From the origins of cruising yachts to wood-based naval construction, until the advent of plywood-epoxy yacht building: how RM Yachts has modernized a unique building process.
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From the origins of cruising yachts to wood-based naval construction, until the advent of plywood-epoxy yacht building: how RM Yachts has modernized a unique building process.
Plywood is a material that is currently used in different sectors, such as:
It looks like a composite sheet, due to the superposition of crossed, 1 to 4mm thin plies of wood.
Plies are obtained after unrolling wood ridges, stoved during 12 to 72 hours depending on the essences. They are then cut, dried, glued and superposed in crossed ways, before being pressed.
The whole process for building a panel of industrial plywood can be described in twelve steps:
The maximum thickness of industrial plywood is 40mm. Panels are balanced, meaning that the different plies are split in a symmetrical way. Panels are also heterogenic, hygroscopic, and orthotropic (they have different characteristics depending on the three perpendicular directions).
The crossed plies confer to the panels a greater homogeneity and a larger dimensional stability, compared to raw wood.
Plywood panels for structural use have become popular thanks to the synthetic resins in the 20th century.
RM Yachts has over 30 years of experience as a French sailboat manufacturer. One of the originalities of our modern cruising yachts is that they are made using plywood, which is assembled on a jig. Our plywood is made in France and comes to us from a factory which supplies laser-cut parts that are ready to assemble.
RM sailboats range in size from 9 m to 14 m, and each model has its own assembly jig on which the planks are positioned and assembled by jointing and laminating. For the vessel’s planking running the whole length of the hull, the parts are butt-jointed by means of a “scarf” joint in which the two ends of the plank are cut slantwise and overlapped, ensuring a very strong, rigid join. The time to build the hull on the jig varies from one model to another, depending on the size of the yacht.
RM boats are fitted with a metal part in the bottom which increases the rigidity of the structure and on which the different types of keels (fin keel, twin keel, or lifting keel) are subsequently mounted.
RM Yachts completes the following different stages to build a plywood-epoxy liveaboard sailing boat:
Once ready on its jig, the hull is then “unmoulded” and, still upside down, moves to the assembly station where the bilges will be coated with epoxy to give the hull its shape.
Whilst the outside of the hull is coated with epoxy, structural lamination is carried out inside the sailing yacht to ensure maximum rigidity. The structural bulkheads are laminated.
RM decks are mostly made of composite produced by infusion moulding to optimise the weight. They are manufactured by the La Rochelle-based company A2J, a neighbour of RM Yachts. Composite is an excellent choice for deck construction, as this technology enables very fluid, rounded shapes to be achieved, which are characteristic of the RM Yachts monohull sailboats designed by the naval architect Marc Lombard.
Whereas the interior bulkheads of our RM sailboats are laminated, and the bilges shaped by applying epoxy hull coating, the deck is given cladding on the inside.
This almost total coverage is completed using plywood, which offers excellent thermal and sound insulation, and additional rigidity. Once this operation is finished, the inside of the deck is painted in a paint booth.
Whilst the cladding and paint are being applied to the deck, the hull is turned over and operations begin to install the interior fittings. This starts by the final lamination and then coating of the bulkheads. A primer is then applied before painting the inside of the hull.
Once the inside of the hull is painted, fitting-out operations prior to installing the deck begin. At this point, the furniture modules made by a local subcontractor are fitted, together with the power and water systems and the engine. All the large or heavy fittings are now in place.
Installing the vessel’s deck can begin
The deck of an RM sailboat is installed just after the furniture, the power and water systems and the engine have been fitted in the hull. The deck fittings are mounted. The deck is then positioned and bonded onto the hull followed by lamination, a solution which contributes to the structural strength. The point where the deck meets the hull (the deck edge) is then coated with epoxy and sanded for a perfect invisible join.
The next stage, lacquering the hull, is one of the longest in building an RM, requiring many different steps separated by drying times.
The RM Yachts shipyard is one of the only ones to paint the hulls of all its boats, thanks to its plywood-epoxy sailboat construction technology.
While the boat is still upside down, the bilges and laminated joints are coated with an epoxy layer. It is then sanded.
Next, a very thick primer is applied by spray gun to correct any unevenness in the surface.
A second thinner, more dilute layer of epoxy primer is then applied to finish. This epoxy “finish” flows better and improves the quality of the finished surface.
