Category Archives: Inside Aureus Yachts

Introducing the Wild Sensations of the Aureus XV Absolute

 

Dear Readers,

We talk a lot about sensational sailing on our blog, and about a special vision of sailing. We built the Aureus XV around the vision of a more hedonist and sensational approach of sailing.

On the Aureus XV, we shot a video in November 2013 and I think this video is helpful to get a better understanding of our vision, so here it is:

 

Do not hesitate if you have question about the Aureus XV, or learn more on www.aureus-yachts.com.

 

Have fun sailing,

Aurelien

Sail around the world with the World Odyssey race 2016-2017

 

What sailor never thought about sailing around the world ? Since Joshua Slocum, circumnavigation is probably the ultimate dream and adventure for offshore sailing enthusiasts. And it did not get better in 20th century with Sir Robin Knox-Johnston  or Bernard Moitessier, the main actors of the first solo sailing race around the world. Then came the BOC Challenge, the vendee globe, etc…

This year Jimmy Cornell, the famous founder of the ARC (Atlantic Rally for Cruisers), has announced the launching of a global race for amateur sailors.

Circumnavigation - Sailing around the world with the world Odyssey

The World Odyssey participants will sail down the Atlantic from France, then sail east to check out all three of the Mythical capes: Cape of Good Hope, cape Leeuwin and cape Horn ! How about that ?  Would you like to add those three capes to your sailing record?

Sailing around Cape of Good Hope
After a sailing trip of more than 8.000 nautical Miles down the Atlantic, check out the cape of Good hope and enter the Indian ocean

 

Sailing auround the world - Sailing Cape Leeuwin
Cape Leeuwin Lightouse, you’re now in the Pacific Ocean

 

Sailing around cape horn. Circumnavigation
and now Cape Horn !

 “I want to give ordinary sailors the opportunity to race on their own terms,” says Jimmy Cornell, the three times circumnavigator.

“In recent years I have spoken to many owners of production boats who are keen to race around the world in a competitive event but see themselves excluded by the dominance of all current offshore races by sponsored high-tech yachts sailed by professional crews. The World Odyssey will answer this demand by bringing back the Corinthian spirit of earlier round the world races.”

In order to keep costs at a reasonable level, only production mono-hulled sailboats between 40 and 60 ft LOA will be eligible, with no performance enhancing modifications being allowed to the standard design. There will be separate classes for double-handed and fully crewed boats. The World Odyssey will be run under the IRC rating rule and is scheduled to be held every two years.

The ten-month-long World Odyssey will start in summer 2016 from a port in Atlantic France (according to the March 2014 Edition of Yachting World, it could be Bordeaux) and follow the traditional sailing route around the three great capes of the Southern Ocean: Good Hope, Leeuwin and Horn.

According Yachting World, who interviewed Jimmy Cornell recently, the race organisation could cope with up to 40 sailing yachts. The entry fees should be around €20.000 and include berthing fees and administration costs. During the race, a tracking device will make it easy for friends and families of the crews to follow each sailboat engaged.

The 28,300 mile route, that will offer competitors mostly downwind sailing conditions, has been divided into 11 legs, with stopovers in ports with good yachting facilities that are also attractive destinations.

Offshore sailing - Aureus XV
Get ready for some serious downwind sailing !

To allow families and friends to join the crews for the Christmas holiday season, a longer stop has been planned in the New Zealand capital Wellington.

Having successfully weathered the Southern Ocean and Cape Horn, an extended sojourn in Ushuaia will allow the crews to enjoy Patagonia, and its magnificent landscapes, during the austral summer.

During their circumnavigation participants in the World Odyssey will take part in a number of oceanographic and meteorological projects by deploying autonomous scientific instruments, gathering and transmitting data from remote ocean areas from where there is an acute absence of up-to-date information on climatic conditions.

In recognition for this valuable contribution to scientific research, the World Odyssey will be run under the auspices of the Intergovernmental Oceanographic Commission of UNESCO and in collaboration with the World Meteorological Organisation and National Oceanographic and Atmospheric Administration (NOAA).

The World Odyssey Race is organized by Jimmy Cornell’s company Cornell Sailing Events. Anyone interested in joining the World Odyssey Race should send an email to info@cornellsailing.com.

At Aureus Yachts, we really enjoy those types of initiatives, that promote offshore sailing, and we hope to see an Aureus Yachts performing in this edition.

Have fun sailing !

