the hull of a racing yacht

In recent years particularly as designers new to boats operating at high Froude numbers have begun to draw more powerful boats, there have been problems associated with bow burying, poor helm control/balance and sometimes erratic behaviour. One way or other these often come down to the design of the aft and forward sections of the boat and their associated rocker.

The effect of rocker is often mis-understood and the forces/effects it imposes are instead associated on boats that have them, with some magical affect caused by chines. This is categorically not the case. Also overlooked in some twin rudder designs we’ve seen is in that bow sections/rocker have clearly not been designed in concert with stern sections/rocker where inappropriately large volumes at the bow have been allied with cut-away stern sections which produce a good deal of rocker at moderate and large angles of heel . To have optimal performance (particularly in moderate and strong winds) while still maintaining sufficient levels of control and handle-ability bow and stern sections  and buttock lines must be designed as part of a whole, not in isolation.

The following paper was written as part of an explanation to a client’s project manager during the concept design stage for a new 77’ day racing design.

Note: The twin rudder hull shown is not the final hull design and is shown here only for illustration purposes. The two narrower waterline beam hull forms were developed for the purposes of performance comparison only.

In order to describe what rocker is and of hulls with different rocker we developed three hulls. In terms of their hydrostatics they are described by the table below. All three hulls had the same max beam, same displacement but by changing their section shape one is able to change the performance characteristics of the different hulls.

Hull #1 is of moderate beam, with a chine which creates a ‘powerful’ hull with the highest form stability. Once can see from the table below that this hull provides 30% more righting moment than Hull#3. This comes at a cost in terms of wetted surface area at 0 angle of heel however, where Hull#1 has @10% more wetted surface than Hull #3. This isn’t the full story by any means however, because by careful design the heeled wetted surface area (at 24 degrees of heel) of Hull l#1 is only 1% more than Hull #3.

Hull #2 is a moderately powerful hull, with a narrower hull form forward compared to Hull #1 and correspondingly without fuller sections aft that are characterised by the appearance of a chine. One can see from the table below that it sits between Hulls #1 and #3 in terms of righting moment, wetted surface area, waterline beam etc.

Hull #3 is of a hull type typical to some IRC designers, narrow fairly vertical forward topsides which are flared aft to put hiking crew as far outboard as possible while maintaining a narrow waterline beam and low wetted surface area.

It’s little understood by most yachtsmen that while wetted surface area and waterline beam are an important player in terms of drag in light airs as slow speeds, as the yachts speed approaches its maximum upwind boat speed (up to this point the yacht is operating in displacement mode) the importance of viscous drag (which is proportional to wetted surface area) becomes far less. While total drag increases with speed, the % of this drag attributed to wetted surface area reduces rapidly. Once the yacht exceeds its upwind boat speed it enters a realm where it is said to be in semi-displacement or semi-planing mode where dynamic forces, displacement and hull form are of far greater importance. Until recently IOR, IMS and IRC designers have been designing boats that haven’t had the kind of performance that required huge study in this spectrum, while open class and multihull design is all about yachts and foils that operate at high Froude numbers. Yacht’s that are just about always operating in semi and full planing mode.

So, while the above static numbers are interesting, Figure 1  illustrates what the shape of center line of the three yachts looks like viewed from the side.

Hull #1 is red Hull #2 is blue Hull #3 is green

These lines show the rocker (the curve of the yacht longitudinally) on the centreline at 0 angle of heel. To make it clearer what’s happening at the middle and stern of the yacht there are two inserts at a higher scale.

Mid-ships around the keel one can see that the trade off in the green hull to having a narrower waterline beam is to have a deeper canoe body. Such that, for the same overall maximum draft the narrower yacht would appear to have a shorter, less efficient keel fin.

However, what we’re more interested in is the affect at the stern (which is highlighted in the sketch of page 3) where the angle of Hull #1 to the waterline is less than Hull #2 and Hull #3.

The two sets of sections illustrated in Figure 2 make it clearer the difference in the hull shapes drawn for the three yachts which result in the figures shown in the table of hydrostatic values. While in profile view it’s not all clear that there is any great difference in the hulls, in section view this is made much more apparent. One can see for instance that if it were not for the introduction of a ‘virtual vertical cutting place’ through Hull #1 that the beam of the yacht would be far greater than the other two hulls. This shows clearly another mis-conception that the chine is somehow an important hull device with magical properties. This is hardly the case; the chine is in fact a result of a decision to terminate the beam of what would be an otherwise very wide hull prematurely. It is the general characteristics of the hull form that are the most important aspect not the fact that there is a chine, although by scrutinising the line of the chine one can discern and make assumptions about some of those hull characteristics.

Figure 3 illustrates the three different sets of hull lines as they approach the transom. In simple terms one can imagine that as water flows along parallel to the hull that it exits in the direction of the three arrows and that the total drag force is represented by F1, F2 and F3.  Note that these forces are not parallel with the waterline and so it follows that there must be a vertical component of force acting downward pulling the stern of the yacht down into the water. Since the angle of F3 is greater to the waterline than F1, the vertical force associated with F1 is greater than F3. In other words, for the same value of drag the stern of the narrower yacht is being forced down more than that of the wider yacht. This is only one area where static values (such as in the table) are over-shadowed by what happens once the yacht is in motion, particularly at speeds approaching and exceeding hull speed.

Figure 4 illustrates the effect of the couple created by F down at the stern and the corresponding F up at the bow. The two forces create what is known as a ‘couple’ about the center of mass/center of buoyancy of the yacht. The greater the value of F down the more sail force and longer it takes for the yacht to escape it’s own stern wave, rise over it’s bow wave and begin to operate in semi-planing mode where the yacht’s displacement is effectively reduced by the overall  lift created by the pressure differences over the underwater body of the yacht . Once in semi-planing/semi-displacement mode as the yacht increases speed the values of F down and F up increase. Again, in simple terms, if the yacht is not correctly designed for high speed/Froude number planing what happens is that the bow rises prematurely and waterline length decreases.

While the bow rising looks cool and is important at some point, particularly at very high speeds and in waves, it is not quick. It’s not rocket science to comprehend that a 77’ yacht displacing 28000kg is faster than a 70’ yacht displacing 28,000 kg.

OCD’s twin rudder moderate beam low rocker hulls are designed to allow a yacht of relatively light displacement to exit displacement mode earlier, begin semi and full planing earlier while maintaining maximum waterline length with minimum drag in the process. The trade off is higher drag at low speeds, but as you will recall this is mitigated to a great extent once the yacht begins to heel by careful hull design.

Figure 5 illustrates another factor with respect to heel, which of course a yacht spends a good deal of its time doing. Illustrated here are the three hulls at twenty four degrees of heel with the resultant static waterlines shown in their three respective colours. This is a slightly simplified situation since as we’ve described the stern is more greatly immersed underway than it is when theoretically static. However, this is a useful graphic since in the real world there are also waves passing down the hull. The centreline of the yacht in each case is in red and one can see clearly that for a yacht of this beam it would not be possible to have a single rudder at the stern. Hence the reason why single rudders are generally pushed further forward on the hull even though this reduced their effectiveness for a given area when turning or balancing the yacht.

