Sweden

Marstrom Composite shipyard

Born as a stripped-out carbon maxi catamaran, <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> is being reimagined as a 30-metre liveaboard platform packed with sustainable tech. But embracing the eco ethos by upcycling a 15-year-old hardcore ocean race winner is not without its challenges.<img src="https://photo-assets.superyachttimes.com/photo/301619/image/large-169cea62ccf80e0f3754d0aaf8db56f9.jpg" data-gid="gid://syiq/Photo/301619">The idea of upcycling an existing hull to give it a new lease of life is hardly groundbreaking and there’s an entire superyacht refit sector based on the principle. But none of those projects are quite like <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a>, because this is no ordinary platform – it’s a full-bore, balls-to-the-wall maxi racing cat being transformed into a 29.9-metre global cruiser.<img src="https://photo-assets.superyachttimes.com/photo/362842/image/large-ec60c75c40151529a9e5d3d421e56a1c.jpg" data-gid="gid://syiq/Photo/362842">For her experienced owners, <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> represents the chance not only to build their dream cruising cat, but to do it in a way that represents their vision of sustainability. From recycling the original race boat to adopting green tech for power and propulsion and using recycled or eco-conscious materials for the fit-out wherever possible, the project will serve as an example of what can be done to mitigate the end-of-life problem that composite and carbon yachts present – an ambitious ask, especially given the yacht’s hardcore race pedigree. The job of reconfiguring the yacht from racer to cruiser has fallen to naval architect Eliot Thorne, owner of UK-based <a data-gid="gid://syiq/Company/7442" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Thorne Yacht Design (Company)">Thorne Yacht Design</a>. <img src="https://photo-assets.superyachttimes.com/photo/301618/image/large-d124aee83b5f07271d80ed43bceb7043.jpg" data-gid="gid://syiq/Photo/301618">“The project was introduced to us by Torbjörn Linderson at <a data-gid="gid://syiq/Company/7514" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Marstrom Composite shipyard (Company)">Marstrom</a>, the Swedish yard that built the hulls and assembled the yacht back in 2007,” begins Thorne. “The owners approached them to buy the boat and renovate it, and we came on board to undertake a feasibility study for the practical, structural and cost elements. The owners had the means to buy a new custom cat but they wanted to give an old boat a new lease of life, modify it to their needs, recycle it and create a positive message, even knowing there would be trials and tribulations on the way.”<img src="https://photo-assets.superyachttimes.com/photo/301616/image/large-1e1fa01c9731d2d81cb67f1ed5a3703f.jpg" data-gid="gid://syiq/Photo/301616">The revamped yacht will feature four guest cabins – two in each hull – while across the bridge deck a carbon superstructure is being added to house a portside master cabin, interior helm and open plan galley, and lounge area to starboard. The helm station in each hull is being retained, and while the yacht will feature Tesumo decking in places, she will keep the original large forward trampolines rather than fill them in with hard deck space. The interior includes some use of flax for a few non-structural elements, natural cores, and countertops and interior finishes from recycled sources.<img src="https://photo-assets.superyachttimes.com/photo/301617/image/large-5b56e0e2e15c2e0dff775c551e6d6cf0.jpg" data-gid="gid://syiq/Photo/301617">Big BuildThe yacht was shipped to <a data-gid="gid://syiq/Company/7513" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Fibre Mechanics (Company)">Fibre Mechanics</a> at Hythe Marine Park on Southampton Water at the end of 2022, where work began in earnest repairing any defects in the original structure and adding new bulkheads, a new nacelle, 2.5-metre extensions to the hulls, and replacing all the wiring, plumbing and systems.<img src="https://photo-assets.superyachttimes.com/photo/301607/image/large-e55cfdc95c55558ec1e56f13c6d480a5.jpg" data-gid="gid://syiq/Photo/301607">As the work progressed, the team started to uncover a number of issues with the structure of the hulls. The boat had originally been built from sketch to launch in around four months which, in spite of being a very simple platform, was a very short timeframe that had been driven by the original sponsor and advertising requirements outside of Marstrom’s control. In addition, there had been a lot of repairs and remedial work done during the service life of the boat when things had got damaged or broken while racing. Finally, it was discovered that one hull actually sits around 80mm further forward than the other – a quirk that has been retained in the refit.<img src="https://photo-assets.superyachttimes.com/photo/312622/image/large-93efa81a8765b4b04ad7001970e9c4be.jpg" data-gid="gid://syiq/Photo/312622">“Between those remedial and rushed work of the original construction there were some areas of the laminate that we felt were not up to standard and which we’ve removed, reinforced and reinstated,” says Thorne. “For the original build, the hull bottoms were autoclaved and the topsides were made as flat panels that were curved in place. The bulkheads were all flat panels. We had done preliminary non-destructive testing (NDT) of some of the high-load reinforcement areas, but it was only once we started cutting, grinding and removing paint that we realised there were more errors than we’d anticipated.”