What hull design features are important for an ocean cruising yacht?

You can sail across an ocean in almost any boat with a keel and a cabin, but some sailboats are much safer and far more comfortable than others. There are a lot of important differences between the hull of a general-purpose cruising yacht and one that’s designed and built specifically for long-distance offshore sailing. Here’s what you need to know.

Size does matter to a certain extent but, as always, perhaps not as much as most people think. Large, medium and small yachts each have their pros and cons for serious offshore sailing. For what it’s worth, most long-term ocean cruising sailors tend to find that their own sweet spot is somewhere between 11m (36ft) and 14m (46ft) long, while 9-12m (32-40ft) seems to suit many solo sailors, but the right size of boat is intensely personal and the increasing reliability and efficiency of powered sail-handling systems has made larger yachts (up to around 60ft) much more practical for a couple or family crew to handle.

You want a hull with a comfortable motion in rough seas, and one that sails well to windward in waves”

Regardless of size, it’s important to have a hull with high load-carrying ability so you can load it up with stores, equipment, fuel and water without affecting its seakeeping or sailing performance. You also want a hull with a smooth, comfortable motion in rough seas, and one that sails well to windward in waves, not just on flat water. For that and for various other reasons, weight distribution is crucial.

You don’t want the sort of hull that tries to round up into the wind as it heels over – and it’s wise to choose one with good directional stability, for the sake of the autopilot and batteries as well as the crew. You’ll want plenty of lateral stability, too: it means less frequent reefing and a more comfortable ride downwind, plus better sailing ability in heavy weather and a lower risk of capsize.

Rustler 57
A hull with low windage is good to have in a strong breeze, but you don’t want too much spray in the cockpit or water over the deck

A hull with low windage (air resistance) is good to have in a strong breeze, whether you’re anchored or under way, but you don’t want too much spray in the cockpit or water over the deck. Low windage also translates into a yacht that is easier to board from a dinghy or alight to a pontoon.

All of these good offshore sailing qualities are designed and built into each of our ocean cruising models: the Rustler 36, 37, 42, 44 and 57. But whether you end up buying one of our boats or somebody else’s, it’s well worth understanding the key hull features that help a boat to perform well offshore.

Soft entry and spoon bow

The gently curved, overhanging spoon bow and graceful positive sheer that you’ll find on all our yachts isn’t just there for cosmetic reasons. It serves a practical purpose, providing extra buoyancy that gradually comes into play as the boat sail through waves, reducing the amount of water coming over the foredeck. Combined with a well-immersed forefoot and soft, deep vee-shaped forward sections, it cushions and reduces the yacht’s fore-and-aft pitching motion under sail, giving a much more comfortable ride. The deep vee shape of the bow also eliminates slamming, which isn’t just unpleasant for the crew, it slows the yacht significantly too. And there’s one more advantage of an overhanging bow: it doesn’t foul the anchor or its chain, so you don’t need a long, protruding bow roller.

Rustler 42
The deep vee shape of the bow also eliminates slamming, which isn’t just unpleasant for the crew, it slows the yacht significantly too

Powerful midships and aft sections

Moving aft, an ocean cruiser should have powerful midships and aft sections because they boost her form stability, and there’s more to form stability than just being broad in the beam. In essence, the shape of the hull should be designed to provide a lot of extra buoyancy when heeled over, working with the yacht’s ballast to keep her on an even keel. Here we break with tradition by building hulls with plenty of form stability. A drawback of classic yachts with narrow beam and an attractive wineglass shape is a lack of form stability, which can give them a horrid rolling motion when running downwind.

A balanced and efficient hull shape

Another important design feature (which has recently come back into fashion for racing yachts, incidentally) is a balanced hull shape. This basically means that the underwater part of the hull retains its hydrodynamically efficient, symmetrical shape as the yacht heels over, rather than becoming asymmetric.