Aurelien

Provisional schedule:

Leg

Nautical miles

Date

1. Start port (tba) – Arrecife (Lanzarote)

1200

Sat 23.07.2016

2. Arrecife – Rio de Janeiro

3650

Thu 04.08.2016

3. Rio de Janeiro – Cape Town

3320

Wed 07.09.2016

4. Cape Town – Fremantle

4720

Sun 09.10.2016

5. Fremantle – Melbourne

1720

Sun 20.11.2016

6. Melbourne – Wellington

1660

Sat 10.12.2016

7. Wellington – Ushuaia

4600

Mon 02.01.2017

8. Ushuaia – Mar del Plata

1180

Sun 19.02.2017

9. Mar del Plata – Salvador da Bahia

1920

Thu 08.03.2017

10. Salvador da Bahia – Horta (Azores)

3200

Sun 26.03.2017

11. Horta – Start/Finish port (tba)

1180

Sun 23.04.2017

Building remarkable sailing yachts

 

To build a remarkable sailing yachts, there is to this day a consensus…you need hard work and a lot of carbon fiber:

 

 

This film was shot in 2012 in the Aureus Factory, while we were working on an Aureus XV Absolute. The film features images for our leather work studio, our “composite” room, in which we realise vacuum infusions and pre-preg work. Finally you see our CNC room that we use for modelling (creating composite moulds ). It was the first of two teasers we released before revealing the boat.

Now the Golden age of Sailing !

 

Sailing, as a leisure, has a great opportunity to enter into brand new era. Today’s better and faster offshore sailing yachts provide a considerably increased safety and the possibility to stay connected to the real world, to your business, your family and friends. Assuming you own a successful business, and with the proper equipment and organization, you don’t have to choose between working and sailing any more, at least for a few months each year.

Aureus XV Absolute - Your new office with a 360° view on the sea
Aureus XV Absolute – Your new office with a 360° view on the sea. ©Aureus Yachts

First, in the late 90s, fantastic new innovations appeared on the leisure boating market, such as vacuum infusion and carbon epoxy laminates. It means lighter, safer and faster sailing yachts. Then in the early 2000s, 3D sails appeared, terrific navigation software (such as Adrena®) were developed and satellite devices became affordable for yacht owners. Sailing boats got even faster, easier to handle and connected.

It means you can get much more sensations out of sailing and you don’t have to go dark any more. You can bring your work, friends and family with you on any trip. This is especially good for the new generation of business owner that are now using cloud computing based solutions to run and develop their business. Can you dream of a better secondary office than a full carbon 50 feet sailing yacht designed to thrill ? A 100 feet full carbon sailing yacht designed to thrill, maybe ? Well, if you can afford it, now is the time to sail and travel, not when you’ll retire.

Nowadays, solutions like the 37signals® “Basecamp®“* allow a business owner to run effectively his business, even if he is away from his office for quite a long time. You keep track of all the news tasks on any projects, share contents, organize meetings with “Campfire®”, or check hourly their sales and prospecting actions on “Highrise®”… and it’s really easy to use for teams. As I’m writing this article, more than 7000 new companies sign up every week for Basecamp®. To me, those are people that take an extra step towards being able to mix travelling or sailing with successfully developing their business and social life (in the meantime, most of us got engaged on Facebook or twitter, Pinterest or Google+).

From your sailing yacht and even while navigating Offshore, you can access all your business data, connect to your team everyday and follow and interact with all aspects of your company’s activity. You can also remain active, for business or personal purpose, on social networks.

So how about an office with a 360° view over the gulf of Kotor ? How inspiring would that be to be able to radically change your working environment for 3 months every year, sailing to the most amazing destinations ?

The gulf of Kotor could be your office for a few weeks
How about setting your office in the Gulf of Kotor for a week ? ©Elena Zarubina

Today, the average boat owner’s age is 49 years old, and closer to 60 years old when it comes to 50 to 65 feet offshore sailing yachts. The time when one could not run a business or keep a social life and enjoy sailing and travelling is over.

Now is the best time to go out sailing.

Aurélien

Could you leave you main office for 3 months ?

 

Carbon-Epoxy for Fast Sailing Bluewater Yachts

 

This article aims at helping you better understand the main differences between the 3 big types of resin and the 2 most frequently used fibers for boatbuilding. A simple and simplified explanation of the main differences between polyester, vinylester and epoxy resins, and between glass fiber, typically E-Glass, and carbon fiber will provide you with a good mapping of what can be achieved in terms of mechanic resistance and stiffness.

I’m trying here to point out key elements for sailing yachts buyers or amateur boat builders to take into account when deciding what composite to choose regarding their own program, budget and care for lightness, speed at sea and durability.

Fibers: Carbon versus E-Glass

Carbon fiber of high Quality - Excellent for vacuum infusion with epoxy resin
Carbon fiber of high Quality – ©Sicomin

Carbon fibers have the highest specific stiffness of any commercially available fibers, very high strength in both compression and tension and a high resistance to corrosion, creep and fatigue. Comparatively, E-Glass fibers have a really bad resistance to fatigue and will quickly loose some of their properties.