What can be seen is how well immersed the smaller twin rudder is and also how it is also almost vertical in the water thereby creating side forces that are more or less parallel to the waterline. On the other hand there is a distinct angle to the single rudder blade and this is not so much important in terms of the loss of effectiveness of the rudder itself and increased drag with heel. More importantly and rarely understood is that as weather helm is applied to bare the yacht’s bow away, because of the angle of the single rudder to the waterline, a proportion of the rudder forces are driving the bow deeper in the water, increasing the forces causing the weather helm in the first place and so a self perpetual negative cycle is in train. This remains a little understood and considerable advantage both in terms of drag and safety/dynamic stability for twin rudder yachts.

Finally page 6, since yachts spend a good deal of their time heeled we don’t design them thinking of them sat at 0 degrees of heel and designers use so called buttock lines to look at what the hull looks like when heeled.

If one imagines a saw blade parallel to the centreline of the yacht and offset say 1.5m outboard. Then, pass the saw blade vertically down through the deck and hull of the yacht one will have cut the boat in two. When viewed from the side you would see a hole in the side of the yacht and the edge of the shape of this hole would be the buttock line at 1.5m.

This is what is illustrated by six coloured lines in Figure 6. In each case they show the 1.5m and 2.5m buttock lines for hulls #1, #2 and #3. The importance of these when were we to zoom in would be that one can see that the angles of the buttocks (effectively the heeled rocker lines) are equivalent to those that we see in Figure 3, in that the lines with the least rocker and so least dynamic drag are for Hull #1.

For more information on the OC 77 described in this article go to: OCD 77 High Performance Day Sailer

For more information regarding OC's design process go to: Naval Architecture

RETURN TO: Home page - Performance Yacht Design 101

Types of Racing Sailboats

Last Updated by

Jacob Collier

August 30, 2022

Sailboats come in many different shapes and sizes depending on a variety of factors. This means there are a variety of sailboat racing boat types on the market.

When you look specifically at racing sailboats, you will notice several different aspects that separate them from other sailboats. You might be wondering, what are the types of racing sailboats?

There are many types of racing sailboats that range from one-man dinghies all the way to 100-foot yachts. Some racing sailboats are classified as keel boats, multi-hull, and even a tower ship. These boats are built primarily for speed, so comfort is usually an afterthought depending on the brand.

For racing sailboats, each one is going to fit within a specific race category. So depending on the type of race will dictate the types of sailboats you will see.

According to sailboat data, racing boats have slightly different designs that stand out compared to bluewater sailboats. Looking at the Olympics is another example of what other racing sailboats are out there.

Table of contents

‍ Characteristics of Racing Sailboats

There are quite a few sailboats made today that are geared specifically towards racing. They have one purpose, which is to go as fast as possible.

Some racing sailboats are advanced far more than the average ones, which is completely up to the buyer. For example, America’s Cup race showcases “foiling boats” that run on foils under the hulls. These allow the sailboats to go faster than 50 MPH.

If you are searching for boats that have characteristics to fit within a specific race type, you will find that many boats can enter different races depending on the rules. The most popular sailboat races are:

• Offshore/Oceanic

There are key features that separate racing boats from other sailboats and allow them to enter specific races. These can be narrowed down to the hull design, the type of keel, how many masts it has, and what type of sails are used.

Size of Racing Sailboats

As mentioned, these boats range from smaller dinghies to 100-foot yachts. Depending on the type of race will determine the type of boat that is being used.

The size of certain boats might prevent them from entering races where only smaller ones are allowed. There are exceptions in some races, like a handicapped fleet race, that will adjust the rating to allow their final time to be adjusted. The reason some races are handicapped to a certain extent is so a captain and his crew can determine the outcome and not a boat that is at an advantage.

Overall Design

With racing sailboats, they are subject to racing against the wind about half of the time. The angles of the boats are still similar to cruisers but greatly differ in the size of the sails to allow the sheets to have a better shape.

As racing boats are typically trying to sheet the sails hard, they are trying to keep them within the centerline. This allows the sails to be flatter and change them as needed.

Over time, the sails will typically wear out faster than the ones being used on regular sailboats. Since they are aggressively being used to stretch in the wind, they are subject to more use than regular sailboats.

Similar Looking Sailboats

There are races that only accept sailboats called one-design. These sailboats are built to exact specifications and are nearly identical to one another.

The reason that these boats are designed is to help combat any potential advantages from one boat to the next. It does not really set itself apart from other boats, but it is a good start to get into racing.

Lack of Interior Accommodations

Racing sailboats typically lack anything special on the inside to help save weight and go faster. Since a lot of features are not available, this means it would be nearly impossible to liveaboard full time.

In most scenarios, a true racing sailboat strictly has one purpose: to go fast. This does not mean that all racing sailboats cannot have luxury or comfort, since boat racing has been in existence since boats were first invented for water.

You would need to find boats that have a great balance between using them on weekends and racing. There are plenty of options to consider for what you want to accomplish in racing and comfort.

Types of Sails Being Used

Another characteristic that separates racing boats from cruisers is the types of sails that are being used. Both are designed for performance but are measured a bit differently. Racing sails are meant for speed, as regular sails are meant for cruising.

Depending on the goal of sailing, such as racing, you could look into purchasing sails that are specific to racing. Would you rather take off an extra minute or two of your time with a long upwind leg during a race or have the same durable sail for another five years out?

This opens up the door to endless possibilities of sail-making materials to get the job done. Most cruisers use Dacron or laminates that use a high-stretch fiber. With racing boats, light laminate sails have proven to be more durable and last longer than previous racing sails.

Popular Types of Racing Sailboats

Since the goal is to be around 50 MPH and have the best handling, many options have to be considered for the type of boat to possess both. Since comfort is not a deciding factor, it is somewhat easier to narrow down a racing boat over a bluewater or cruiser boat.

The types of racing sailboats that cater to you will all depend on your budget and your main goal of use. Each series of boats has its main purpose, with some having a little bit of comfort with racing.

Yachts and Super-Sized Sailboats

Yachts that specialize in racing tend to have a solid mix between speed and comfort. With a fiberglass hull and roughly 50 feet or so in length, these boats are not easily handled by just one or two people like others or there.

With that being said, they are also the most expensive out of the group. Even with exceptionally older models, you are still easily looking at $100,000.

You can expect to see racing yacht sailboats to reach about 17 MPH. Depending on the size, they can go faster or slower.

High-Performance Cruisers

Some boats can do it all when it comes to all-around performance . If you are looking for a boat that you can race for fun but still want to take it out offshore and live on, then you need to look at high-performance cruisers that can do both.

These boats generally range between 25 to 40 feet and are similar to yachts. However, they do not have as much luxury in comparison but the price tag is not nearly as heavy.

