By Thomas P.

When the excellent construction quality is combined with the high performance at all levels, it is therefore certain that the product will be at the top of its class. It’s about AirHull, which is a highly remarkable brand in the field of rigid inflatable boats raising the standards of competition quite high.

AirHull 25 Cabin

The principle of AirHull for the construction of each rib is the use of top quality materials without compromising on comfort, functionality and safety. It is worth mentioning that our well-known «marine wood» has been completely replaced by pvc-foam and so the transom, for example, the most important and stressful area of a rib, is 7 times more durable, lightweight, with zero water absorption and enormous corrosion resistance.

AirHull 25 Cabin is another one example that stands out for its excellent build quality and superb attention to every detail, but also for its particularly high performance.

The 7.80m rib offers anything a demanding buyer would need, who wants to travel safely and comfortably, to achieve high top speeds, have high cruise speeds with low consumptions, providing also the ability of a multi-day stay in its finely finished spaces.

Οf course, what impresses at first glance is its innovative hull.
A hull, which when first appeared a few years ago, was radical and challenging for the boatbuilding establishment.

AirHull’s hull is manufactured using the method called «Dimpled & Stepped Hull technology» and consists hundreds of dimples.

AirHull 25 Cabin

Airhull is the first company in the world which uses the technology of dimples in rib’s hulls, with the ultimate goal of optimizing their performance, beyond the greater rigidity they offer.

In order to attract a bit of your interest, we mention that the technology of dimples is applied to the golf balls for many decades now. It is worth mentioning that when a smooth golf ball is struck by a professional, it can cover only the half of the distance than of a dimple one can.

Dimples on a golf ball create a thin turbulent layer of air that clings to its surface and so reduces about half its drag in relation with a smooth ball. In addition, a dimpled ball creates more spin and rises higher into the air because it has more lift.

AirHull, therefore, focused on the two above-mentioned and very important observations concerning the drag and lift, two very important factors which also ultimately affect the performance of each hull.

AirHull 25 Cabin

When all the researches show that dimples on a golf ball can increase lift and reduce drag, it is very interesting to see if the same principle could be applied to a planning hull.

On Deck

The AirHull 25 Cabin is certainly one of the most best looking cabin-ribs and I wouldn’t hesitate to describe it as a «small luxury cruiser», which offers much more than any other rib in this size range.

AirHull 25 Cabin

With great attention even in the last detail, the entire deck is very beautiful and smartly designed, ensuring passengers safety and comfort. Of course, its strongest point is the cabin, which ensures very large interior spaces without adversely affecting the very elegant and sporty appearance of the rib.

Indeed, by descending the one step that leads inside, I felt like I was in a small suite that I never expect to find in a medium sized inflatable boat.

AirHull 25 Cabin

Indeed, by descending the one step that leads inside, I felt like I was in a small suite that I never expect to find in a medium sized inflatable boat.

To the port there is a plexiglas door that leads to a small individual room which houses the electric toilet and wash basin with a faucet and a shower wand.

Opposite, to the starboard there is the fridge and just above a small TV. The hallway, which extends from the entrance door to the bed, has a height of almost 1.80m allowing us to move with great comfort.

Directly ahead is located the bed, with dimensions 2.4m x 1.85m, which can accommodate with great comfort two adults while being an ideal gathering place and playground for children. Beneath the bed there are large lockers for the necessary equipment.

Of course, it would be a great omission if we did not refer to the extra cabin lighting and ventilation. The two elongated windows that extend trough all the way, each side of the cabin, are one of the most impressive elements of the rib, which, beyond their very sleek design, flood the cabin with natural light and offer magnificent, wide-view to the sea.

Most of the cabin roof is occupied by a large hatch, which, except of the excellent ventilation it provides, also constitutes the exit door that gives easy access to the foredeck and the anchor.

AirHull 25 Cabin

Outside the cabin, left and right of it, at the height of the tubes, there are comfortable passageways covered with non-slip material for easy access to the foredeck.
The foredeck of the AirHull 25 Cabin is very smartly designed and coated also with non-slip rubber surface, without any obstacle, thus facilitating comfortable and safe boarding.
Here is also hosted the electric windlass’ locker, which is revealed if we open the large hatch cover on its roof.

AirHull 25 Cabin

AirHull 25 Cabin

To the port and starboard of the cabin entrance door, which is centrally located, are the driver’s and co-driver’s seats.

As a result of AirHull's co-operation with DAIS inox, the seats are equipped with hydraulic suspension system for absorbing vibrations and can be adjustable in height, while they are ideally placed from the engine control and the dashboard, allowing the instruments’ immediate inspection and complete freedom of knees’ movement without the risk of injuries when we are riding in rough seas.
They are designed to provide full lateral support, allowing the operator to have absolute control of the rib even in tight manoeuvres at high speeds or under bad weather conditions.

AirHull 25 Cabin

When seated while underway we will find the footrest, which is coated with non-slip material and extends over the entire width of the deck forming part of the cabin mold, very useful and very comfortable.

And of course, one of the most important features of the helmseats is that they occupy a minimum of space, providing plenty of room and complete freedom of movement between them and the four-seater rear sofa.

At the stern of the AirHull 25 Cabin we find a truly four-seater sofa, with a width of 1.91m and a length of 0.41m dimensions that we will not find in any other 7.80m inflatable boat.

AirHull 25 Cabin

Behind the 4-seater sofa the sun bed aft lays, which is also very comfortable, while the pillows are made by Viotap, coated with waterproof leatherette.

Underneath the sofa and the sunbed of the stern, there is a huge storage compartment that can be easily converted into a second cabin measuring 2.10m x 1.15m.

