Monsoon 31: Greenfit instead of refit, what does that mean for the 50-year-old Hallberg-Rassy?

When Christoph Rassy, who had emigrated from Lake Starnberg to Sweden, began building the first Monsun 31 in 1973, nobody could have imagined that the shipyard founder would create a GRP classic with a legendary reputation. The boat was the nucleus of Hallberg-Rassy and also became the shipyard's biggest production success to date. A total of 904 yachts were built between 1973 and 1982. Half a century has passed since then, and yet almost all Monsuns are still sailing today, many on the Baltic Sea, but some of them also on long voyages.

Monsoon 31, construction number 1 is revived

Construction number 1, which lies before us on the jetty under the name "Zeasy", has also had a long journey. Originally delivered to the USA, she was transferred back to Germany in 2008, where she spent a long time in a deep sleep. "It was a chance find. When we came across the sale advert, the boat had already been ashore for eleven years," says owner Carl Brockhausen.

"The previous owners had already started the refit, but had left behind various construction sites. We also didn't just want to refit the boat, we wanted to greenfit it," says Brockhausen. This is also reflected in the boat's name. "Zeasy" stands for zero emission and sustainable yachting. With the company of the same name, Brockhausen wants to support shipyards and owners in making old boats attractive again and at the same time equipping them with environmentally friendly technology. The Monsun serves as a kind of showcase and test vehicle.

The Monsun 31 was fitted with an electric drive

The electric drive is a prime example of this. Like many old yachts, the used Hallberg-Rassy was equipped with the original diesel engine. After a long period of disuse, Brockhausen didn't even try to start it, especially as an unholy mixture of fuel, oil and water was sloshing around in the bilge.

Instead, "Zeasy" was fitted with a ten-kilowatt electric drive and two lithium batteries, each with a capacity of 6.5 kilowatt hours. On paper, this results in a range of 8.5 nautical miles on full power. However, how the electric motor performs in practice will only become clear when you are actually travelling with it.

The biggest challenge on the cruise for the shipyard's anniversary was the weak electricity in the harbours, we could hardly load properly"

The baptism of fire was the 240 nautical mile trip to Ellös to celebrate the shipyard's fiftieth anniversary. "The biggest challenge was the electrics in the harbours. We had installed a very powerful charger. However, the harbours in Denmark and Sweden were often not fused well enough. The power often failed and we could hardly recharge. We now also have a weak charger on board as a backup, so we can charge overnight without the fuse blowing," says Lorenz Pinck, who took care of the electrical installation.

The Monsun 31 motors as if under sail

During the test run with full batteries, the drive from Dutch supplier Waterworld shows its best side. The Hallberg-Rassy 31 glides almost silently out of the box and across the Schlei. A hiss only becomes audible above five knots. These are the propeller noises that are normally drowned out by the noise of the diesel engine.

Thanks to the silent motor, they are present, so that you intuitively reach for the power regulator and take out some speed. Calm returns. We sail along the Schlei at four knots instead of five and a half. The fascinating thing is that the motorised stage almost feels like sailing, as there are no vibrations and the lapping of the bow and stern wave dominates the acoustics.

As a welcome side effect of the slower speed, the range of the Hallberg Rassy increases significantly. According to the battery management system, we could travel around 16 nautical miles at this speed, which is twice as much as at five and a half knots. If necessary, the ten kilowatts of engine power accelerate to around six and a half knots and stop the boat within a boat's length thanks to the enormous torque and a corresponding propeller.

Another advantage of the electric drive is the small space requirement. The entire technology fits into the old engine compartment of the Monsun. There is even room for the supply battery. This keeps the cable routes short and frees up storage space elsewhere. The forecastle box was occupied by the old batteries, and a makeshift tank was also installed there. "The diesel tank is actually laminated into the keel underneath the engine. However, it was so dirty that one of the previous owners had already decommissioned it. Even when we had the old Volvo outside, we could barely get to the tank to clean it. As it was no longer needed, we finally sealed it," says Brockhausen.

The sails of the Hallberg-Rassy are also sustainable

Once we reach the Kleine Breite, we set the sails. They come from Elvstrøm and are made from Ekko laminate. This is recycled polyester made from used PET bottles. Sheets, halyards and mooring lines are also made from recycled PET.

The mast, boom and furling system, on the other hand, are new standard products from Seldén. Safety came first when it came to the rigging, so there was no question of overhauling the fifty-year-old mast. The new rig also contributes to the visual modernisation.

Of course there is no new teak deck

The deck also makes a major contribution to this. Although it looks like teak, it is a polyurethane-based replica. The product is called Ecodeck and is expected to have a service life of around 20 years. It can then be completely reused. The material has been on the market since 2012 and is also offered by Hallberg-Rassy as an alternative to wooden decking.

Originally, "Zeasy" was travelling with a GRP deck with an anti-slip structure. However, the balsa core was taking on water in some places around the cleats and handrails. "There was only peat left, so we had to cut the deck open and re-laminate it. In the saloon, this was done invisibly from below. On the foredeck, however, we had to work from above. To cover these repairs, we had to apply a covering," says Brockhausen.