Trailerable Sailboats

Trailerable sailboats fall into similar categories like the dinghy and small racing boats. These boats can range in length up to 27 feet but are limited in their height and weight.

These serve a purpose for just about anything to do with sailing, but the racing ones are strictly for racing. Their design is meant for speed, not the comfort of heavy-duty performance offshore.

Small Racing Sailboats

Smaller racing sailboats are built to be lighter and have practically nothing on board compared to cruisers or dinghies. Due to their smaller size, they often get mistaken for larger dinghies even though they typically range between 20 and 70 feet.

These smaller racing sailboats are related to cruising sailboats but are a bit smaller. They are cousins to sailing dinghy boats that are used for racing. They also have fin keels and utilize laminate sails.

Sailing Dinghies

Dinghies are a category of small boats that have a wide variety of uses. If you are new to boating, it is a great place to start learning due to its size and simplicity.

These typically only need one or two people at most and are no longer than 15 feet in length at max. Many of these boats are competitively raced and will also result in a wet ride no matter what you do. You will see these types of boats used in certain Olympic events.

Racing Cruising Sailboats

Cruisers have a wide range in size and length, as they range between 16 and 50 feet or more. They feature cabins for extended cruising and have standing headroom below deck if over 26 feet.

Popular brands on the market have introduced models that are fit for racing. These are great for fleet races or for boats that are associated with cruising. With that being said, it is a great compromise for boaters that enjoy racing but also want to cruise whenever they want.

The cutter features a single mast and mainsail, which is very similar to common sailboats like a sloop. A cutter sailboat has the mast further aft which allows the attachment of the jib and staysail.

In high winds, a smaller staysail can still be flown from the inner stay. This used to be a traditional racing design back in the day.

Cutters are great for both offshore and coastal cruising. In addition, they can still be utilized as a racing boat depending on the conditions.

Fractional Rig Sloop

Fractional rig sloop sailboats were popular in the 60s and 70s, but have steadily made a comeback in today's market. This sloop’s forestay will not cross at the highest point of the mast, meaning it attaches at a lower position.

On fairly windy days when you do not have to utilize full power, the fractional rig allows the crew to slightly bend the tops of the mast and flatten out sails. This greatly affects performance and is a great option for cruising, one-design races, and even handicap sailing.

Schooner Sailboats

These particular sailboats have multiple sails which are protected by two masts. These are known as the mainmast and foremast, with the foremast being close to the ship’s foredeck and a lot shorter than the mainmast.

Depending on the size of the schooner, additional masts can be added to allow more sails. These are great for offshore cruising and sailing but can be an effective racing boat.

Trimarans and Catamarans

Trimarans have three of their hulls side by side and “cats” only have two. In comparison, they both share very similar characteristics for racing and overall performance.

Trimarans are quicker and easier to build than catamarans, so, therefore, they are more common. They both have similar restrictions on space and can be used for day sailing.

In addition, they are not as stable as compared to other sailboats out there. There are still various ways to use them and they make for great racing boats since they can reach up to 10 MPH.

How Can These Boats Go Faster?

Each person will select a racing boat that fits their needs accordingly. If you enjoy racing, but continue to lose against boats that are the same, you might want to consider either your team, the technique behind it all, or the boat itself. Routine maintenance is going to be the best thing you can do when checking to see if your racing sailboat can go any faster.

The hull has to be in top shape and needs to be able to hold tension. The sails also need to be checked to make sure they are not overly stretched or worn out.

The masts also need to be of the right stiffness, as they are bending with tension from the rigging. This one might have to be professionally calibrated if you do not know how to do it, especially since every boat with its mast is going to measure differently based on size and shape.

Finally, the weight of the boat could be the determining factor in winning or losing. Make sure the weight is appropriate and the maximum amount for the boat is not exceeded.

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Born into a family of sailing enthusiasts, words like “ballast” and “jibing” were often a part of dinner conversations. These days Jacob sails a Hallberg-Rassy 44, having covered almost 6000 NM. While he’s made several voyages, his favorite one is the trip from California to Hawaii as it was his first fully independent voyage.

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Yachting World

• Digital Edition

America’s Cup boats: How they work and why they’re unique

• Toby Heppell
• February 5, 2021

The America's Cup boats to be used on the 2021 edition of the event are unlike anything we have seen before. They might be officially sailing craft but they behave in some remarkable ways.

The AC75s, the America’s Cup boats currently racing in the Prada Cup and that will be used for next month’s Cup match showdown, are arguably the most radical boat the America’s Cup has ever seen. 

The America’s Cup is, fundamentally, a design competition, and successive America’s Cups have featured the most extreme yachts yet – for their time – ever since the first race in 1851 .  

However, the foiling boats we have seen in the last three editions of America’s Cup racing (the AC72 and AC50 catamarans, and now the AC75 monohulls ) do represent a new direction for the highest level of sailing. 

There are plenty who argue that this technology is so far beyond the bounds of what most people consider sailing as to be an entirely different sport. Equally, there are those who believe this is simply a continuation of the development that the America’s Cup has always pushed to the fore, from Bermudan rigs, to composite materials, winged keels, and everything in between.

Good arguments can be made either way and foiling in the world’s oldest sporting trophy will always be a subjective and controversial topic. But one thing is certain: the current America’s Cup boats, the AC75s, are unlike anything seen before and are showcasing to the world just what is possible under sail power alone.   

American Magic hit an impressive 53.3 knots on their final weekend of racing. Photo: COR 36/Studio Borlenghi

1 Unimaginable speed

In their final race before being knocked out of the competition , American Magic’s Patriot registered a top speed of 53.3 knots during a bear away. 

Topping the 50-knot barrier used to be the preserve of extreme speed record craft and kiteboarders. A World Speed Sailing Record was set in 2009 of 51.36 knots by Alain Thebault in his early foiling trimaran, Hydroptere , and was bested in 2010 by kite boarder, Alexandre Caizergues who managed 54.10 knots.

O nly one craft has ever topped 60-knots, the asymmetric Vestas Sail Rocket , which was designed for straight line speed only and could no more get around an America’s Cup course than cross an ocean. Such records are set by sailing an average speed over the course of 500m, usually over a perfectly straight, flat course in optimum conditions.

America’s Cup class yachts, designed to sail windward/leeward courses around marks, are now hitting speeds that just over a decade ago were the preserve of specialist record attempts, while mid-race.

Perhaps even more impressive, in the right conditions when racing we have seen some boats managing 40 knots of boatspeed upwind in around 17 knots of wind. That is simply unheard of in performance terms and almost unimaginable just three or so years ago. 

Photo: COR 36/Studio Borlenghi

2 A storm onboard America’s Cup boats

Related to the speeds the boats are sailing through the water, particularly upwind, is the wind speeds the sailors will feel on deck. 

When sailing, the forward motion affects the wind we experience onboard, known as apparent wind. The oft’ trotted out explanation of how apparent wind works is to imagine driving your car at 50mph. Roll down the window and stick your hand out of it and there will be 50mph of wind hitting your hand from the direction your car is travelling.