One can manufacture lighter pieces in carbon fiber than with a traditional E-glass, because the mechanical properties of carbon fibers are much greater than those of E-glass, meaning you need less fiber, in grams per square meter, to get to the same structural strength and rigidity. Basically, it allows, on any given structural composite piece to reduce the number of layers or their grammage to get a lighter structure. Of course, there are different types and grades of carbon fiber (aeronautical uses very high-tech and thin fibers) as there are different types and qualities for glass fiber, E-Glass being the most frequently used. Carbon fibers range from 1K to 24K, 1K being the best quality (used on fighter aircrafts) offering the best mechanical properties (we talk about Ultra High Modulus). Detailing the different qualities and fibers inside the carbon family would request a full book, but buyers must remember to ask for a detailed definition of what types of carbon fibers were used for the construction of the yacht, it gives an idea of how hard the builder is fighting weight.

Also, by its rigidity, carbon is a better fiber for sailing yachts as less sail power, or keelforce, is absorbed and lost by the softness of the structure (hull and deck). Fiberglass or E-Glass create a bigger waste of energy, and a heavier structure, resulting in less accelerating power.

There are a few downsize to the use of carbon. For instance, carbon has a quite low elasticity (elongation before brake) and will brittle more quickly in case of a shock. This is why I would not recommend the use of carbon on thin objects, such as boat’s wheels.

You should also know that carbon fiber is a much better electricity conductor than glass fiber, meaning the effort and investments to make a proper isolation from hull and deck equipment, especially aluminium parts, will be more important. If you are not planning to get a specialist to take care of the isolation of your system, than I would recommend to both small builders and users to stay away from full carbon hulls…unless you accept to change your winches or deck equipment on a frequent basis…galvanic corrosion between carbon and aluminium works really fast, and aluminium will quickly corrode to death.

Finally, due to the complex fabrication process, carbon fibers still cost 10 times more than the standard E-Glass fiber used by most of the boat builders, but their price tend to go down as production rises (The wind energy industry is a heavy consumer).

Resins: Polyester vs. Vinylester vs. Epoxy

Polyester, Vinylester and Epoxy are the main resins available for boat building.

First of all, I would say Polyester and vinylester are much easier to work and can tolerate mistakes, but epoxy can’t. Epoxy requires very precise mixing, and after mixing Epoxy resin and hardener, temperature rises very quickly, reducing the amount of workable time. Epoxy also makes post curing compulsory. Finally, epoxy resin is by far the most expensive, its price being related to its mechanical performances.

Polyester is the cheapest resin, and the one with the worst mechanical properties and sensibility, or resistance to water. Epoxy completely resists moisture where polyester does not, hence the osmosis. Because the resin is very fragile, it will brake quickly under a lot of stress. The “Polyester and E-Glass” mix is the cheapest but also the heavier, weakest and less durable composite. It’s not recommended for offshore cruising.

It is useless to use carbon mixed with polyester; the very low “elongation at break” of the resin will not allow the carbon mechanical properties to be solicited before the resin breaks, creating a weak point in which humidity will penetrate quickly and delamination will occur. Polyester is easy to work on, with all techniques from traditional wet-laid process to vacuum infusion or RTM (closed moulding technique), it will not heat up too fast and the acceptable range of temperature while using Polyester is wider.

Vinylester has better mechanical properties and percentage of elongation at break than polyester, which means it will not brake before the fibers reinforcement has been solicited. Vinylester also offers a better resistance to moisture. You can gain a little weight with a good architect and builder but more likely  you will have a stronger hull or deck using the same grammage. Vinylester is 1,5 to 2 times more expensive than basic polyester, but the safety of it can worth the investment on the long term.

Polyester and vinylester don’t necessary require post curing, although it’s always better to reach the full mechanical properties in the mould. If you don’t cure the pieces you manufacture in polyester or vinylester, you will probably get only 60 to 70% of the mechanical properties (strength, stiffness) but your boat will slowly post cure under on sunny days. That can create a few marking on hulls that you would avoid by curing the hull or deck in it’s mould after manufacturing it.

Epoxy resin is 2 to 3 times more expensive than vinylester and much more complicated to process for builders. It requires a steady temperature, a much greater precision and control of mixing (resin and hardener), and also can lead to a massive exothermic reaction. Left too long in the pot, a mix will quickly heat up. It’s an exothermic reaction (see a video) and the temperature can, within 5 minutes, rise from 40 to 50 C° to more than 150°C creating physical risks for the people around. A post curing is mandatory for pieces manufactured in epoxy, generally between 50 to 80°C for vacuum infusion to 120°C for pre-pregs. But, if you find the budget and gather good specialists, then you can manufacture extra strong and extra light boats.