<img src="https://photo-assets.superyachttimes.com/photo/301609/image/large-a844ccca05e64e99fce92d265d211398.jpg" data-gid="gid://syiq/Photo/301609">The biggest challenge was uncovered while drilling holes into the hull bottoms for through-hull fittings where it was clear there had been water ingress into the Nomex core.“It looked like there’d been an impact on one of the daggerboards, and that had split the skins around the back end of the daggerboard case, allowing water to work its way between the two skins,” explains Thorne. “So on the front half of the starboard hull we ended up having to remove the outer skin and Nomex core, repair it, add foam and reinstate the outer skin. We knew about various bits of delamination, mainly from dock impacts, but that was definitely a bit of a surprise!”<img src="https://photo-assets.superyachttimes.com/photo/301604/image/large-8651b6a34170c206ed60d5576c8170c2.jpg" data-gid="gid://syiq/Photo/301604">As with any refit, weight has become a critical factor, especially given the yacht’s original purpose as a high-performance racer, built to fly a hull and stripped out below but for a nav station and pipe cots.“We’ve added a considerable about of weight,” says Thorne. “The target was just over double the original displacement of the boat, but that’s grown a bit over time – although we’ve also balanced that out by extending the transoms.”&nbsp;That structural alteration has not only offset some of the weight gain with additional displacement but has also allowed for the addition of a bathing platform, various practical enhancements for cruising, and additional storage space.Rigged OutcomesIn keeping with the idea of recycling and upcycling, the intention was to reuse the original rig, but as the team undertook remedial work they uncovered more unwelcome issues. It was a monolithic rig with a wing section design and Nomex-stiffened sidewalls to support the chord length, but a lot of Nomex had de-bonded from the inner skin and it eventually became apparent the rig was no longer viable. The obvious solution would have been to order a new one, but that wouldn’t have been in the spirit of the project. <img src="https://photo-assets.superyachttimes.com/photo/301602/image/large-db4b1498dab9e38e495ede3b2c24eb9d.jpg" data-gid="gid://syiq/Photo/301602">“Keeping with the mindset of recycling something that’s no longer being used, we went on the hunt,” says Thorne. “As luck would have it we found a spar from a 90-foot high-performance cruising cat – there’s probably only one of them out there in the world! We’re slightly modifying it by cutting off the lower four metres and putting reinforcements on it. However, the original sail plan and the new one with the new mast are unbelievably close in terms of the sails’ IJPE measurements, so it’s really just minor tweaks we’re having to make. What’s more, the rig tweaks are being completed at <a data-gid="gid://syiq/Company/7514" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Marstrom Composite shipyard (Company)">Mastrom</a>, adding a pleasing symmetry to the project.” <img src="https://photo-assets.superyachttimes.com/photo/301601/image/large-cfd1b702fea3573a104b574bfad7d819.jpg" data-gid="gid://syiq/Photo/301601">The team has also taken a sustainable approach to the new tooling required for the superstructure roof, which is constructed in six pieces that are largely flat panels made on a standard table rather than needing a custom mould.“We modified the curve of the main roof in the design so that it could be built flat and then cut on the underside to give the curve,” says Thorne. “It meant that tooling was only required for a couple of smaller, more complex pieces. Tooling is expensive and it’s not very green, because it just ends up in the bin on a custom project. Finding ways to minimise it, simplify it and recycle it was an important part of the ethos from the beginning.”Power PlayBut the conversion of <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> not just about using sustainable materials. The owners’ brief specified eco-friendly power and propulsion systems, as well as the ability to sail off-grid for weeks at a time. The original plan was to run with fuel cells, with tankage for gaseous hydrogen and an electrolyser to make hydrogen onboard from seawater with three hydrogen tanks each side feeding a fuel cell in each hull.<img src="https://photo-assets.superyachttimes.com/photo/301599/image/large-3850346126b1832d0704aa2180f9d1ac.jpg" data-gid="gid://syiq/Photo/301599">“It was doable and the technology is out there, but we discovered that the electrolyser systems are fragile – great for slow shoreside hydrogen production but not for mounting on board,” Thorne points out. “That’s the bit of the tech that has its limitations right now.”Instead, the yacht will carry 330kWh of batteries, housed largely in the new nacelle, which is the same size as a TP52 raceboat hull. The batteries will be fed by an array of photovoltaic cells on the new superstructure roof and hull tops, with additional harvesting from folding panels that can be deployed at anchor. In addition, hydro-generation will provide a few kilowatts extra when sailing. The electric motors, one in each hull, are rated at 100kW each for power cruising in the teens and a small diesel generator serves purely as an emergency range extender.It's been a long road for the project and there’s still a fair way to go, but with the core structure nearly complete the remaining stages of the boat are coming into focus. At the time of writing, the intention was to launch and head out for sea trials in early 2025, albeit with no interior joinery nor paint, while aiming for a formal handover to the owners at the end of the year.