It is then sanded again.
Next, an ultra-smooth polyurethane primer is applied.
Once this layer is dry, the completely personalised bi-component polyurethane high-gloss lacquer topcoat is applied to produce the perfect cruising yacht for each customer.
Once the hull has been painted in the paint booth, the final steps can be completed to finish the inside and outside of the RM.
The portholes, interior lighting, electronic equipment, ceilings, panelling, and doors are fitted.
The very last stage before delivery is the installation of the keel. The shipyard offers three types of keels: fin keel (a single keel), twin keel, or lifting keel.
Martin Lepoutre, General Manager, RM-Yachts:
“RM Yachts benefits from a unique experience and history of building sailing yachts with plywood-epoxy. Since inception, more than 500 sailboats, from 30 to 45ft, have been built here in our French shipyard, in La Rochelle.
Today, our range of modern plywood sailboats include:
Year after year, we have constantly improved our building process:
RM Yachts is unquestionably the shipyard with the longest experience and track record in this area. Thanks to this efficient sailboat building technology, the achievements are:
Interview of Marc Lombard, architect of the RM Yachts.
What are the benefits of plywood-epoxy for blue water cruising yacht building?
The benefits are not only for the blue water or expedition yachts, but for all yachts! The benefit of this technology stands in the material itself: plywood-epoxy. Wood is not a dense material and offers an interesting solidity/weight ratio. If you think the other way around, what we first need on a sailing yacht is solidity.
If you build it with plywood-epoxy, you’ll get a lighter boat than its equivalent in aluminum or GRP. If she’s lighter, it means we can build an even more solid yacht for an equivalent weight or build one with a higher load capacity.
When it comes to blue water cruising sailboats, it’s a balance between this light displacement and the ability to benefit from this extra load capacity. If you want a super solid sailboat, she’ll always be lighter than the equivalent in other materials such as iron, aluminum, or GRP.
Raw wood is a hard-to-process material. For the past 25 years, we’ve worked hard with RM Yachts to finetune this plywood-epoxy sailboat construction process and make it economically viable and competitive. It’s quite a challenge, as it costs more money compared to monolithic polyester, but it offers many more benefits in terms of solidity, lightness, and insulation.
When it comes to insulation, the first benefit is clearly a moisture-free atmosphere. There’s no mistiness with 18mm planking, while iron or aluminum would require additional insulating materials. Not to mention the easiness to repair plywood-epoxy.
(ActuNautique.com, 2016).
Marc Lombard and the sailor of the future, Voile Magazine, April 2021.
25 years ago, Marc Lombard designed the RM800. An easy to clean, easy to store, easy to live, great little boat. A seaworthy design, able to sneak in the tiny coves thank to her reduced draft, but also capable of offshore passages. In a nutshell, a yacht in which Marc Lombard put the best of himself. “At that time, the twin-keel yachts were solely English”, but he worked hard to make them more performant. Using plywood-epoxy, that he had discovered when working with Walter Green and the West System technique, he knew he was in the right direction. Since inception, RM Yachts range has evolved and the sailing yachts have become more and more performant and comfortable, yet elegant. But they have kept this original philosophy of seaworthiness. RM Yachts are made to munch miles, and their owners usually buy them for this purpose. Even if they are looking for comfort. A requirement Lombard takes seriously into account, when he reduces the number of steps in the companion way, between the cockpit and the saloon area. Not yet like a cruising catamaran, but that’s the idea behind it. RM Yachts will continue to evolve, but maybe not with foils or scow bows! Because all offshore innovations are not necessarily adaptable on cruising yachts. According to Marc Lombard, the question is not about the yachts of the future, but about the sailors of the future. What will be their expectations? What will they look after? A way to underline the fact that we have the yachts that we deserve!
Plywood sailing boat building started back in the 1960’s. The first naval architects to use this technique were Harlé, Herbulot or Van De Stadt. In France, they gave birth to legendary yachts such as the Muscadet or the Corsaire. Plywood was lighter, waterproof, and required less maintenance than raw wood.
Sometimes seen as an amateur, non-professional technique, with perfectible finishings, this building process has quickly evolved to finally be mastered by shipyards such as RM Yachts, thanks to Marc Lombard’s design. Today, plywood is combined with epoxy.