The epoxy resin is very stiff, has a very high elongation at break that allows fibers to be fully solicited, hence delivering a very strong and stiff hull or deck with light grammage of fibers (don’t use anything else but epoxy if you pay the premium for carbon). Epoxy remains great in time and keeps its high mechanical properties much longer than polyester or even vinylester and the water cannot infiltrate it, making it safer for structure exposed to risks of in water collision. Finally, epoxy resin resists much better to high temperature.

All in all, a carbon/epoxy hull costs 5 or 6 times the price of a standard E-Glass/Polyester hulls, and 2 to 3 times the price of an E-Glass/vinylester hull but delivers without any doubt the best technical and durable hulls and decks, with the ability to gain a lot of weight at constant strength. If you go for carbon/epoxy, find a really good and experimented builder that can rely on modern tools, skilled workers and a tempered environment.

A good alternative is vinylester with E-glass fiber and local carbon reinforcements, if you don’t care too much about weight and can afford a prime for safety (osmosis prevention) and better durability the vinylester offers compared to polyester.

Once you have chosen your fibers and resin, it’s time to care about choosing the foam to put in the sandwich, to add stiffness while not adding too much weight.

Core Material: Forget Balsa and hesitate between PVC and SAL Polymer:

The flexural stiffness of any panel is proportional to the cube of its thickness. By increasing the thickness of the laminate with a low density material, architects and builders can increase the laminate’s stiffness for very little additional weight. The core material also helps to improve thermal isolation.

There are many types of foam but the most common are:

  • Honeycomb, such as Nomex® (very low weight, very high mechanical properties but also very high price – 3 times more than PVC or SAN – and difficult to use. But if you can afford it…it’s a perfect addition to a pre-preg hull).
  • Closed cell PVC like Areix®,
  • SAN Polymer like Corecell®,
  • Or the cheaper Balsa (I exclude this one as it has a relatively high density and absorbs large quantities of resin during infusion)

The choice of the foam is equally important as the choice of fiber and resin, to get a good laminate. Regarding the properties, I would define good foam as foam:

  • That will absorb a minimum of water if the hull is damaged
  • That will absorb, during the vacuum infusion process, a minimum of resin while letting it flow between fiber’s layers properly.
  • With a good shear strength, compression resistance and stiffness,
  • With a good resistance and stability at high temperature (a dark navy hull can go really hot under the Caribbean sun). Some core material are more sensitive to high temperature than others and will quickly, and permanently, loose some mechanical properties.
  • Ideally with a good elongation at break, to absorb shocks between the layers of fiber.

Good quality PVC foam (such as the widely used Aireix®) and SAN Polymer both meet the above requirements. SAN polymer, such as Corecell® are said to offer a higher Elongation at break, which is a good thing to limit damages in case of a shock.

Foam will usually be used in curved areas and need to be shaped to follow the curves.

The most frequently used and easier way to shape the foam is to use grid-scored sheets. It’s very easy but a lot of resin goes between each square of the grid, increasing the structure’s weight without making it any better.

Thermoforming is more expensive and requires both additional tooling and real skills, but the result is a much lighter structure.

What’s in it for Offshore sailors ?

Why being so demanding with the laminate ? Because the lighter your structure is, at constant mechanical resistance and stiffness, the faster your boat will be. Carbon opens new possibilities for sailing yachts, the opportunity to reduce the structural weight of hulls and deck while maintaining the mechanical properties (strength, stiffness) and improving their durability. Keep in mind that the heavier the composite structure is, the heavier the keel must be to maintain the displacement/keel ratio. It means basically that the weight you gain on you structure can be gained a second time on the keel without reducing the displacement/keel ratio.

The virtuous circle of weight

If a boat without its keel (structure + Equipment + rigging and deck fitting) weights, for instance 12 Tons (it’s a big boat), you need an 8 tons keel to reach a 40% displacement ratio.

Now, here is the virtuous circle. The 12 tons of the boat without it’s keel are roughly 6 tons of structure and 6 tons of equipment. Imagine you skip from E-Glass and Polyester to Carbon-Epoxy, use a good core foam (as opposed to the cheap old solutions usually used by the majority of builders), and a well-executed vacuum infusion process: In result, you’ll gain around 40%* in weight for the same mechanical strength. This is a reduction by 2,4 Tons in our example.