<img src="https://photo-assets.superyachttimes.com/photo/301609/image/large-a844ccca05e64e99fce92d265d211398.jpg" data-gid="gid://syiq/Photo/301609">“The systems will be ready, and the intention is to take the platform out, load it up, stress-test it and make sure there aren’t any unknowns we haven’t discovered yet, either within the existing structure or the new structure we’ve added that isn’t able to be anticipated in the FEA studies,” says Thorne. “We’ve done our absolute utmost to pre-empt any issues, but there can always be areas that you can’t anticipate when you’re dealing with a heavily reconfigured structure.”Thorne’s initial VPPs suggest that even with the additional weight and structure, <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> should still offer a good turn of speed. The original powered-up platform has been reduced by raising the boom and decreasing the sail area, including some of the headsails. <img src="https://photo-assets.superyachttimes.com/photo/301606/image/large-8e3a478ed9b720f45712e640f1b2e748.jpg" data-gid="gid://syiq/Photo/301606">“She will start with a reduced sail wardrobe with no gennaker or spinnaker, just a Solent staysail and main for the purpose of getting the boat up and running, and then we will add sails down the line,” says Thorne. “But she should still be able to achieve reasonable performance and be a windspeed boat – assuming the right conditions in terms of wind direction and sea state, if it’s blowing 20 knots she should be able to sail at 20 knots.”Loading UpWith <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> gaining considerable displacement in the conversion compared to the original race-ready platform, Thorne paid close attention to the righting moment and to the impact of a high-performance rig design on what is now effectively a performance liveaboard cruiser. Loads cells installed everywhere from the forestay to the mast base, runners, mainsheet and elsewhere, will monitor load parameters to ensure no particular aspect is exceeding a specified load case. <img src="https://photo-assets.superyachttimes.com/photo/301605/image/large-8267558359cd77165626e0e7243abbd9.jpg" data-gid="gid://syiq/Photo/301605">“The system isn’t meant to tell you you’re overloading any individual piece of the structure, but rather serves as an indicator that the loads are getting high within the overall platform,” Thorne says. “The system will alert you to start with, and if anything gets wildly out of bounds and no action is taken by the crew, it will automatically release the mainsheet and headsail sheet to keep those loads down and ensure the safety of the platform.”Lessons LearntKey takeaways for anyone considering a similar conversion include making greater allowance for the unexpected. Thorne and his team were lucky to have a good relationship with the original builder and <a data-gid="gid://syiq/Company/7514" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Marstrom Composite shipyard (Company)">Marstrom</a> provided a huge amount of information – the project would have been a lot more challenging without a good set of initial data.“The second aspect is anticipating at an earlier stage the amount of wiring required for the electrical system on a boat like this, which would have saved us some headaches down the line,” Thorne admits. “We have 14 kilometres and two tons of wire on board the boat, which is a little over double our initial estimate even though we’ve been installing hybrid systems for over a decade. The size and beam of the platform means long wiring runs and that drives up the wire size; collaborating with electrical contractors from a very early stage would certainly be beneficial in any project like this.”<img src="https://photo-assets.superyachttimes.com/photo/301600/image/large-5d0ddc3b5cd36ddd248ca545fc23a8ec.jpg" data-gid="gid://syiq/Photo/301600">Finally, Thorne believes the yacht industry could improve when it comes to appreciating and offsetting the environmental impact of building or refitting a yacht. The team continually updates its initial lifecycle analysis of the boat to come up with a record of its carbon footprint throughout the rebuild process, which is not as straightforward as it seems.“Trying to find good-quality data for some of that is really difficult,” says Thorne. “Understanding the amount of carbon it takes to make one kilo of carbon fibre is easily quantified, but it’s the parts like a bilge pump that are far more challenging in terms of where did all the parts come from, where was it assembled, how’s it been shipped to you? And I think that’s something that as an industry we can definitely do better at.”This article was featured in <a href="https://issuu.com/superyachttimes/docs/how_to_build_it_-_issue_7_spring_2025" target="_blank">Issue 7 of How To Build It</a>. You can read all the articles from this edition <a href="https://issuu.com/superyachttimes/docs/how_to_build_it_-_issue_7_spring_2025" target="_blank">here</a>, and stay up-to-date with all previous editions <a href="https://issuu.com/superyachttimes" target="_blank">here</a>.