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So when an AC75 is sailing upwind in 18 knots of breeze at a boatspeed of 40 knots, the crew on deck will be experiencing 40 knots of wind over the decks plus a percentage of the true wind speed – depending on their angle to the wind. 

The AC75 crews might be sailing in only 18 knots of breeze – what would feel like a decent summer breeze on any other boat – but they experience winds of around 50 knots.

To put that into context, that is a storm force 10 on the Beaufort scale!

Once up on the foil, everything to windward of the leeward foil generates righting moment. Photo: COR 36/Studio Borlenghi

3 Righting moment changes  

The single most radical development of the AC75 is to take a 75ft ‘keelboat’, but put no keel on it whatsoever. 

When the America’s Cup Defender and the Challenger of Record, Emirates Team New Zealand and Luna Rossa Prada Pirelli respectively, announced the 36th America’s Cup would be sailed in 75ft monohulls, conventional wisdom had it that the boats would look something like a TP52 or a Maxi72 – both impressively high performance keelboats.  

By doing away with the keel entirely, the design is now like nothing we have ever seen, particularly when it comes to how dynamic the power transition is between foiling and not foiling. 

The boats are designed to foil on the leeward foil, with the windward one raised to help increase righting moment: to help balance the boat. This means that when the AC75 is not foiling they are extremely tippy – much more so than most other boats of the same size.

Essentially, when the wind catches the sails, the boat wants to fall over as there is too much sail area for the amount of weight underneath the boat – something a lead keel usually counters on a yacht or keelboat. 

Once the boat is up and on the foils, however, that all changes, as everything to windward of the single foil in the water balances the sails. That means, the hull, the crew weight, the sail and rig weight, and the windward foil, all work to counter the sails. 

What all this means is that the boats go from being extremely tippy, to hugely powerful in just the few seconds it takes to get up on the foil. “The [AC75s] are really very tippy pre-foiling and then they go through the transition where they will need to build significant power. Then immediately [once they lift off] you have more stability than, well, take your pick, but certainly more righting moment than something like a Volvo 70 with a big canting keel.

“That change all happens in a very short space of time,” explained Burns Fallow of North Sails, who was one of the team who developed the soft wing concept back when the concept was revealed. 

With lift created to windward by the foils, it is possible that the boats can sail diagonally to windward. Photo: COR 36/Studio Borlenghi

4 America’s Cup boats may not be heading where they point

With the AC75 sailing on its foil, drag is dramatically reduced, vast amounts of power can be generated and so speeds rapidly increase. But the foils can serve another purpose too. 

In order to be able to lift each foil out of the water, the foil arms must be able to be raised and lowered. Hence the foil wings, which sit at the bottom of the foil arms (and are usually a T or Y shape), do not always sit perpendicular to the water surface and the AC75s often sail with them canted over to something nearer 45º to the surface.

The further out the leeward foil arm is canted – essentially more raised – the closer the AC75 flies to surface and, crucially, the more righting moment is generated as the hull and rest of the boat gets further from the lifting surface of the foil.  

There is another positive to this: as the lifting foil is angled, it produces lift to windward, which can force the boat more towards the wind than the angle it is sailing. 

Due to this negative leeway (as it is known when a foil creates lift to windward) the boat can be pointing at a compass heading of say 180º but in fact will be sailing at eg 177º as the foil pushes the boat sideways and to weather, essentially sailing to windward somewhat diagonally. 

5 The foils are heavy. Very heavy.

As the foils work to provide stability to the boat (when it is stationary both foils are dropped all the way down to stop it tipping over) and to provide massive amounts of righting moment, they are incredibly heavy.

A pair of foil wings and flaps (excluding the one-design foil arm which attaches them to the boat and lifts them up and down) weigh 1842kg. To put that into perspective, the entire boat itself with all equipment (but without the crew) weighs between 6508kg and 6538kg. So the foil wings at the base of the foil arms are nearly ⅓ of the total weight of the boat. 

It is partly due to this that you will see some teams with bulbs on their foils. If you decide to go for a skinny foil wing (which would be low drag and so faster) then there will not be enough volume to cram sufficient material in to make the foil weigh enough. So some teams have decided to add a bulb in order to make it weigh enough but to also keep a less draggy, slimmer foil shape. 

6 Sails can invert at the head

As with everything on the AC75, the mainsail is a relatively new concept. It consists of two mainsails which are attached to both corners of a D-shaped mast tube. This has the effect of creating a profile similar to a wing. 

It is well established that solid wing sails are more efficient at generating power than a soft sail and for this reason solid wings were used in both the America’s Cup in 2013 and 2017. But there are drawbacks with a wing: they cannot be lowered if something goes wrong and require a significant amount of manpower and a crane to put it on or take it off a boat. 

One reason a wing makes for such a powerful sail is that the shape can be manipulated from top to bottom fairly easily with the right controls. With the AC75 the designers wanted a sail that could have some of this manipulation, produce similar power but could also be dropped while out on the water. The twin skin, ‘soft wing’ is what they came up with for this class of America’s Cup boat.

In addition to the usual sail controls, within the rules, the teams are allowed to develop systems for controlling the top 2m of the mainsail and the bottom 1.5m. 

What this means is that the teams are able to manipulate their mainsail in a number of different ways to develop power and control where that power is produced in the sail. But it also means that they have the ability to invert the head of the sail. 

Doing this effectively means ‘tacking’ the top of the sail while the rest of the sail is in its usual shape. The advantage here is that instead of trying to tip the boat to leeward, the very top of the sail will be trying to push the boat upright and so creating even more righting moment. The disadvantage is that it would come at the cost of increased aerodynamic drag. 

We know that a number of America’s Cup teams are able to do this, though whether it is effective is another question and it is very hard to spot this technique being used while the boats are racing at lightning speeds.

Photo: Emirates Team New Zealand

7 An America’s Cup boat generates lots of data

A new America’s Cup boat is a vastly complex bit of kit. Each team has incredibly powerful Computational Fluid Dynamics (CFD) software packages and simulators in order to try to understand the various gains and losses. 

To make these simulators and computer projections as accurate as possible each team has been getting as much data as they can over their three year development cycle.

In the case of this America’s Cup it does seem the development process is genuinely getting closer to Formula 1 (albeit with smaller budgets than a modern F1 team has behind them).

INEOS Team UK have been able to work alongside the all powerful Mercedes F1 team (both of who are backed by INEOS) and have been open about how much this has helped their development process. They even have some Mercedes staff out with the team in Auckland assessing their data.  

“It’s really similar to F1,” explains Mercedes Applied Science Principal Engineer Thomas Batch who has 11 F1 titles to his name and is with INEOS in Auckland. “Certainly in this campaign the technology is close to what we have in F1. 

“In terms of raw sensors on the boat you are probably talking in the 100s but then we take that and we make that into mass channels and additional analysis with computational versions of those channels that we then analyse and get into in more detail. So you are looking at 1000s of plots that we can delve into [per race or training session].

