By Thomas P.

Top class, excellent design, great performance!
These definitions come spontaneously into my mind trying to describe the AirHull 25 S rib, which is worthily at the top of its class, constituting a real jewel in the field of the Hellenic Boatbuilding School.

AirHull 25 Sport

Gaining the respect and appreciation of anybody considered as objective who doesn’t hesitate to reward the remarkable efforts, AirHull's ribs stand out at any level. It is really impossible to distinguish any imperfection even when inspecting them in every detail.

The perfectly maintained and polished molds combined with materials of top quality and the manufacturer's inexhaustible passion for producing excellent products are some of the key elements that make up the recipe of this success.

The category of this size range inflatable boats, may be the most popular in the market since it gathers the most advantages without, at the same time, carrying any negative elements that larger ribs have in terms of cost, maintenance, fuel consumption, ease of transport and launching as well as the requirement of using two engines.

AirHull 25 Sport

One of the main reasons that lead someone in the 7-8 meter rib’s category is that among his priorities are also the long trips, with the best possible quality of riding combined with low fuel consumption, features that, as we shall see below, are included in the long list of AirHull 25S capabilities.

AirHull 25 S runs on our well-known deep V hull which, with a sharp bow entrance of 52 degrees and a transom deadrise of 24.5 degrees, is characterized by two ventilated steps and the world's unique application of dimples technology.

The excellent design of the steps, coupled with the hundreds of dimples located on most of the hull, lead to a proper ventilation and a significant friction’s and drag’s reduction, having as a result AirHull to be able to run faster, without requiring a lot of fuel, and record unique performances.

AirHull 25 Sport

On each side of its hull, we distinguish a medium-sized chine and three spray rails, the negative slope of which ensures a completely dry deck during the ride, while enabling to experience remarkably sharp turns without any tendency of a slip sideway even when running at high speeds.

On deck

The elegant design of the deck and the ultimate harmony of all the components that make it up, ensure maximum functionality while at the same time highlighting the sporting character of AirHull 25 S.

AirHull 25 Sport

The stylish console is centrally located leaving a large space on its port and starboard for comfortable passenger movement.

The inclination of the instrument panel is ideal to ensure their direct inspection by both the driver and the co-driver.

The engine's control is centrally located, nested in its own separate area, while the steering wheel is on the left side of the console. Just above the steering wheel there are the engine’s gauges and GPS, while the electric switches are located in the right.

Even the design of the right and left handholds on the console is ideal by providing the necessary support for the driver and co-driver.

AirHull 25 Sport

The engine's control is centrally located, nested in its own separate area, while the steering wheel is on the left side of the console. Just above the steering wheel there are the engine’s gauges and GPS, while the electric switches are located in the right.

Even the design of the right and left handholds on the console is ideal by providing the necessary support for the driver and co-driver.

It is worth mentioning that the selection valve of the fuel tanks is on the right and a little lower than the control panel, in a special cabinet, so we do not have to go back every time we want to change our fuel supply.

Lower on the console the footrest is integrated which is lined with anti-slip material and has the right inclination for resting the legs when driving seated.

AirHull 25 Sport

AirHull 25 Sport

The interior of the console is 1.75m in height and can be comfortably accommodated with a toilet and a second shower. Its access is possible from the front side of the 50cm x 90cm tilting door, which has a built-in seat.

The two separate polyester bucket driver and co-driver seats match so well with the console but also with the overall elegancy of the rib having an ideal distance from the helm and leaving plenty of room around them for uninterrupted passenger movement.

These seats are the result of the exclusive collaboration between AirHull and Dais Inox Company, offering very good lateral support with a shock absorbing mechanism and adjustable hardness and height.

AirHull 25 Sport

Both seats have rear-mounted stainless steel handles to support passengers when they want to travel upright.

At their lowest point there are two particularly useful storage spaces, while on the left side of the driver's seat there is a special fire extinguisher receptacle, and on the right side of the co-driver's seat there are the stainless steel filling caps of the fuel tanks.

AirHull 25 Sport

In front of the console there is plenty of room for free movement of passengers, while afterwards we meet the polyester superstructure where the big locker of the bow is placed which is revealed when we open the two separate hatches of its roof.

Under the bow locker the 50-liter water tank is also located.
With the appropriate extension, the bow sun bed measures 1.95m x 1.50m and is capable of accommodating two adults with comfort.

AirHull 25 Sport

On the polyester bow we meet the foredeck which is very smartly designed and lined with anti-slip material.

The cleats are placed laterally and the windlass internally, leaving free step without any obstacle, thus facilitating comfortable and safe boarding.

The windlass is revealed if we open the large hatch on the foredeck’s roof. On the left are the stainless steel water filler cap and the windlass's switches, while the locker has quite great depth for the chain.

AirHull 25 Sport

The aft couch is four-seater and accommodates three separate storage spaces. Centrally located is the specially designed and self-draining space for the 55 liter refrigerator housing, while on its right and left are the watertight spaces of the rib’s battery.

Immediately backwards, the aft sundeck with a total width of 2.10 meters and a length of 95 cm rises, below of which there is the largest storage space of the rib, where the bilge pump, the pressostat shower pump and a part of the electrical installation are housed, the latest of which is perfectly designed and protected with plexiglas.