*Note that those kind of gains can only be achieved by skilled and well-equipped yard, mastering the infusion and reaching good FVF around 55% or more  (FVF stands for Fiber Volume Fraction, i.e the percentage of fibers in the total weight of a laminate pre-preg used in the aerospace industry can reach FVF 60 to 70%). Resin is a bonding agent for fibers, an excess of it won’t make the bonding better since tough job is done by fibers. Unfortunately, it is not rare to see FVF under 40% (in 1kg of laminate, more than 600 grams are resin…most probably mediocre resin such as ortho Polyester) in yards that do not master vacuum infusion properly or still laminate using the wet laid process, in which an operator manually apply the resin (a huge amount of it to be sure) on each layer of fiber.

Back to our example. Since you gained 2,4 Tons on the structure (20%), you can automatically reduce the weight of the keel by 2 Tons (20% of the initial keel) while maintaining your displacement/keel ratio at 40%. It means, in that example, that by reducing the weight of the composite structure (lighter carbon/epoxy hull, deck, bulkheads) by 2,4 Tons, you can actually make the whole boat 4,4 Tons lighter. You’ll also gain a few more kilos by adapting mast, rigging, anchor, etc. to the new weight of the boat. You have gained stiffness in the trade.

For offshore cruising yachts, the weight gained in the structure can also be transferred, to comfort and sailing equipment, without making a too heavy boat.

This virtuous circle, achievable thanks to carbon/epoxy and vacuum infusion, opens new possibilities for producing “state of the art” Light displacement offshore sailing yachts, faster, as safe and more durable than traditional heavy displacement sailing yachts.

More and more builders are now mixing E-Glass and carbon. The carbon is used in monolithic areas, where a lot of fiber layers are piled up. It’s a good option if you can’t afford a full carbon option. It allows quick weight gains, but does not really make the boat much stiffer. The mix carbon/Kevlar is also a good solution for the outside layer, to improve resistance to shocks (one of the rare field, with pricing, where carbon is actually not better than E-Glass).

I hope this can help you in your choices, please post a comment if you want to react, I hope my English, especially when it comes to technical words, didn’t make this post too hard to read.

Thanks for reading,

Aurelien

If you want to increase your knowledge about composite, I strongly recommend the book “Introduction to composite materials design” by Ever J. Barbero.

Tough it’s quite a big book (562 pages) for an  “introduction to”, it’s easy to read, well illustrated, properly organized and up to date (second edition from 2010, so they include modern pre-pregs, vacuum infusion, aeronautical grades of carbon fibers, etc. ).

The book covers all the subjects you might be interested in as someone looking to understand more about your boat when it comes to composite.

Light vs Heavy Displacement monohulls in 14 facts

 

Light displacement versus Heavy displacement sailing yachts is an old and passionate debate in the monohull offshore cruising world (Luckily this debate is long gone when it comes to multihulls).

First of all, let me tell you what I mean by “Light displacement“, or “Heavy displacement” hulls, yachts or designs, and what exactly will be compared in this post:

In both cases, I assume boats are properly built, and especially the composite parts. Achieving a proper building and reaching the optimal mechanical properties to weight ratio for the composite mix you use (fiber, resin and core material) requires a lot of skills, experience, tools, researches, tests and above all care for “the state of the art spirit”. Producing state of the art offshore yachts requires curiosity, as technologies are evolving quickly, and a passion for sailing of course. A properly built heavy displacement sailing yacht will always be a better offshore yacht than a light to medium displacement yacht built without caring for details and/or with bad processes…and vice versa.

When it comes to safety, I assume that both light displacement and heavy displacement yachts are well prepared, and carry a full safety inventory that matches the ISAF recommendations. The first safety is the sailor’s care for safety. Wearing an adequate inflatable life jacket when on the watch, a harness together with a reliable safety line, a multi purpose knife and a personal MOB device (alarm + AIS) makes any boat safer for offshore cruising. The preparation and a good knowledge of the boat are also very important.

Now, to give you a precise idea of what I call, in this light vs heavy displacement article, “light” and what I call “heavy”:

  • A typical heavy displacement 50 ft monohull offshore cruiser weights 18 to 21 tons,
  • A typical light displacement 50 ft monohull offshore cruiser, with the same level of equipment, weights 12 to 15 tons thanks to carbon/epoxy composite and T-shaped keels.
  • Today’s offshore racing sailing yachts are “ultra Light” displacement yachts. For instance, the extreme IMOCA’s 60 footers , that run the Vendee Globe, weight under 8 tons.

For more than 2 decades now, offshore sailors are debating “light vs heavy” and strangely the dominant argument of the heavy displacement enthusiasts is Safety.