This combination with epoxy resin enables an even better waterproofing and facilitates maintenance. Combined with fiberglass, it becomes a fantastic material to build yachts, with a weight/resistance ratio clearly more favorable than the ones of aluminum or monolithic polyester.
For the record, a composite material is the assembly of at least two non-miscible components, whose specifications are complementary. the material obtained by this assembly is heterogenic and offers resistance characteristics that the sole components do not have.
Marc Lombard is one of the first naval architects to have imported in France the concept of plywood-epoxy sailboat construction. It is actually a technique that American yacht builders already mastered, thanks to the discovery of a marine-grade resin, called West System, created by the Gougeon Brothers.
The Gougeon family, originally from Chicago, IL, set up a new process: saturating a plywood panel with resin. The first application of this technique was the building of “ice-boats”, designed to navigate on the frozen waters of the great lake’s region.
They eventually designed a few sports multihulls and won a few local regattas and championships. In 1975, they decided to stop competition, and focused on the fabrication of this specific resin, aiming to sell it to other boat builders.
In 1979, they wrote a book on boat construction using plywood-epoxy. This book became the bible for many architects. It was re-edited 5 times, until 2005.
In this book, the Gougeon brothers will explain the virtues and benefits of plywood combined with epoxy, comparing it with other materials used for boat construction. Starting with solidity and rigidity.
Among the various plywood boat building processes, the one preferred by the Gougeon brothers is the “compounded” one. It consists in assembling plies, impregnated with resin, and to press them to obtain a desired given shape.
Below is the 35-footer trimaran “Ollie”, built by the Gougeon Brothers back in 1985.
This plywood boat construction technique will be used by Dick Newick to build his first multihulls, but also by Walter Green, in Yarmouth, Maine. Guess what? The latter will welcome the young Marc Lombard as a trainee, when working on “A Capella” for Charlie Capelle, sistership of the little yellow trimaran Olympys, commissioned by Mike Birch, winner of the Route du Rhum in 1978.
“For me, there is no other option for boat building but wood. When you come aboard a yacht, you have to feel something, an atmosphere, some emotions. In a GRP boat, this is quite hard to feel, while in a wooden boat, you’ll immediately feel a soul, a spirit, a strength. There’s something happening because it’s a material that is alive. In terms of solidity, when it is properly worked out, and well maintained, you know it will last forever. A Capella is a great example: she spent a year and a half upside down, tossed by the waves on the beach, and she is still in pristine conditions”
(Charlie Capelle, Voiles & Voiliers magazine, 2014).
No one exactly knows when the first sailing boats were used for leisure purposes. The first leisure sailors probably used a mix of sails and oars as auxiliary source of power. Since Antiquity, some ships were used for celebrations, anniversaries, and even races. Sailing on the Nile river and later on the Med has been recorded by antique Assyrian, Phoenician or Egyptian civilizations.
The origin of leisure sailing or “cruising” is more recent and has been found in the Netherlands and the UK.
In 1601, a Dutch named H. Voogt managed to get an authorization to sail from the Netherlands to London, for fun. This marks a kind of milestone in the definition of cruising. But what is the exact definition of leisure? “Use of free time for enjoyment”. That’s a good start, isn’t it?
When it comes to “cruising”, Cambridge’s dictionary says: “the activity of going on a journey on a ship for pleasure”.
Sailing a yacht for enjoyment, could be another definition. At least, this is the one that corresponds the best to RM Yachts philosophy!
Nowadays, leisure sailing comes in many forms and liveaboard sailboats are used by couples, families and solo sailors for port-hopping, coastal cruising, bluewater sailing, ocean crossing, etc.
The English word “yacht”, today commonly used to design a sailing vessel, has Dutch roots: the jaght schip was originally used in the late 16th century. The verb jaghen meaning chasing, going after, and the word schip meaning ship or vessel. This etymology underlines the fact that the notion of a fast sailing yacht has been key to the development of leisure crafting.
Cruising and leisure sailing will give a second chance to sailing. In the second half of the 20th century, this activity will be democratized. A good example of this spectacular boom is the Vaurien, an affordable and solid 13ft dinghy. Built using just one single sheet of plywood.
How were the first cruising yachts built?
It seems the construction of sailing boats was done using the materials that could easily be sourced locally. Logically, wood, easy to cut and assemble, has been mostly used in different parts of the world, until plywood and its many benefits came in.
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