aft and the skeg makes it reluctant to stall, while skeg and shaft log assist directional control like flights on an arrow. Gybing in rough water is positively a pleasure, we have never experienced a bad broach, and we usually trust the boat to take care of us in hairy conditions.

This first happened when we were running through a narrow slot between two rocky Scottish islands and a squall came up astern. We were grossly over-canvassed, with no room to round up for reefing, and I was worried, yet the boat remained under easy control, carrying full sail until through the slot and clear of the rocks.

Nowadays, we often reef while on a run, rather than rounding up, because we can sheet the main hard amidships and then steer dead downwind without qualms, encouraging the sail to go slack and flap from side to side while the reefs are taken in.

If the crew of the She 31 had been able to do that they might have overtaken our Alacrity.

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