I say “strangely” because the obvious and main reason to go for heavy displacement hulls today is because of the bigger inside space that can be offered and the big amount (and weight) of equipment that can be put on-board (generator, washing machine, air conditioning, water maker, etc.). As you will discover in this article, light displacement yachts, when properly built by skilled and carrying craftsmen and properly equipped, are now as safe as heavy displacement sailing yachts, can be almost as comfortable and carry an impressive equipment inventory…and they are much faster.

As the passionate builder of the Aureus XV, you might argue that I have a strong bias in favour of light displacement hull designs, and of course you would be right. I believe light displacement sailing yachts are the best fit for demanding offshore sailors, and my point here is to illustrate why, with facts.

Aureus XV Absolute out of the Aureus Factory
Aureus XV Absolute out of the Aureus Factory. This is a full carbon light displacement built with passion for osshore sailing. ©AP Yacht Conception/ Aurélien Poncin

This being said, it’s also important to notice that whatever your choice is, none of those philosophies can, alone, make a great offshore sailing yacht.  There are great boats, properly conceived and manufactured in both categories. It is crucial to look for a builder that is coherent, masters the composite technologies and cares about all the details involved in the construction, and there are a lot. The best way for this is to visit the yard and talk to the technicians. There is nothing worst than a light to medium displacement design that ends up weighting 15% or 25% more than the architect’s and builder’s optimal target, by lack of care or skills. Those boats are usually bad performers, uncomfortable yachts, and less safe (the center of gravity always suffers from such a non predicted weight gain). Keep in mind that such designs won’t tolerate laxity or approximation from the builder. Being 2 tons heavier on a heavy displacement design is also bad, but the effect on the behaviour and safety of the boat won’t be as bad as on a lighter boat.

A boat is a long chain of choices to be made that must remain coherent with the initial choice of displacement type. Each piece of equipment is chosen not only for it’s general quality, reliability and fair price, but also for their compactness and their weight (or the weight they allow you to save elsewhere on the boat).

A “state of the art” boat builder, after he has chosen the design, sets a realistic target of weight and develop a coherent and balanced yacht keeping those targets at the center of any construction steps. There are now luckily many materials and technologies that offer the same quality, resistance, reliability and durability for less weight.  Those materials and technologies allow builders to offer boats that are very well equipped and still light. Here are the most common and popular ones:

  • The infusion process, when done well, considerably reduce the amount of useless (excessive) resin in any composite part. In comparison, the way it was done 20 years ago, and is still done in some traditional shipyard is pre-historic. The pre-preg technology goes even further, pre-impregnating all the fibers with just the sufficient amount of resin.
  • Carbon fibers and epoxy resin allow builders to manufacture lighter, stiffer and more durable hulls, structure and deck. It’s even more true for masts and rigging. The result is a need for a less powerful, thus lighter engine, less demanding in Gasoil. It’s a virtuous circle.
  • New batteries (gel or Lithium-ion technologies) and renewable energies sources on-board allow builders to put less battery weight, while maintaining a high capacity for a good electronic installation and modern electrical comfort equipment. A Hydro-generator, under sail, and solar panels at mooring can produce a lot of energy. On a well-conceived boat, it allows to reach a high level of comfort without having to run the generator too often (reduce the amount of Gasoil to carry).

A careful selection of each piece of equipment, and accessories can lead to another saving of a few hundreds (yes hundreds!) kilos.

During the last decade, more and more light to medium displacements sailing yachts have participated to offshore rallies and they are now overtaking heavy displacement yachts in most of the events, such as the ARC. Of course, light displacement yachts trust the winnings and they have proven to be as safe as their heavier competitors in offshore conditions.

Here are 14 key facts to help you make up your mind, or remake it up…

Safety at sea

  • #1: Though they have usually a keel ratio around 40%, which is high, the center of gravity is usually higher on any heavy displacement yachts than on good light to medium displacement sailing yacht. This is due to the slightly deeper T-Shaped, , keels of the light to medium displacement. When it comes to safety, know that the lower the center of gravity of the boat is, the better. The center of gravity is very important when the boat is brought to extreme angles (above 90°) as the lower the center of gravity is, the more chances you’ll have not to capsize (we’re talking about really extreme conditions here, that can be avoided with a serious weather analysis). It means a well designed and properly built light displacement sailing yacht will perform better and be as safe in hard conditions. By the way, the center of gravity both vertical and longitudinal of your boat are precious data to collect.
Comparison heavy and light displacement yachts - center of graivity for the boat and the keel.
Comparison heavy and light displacement yachts – center of gravity for the boat (blue points) and the keel (green points). Those are two typical designs. The light displacement is a 13 T (Keel 4.8T – Draft 2,95m) Aureus XV Absolute, fully equipped for offshore navigation . The heavy displacement, on the left, is based on an average 50 ft heavy displacement central cockpit, weighting 19 T (Keel 8T – Draft 2,35m)

I must say that when comparing two stability curves, heavy displacement yachts will prove to have a better stability between 30° and 120°. It means their weight will reduce the amplitude of movements. It’s an advantage of heavy displacements, the disadvantage being a lower speed. But the curves also show that at threatening bank angles, the light displacement will offer a higher stability (capsizing at a higher angle and being easier to redress). Finally, the stability in the common angles (0° to 35°) is quite close for both design. To sum it up, both designs offer a very good stability in common angles, Heavy displacements will be more stable (less amplitude and slower movements) in the uncomfortable zone between 40° and 90°, but will lose their advantage in critical angles, above 120°.