AirHull 25 Sport

AirHull 25 Sport

At Sea

The AirHull 25 S is not a new model since it has been in production for several years. The reason that challenged us to try it was that the 300-horsepower Yamaha was mounted on its transom for the first time while its fuel tanks were made of aluminium, reducing some of the rib’s weight.

AirHull 25 Sport

We had the AirHull 25 S at our disposal for a whole day, a fact that allowed us to understand better the behaviour of its hull and thus be more objective in our judgment. On the day of our trial we were fortunate to have 4bf seas and so we would be able to validate the quality of its ride.

Initially, we were confined to short rides by turning our bow against each direction of waves, without pushing the rib to its limits. Our first goal was to get a feeling of how the AirHull 25 S hull co-operates with Yamaha's 300hp engine coupled with its mounting height and the HS4 15" x 21" 4-blade propeller we had matched. The existence of the 6-inch power lift on the rib’s transom enabled us to experiment enough so as to achieve the best possible set-up.

Once again, we were finding out the excellent AirHull’s ride quality, the hull of which responded remarkably in head, beam and following seas.

The robust construction, exceptional agility, stability even in sharp turns, dry and soft cruise resulting from the very good hull design are just some of the key features included in the long list of AirHull 25 S capabilities.

AirHull 25 Sport

However, although the numbers, even they are relatively and influenced by many factors, are the mirror of each rib’s performance and clearly the most objective judge of all, often overshadowing even the best words, let’s look at some of our measurements.

It is noteworthy that the planning speed was steadily under 4 seconds either we had set the power lift on its lower position or at position 1 or 2. The acceleration time from 0 to 30 knots was less than 8 seconds with the engine mounting height setting from the position 0 to 2 of the power lift. The above figures are particularly low and impressively implying explosive acceleration.

With 4 bf seas offshore during our sea trial, three people and 120 litters of fuel, the rib was standing on plane at 1900-2000 rpm maintaining a constant speed of 9 knots, a really great performance that we will rarely see on other boats. And it's truly very important to be able to travel for many hours in heavy weather being on plane at low speeds, which means lower fuel consumption and more comfortable cruising.

AirHull 25 Sport

At 3100 rpm the cruising speed ranged from 25 to 27 knots, depending on the sea conditions, with the fuel consumption dropping even under one litter per nautical mile. The remarkably point, is not only the low fuel consumption but the overall lift of the AirHull 25 S hull which was running high in the water and maintaining an ideal riding angle despite the low engine’s rpm, when many boats at these rpm ride almost immersed in the water with a clearly tendency to raise their bow high. Indicatively we mention that we were travelling for about half an hour, with these specific speeds at 3100 to 3200 rpm, actually enjoying the soft and light ride of AirHull 25 S.

After 3200 rpm the Yamaha's torque was explosive and just a simple touch of the throttle was enough to stick us back, on the backrests’ seats. Of course, the explosive throttle response is not only a result of the Yamaha's huge torque at low rpm but also the result of its combination with the 4-blade propeller and the very good geometry of the AirHull 25 S hull, which stands high in the water at the particular rpm which means reduced wet surfaces and thus significant reduction of the propeller’s slip.
The excellent combination of all the above factors reveals a very good match that takes off the performance.

At 3500 rpm our speed was 31 knots burning 1.1 litters per nautical mile while at 4000 rpm we were travelling with 35 knots burning 1.28 litters per nautical mile.

In other words, we are able to quickly cover a distance of 100 nautical miles by consuming almost about 100 litters.

At WOT, the engine reached 5700 rpm and our speed at 52.2 knots. What was remarkable is that although the entire length of the hull was high in the water, its stability was excellent with no signs of chine walking, largely due to the wide pad and the intensively negative slope of the lower spray rails, which help the hull to retain its minimum water at high speeds.

AirHull 25 Sport

Of course, the distributions of loads as well as the perfectly balanced rib play a very important role revising a crucial factor especially in the stepped hulls. And the perfect balance of the AirHull 25 S is certainly not accidental, but it hides endless hours of study, effort and sea trials.

You can see our detailed measurements in the PDF below:

Perfomance data by  e-Ribbing pdf

From just a curiosity, at the end of our sea trial, we raised the engine excessively high until the power lift’s indicator show the number 5, in order to see the behaviour of the rib at this mounting height. The propeller’s bite and extraordinary acceleration were also impressive, even at 4000 rpm, despite the very high setting of the engine and operation of the propeller on the surface of the water, which insisted on showing no particular signs of any ventilation.

AirHull 25 Sport

With absolute certainty we can say that the Yamaha F 300hp is ideally matched with the AirHull 25 S hull, delivering great acceleration.
It is also clear that the rib performance can be further improved by switching to a 15 ¼" x 21" 3-blade Saltwater Serries II propeller, if we consider that 3-blade propellers typically deliver lower fuel consumption and higher top speed than the 4-blade ones, while it will allow the engine to gain about 150 rpm more, approaching to its redline of 6000 rpm.

...keep Ribbing!

 

 

Airhull 25
  • Length overall: 7.45 m
  • Beam: 2.85 m
  • Weight: 950 kg
  • Champers: 4
  • Tube's diameter:0.38 - 0.46 m
  • Bow deadrise: 52ο
  • Transom deadrise: 24.5ο
  • Max horsepower: 350 hp
  • Fuel capacity: 680 lt

Manufacturer:
AirHull
Pavlos Kalogeropoulos
Tel.: +30 210-6717711
www.airhull.gr
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.