AirHull 25 Cabin

AirHull 25 Cabin

At sea

Apart from the quality and finish of AirHull 25 Cabin that impressed us, its exceptional ride was really even more impressive. Without any exaggeration, many well known ribs and famous hulls would «envy»  its ride quality.

The Yamaha F 300hp engine - with a Saltwater Series II 15 ¼"x 19" propeller, was hung on the 4-inch power lift that was mounted on a 30cm inox bracket, designed by AirHull, yet another small artwork that adorns AirHull 25 Cabin.

AirHull 25 Cabin

Going from Anavyssos to Sounio, we came up against a swell with a wave height about 1.5 meters and period less than 5 seconds, challenging us to nail the throttle.

We restrained, however, because it was the first test of AirHull 25 Cabin at sea and first we wanted to get the sense of its hull behaviour. Ten minutes of ride were enough to see the hull operation, which was really indifferent to the cabin carried on the bow, giving us a strong sense of driving an open rib.
By pushing the throttle forward, Yamaha's power released, and AirHull was hurling without any lift of the bow.

The 24.5 degrees at the transom offered us an extremely soft ride even when the entire hull was taking of, while the negative slope of the three spray rails in each side kept the spray low ensuring a very dry deck.

Everything seemed that we were riding a very well balanced rib, which, despite the weight of the cabin on its bow, did not tend to nail and was running over the top of the waves without having the need to trim the engine out so much, even when running in following seas.

AirHull 25 Cabin

In each landing, the hull fell down with its keel on the water, without requiring any handling from the driver, offering us an extremely smooth ride.

Having enjoyed the superb and safe ride experience of AirHull 25 Cabin, running in every direction of waves, we finally approached Makronisos Island where, in a calm sea, we would start recording our measurements and evaluate its performance.

I started slowly to push the throttle forward so that I could find the minimum speed at which the rib was standing on plane, while testing different settings of the power lift.
I was surprised when I found out that as I was bringing the propeller close to the water surface, though a 3blade one, the engine’s wake remained flat, and so, due to the reduced load on the engine caused to the reduced lower unit’s exposure in the water, I was able to bring the throttle enough backward keeping the engine’s rpm very low.

AirHull 25 Cabin

Eventually, the rib was getting on plane with great ease and we were travelling with 10 knots at 2400 rpm, having the power lift on the 3rd setting, which shows that, among other things, the dimples work very well at low rpm as well as the 7, 80 meter rib can run very comfortably with smaller horsepower on its transom.

And of course, the above numbers are excellent considering that our test rib was full of loads, with 350 litters of fuel, 2 passengers, a second small engine, windlass and two anchors, and generally all the necessary equipment.
I do not remember having tried another rib of this category, even an open one, which with these certain loads could travel standing on plane at 10 knots, even if its engine was equipped with a larger diameter propeller or a 4-blade one with much more blade area.

AirHull 25 Cabin

Yamaha's 19" propeller got the rib on plane in 4.5 seconds while we reached 30 knots in 10.6 seconds.

With the engine standing on the transom very quiet at cruise speeds, at 3500 rpm the GPS showed 25 knots with a fuel consumption of 1.36 litters per nautical mile while at 4000 rpm we were riding with 31.5 knots burning 1.4 litters per nautical mile.

At full throttle, our top speed reached 48.3 knots, with the engine turning 5900 rpm, an indication showing a great set-up for the specific load and use of the rib.

You can see our detailed measurements in the PDF below:

Perfomance data by  e-Ribbing pdf

Cruising for a long time at low and medium rpm, I was impressed by the capability of its hull to run so high from the water, which is obvious only by taking a simple look at the minimum wakes leaving behind, ensuring high speeds and great fuel economy.

It is characteristic that even when we let our hands from the wheel, the rib was still running in a straight line, even in waves, letting us wondering how it manages to counterbalance the propeller's natural clockwise torque.
But even when we were driving it to its limits, its stability was excellent without traces of chine walking, inspiring great confidence to the driver.

We were feeling the same sense of safety even when we tried tight turns at high speed, without any tendency of a slip sideway and this was not due to the propeller – we just had a 3-blade one-, but to the proper spray rails’ and chine’s inclination.

AirHull 25 Cabin

Of course, one of the brilliant things is the ideal ride attitude – a crucial factor for a rib’s performance - AirHull 25 Cabin’s hull maintains through the entire rpm range, a fact that shows its very good operation, proper weighed distribution and an ideal set-up.

AirHull 25 Cabin

Yamaha F 300hp showed that it ideally matches to the AirHull 25 Cabin’s hull and weight and has provided outstanding acceleration throughout its whole rpm range while keeping fuel consumption low.

Testing the new Yamaha’s 4-blade HS4 15" x 21" propeller the engine was turning 5500 rpm at WOT, achieving 48 knots of top speed, 400rpm i.e. less than the 3-blade S.S. 15 ¼" x 19", which is due to the extra blade and two inches of its longer pitch, minus a quarter of its smallest diameter.
Ideally, for this particular boat-engine combination the HS4 15" x 19" prop would be, but is not currently available in this pitch size.

It is obvious that if we switch to a proper 21" pro-finished 4-blade propeller, AirHull 25 Cabin will easily overcome 50 knots with these loads, will travel at even faster speeds at 4000 rpm, resulting in better fuel economy, and of course will be able to flirt with 55 knots if we run it with the minimum possible weight.
A speed that seems inaccessible, even for open inflatable boats of about eight meters!

...keep Ribbing!

 

 

AirHull 25 Cabin
  • Length overall: 7.80 m
  • Beam: 2.85 m
  • Weight: 950 Kg
  • Number of tubes: 4
  • Tube diameter: D - 0.38-0.46
  • Bow’s deadrise: 52
  • Transom’s deadrise: 24.5ο
  • Max hp: 350
  • Fuel capacity: 380lt

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.