Stability cruves. Light vs Heavy Displacements
Stability curves. Comparison between the curves. In blue the heavy displacement (the one from the drawings above), in Red the Aureus XV Absolute. Both designs offer a nice stability in the common angle. The heavy displacement stability is better in the “unusual angle zone”,between 30 and 110°, due to its superior weight. But the light displacement will offer a better stability in the “critical zone” where it’s about not capsizing, or recovering from capsizing, due to its lower center of gravity.
  • #2: In tough downwind conditions, when the boat is running with the waves, heavy displacement sailing yachts will be caught-up by waves more easily, due to their reduced speed potential. That will affect the steering reactivity, which is not good in hard conditions (note that the term “hard conditions” is relative. A professional offshore sailor will be just fine in 8 to 9 Beaufort, whereas some people will define “hard conditions” as a wind above 6 Beaufort, probably 5 when sailing upwind).
  • #3: Both heavy and light displacement yachts can equally benefit from fully centralized manoeuvres at the helm station (automatic reefing system, electric or hydraulic furlers, electrical winches, etc…) thus allowing crew members to stay attached in the cockpit when conditions are tough.
  • #4: Speed is also a safety issue. When faced with the imminent arrival of hard conditions, speed allows you to get away as fast as possible or reach a shelter.

Speed and sensations

This is the tipping point. A light displacement sailing yacht is a much better performer than a heavy displacement one, both in terms of speed and sensations.

  • #5: Light Displacement yachts are faster, the sail area/displacement ratio is more important giving the boat more power. Light displacement yachts offer less resistance to water (reduced “wet surface”) and their hull designs are less asymmetrical, meaning a light displacement design will create less rolling downwind. It’s an important point to consider, since downwind is what offshore sailors are looking for when planning trips.
  • #6: When it comes to performance and balance, Light displacement yachts’ T-shaped keel are much better than the traditional long shoal fin keels usually fitted under the heavy displacement hulls. The downsize is that they have a bigger draft (the center of gravity of the keel is as much important in its efficiency than its weight). If you want to solve that issue on a light displacement yacht, go for a lifting keel.
  • #7: Light displacement monohulls can sail to descent speed in light winds, where heavy displacement monohulls will have to use the engine propulsion. It means you need to embark and burn much more Gasoil and will be sailing less often. I think this is a very important point pleading for light displacements. Generally, many things on a heavy displacement must get heavier to get the same level of resistance or reliability as the light displacement yachts. A heavier anchor, a heavier mast, heavier rudders, heavier keel to balance the heavy structure and equipment, and so on. This is a vicious circle.

Here is a video of the light displacement yacht “Aureus XV Absolute” sailing in a breeze between 15 and 20 knots, with both upwind and downwind sailing to illustrate the “speed and sensations” advantage of the light displacement.

 

Note that this sailboat remains a “light displacement” around 13T, including 4,8T of T-Shaped keel, though it is equiped with:

  • Generator 9Kwh,
  • Hydrogenerator 500W/h
  • Bow thruster
  • Battery park for offshore cruising (Gel batteries)
  • Hydraulic mainsail trimming,
  • Hydraulic Boom Vang
  • Hydraulic Garage Door
  • Hydraulic retractable anchor arm,
  • 2 electric furlers (one for the genoa and and one for the Code, Gennaker or Asymmetric Spinnaker)
  • 4 ST.60 electric winches
  • Air Conditioning in all cabins and saloon
  • Dishwasher
  • Watermaker 110L/h
  • Fully equipped tool box
  • Stainless Steel Fridge and Stainless Steel Freezer

Nowadays a sailing yacht can be both light and equipped for the offshore cruising life .