Many general-purpose sailboats have unbalanced hull shapes to increase the size of their aft cabins, so they need to be sailed upright. That means more effort for the crew: playing the mainsheet, reefing and unreefing the sails, and actively steering which leads to excessive drag from a sideways rudder. Twin rudders can help with this of course, but as we’ll explain in our article on rudders, they’re not an ideal solution.

Rustler 57 stern
Rounded aft quarters are more comfortable and they give a gentler motion than wide-transomed yachts with hard chines

Rounded aft quarters

Related to this, there’s a good reason why you rarely see hard-chined aft quarters on a purpose-built ocean cruiser. They’re a fashionable feature on coastal cruising yachts – again, to enlarge the aft cabins – and they boost a yacht’s form stability, allowing more sail to be carried on a beam or broad reach.

For a racing yacht that’s optimised for power reaching in strong winds they make a lot of sense, but the downside is a harsher motion in choppy seas and a hull that’s designed to be sailed upwind at a steeper heel angle. And in light airs this type of hull tends to need more breeze to get going than one with rounded aft quarters.

Generous rocker

For good load-carrying ability and better weight distribution, an ocean cruiser needs a generous amount of rocker. This means that the bottom of the hull curves down from both bow and stern towards the keel, rather than being a flat surface.

The rocker creates a deep bilge inside the yacht, with plenty of space above and around the keel to store heavy items and install systems like the engine, generator, watermaker, water and fuel tanks, and so on. Located here, low down and central, they enhance the yacht’s ballast rather than working against it.

Careful weight distribution is a very effective way to improve her motion comfort – and her performance”

General-purpose cruisers don’t carry so much heavy equipment, they have smaller tanks and don’t need so much space for stowage, so they don’t need as much rocker as a purpose-built ocean cruiser. However, for any type of yacht, careful weight distribution is a very effective way to improve her motion comfort – and her performance.

Moderate freeboard

Freeboard is another consideration, and one that’s increasingly overlooked. You do need a certain amount of freeboard for ocean sailing but a yacht with relatively low topsides and cabin top will behave much better when lying to her anchor than one with high topsides or a tall superstructure, which will have a greater tendency to be blown around and to sail around her anchor in gusty winds. At sea, moderate freeboard helps a yacht to sail upwind more efficiently in a strong blow, and generally improves the boat’s weight distribution.

It’s also worth knowing that high freeboard makes mooring and coming alongside much more awkward. You should be able to reach down from the foredeck, or at least from the cockpit, to thread a line through the top of a mooring buoy – they don’t all have pick-up lines rigged. When coming into a marina berth, the deck height of many yachts requires someone to make a big leap down to the pontoon, or else you have to rely on successfully lassoing a cleat in the heat of the moment. It’s much less stressful if you can just step down onto the dock with one hand on the cap shroud to steady yourself.

So why do so many yachts have such high freeboard? With a broad-beamed, shallow-bodied, light displacement hull you need tall topsides to have standing headroom down below. With a deep-bodied hull, you don’t have that problem.

Rustler 57 transom
The shape of our transoms increases the cockpit volume, and make for a quiet night’s sleep

A well-judged stern and transom rake

The broad, raked transom that you’ll see on our ocean cruisers is a traditional feature with two practical purposes. It increases the volume of the cockpit and, like the overhanging bow, it provides just the right amount of extra buoyancy to lift the stern gently with each passing wave when you’re sailing in a following sea. The transom rake must be perfectly judged – too much buoyancy here is bad – and with more than 40 years of experience, we know we’ve got it right.

While we’re on the subject of sterns, there’s another good reason why you don’t want a hull with a flat run aft from the keel to the transom. The reduced wetted area does give a small performance advantage under sail, but when you’re in an anchorage or harbour with a little bit of swell or surge, the ‘stern slap’ noise will resonate through the hull – and it can often be loud enough to keep the occupants of the aft cabins awake all night.

More things to consider

Hull design is just one of the primary factors you need to consider when choosing an ocean cruising yacht. Hull materials and construction, keel design, rudder configuration, the type of drivetrain, deck and cockpit design, rig and sailplan are all equally important considerations and we’re covering them in separate articles.

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