In conversation with Eliot Thorne of Thorne Yacht Design on the radical refit of Gemini 3

SYT talks to naval architect Eliot Thorne about the refit of Gemini 3, a 30-metre liveaboard platform packed with sustainable tech.

In conversation: Eliot Thorne of Thorne Yacht Design on the radical refit of Gemini 3

Sophie Spicknell dives into the history of one of the industries most interesting rebuilds.For the past three years, UK-based yacht designers <a data-gid="gid://syiq/Company/7442" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Thorne Yacht Design (Company)">Thorne Yacht Design</a> have been working on the extensive rebuild and refit of the 27.4-metre maxi sailing catamaran <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a>. The ambitious project aimed not only to breathe new life into the vessel, but to push the boundaries of design, performance and sustainability. <img src="https://photo-assets.superyachttimes.com/photo/301619/image/large-169cea62ccf80e0f3754d0aaf8db56f9.jpg" data-gid="gid://syiq/Photo/301619">Built in Sweden in 2007, the <a data-gid="gid://syiq/Company/7514" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Marstrom Composite shipyard (Company)">Marstrom</a> 90 yacht <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a> boasted a formidable reputation as a world-class racing vessel for over a decade. Throughout her illustrious career, she clinched numerous victories on the global racing circuit, solidifying her status as a true champion of the seas. <img src="https://photo-assets.superyachttimes.com/photo/299846/image/large-1b15b98600df9743776c1901cee89bfd.jpg" data-gid="gid://syiq/Photo/299846">Around 2020, a client contacted <a data-gid="gid://syiq/Company/7442" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Thorne Yacht Design (Company)">Thorne Yacht Design</a> prior to the purchase of <a data-gid="gid://syiq/Yacht/13633" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Gemini 329.9m (98'1&quot;)Marstrom Composite shipyard2007">Gemini 3</a>, with the vision of transforming the ocean racer into a capable bluewater cruiser. “The boat was in a very basic form as a racing yacht when we were first contacted,” explained Eliot Thorne, owner of <a data-gid="gid://syiq/Company/7442" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Thorne Yacht Design (Company)">Thorne Yacht Design</a>. “The client wanted to do a feasibility study on the boat to understand whether we could turn it from its racing heritage to a liveaboard platform.”<img src="https://photo-assets.superyachttimes.com/photo/299843/image/large-cfd00b24e9023f375f24c06952e70af9.jpg" data-gid="gid://syiq/Photo/299843">Following these discussions, the yacht was purchased and transported to Hythe, Hampshire in the United Kingdom in November 2022, where it was taken into care by <a data-gid="gid://syiq/Company/7442" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Thorne Yacht Design (Company)">Thorne Design</a> and <a data-gid="gid://syiq/Company/7513" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Fibre Mechanics (Company)">Fibre Mechanics</a> for the refit construction work. The yacht arrived as a dormant frame, providing the team with an almost blank canvas to start designing from.<img src="https://photo-assets.superyachttimes.com/photo/299844/image/large-8c09b9071822d86590e08cdb835158b2.jpg" data-gid="gid://syiq/Photo/299844">The process now began to convert and re-use this racing catamaran, and to showcase cutting edge sustainable technology, whilst creating a comfortable cruising yacht. “The original intention was to convert the sailing yacht to have the auxiliary power system as a hydrogen propulsion system,” said Eliot Thorne. “However, our research showed that this wasn’t a feasible solution, due to the technology surrounding hydrogen not quite being at the level we needed, to be able to create your own hydrogen onboard.”<img src="https://photo-assets.superyachttimes.com/photo/301600/image/large-5d0ddc3b5cd36ddd248ca545fc23a8ec.jpg" data-gid="gid://syiq/Photo/301600">The team instead opted for a full-electric propulsion system, with a huge solar array to create a sustainable, yet efficient cruiser. &nbsp;“Every decision that we have made onboard has very much an awareness and consciousness of trying to make sure they are sustainable, using cutting edge technology to leverage this wherever possible.” added Eliot Thorne.