The purpose was to build not only a fast inflatable boat but also very seaworthy in harsh weather conditions which will make the difference in the difficult and demanding category of 39 feet’s length.
A Rib that will be intended for nautical use and its owner will feel safe and calm when sitting at the helm, which will withstand the passage of time and will not be intended for mass production, as handmade should be functional to the last detail.
A Rib that will have such an efficient hull that won’t need huge horsepower to break the 50 knot barrier, but at the same time will not sacrifice the high levels of damping and directionality that are necessary in bad weather conditions.
With these criteria the foundations for the creation of ZEN 39 were laid.
To achieve the above, the manufacturer Dr. Nikas Nasos personally undertakes the role of Project Manager for each ZEN boat that is built, creating a team not only of specialists, but as he claims, also passionate professionals (i.e. well-known shipbuilding design office, shipyard, etc.), strategically following the model of outsourcing in the construction of each boat.
«The experience of chartering was a great "school" for understanding the wishes of the most demanding customers, but also the need for safe and comfortable voyage in the difficult waves of the Aegean sea. It was quickly realized that the days with the well-known "meltemi" of the Aegean, could not be "lost" and the passengers be dissatisfied», said Mr. Nikas, who has been active professionally in the fields of chartering since 2014 through the company Sea - Arrow, making a dynamic appearance in the rental of inflatable boats over 9-10 meters.
The manufacturer also explains: «the buyer of a ZEN 39 buys tangible quality. Each ZEN 39 is manufactured with Reichhold branded materials. In the construction of the hull there is a combination of vinyl ester and polyester which of course have certification for marine use and this is reflected in their price. For the electrical installation are also used the best materials of the market of well-known companies such as BlueSea, Raymarine, CZONE, tinned and certified cables suitable for marine use and much more.
ZEN 39 has also been certified with CE for cruising category B - offshore and at sea 8Bf».
The hull with steps has many advantages such as increased economy and speed due to the reduction of drag and the ventilation of the rear part of the boat.
ZEN 39 follows the American School of Single Step in its hull, as it has been observed to be extremely efficient and effective in a properly weighed boat, offering advantages over multiple steps such as steering, grip and economy.
At low speeds, however, according to the international literature, it shows intense drag and the boat loses the point of support, where the phenomenon of vacuum occurs. The purpose of the Twin Delta Keel applied in ZEN 39 serves to reduce this phenomenon, so that the boat has higher buoyancy and a larger support surface when riding at low speeds. As the speed increases the intervention is getting less and less as the ventilation of the rear part reduces any friction, balancing the countervailing forces exerted at low speeds. This technology has been patented by ZEN MARINE.
The rails behind the step have been designed to guide the air bubbles between them, in order to achieve greater buoyancy in the specific area. They also stop any vortices created by the step operation after "leading" the air to the desired point.
At tight maneuvers, the boat finds more support and grip on the centrifugal forces as they serve as "tracks" of grip, reducing slippage.
At this sea trial, ZEN 39 was equipped with two V6 4.2L 300hp Yamaha engines, the lower units of which, with a gear ratio of 1.75: 1, were turning the three-blade 15"x 20" Saltwater Series II propellers of Yamaha.
You can see the detailed presentation of the deck of ZEN 39, but also of its performance at sea with the two V8 300hp Verados, in our previous article: ZEN 39 – Twin 4.6L 300hp Verados
So, with the Yamaha on its transom, ZEN 39 was traveling with 19 knots at 3000 rpm burning 2.7 liters for every nautical mile.
At 3500 rpm we ran at 26 knots consuming 2.7 liters per mile, while at 4000 rpm our speed was 32 knots burning 2.8 liters per mile.
These were also the most economical cruising speeds we recorded. It is worth noting that at the speed range from 19 to 32 knots, the fuel consumption is almost constant, which I really consider a great achievement for this hull and is probably due to the Twin Delta Keel implemented by the ZEN marine Shipyard.
At 4500 rpm, we were riding with 36 knots and 3.2 liters per mile of fuel consumption, while at 5000 rpm with 41 knots burning 3.7 liters per mile.
At full throttle, the engines reached 5900 rpm and ZEN 39 at 51 knots of top speed, burning 3.9 liters per nautical mile.
The detailed measurements can be seen in the following table:
You can also compare the performance of Yamaha with that of Verado in the article mentioned above, since the engines were of the same horsepower, the sea trials took place with a similar Rib with relatively similar loads, at the same time, in the same sea area and with the exact same weather conditions.
From this comparison you will find out that the combination with the twin Verados, which although with a "slower" lower unit and shorter pitch of propellers, gave better performance in terms of cruising speed and fuel consumption.
Of course, this does not mean that Verado engines are better than Yamaha ones. As we have often pointed out, the engines or horsepower are not those which propel a boat, but the propellers do that.
So, the answer, then, lies on the propellers’ slip percentages!
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