In addition to Ecodeck, cork was also an option. Brockhausen explains the decision in favour of the synthetic material as follows: "The stable, waterproof carrier board made of wood fibres was the deciding factor. This means that the PU flooring can also be laid on substrates that are not perfectly flat. With a cork deck, we would have had to do a lot of levelling, because the GRP deck was not really level, as is the case with many old yachts."

Another advantage of Ecodeck: the material harmonises very well visually with real teak, so the gunwale and wooden handrails could be retained. In addition, the wooden deck look gives the Monsun a much more valuable appearance, which fits in well with Brockhausen's idea of the Greenfit - it's not just about sustainability, but also about added value for the owner.

The character under sail was preserved

However, the new features do nothing to change the cosy, leisurely character of the Monsun. Those who are used to more modern yachts will feel like they are in slow motion on the aged Rassy. The rudder, which is not pre-balanced, requires a strong hand to change course, but with well-trimmed sails, you can confidently hold the tiller for a few minutes without veering off course. Tacking and jibing are, shall we say, decelerated.

Especially when there is only a light breeze, as was the case on our test run, the Monsun teaches you to remain calm when she turns through the wind with stoic calm and you can first loosen the genoa sheet and then tighten the new leeward sheet minutes later.

It is still fun, or perhaps because of the forced relaxation. The son of the shipyard founder, Magnus Rassy, aptly describes the monsoons as:

Long-distance sailing yachts that were never modern, but will never go out of fashion"

The inside of the boat has been lumbered

However, this does not necessarily apply to the design of the interior. The demands there have changed significantly over the last 50 years. Ceilings covered in beige-coloured vinyl and a bare GRP floor are no longer in fashion. That's why it was time to declutter below deck. The Monsun was to retain its classic character, but with a lighter and more modern look. This included removing the old vinyl coating and a complete repainting.

"We tried to make everything as sustainable as possible, but you quickly reach the limits with paintwork, after all, the result should also be robust and durable. There is hardly any way around solvent-based two-component products," says Brockhausen.

Brockhausen and Pinck did around 80 per cent of the work alone and invested around 1,000 hours. Martin Dittmer, head of Blaupause Bootsbau GmbH in Kappeln, was responsible for the laser measurement of the deck, the saloon floor and the ceiling. Using the data, he designed the new ceiling panelling and milled it to a precise fit. This eliminated the need to make templates and tedious adjustments.

Sustainable materials were also used below deck

This comparatively simple wooden part with the milled moulding look alone changes the look of the Rassy enormously. Together with the white paintwork and the light blue upholstery made from recycled and breathable artificial leather, the interior has been given a real makeover. Other innovations, such as the Bluetooth-networked bus system, are less obvious. It makes the electrical installation much easier and saves several metres of cable. The complete 12-volt wiring only took one day.

The trick is that only one two-pole supply line is laid through the ship. Each consumer is looped into the line with a small box called a node. The boxes contain the switching and monitoring electronics and communicate wirelessly with a central unit that can be controlled and set up using an app. "The system comes from the start-up Revotion and is manufactured in Germany," says Pinck.

He promptly demonstrates on a tablet how easy it is to set up. After just a few clicks, a virtual control panel is created that can be used to control the lighting. Fuel gauges, temperature sensors and a battery module for monitoring the state of charge can also be integrated.

Something like this was probably even less imaginable in 1973 than the lasting success of Monsun 31, which entered its next 50 years with "Zeasy".

Technical data

• Designer Olle Enderlein
• Hull length 9.36 m
• Waterline length 7.50 m
• Width 2.87 m
• Draught 1.42 m
• Weight 4.2 tonnes
• Ballast/proportion 1.9 t/45 %
• Mainsail 21.0 m²
• Furling genoa (100 %) 18.0 m²
• Electric motor 10 kW/14 hp
• Battery capacity 13 kWh

Further topics in the sustainability special:

• 25 tips to help you sail more environmentally friendly
• These projects are available for marine conservation
• Sailing yacht vs. motorboat: which model is more sustainable?
• Boatbuilding ecolution: These shipyards are working on sustainable concepts
• Shipyard portrait Greenboats: Boats made of flax and components for Boris Herrmann
• Sustainable fashion: oilskins and other functional clothing - the best products
• Sail recycling: not just stylish bags - what happens to old cloth
• Boat recycling: the never-ending story of GRP
• "Losing is not an option" - Boris Herrmann on sustainability in motorsport
• Sustainable management: Wooden boats in charter operations
• Equipment: Every sailor should reach for these green alternatives
• Drinking water on board: you can filter water correctly using these methods
• Baltic Sea: How does a harbour become sustainable?
• Research yachts: Climate protectors under sail
• Pallets, bottles, flip-flops: creative recycling ideas in boatbuilding
• "Nomade des Mers": a catamaran as a low-tech laboratory
• Self-build yacht "Ya": Totally self-sufficient on a trip around the world
• Sustainable boat project: 55-foot catamaran made from recycled aluminium
• The Schwörer family and the "Pachamama": on a long voyage for climate protection
• Nike Steiger on her recycling project