Extraordinary boats: Scow-bowed Ace 30

The Ace 30 is a new design intended to bring the scow bow concept, popular among offshore racing machines, to IRC yachts

Scow bow designs are still very rare in the UK and mostly elsewhere in northern Europe. The exception is France, especially on the Atlantic coast, where their distinctive spatula-shaped forward sections are an increasingly common sight on Mini 650s, Class 40s and IMOCA 60s, and now the new Ace 30.

Scow designs are now even pushing into the cruising domain. The Mojito 650, for instance, is a detuned version of the phenomenally successful Maxi 650 that took five of the top nine places in the last Mini Transat, with demand outstripping the rate at which builder IDB Marine can produce them. The Mojito 650 offers huge accommodation volume for a 21-footer, along with distinctive style, yet still offers planing performance downwind and a surprising turn of speed close hauled.

With the explosion of interest in short-handed offshore racing on both sides of the English Channel, it’s perhaps no surprise to find a new scow bowed yacht aimed at IRC racing, even though that’s a much harder challenge to overcome. While planing designs now dominate among new IRC boats launched in the 40-45ft and upwards sector, the opposite is the case for smaller boats, where heavier displacement designs still dominate.

Scow hulls aim to keep the boat going above the waves rather than through them. Photo: Photo Ludovic Fruchaud/EYOTY

The problem is that getting a decent IRC rating for a smaller lightweight boat is seen as being next to impossible. As a result, some of the most successful designs this season, such as the
JPK 10.10 and Jeanneau Sun Fast 3600 – between them accounting for all of the top four places in the 2022 RORC overall season’s points, weigh 4 or 5 tonnes and therefore have relatively heavy displacement length ratios.

Attempting to disrupt the status quo with a radical lightweight design is a brave move, but that’s what the new Ace 30 is hoping to achieve. At the same time, the boat is intended to appeal to former Mini 650 owners – this class has a huge number of alumni, many of which continue to seek fast and innovative new boats.

Downwind performance should be impressive. Photo: Ludovic Fruchaud/EYOTY

Ace 30 – a tardis concept

When viewed from the dock the Ace 30 looks like a small boat with slab sides and a big chunky coachroof. However, once on board, whether above or below decks, it feels like a much larger vessel with very impressive stability. The reverse sheer is not a style statement. It increases the intrinsic stiffness of the hull, increases volume in the central parts of the accommodation and reduces weight in the ends of the boat.

The deck layout is very similar to that of JPKs and Sun Fasts, although the benches forward lack even the smallest of coamings. Even so, anyone who has sailed these or similar boats will feel instantly at home.

My sail on board wasn’t in optimal conditions for the boat, with true wind of mostly 5-6 knots. Nevertheless, it immediately proved to be quick, with boat speed of 6-7.5 knots even when VMG running at 140° true wind angle in these light airs. Upwind 5-6 knots was possible, though you have to sail at wide angles of around 50° TWA and it’s important not to pinch too close. Bearing away as little as 5° can increase boat speeds by 1 knot and markedly reduces slamming.

The cockpit layout of the Ace 30 is broadly similar to that of Sun Fasts, JPKs and similar boats of this size. Photo: Ludovic Fruchaud/EYOTY

In stronger winds during the European Yacht of the Year trials at La Rochelle, we could see the boat matching the close hauled speeds of around 7 knots achieved by the much larger Linjett 39 and First 36, albeit sailing noticeably lower.

Like other scows it’s when power-reaching and downwind in a blow that this boat will really come into its own. A very different setup and sail trim are required compared to conventional boats. The mast is very well aft in the boat and needs a lot of both mast rake and bend.

Transom-hung rudders reduce weight and complexity, while also allowing easy adjustment of toe-in angle. Photo: Ludovic Fruchaud/EYOTY

Designer and builder Antoine Mainfray of Atelier Interface in La Rochelle says he worked hard to keep the IRC rating down, while also keeping the weight of the boat low. During the design process he applied for three trial certificates, with the last of these coming in at a respectable 1.014. During the build he moved the engine back slightly to trim the stern down, made the interior more comfortable, and further tweaked sail sizes.

The final rating of 1.001 also reflects the setup of the first boat, which is optimised for transatlantic races such as the Transquadra, Cap Martinique, and RORC Transatlantic. It therefore has a very short luff J2 jib and is not rated with the J1 that would be needed on shorter offshore races, where more light air upwind sailing is likely to be experienced. Nevertheless, this is a figure very close to that of older successful and heavier designs such as the JPK 10.10 – and several per cent lower than the Sun Fast 3300.

The stability of this boat is such that the J4 doesn’t need to be used until the true wind speed is greater than 25 knots. Equally, the 100m2 A2 spinnaker – a very large sail for a boat of this length and weight – is intended for use in true wind of up to 25 knots, after which you switch to the A5.

Eco footprint

Sustainability is also an important element of the concept and Mainfray, who has also recently delivered a foiling Mini 650 that uses bamboo – “a material that can have a negative carbon footprint” – in the structure, appears to do as much as possible to live by his values.

This is one of the reasons for the plywood build of the Ace 30. The carbon footprint of this boat is 1.9 tonnes, whereas an equivalent GRP hull would be over 6 tonnes, even before making allowance for building moulds.

Plywood is also inherently lightweight and stiff, making it ideal for building one-off raceboats and small production runs without a mould. This boat also includes carbon reinforcement, primarily around the chainplates and a spider of unidirectional fibres on the coachroof.

The okoume ply used for the hull is mostly 12mm thick, with 15mm used for some parts of the structure. Outside of this are two layers of biaxial rovings, plus a third at 45°. These are laid up using bio resins and increase strength, particularly around the keel, where the lay-up is thicker, while also providing impact resistance to protect the timber. Inside the boat, the ply is coated and impregnated with epoxy, but is not sheathed with glass.

Interior is functional but spacious and light and includes a settee each side, central table, nav station and galley. Photo: Ludovic Fruchaud/EYOTY

The coachroof is partly made of GRP, using bio epoxies and recycled PET cores, but again without a mould.

Mainfray says that in areas without much curvature the sandwich can be laminated and infused in one go. Where complex curves are required he moulds one skin on a jig or template, then adds the core material and the second laminate in another phase.

The computer monitor is on a big swing arm, so can be moved to each side of the boat or viewed through the companionway when on deck. Photo: Ludovic Fruchaud/EYOTY

Roomy interior

Below decks is functional, but surprisingly spacious, with enough volume to make a reasonable ultra-fast cruiser. The low freeboard means there are no sole boards, so you stand on the hull and have to step over the structural members to get around. This gives reasonable 1.75m (5ft 9in) headroom near the table, increasing to well over 6ft under the cuddy.

The saloon has a long settee each side, with sitting headroom under the very wide side decks, plus a central table that houses the diesel tank, keeping weight central and low down. There are twin open plan double berths aft, and seats each side for taking a nap near the companionway.


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