“That level of data analysis and then feedback with the sailors is very similar to working with an [F1] driver.” 

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Practical Boat Owner

• Digital edition

Boat hull design: how it impacts performance

• Peter Poland
• August 7, 2023

Peter Poland explains how boat hull design has evolved over the years and how it affects boat handling and accommodation

Near-vertical stem and stern on the new Dufour 32 increase hull speed and space. Credit: Jean-Marie Liot Credit: Jean-Marie Liot

The search for the ideal family cruiser can be a complicated business at the best of times, especially if you’re looking for a new yacht less than 30ft long.

Gone are the days when Jaguar 27 s, Maxi 84 s and Mirage 28s were widely used by charter companies and private buyers alike.

These days, sailors hunting for smaller cruisers have little choice but to browse classified ads and brokerage lists.

Many conflicting factors are needed to achieve that most elusive of goals – the best compromise between seagoing performance in a full range of weather conditions and maximum living space when in port.

Major builders like Beneteau now make extensive use of infused or injection mouldings. Credit: Nicolas Claris

I say ‘in port’ because maximum accommodation space when at sea is less relevant.

If you are not in the cockpit and sailing, you could be down below cooking (as securely as possible), eating (spilling as little as possible), in the heads (as briefly as possible), navigating (as accurately as possible) or sleeping (as comfortably as possible).

The size of the areas used for these tasks is often seen as insignificant compared to how effectively each task can be performed.

Then there’s the small matter of weight.

New boats with heavier displacements for their size are rarely seen at boat shows these days for one simple reason: they cost more to build.

But that doesn’t mean they are ‘out of date’. Far from it, because the cruising sailor – whether she or he is looking for massive or moderate amounts of accommodation below – will find a heavier displacement boat with a lower centre of gravity more forgiving and less twitchy to sail than a lighter boat with a voluminous interior.

Boat hull design: waterline length grows

One notable change to boat hull design has been gaining ground recently and becoming widespread.

Like many design evolutions, it traces its origins back to the racing world.

There is a saying that ‘racing improves the breed’ and this can be true even in the world of cruising yacht designs.

This trend relates to overall and waterline length. In the past, waterline length was invariably far shorter than overall length.

The Beneteau Oceanis 51.1 follows a new trend by offering three versions of the same model, with emphasis on either performance or comfort. Credit: Beneteau

Elegant bow and stern overhangs were the visible evidence.

The reason was that a yacht’s Royal Ocean Racing Club (RORC) and later International Offshore Rule (IOR) handicaps were partly based on its static waterline length .

As later racing handicap rules put less emphasis on static waterline length, racing boat designs developed increasingly ‘upright’ stems and transoms.

As a result, the waterline length often becomes similar to overall length and thus makes an important contribution to hull speed.

Cruising boats have been quick to follow this fashion, and some modern cruisers (such as the latest Dufour 32 and 34) now have race boat style near-vertical stems and sterns.

Modern hull forms, like this Jeanneau SO440, use chines to create volume forward while keeping a narrow entrance at the waterline. Credit: Graham Snook

But the cruising yacht derives an extra advantage from this development in addition to increasing its speed potential.

By increasing waterline length in relation to overall length, the designer wins extra space below.

This can be put to good use by making the forepeak a bit longer and taking the bunks further forward.

So as well as going faster for its overall length, the new generation ‘long waterline’ cruisers can pack in more accommodation.

I believe that many future cruising designs will move closer to vertical stems.

Accommodation at a premium

It’ll be fascinating to see how yacht design evolves over the next 10 years.

The big builders will be looking for opportunities to upgrade their products – if only to increase their ability to compete with ever-expanding fleets of sound second-hand yachts.

To see how far this trend has progressed over past decades, you only need to compare the shape of, say, a Rival 32 or Contessa 32 with their modern equivalents.

The Rival achieves its headroom because the hull is deep, while the freeboard remains moderate and the coachroof is low and sleek.

The modern equivalent, on the other hand, has a shallower hull with higher freeboard and coachroof to achieve similar headroom.

As a result, the Rival has more boat under the water, while its modern equivalent has more sticking up above it, putting the centre of gravity higher and increasing windage .

The Jeanneau Sun Odyssey 440 shows off the amazing amount of space available in modern yachts. Credit: Jeanneau

As Scotty said to Kirk on Starship Enterprise: “You cann’ae defy the laws of physics, Jim.”

Then compare the maximum beam. A Contessa 32 (9ft 6in/2.9m) has enough to accommodate settee berths and a table in the saloon, with sufficient cabin sole width to move around the boat.

The heads compartment is located between the saloon and forecabin and has sufficient space for ‘the necessaries’.

The modern cruiser, on the other hand, has a greater beam to length ratio, so the cabin sole is wider.

The enlarged heads area needs more space so it moves aft to where the beam is wider.

A deep hull gives plenty of headroom on the older Rival 32, but still has a low coachroof and moderate freeboard. Credit: Graham Snook/YM

It’s more spacious… but does it work any better when the boat is bouncing around in a lively seaway, rather than sitting motionless in harbour?

And what about those large aft cabins? They are luxurious in harbour, but perhaps not so user friendly when a tired crewmember is grabbing a bit of shut eye on a cross-Channel beat.

There’s a lot of space to roll around in – compared to being held snug and secure in a narrower quarter berth.

Performance in wind

But the real difference between the moderate beam and lower freeboard of an older style design and the wide beam, wide stern and high freeboard of some contemporary designs becomes most apparent when sailing – especially when the wind is strong.

To keep the crew happy and the boat ‘on track’, you need to be more alert when assessing sail area, trimming sheets and steering the boat.

Why should this be?

We’ve all occasionally seen a boat with a wide beam and stern suddenly round up in a stiff breeze.

While the skipper struggles to apply more helm, the rudder aerates then loses its grip.

Gypsy Moth III was well balanced due to a deeper, heavier displacement hull. Credit: Getty

A wide, shallow-hulled boat with a broad stern is more prone to such gyrations because the immersed shape of the hull changes dramatically as the boat heels.

The older-style boat with balanced ends and a deeper, heavier displacement hull retains a similarly balanced immersed shape even at considerable angles of heel.

The ultimate example of this was the ‘metacentric’ hull championed by the great Robert Clark – whose famous designs included Sir Francis Chichester’s Gipsy Moth III (winner of the first solo Transatlantic Race) and Sir Chay Blyth’s British Steel (the first yacht to girdle the globe sailed single-handed and in the wrong direction).

To see how ‘balanced’ hull lines look when the boat is heeled, select a suitable yacht laid up ashore, stand facing her bow (and then stern) and lean your head to one side.

You’ll soon see the differences if you repeat this exercise on a modern broad sterned boat.

And what happens to the wide-bodied, broad-sterned hull when it heels? Why does this encourage loss of directional stability?

It’s down to immersed shape. As soon as the hull heels, the enormous buoyancy in the wide aft sections (which increases when heeled) lifts the stern as the immersed shape changes.

So it begins to lift the rudder out of the water (unless the yacht has twin rudders).