Comfort on board

  • #8: Heavy displacement hulls generally offer more living space at comparable length. To get the same level of equipment and space on a modern light displacement hull, the solution is to go for compact and clever accessories. Their draft is also generally lower (60 cm in our example), meaning you can go closer to the beach.
  • #9: Heavy displacement sailing yachts are generally slower and less comfortable downwind. But in return, they can provide an improved comfort at helm station. The reduction of the boat’s windage is not a real concern on heavy displacement yachts, and a lot of them offer central cockpits with hard tops structures. The aesthetic is not really modern, but the result is a dryer helmsman in agitated condition. Basically, if getting a little wet in tough conditions is a central concern to you, a heavy displacement is what you need. I really consider this as a comfort issue, not a safety issue. A light displacement sailing yacht’s cockpit is as safe as the cockpit of a central cockpit, but definitively exposes the skipper more to water projections and wind. I find those conditions thrilling and rely on a modern, very comfortable and light full weather Gore Tex® gears, but others are OK to trade the thrill for a dry place under heavy conditions.
  • #10: Light displacement sailing yachts tend to roll less downwind.
  • #11: Light displacement sailing yachts above 50 feet can now benefit from a lot of equipment without having to embark tons of fuel and dozens of heavy batteries. Modern batteries offers 2 to 5 times more disposable energy than traditional lead batteries and their lifecycle is 2 to 3 times longer. And wait for it: They are lighter, at comparable capacity. With integrated hydro generators, light displacement yachts are now rewarded with an easy and durable energy source while sailing and the fact that they sail faster allow them to reach an incredible autonomy at sea. A single very low drag hydro generator, such as a Watt and sea hydro generator can produce up to 500W at 8 knots, and you won’t see the difference in your speed.  Have a try of the Aureus XV absolute and you will be amazed by how effective a modern sailing yacht can be in terms of energy consumption and production.

Price and value

There was a time, in the boat industry, when people said: you can estimate the price of a yacht looking at its weight, and this was quite coherent. This was correct when all builders and brands were stuck with the same materials (Basic Fiberglass and poor quality Polyester). Since everybody was using the same materials, the heavier the boat was, the more raw material was included, the higher the cost. So naturally, heavy displacement yachts were higher priced and considered as the “premium or luxury solution”.

But now, carbon fibers, quality sandwich panels, titan and new technologies are available on the market and allow major gain in weight…at a relatively heavy cost. So this old wisdom is not right any more. Now you can reach the same mechanical properties at half the weight. A carbon hull costs more to (properly) produce than a heavy displacement hull, even twice as heavy. A multiplexed DC cabling is half the weight of a traditional DC cabling but also costs three times more. Gel batteries cost twice as much as standard lead batteries and Ion-Lithium batteries 10 times more (at the time I wrote the article), though their price will go down as the market grows.

  • #12: Today, to offer the same level of comfort and equipment as a heavy displacement sailing yacht, a light displacement sailing yacht must be built in carbon/epoxy using vacuum infusion (or pre-preg) process. This is the only possibility to counter the weight of equipment such as Generators, descent fridge and freezer, dishwasher, water maker, hydraulic and electric manoeuvres, etc… So a state of the art offshore cruising light displacement sailing yacht will be more expensive to build than a heavy displacement yacht.
  • #13: On the other hand, carbon/epoxy hulls are much more durable than Polyester or Vinylester hulls. A remarkable light displacement yacht using carbon/epoxy offers, contrarily to what is generally said, a much better durability than a traditional E-glass (fiberglass) using polyester or vinylester. This value in time is to be considered. To learn more about resins or fibers, check out our post: Polyester vs Epoxy and Fiberglass vs Carbon.
  • #14: Light displacement offshore sailing yachts have considerably reduce their dependence to combustion engine or generator. It reduces the need for Gasoil consumption, isn’t that good news for environmental concerned sailors ?

Most of the heavy displacement sailing yachts brands keep using the same materials as 20 years ago (Fiberglass, Polyester resin and plywood).

In the meantime, materials like carbon and epoxy have made their proof on hundreds of sailing yachts’ laminate, they are now totally reliable and allow innovative builders to produce much faster, safer and durable yachts. I really think that a “state of the art” modern light displacement sailing yacht is the best fit for offshore sailing, even though the appearance of a good old heavy displacement keeps on reassuring some sailors.

I think a  lot of brands are very conservative both in design and construction because they are used to it, and because a lot of customers are also used to those good old materials and design. They assume their qualities are better, since they are used for years on good quality yachts, and they assume they will naturally last longer. Well, that’s kind of wrong ! A properly built epoxy hull will automatically last longer and with better performances than a Polyester hull or deck, plus you don’t have to fear any osmosis any more.

I hope this plea for lightness will resonate and encourage sceptical sailors to give a try to well-built light displacement offshore sailing yachts, for more sensations.

Please feel free to disagree or comment, for the sake of the debate. Thanks for reading,
Aurelien

Here are a few great books to go further in the analysis of the sea worthiness of such or such design, and to learn more about naval architecture, especially for sailing yachts: