Gerris, as the French call the small insects that can move on the surface of the water and are therefore also called water striders here. Inspired by this, the Brothers Raphaël and Erwan Censier on the Quiberon peninsula on the French west coast realised their project under the slightly modified name Gerys 4.7. The two inventors' idea was to build a small and simple boat that all sailors could handle quickly and easily, regardless of age or ability. And: it should be a boat with which everyone can experience the sensation of foiling, i.e. sailing fast on hydrofoils above the surface of the water.
As a naval architect, Raphaël Censier worked out the design, while his brother Erwan, a trained boat builder, was responsible for the realisation. The prototype of the Gerys 4.7 was initially created in the garage at their parents' home. Since then, the company has grown rapidly with its own production facility. The Censier brothers have built five boats in just one year, five more have been ordered and are now under construction. A great success for this ambitious and courageous project.
Gerys 4.7- More than a foiler
However, the Gerys 4.7 is not just a foiler, but rather a kind of hybrid. The boat also sails quite well without the hydrofoils and with a centreboard and rudder alone, for example in very light winds or with inexperienced people on board who want to learn to sail rather than fly. To do this, the J-shaped wings can either be fully raised or completely removed and left on land. This is quick and easy to do. In this case, the guides for the foils in the fuselage are closed with suitable plugs. The Gerys 4.7 is therefore also aimed at sailing schools, which can offer the boat for training both as a displacement boat and later as a foiling boat for advanced sailors. Both modes are possible, without compromise.
The Gerys 4.7 offers inexperienced sailors the opportunity to quickly learn how to sail fast on hydrofoils. The boat floats unusually stiffly - almost like a catamaran - due to the unique shape of the hull with a pronounced concave underwater hull. This allows the crew to concentrate on making the boat fast so that it can soon take off. Ten knots of wind and around 6.5 knots of boat speed are sufficient for this. The furling Code Zero provides a valuable boost, ensuring the necessary basic speed for a successful take-off. In this respect, the additional sail is actually part of the general rig concept, but is only available as an option and must be ordered at extra cost. The standard self-tacking jib is only sufficient for foiling in fresh winds from 15 knots. Once on the stilts, the Gerys 4.7 is a fast ride, and the GPS tracker permanently records double-digit speed values. Record in the YACHT test in single-handed mode with Code Zero: 14.2 knots with half the wind. A little experience in handling planing dinghies naturally helps to keep the boat stable in flight. If you steer carefully and work actively with the sheets, you can foil continuously over long distances, even on deeper room wind courses.
Flying course changes are also easy with one hand
After a few attempts, jibing is also easy without falling off the foils. However, this requires a crew of two if the boat is sailed with Code Zero. With a self-tacking jib and more wind, the flying course change should also work single-handed without any problems. When tacking with only a jib, it is more difficult to get the 140-kilogram boat onto the wings and keep it up. This requires practice and significantly more wind than in the test.
The Gerys 4.7 is launched like any other dinghy via the ramp or on the beach. The brothers have come up with a clever idea for this. Instead of a launching trolley, the wheels are inserted into suitable guides in the side of the hull. When the boat is afloat, they are of course removed again and can be stowed in special compartments in the cockpit. The big advantage: it is still possible to launch the boat anywhere, for example if the trip does not end where it started.
The Gerys 4.7 is built as a GRP construction with a foam core using the vacuum infusion process with epoxy resin. If you add around €10,000 to the basic gross price of €27,370, you can have the hull and deck made of carbon fibre. The associated weight saving is around 20 kilograms, which is significant for a small and foiling boat. Accordingly, three of the five models built to date are made of carbon fibre.
The highly stressed foils and the rudder blade with the elevators are also made of carbon fibre. And instead of the very simple and rather weak aluminium rig, a carbon mast is available as an option. This is stiffer and should therefore offer significantly better performance, especially when foiling at higher speeds and therefore higher loads.
Differences to competitor boats
The current market essentially shows two comparable competitor boats to the Gerys 4.7. Both foilers also come from France. The Birdyfish has an identical format and is also roughly the same weight. The basic version of the model costs around 23,000 euros gross and is therefore slightly cheaper than the Gerys 4.7. The Peacoq foiler, which is built in parts from carbon fibre, is slightly shorter with a hull length of 4.20 metres, but is of a higher quality and more extensively equipped and therefore also slightly more expensive. Its price: 33,300 euros gross, ready to sail.
With boats such as the Gerys 4.7, foiling can now reach a wider audience. And it impressively proves that sailing on hydrofoils is no longer magic.
Technical data
- CE design category:D
- Torso length: 4,70 m
- Waterline length: 4,10 m
- Width:1,84 m
- Draught (with sword):1,20 m
- Mast height above WL: 6,40 m
- Theor. torso speed: 4.9 kn
- Weight: 140 kg
- Mainsail:10,5 m²
- Self-tacking jib:3,9 m²
- Code Zero/Reacher: 12,5 m²
- Shipyard and distribution: Gerys Chantier naval, Erwan & Raphaël Censier; 56410 Erdeven (France), www.gerys.fr
Hull and deck construction
GRP sandwich (opt. carbon fibre) with epoxy and foam core, laminated with vacuum infusion. The foils are made of carbon epoxy
Equipment and prices
- Base price ex shipyard: 27.370 €
- Price ready to sail:27.370 €
- Price Carbon version:39.270 €
YACHT rating
The Gerys 4.7 makes foiling suitable for everyday use and accessible to all sailors. The boat from France works both with and without foils. The price including the foils is moderate
Design and concept
- + Universal range of applications
- + Innovative design
- + Wing removable
Sailing performance and trim
- + Foiling from 10 knots
- + Very easy handling
- + Also suitable for one-handed use
Equipment and technology
- + Carbon fibre foils
- + Insert wheels instead of slip carriage
- - Weak rig in standard