Adapting sailing techniques

Given that the majority of sailing families and charter companies still prefer the space and comfort offered by high freeboard, wide beam and broad sterns, how does one avoid the broaching scenario?

It boils down to appreciating the attributes of such hull shapes and sailing them accordingly.

The most obvious way to stop the change in the immersed hull shape as the boat heels too far is to stop this happening in the first place by sailing the boat flatter.

Just because the skipper sailing a nearby ‘balanced ends’ design is lounging on the leeward side of the cockpit with the tiller loosely held between finger and thumb as the boat’s deck dips elegantly towards the sea in the gusts with the wake stretched out behind, don’t think you should (or could) be doing the same.

Just tuck in a reef or roll in a bit of headsail – or both.

You can achieve better directional stability on a wide boat by flattening the sails, especially to windward. Credit: Lester McCarthy

Most modern hulls sail straight at around 15° of heel. But let the boat lean much further and you risk getting into broach territory.

Besides which, if you sail her flatter, she will sail quicker. As an added bonus, you won’t alarm the children or spill the gin!

As wide boats encounter strong winds (especially when sailing upwind), correct mast rake and flattened sails also help directional stability.

If you have too much aft mast rake , this will increase weather helm , which aggravates the situation.

The same applies to full sails.

A Cunningham or flattener takes ‘the belly’ out of a mainsail and moves its draught forward.

Also check that the jib sheet cars are not too far forward, reducing ‘twist’ at the head of the foresail, thereby increasing its power.

Continues below…

Keel types and how they affect performance

Peter Poland looks at the history of keel design and how the different types affect performance

Sail boat rigs: the pros and cons of each popular design

Peter Poland looks at the history of popular rig designs and how the different types affect boat performance

Improve performance by understanding boat design

Øyvind Bordal explains how form stability, LOA, LWL, speed tables and polar diagrams can help you choose the right boat…

Popular yacht designs of the 1990s

The 1990s began with a recession that saw a massive dip in the number of new boats sold, in a…

Above all, don’t over-sheet the mainsail. If a powerful gust still succeeds in catching the skipper off guard, the first port of call is the mainsheet.

If you have a traveller, drop this down to the end of its track. If not, you may need to ‘dump’ the mainsheet – having first warned the crew and made sure there are no heads in the way.

Boats with short mainsheet tracks located on the roof in front of the main hatch are also tricky because the fall of the sheet is beyond the helm’s reach.

In this case, the crew needs to know what to do and when. Anticipation is essential for nipping a broach in the bud.

Motor-sailing is another area where owners of wide-sterned yachts need to be careful.

If you are confronted by a long beat in strong winds, your yacht will point higher and sail faster (with sail reduced) with the engine running at low revs. But if you let a broad sterned boat heel too much, the prop gets too close to the surface as the stern is levered out of the water.

As a result, the engine can ‘race’ – which is not good for it.

Excessive heel when motor-sailing is also not a good idea because the engine’s oil can cease to circulate properly.

The best of both worlds

What type of hull shape does give the best compromise between ‘balanced performance’ and maximum accommodation – and between light and heavier displacement?

As in many walks of life, the old adage of ‘moderation in all things’ gives the best clue.

Very low freeboard can mean a wetter ride, while high freeboard can add to windage and lift the centre of gravity.

An excessively narrow stern can induce rolling when sailing down-wind in a blow, while a fat stern can encourage broaching up-wind in heavy gusts.

Narrow overall beam reduces initial stability and space below, while excessive beam means you need to sail the boat flatter.

As ever, a sensible compromise can be the answer.

The Sun Odyssey 319 is one of the smallest recent Jeanneaus available. Twin rudders, bulbed fin keel, optional swing keel, fractional rig and spacious accommodation add to its appeal. Credit: Jeanneau

Which brings us on to more mundane developments in hull detail and deck design.

I expect the trend towards setting fixed windows into cruising yachts’ topsides to develop further.

As designers find neat ways to engineer this and builders source stronger adhesives and ‘glazing’, hull windows will get bigger and more numerous.

It’s nice to be able to sit in the saloon and still see out.

There are also a few changes to yacht design being brought about by global warming phenomena and our desire to save energy.

Some builders now incorporate substantial structures to support a bimini over the cockpit.

As these develop more, they can also carry solar panels , a wind generator , a radar dome and the transmitters and aerials for electronic gizmos.

These structures can fulfil many useful functions. If summers become hotter and sunnier, a bimini could become as useful in the Channel as it is in the Med.

The cockpit itself will also get more use as a social and dining area, so the current trend towards well designed fixed cockpit tables could develop further.

An Oceanis 48 model we chartered even had a light socket beside the cockpit table so an outside lamp could be plugged in for al fresco dining at anchor after dark.

Sail wardrobe

This leads us to deck layouts and sail handling systems.

To start at the bow, most sailors now take roller headsail systems for granted.

But more builders are following the example of firms such as Hanse by offering self-tacking jibs as standard.

True, there is an extra cost element; especially if the owner also buys a full-sized Code 0 headsail for reaching or beating in light winds.

But the ability to sail closer to the wind – thanks to the close sheeting angle – and to tack without touching a sheet makes a pleasant change.

A fractional rig with a larger mainsail and smaller headsail also has many advantages.

And when someone comes up with an economical ‘in boom’ mainsail reefing system operable from the cockpit, you have a low-effort-high-efficiency sail plan.

The Hallberg-Rassy 40CC shows the change in yacht design with the broad hull and near vertical topsides. Credit: Richard Langdon

‘In mast’ mainsail reefing puts extra weight where you don’t want it (up in the air), necessitates an inefficiently shaped mainsail (without horizontal battens) and is a nightmare if it decides to jam when the sail has been partially rolled.

And what about the rig itself?

Most production cruisers have aluminium masts held aloft by stainless steel standing rigging.

The racing fraternity, however, is beginning to choose carbon fibre masts.

As a result, huge amounts of weight are saved aloft.

The more weight you put up in the air, the more ballast you need to plant under the boat to counteract it.

Carbon spars currently cost considerably more than extruded aluminium tubes. But things can change.

I see a day when the cruising yacht can increase its stability and reduce its tendency to pitch by cutting down on weight aloft.

Such rigs may start as pricey extras – but some owners might happily pay the premium. And what might disappear?

Perhaps it’s time for yachtsmen to go ‘cold turkey’ on teak and help save a few rain forests?

It’s already happening in yacht interiors where builders offer veneers in light oak, cherry and other lighter woods as an alternative to teak .

Some of these finishes look very elegant. Teak decks also consume many venerable trees.

Do we really need to slap hundreds of kilos of teak and Sikaflex onto decks when there are effective lookalike equivalents such as Flexiteek , Tek-Dek, Esthec and Permateek?

Boat hull design and its impact on speed

When it comes to hull shape, a boat of moderate displacement will be steadier and better mannered – even after squeezing in stern cabins with double beds!