<img src="https://photo-assets.superyachttimes.com/photo/312622/image/large-93efa81a8765b4b04ad7001970e9c4be.jpg" data-gid="gid://syiq/Photo/312622">The key challenge however, has been to accommodate the additional structure and cruising gear. Her refit includes a transom extension, giving the yacht a new length of 29.9-metres. This additional flotation helps to offset the increase in displacement, while maintaining focus on weight efficiency and performance.<img src="https://photo-assets.superyachttimes.com/photo/301604/image/large-8651b6a34170c206ed60d5576c8170c2.jpg" data-gid="gid://syiq/Photo/301604">“Working in close collaboration with experienced owners, our team is ensuring an exceptional level of finish and performance in this innovative endeavour. This project gives us the opportunity to showcase the most up-to-date design and systems, with emphasis on lightweight composite structures and sustainable material technology.”<img src="https://photo-assets.superyachttimes.com/photo/301602/image/large-db4b1498dab9e38e495ede3b2c24eb9d.jpg" data-gid="gid://syiq/Photo/301602">Once completed the M90 yacht will be able to accommodate up to eight guests across a four stateroom configuration, with a stateroom aft and forward of each hull, with her aft-facing master stateroom situated on the bridge, alongside a saloon area.<img src="https://photo-assets.superyachttimes.com/photo/301605/image/large-8267558359cd77165626e0e7243abbd9.jpg" data-gid="gid://syiq/Photo/301605">&nbsp;Her exterior will feature a drastic overhaul, with twin staircases providing access onboard from each hull. Her large aft deck sits behind the cabin house, with seating providing the perfect opportunity to entertain guests. The side decks of the M90 yacht include a helm station on either side, taking the total up to three, with an additional one situated in the middle of her interior space. <img src="https://photo-assets.superyachttimes.com/photo/312621/image/large-bbfa0b8d88b993af8b6031d1fa59b16c.jpg" data-gid="gid://syiq/Photo/312621">Forward is her trampoline, with an oversized sunbed allowing guests space to top up their tans. The M90 yacht also uses an array of photovoltaic panels to boost her solar power collection. Some of these are permanently installed, while others can be folded up when sailing, and laid out when at anchor to generate a new lease of energy. The quantity of solar panels is sufficient to allow complete autonomy.<img src="https://photo-assets.superyachttimes.com/photo/301608/image/large-c97014a3fd281b068d91e0be7e7a1035.jpg" data-gid="gid://syiq/Photo/301608">The owner's decision to forego the conventional route of purchasing a brand-new sailing catamaran speaks volumes about their commitment to promoting sustainability within the marine industry. This decision presented the team with a unique opportunity to showcase the potential of recycling boats and ushered them into a new era of functionality and purpose.<img src="https://photo-assets.superyachttimes.com/photo/301616/image/large-1e1fa01c9731d2d81cb67f1ed5a3703f.jpg" data-gid="gid://syiq/Photo/301616">“The owners could have gone and bought a large brand-new sailing catamaran from a whole variety of different places. But they wanted to create a positive message about what can be done in the marine industry and used as a showcase for sustainability.”<img src="https://photo-assets.superyachttimes.com/photo/301618/image/large-d124aee83b5f07271d80ed43bceb7043.jpg" data-gid="gid://syiq/Photo/301618">“The opportunity to recycle an existing boat and give it a new life poses a number of challenges, but it is one that our team relishes and believes is a great way to promote greater awareness of viable solutions.”<img src="https://photo-assets.superyachttimes.com/photo/301617/image/large-5b56e0e2e15c2e0dff775c551e6d6cf0.jpg" data-gid="gid://syiq/Photo/301617">The <a data-gid="gid://syiq/Company/7514" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Marstrom Composite shipyard (Company)">Marstrom</a> 90 yacht will enter the water this summer to test her hybrid propulsion system and onboard systems. She will then come out again for further outfitting and will be fully completed by Spring 2025.&nbsp;This article is featured in&nbsp;Issue 49&nbsp;of the SuperYacht Times newspaper.&nbsp;You can find a full archive of all previous SuperYacht Times newspapers&nbsp;<a href="https://www.superyachttimes.com/newspaper" rel="noopener noreferrer" target="_blank" title="">here</a>.&nbsp;

The radical rebuild of Gemini 3: From racer to bluewater cruiser

Sophie Spicknell dives into the rebuild of the racing yacht Gemini 3 with Thorne Yacht Design, to become a luxury yacht called M90. 