After One Tonners stormed the sailing scene and opened the door for GRP fast cruiser spin-offs , other Ton Cup rating bands soon followed suit.

These high-profile international Ton Cup regattas gave designers and builders massive PR exposure.

Ton Cuppers of various sizes became hot development projects and those who headed the field were quick to cash in, offering de-tuned versions to the fast-growing cruiser-racer market.

Following the One Tonner, the next size down was the Three Quarter Tonner.

Typically around 33-34ft (10-10.4m) long, this Ton Cupper makes a very popular size of fast cruiser that is quick and powerful enough to cover distance at speed, yet compact enough to be handled by a small crew.

Little wonder that as Three Quarter Ton designs evolved between the 1970s and early 1990s, they became the inspiration for many top selling production fast cruisers.

Unlike the One Tonners before them, Three Quarter Tonners came on stream after the old RORC rule had given way to the new IOR and the later Channel Handicap System (CHS) regime introduced in 1983.

So long keels with attached rudders , deep-bilged ‘wine glass’ hull sections, relatively narrow beam and heavy displacement hulls no longer held sway.

The world of performance sailing had moved on to fin and skeg or spade rudder configurations, flatter bilged hulls, broader beam and pinched ends (later replaced by wider sterns).

The Three Quarter Ton field proved to be a fertile ground for a new generation of designers who challenged the established greats such as Olin Stephens, CA Nicholson, Alan Buchanan and Kim Holman.

These youngsters – including Dick Carter, Doug Peterson, Ron Holland and Bruce Farr – must have rubbed their hands with glee.

In 1975, for example, the winning Half Tonner, Three Quarter Tonner, One Tonner and Two Tonner were all designed by Doug Peterson.

Everything changed once rudders became blades under the transom and keels became separate ‘bolt on’ foils with lift-inducing National Advisory Committee for Aeronautics (NACA) sections.

It’s reckoned that the closest to the wind a competent long keel cruiser of 20th century vintage could sail was around 45°.

Yet later, fin keel cruiser-racers could get to around 40°.

Closer sheeting angles and better cut sails contributed to this improvement, but much of the sharpened performance was down to underwater foils that induced lift and reduced leeway.

Boat hull design: a new generation

One of the first ‘new wave’ designers to come up with a GRP production yacht of Three Quarter Ton size was Dick Carter.

He had already excelled in the late One Ton era with the Tina design and was approached by Olympic Yachts to come up with an ‘IOR-friendly’ 33-footer.

The Carter 33 (not to be confused with the more extreme Carter ¾ Ton) hit the scene in 1974 and was an instant success as Olympic Yachts set up dealerships far and wide.

The Carter 33 is a handsome yacht with a sleek, long coachroof. Her cockpit is on the small side but is extremely secure and ideal for long distance cruising.

With an LWL of 25ft 8in/7.8m, a reasonable beam of 11ft/3.35m and higher freeboard than a pre-IOR yacht of similar size, the Carter 33 offers excellent accommodation space for a yacht of that era.

Maximum beam on the UFO 34 is carried almost amidships, giving ample accommodation in the saloon. Credit: David Harding

It’s easy to see why it’s still sought after by discerning sailors looking for plenty of performance at a budget price.

But the new generation overseas designers did not have it all their own way.

One successful British designer who’d excelled in the RORC days and made a seamless transition to the new IOR/CHS eras was Kim Holman.

His UFO 34 Three Quarter Ton-inspired design became a popular performance cruiser and retains this reputation to this day.

With a waterlength of 28ft 1in/8.56m and a beam of 11ft/3.35m, the UFO 34 offers good-sized accommodation.

Her ballast of 5,510lb/2,500kg out of an all-up weight of 10,214lb/4,633kg – allied to a 5ft 6in/1.68m draught – makes her a stiff and powerful yacht.

Many UFOs were finished by different builders from mouldings supplied by Colvic Craft, so interior finish and detail varies.

The Contessa 32’s narrow stern means the boat slices upwind well. Credit: Graham Snook/YM

A Landamores-finished example is often the best.

Having made his name in the 1970s, it’s not surprising that another early Three Quarter Ton cruiser-racer to hit the sweet spot was the Contention 33, designed by Doug Peterson.

Following his victory in the 1975 Three Quarter Ton Cup with Solent Saracen, British builders Southern Ocean Shipyard approached Peterson for a GRP production development.

The Contention 33 (launched in 1976) is a fine-looking yacht and sold well.

At 32ft 8in/9.95m overall, she has a waterline length of 28ft 6in/8.68m and beam of 10ft 4in/3.14m which made the Contessa 32’s 9ft 6in/2.89m beam seem skinny.

The Contention 33’s weight of 9,300lb/4,218kg (ballast 4,233lb/1,920kg) is close to the Contessa 32’s 9,480lb/4,300kg (ballast 4492lb/2038kg).

Yet, in common with many racer-derived designs, the Contention has a generous amount of freeboard, wider beam and it’s easy to see how this generation of yacht offers good internal space.

Like the Contessa, she has a narrow stern which makes her great for slicing upwind, but likely to induce scary moments if pushed hard downwind under spinnaker.

The next generation of wider-sterned yachts (that could also accommodate stern cabins) had not quite arrived.

Creating a classic

Ron Holland was another rising star of the IOR era.

He’d already designed Ton Cup winners of various sizes when he was approached to design a Three Quarter Ton based GRP cruiser racer.

But what was more interesting about Holland’s commission was that it came from the longest standing and most revered name in British yacht building: Camper & Nicholsons.

Holland designed a great yacht – the Nicholson 33.

Her dimensions and ‘look’ were similar to Peterson’s Contention 33, while interior finish – especially on the cruising versions – was pure Nicholson; classy, elegant yet functional.

And the prototype of the tweaked racing version, called Golden Delicious , carried off the overall winner’s trophy in the 1975 Fastnet Race.

The Dehler 34 has a long, slim waterline plane, comparatively low topsides and a high coachroof and retains its beam aft, which allows for accommodation in the quarters. Credit: David Harding

If you fancy a 33-footer with a fine pedigree but at not too fancy a price, a Nicholson 33 is well worth a look.

The Nicholson 345 that followed in 1979 also has much to offer.

Camper & Nicholsons asked Holland for a ‘bigger sister’ and the 345 put even more emphasis on combining Nicholson quality and finish with genuine performance.

The 345 is 34ft 6in/10.51m long with a waterline of 29ft 6in/8.99m.

Her beam of 11ft/3.35m and displacement of 11,500lb/5,216kg ensures ample internal volume and a more stylised coachroof design gives plenty of light below.

As a bonus, well sailed examples still do well on today’s handicap systems.

Her Three Quarter Ton genes shine through; she’s a quick yet civilised yacht. Cees van Tongeren from the van de Stadt design office designed the Dehler db1 and db2 racer-cruisers which won trophies galore, but these high-tech and stripped out flyers didn’t appeal to cruising families.

The Nicholson 345 has plenty of accommodation down below due to the 11ft beam, and the windows provide lots of light. Credit: David Harding

However, the Dehler Optima 101 and Dehler 34 – which share the same db1 hull – fit the fast cruiser bill superbly.

They sold in huge quantities throughout Europe.

What’s interesting about the sleek Dehler 34 is that its ‘donor hull’ had enough beam aft to make room for a stern cabin; unlike many other Three Quarter Ton derived hulls.

Owners could enjoy genuine performance combined with the newly popular ‘aft cabin and heads’ layout.

And most agree that the Dehler 34 has elegant looks.

It’s the epitome of the handsome racer-derived fast cruiser. It has stability (3,748lb/1,700kg ballast and an all-up weight of 8,818lb/4,000kg) and boasts decent width side decks and a well-proportioned foredeck.

If ever a boat proves that racing improves the breed, the Dehler 34 does.

Evolving design

Three 34/35ft Three Quarter Ton-inspired Beneteau cruisers, designed by the same team for the same builder over a span of nine years, dominated the market; the Berret-Racoupeau-designed First 35 (1980), First 345 (1985) and First 35.5 (1989).

These three Firsts evolved from Oesophage Boogie, a top Three Quarter Tonner designed by Berret.

The LWL grew slightly in proportion to overall length, maximum beam actually reduced a smidge, sterns got fuller, bows became more upright and the ballast ratio came down slightly.

The 35 and 34.5 keels are a typical IOR shape, while the 35.5 grew winglets at the base of its shallower draught options and its deepest fin had the latest ‘mickey mouse ear’ profile.

But the real differences came in styling and interior layouts.

The 1989 Beneteau First 35s5 shows the move towards higher topsides, steeply sloping transom and wrap over windows. Credit: David Harding

The First 35 (1980) has a relatively narrow stern so although it squeezes in a couple of wide quarter berths either side, these hardly constitute genuine doubles.

The galley and navigation stations are aft in the saloon, which features settee berths and a pilot berth to port.

There’s a traditional, spacious heads/washroom compartment forward of the saloon and a relatively small forepeak for sail stowage and occasional berths.

It’s a practical seagoing layout.

The 1985 First 345 is slightly wider at the stern, allowing space for an aft double cabin and aft heads; or twin aft cabins with the heads moving to ahead of the main bulkhead.

As a result, the forecabin becomes pokier than the much more spacious alternative on the aft heads version.

I’d go for the single aft cabin version; especially if sailing with a smallish crew.

From an aesthetic point of view, the 345 is a great success.

It showed how competitive race boats could morph into desirable fast cruisers.

Precision robot cutters at work on a deck moulding in a Groupe Beneteau factory. The time savings must be enormous. Credit: Nicolas Claris

Proving its popularity, as was the case with the earlier 35, over 450 First 345s were built.

Then came the 1989 First 35s5, and it showed how fashions had changed.

Not only does the hull profile look very different, with higher topsides, more upright stem, steeply sloping transom and futuristic ‘wrap-over’ windows, the accommodation is given bold styling by Philippe Starck.

Dark mahogany and polished metal features make this yacht’s interior very different. People love it or loathe it.

Extra volume aft makes the stern cabin(s) more spacious. The sail boat rig also evolved.

At long last the small mainsail/large genoa format was replaced by a fractional rig with a bigger main and smaller headsail.

The easily handled fractional rig had finally made a comeback.

This followed other later generation Three Quarter Ton inspired cruiser-racers such as the Dehler 34.

Designers had realised that the fractional rig worked fine within the IOR, CHS and IRC formats and this development filtered through into the production cruiser-racers.

Enjoyed reading Boat hull design: how it impacts performance?

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The market for multi-hull superyachts has skyrocketed in recent years as owners begin to favour the high volumes and superlative stability on offer. Once the novelty of a small group of owners, a recent slew of multi-hull concepts and the success of shipyards such as Sunreef has confirmed that two and three-hulled superyachts are well and truly on the up. We remember some of the most ground-breaking multi-hull launches...

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In 2011,  Hemisphere was launched as world’s largest sailing catamaran with an LOA of 44.2 metres - and she remains so to this day. Built for American owners who had previously chartered a catamaran in the Caribbean, this British yacht was a bespoke project by Pendennis . Fully kitted out for diving, Hemisphere ’s port hull contains a dive centre capable of refilling both air and Nitrox tanks.

Yachts for charter

Launched in 2015,  Spirit is a 35 metre New Zealand Yachts powercat featuring  Ken Freivokh interiors and naval architecture by Bakewell-White Design . A perfect example of how catamarans can help to maximise the living space available, Spirit has the interior volume you might expect from a 45 metre monohull. Her unconventional looks will make her stand out from the crowd in her new home of Australia, but Spirit is just one of many striking multihull superyachts to have hit the water in recent years.

Pilar Rossi

Formula One racing legend Nelson Piquet’s yacht Pilar Rossi was built in Turkey as a modest 33 metre Alucraft motor yacht. But his uncle, a Brazilian naval architect, helped Piquet convert her into a 64 metre sailing trimaran by adding outriggers and two masts. The reborn trimaran can accommodate up to 18 guests.

Galaxy of Happiness

Unveiled to the world in May 2016, Galaxy of Happiness  is one of two 53 metre trimarans to be launched by Latvian yard Latitude Yachts . This multihull superyacht is built from a GRP and carbon fibre composite and is capable of a top speed of 30 knots. The interior, designed by Latitude Yachts and Jean-Jacques Coste , features an owner’s cabin and two guest cabins.

Launched in 2004, this Chinese catamaran from Pride Mega Yachts may look like a vision of the future, but the inspiration for Asean Lady is actually ancient. The twin hulled 88.15 metre yacht is based on the proa design that has been used for more than 2,000 years to build fishing boats in the Pacific region. Her stability was put to the test in December 2004 when she survived the Indian Ocean tsunami while moored off Phuket.

Flexibility is the key word that informed the design of the 33.7 metre  Quaranta . Launched at Turkish yard Logos Marine in 2013, this catamaran superyacht features the kind of interior volume more commonly associated with a 40 metre yacht. All six guest suites are located on the main deck and the absence of structural bulkheads means that they can easily be reconfigured. This innovative system helped Quaranta to win the catamaran award at the 2014 World Superyacht Awards .

Popular among commercial buyers, SWATH (Small Waterplane Area Twin Hull) designs are becoming increasingly sought-after by private clients due to their internal space and sea keeping abilities. The most prominent example of this is the Abeking & Rasmussen designed Nurja (formerly Silver Cloud ) , a 40.54 metre SWATH that was launched in 2008. The torpedo-shaped submerged hulls contain the engines and as a result the vibration levels on board are significantly reduced.

This 27.43 metre catamaran was first launched in 2004 as a fishing vessel, before being refitted in 2015 by Ocean Voyager and relaunched under the name Rogue . Sold in June 2018 she was renamed Basilisk . Ideal for long cruises, she boasts a maximum range of 7,000 nautical miles at 12 knots, while the eight-tonne deck crane means that all manner of superyacht water toys can be stored aboard.

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