Megalodon in Holland

For a considerable time the Megalodon rebreather from Innerspace is a well known unit in the United States. Until recently no one in Holland had seen this unit live on the waterside in Holland! Fortunately this has changed. Johan Duits phoned me to tell me he bought a Megalodon. He recently travelled to Egypt to attend a dive course from Chris Hutchinton from Megalodon.

Why would anyone spend $ 7,500.–  dollar on a unit without CE certificate and why not make the training hours in Vinkeveen or Zeeland? That question came up when I decided to hear Johan out.

Johan was not a total stranger to me. He was one of the first to be occupied with MCCR diving (manually closed circuit rebreather diving). During a meeting  of pioneers, some years ago, we met and we talked about cc diving for quite some time.
Recently Johan and I decided to dive together and compare the Inspiration with the Megalodon. This took place last September 17.

Starting point was that we liked to get to know each other better, and of course Johan could not wait to tell me about his new unit. No denying he was very proud of his unit. He referred to ‘it’ as if it was a ‘she’……  Strange. I had to know more!

In Holland there is a well known diving place called ‘De Vinkeveense plassen’. This diving location is 10 kilometres South of Amsterdam and is ideal when Johan drives from Nijmegen and I drive from Oosthuizen (30 kilometres North of Amsterdam). We meet at 13.00 hours and soon after a cup of coffee we both stare at our rebreathers. The first thing that catches the eye is the neatly arranged construction of the Megalodon.

What you can see in fact are a wing, a back plate, a scrubber and two cylinders. Contrary to the Inspiration no housing has been used to hide the scrubber and bottles. The first impression of the Megalodon is that the unit is constructed in a very solid fashion. The materials have been very well chosen and concerning the strength no concessions were made.

Striking is the robustly looking scrubber and the T-pieces on the counter longs that have been constructed without connectors. The loop has been assembled in a really splendid manner, however, it works in reverse direction compared to the Inspiration. The oxygen injector is located on the right hand side (for the diver) as well, however the loop runs anti-clock wise. Of course we discussed the advantages and disadvantages and we concluded fairly quick that each system has it’s own benefits.

The Dive Right Trans Pac wing concept used by Johan offers advantages when using side mounts, however the wide hooks that are used to hook up the webbing on top of the cylinders can cause problems for large persons. The hooks seem to sometimes cause bruises.

Very special is the way of switching the system on and off. For that the scrubber has to be opened. In the scrubber lid there are two switches on the battery housings which activate both hand sets. After switching the unit on the unit has to be put together again. The hand sets will show the Megalodon logo as soon as the switch is turned to ‘on’.

After ten minutes the displays are blank in order to save power, the rebreather is still operational though. By pressing a button at the side the displays are activated again. The calibration takes place with either air or oxygen and should be done for the primary first and thereafter for the secondary display. For this rebreather too we all supposedly are young gods with good eye sight. The letters on the display are rather small.

You have to place the display straight before your face in order to read the numbers and letters. The calibration itself goes without problems, however, it was new to me that the calibration for the secondary display has to be done separately. It appears that the Megalodon has no redundant computer system and the secondary display therefore really functions as a second display.

The secondary display cannot control the solenoid. To clarify: the calibration of master and secondary display are done simultaneously in the Inspiration rebreather. This calibration takes place with 100% oxygen, after which master and secondary display show the measured values.

When the master controller fails, the secondary display takes over the function of the master. Also, the secondary display takes over control, in case the battery of the master is not able to  control the solenoid. This redundancy offers an extra piece of security and enables the diver to stay on CCR mode longer. For the Megalodon the unit does not offer this redundancy. When the primary handset is broken the reading on the second offers the diver the possibility to abort his dive in manual controlled CC or SCR mode.

The Megalodon has a primary that controls the solenoid, and a secondary display that displays cell readings. If the primary is broken there are still the PO2 readings of the cells, however the secondary display won’t fire the solenoid and one has to switch to manual operation. For a well trained CCR diver this not really present a problem.

The primary handset indicates the oxygen sensor values. The Innerspace Systems Corperation has put a reliable controller on the market with the 2.01 Apecs software. The setpoint can vary from 0.4 to 1.4 bar oxygen pressure. New in the Apecs software is the solenoid test. During set up three solenoid injections are carried out that will enable the user to determine the functioning of the solenoid.

The Megalodon can be equipped with a Head Up Display ($ 225.-). During set up the HUD is tested by means of a self diagnosis, however, the diver can perform the same test via the secondary during the dive at any given point in time.

An advantage of the Megalodon is that it does not have the often discussed switches of the Inspiration and the controlling electronics altogether  have been placed in the scrubber lid. In case a cable or wire is destroyed no water can enter the scrubber. The inspiration however, has an ambient system by which the hose to the handsets is under pressure of the loop.

Ambient Pressure Diving has applied this advantage in and has built a fibre – optic system in its new Vision electronics for the Head Up Display. Now the wrist set is not a part of the loop anymore but is still wired to the electronics. The Vision also has all the electronics potted (i.e. watertight sealed) in the scrubber lid. The Vision wrist set – displays both controllers, as does the 2 x HUD light sets i.e. 3 independent displays in total. The Vision handset is at ambient pressure but it is done quite differently to the Classic version of the Inspiration. The Vision wrist set is gel-filled like the mass-production dive computers and is maintained at ambient by a flexible panel built into the handset.

Ambient Pressure Diving has applied this advantage in and has built a fibre – optic system in its new Vision electronics for the Head Up Display. Now the wrist set is not a part of the loop anymore but is still wired to the electronics. The Vision also has all the electronics potted (i.e. watertight sealed) in the scrubber lid. The Vision wrist set – displays both controllers, as does the 2 x HUD light sets i.e. 3 independent displays in total. The Vision handset is at ambient pressure but it is done quite differently to the Classic version of the Inspiration. The Vision wrist set is gel-filled like the mass-production dive computers and is maintained at ambient by a flexible panel built into the handset.

The Megalodon is also equipped with a very nice ADV (Automatic Diluent Valve). This valve is integrated in the left counterlung. It works like the demand system of an oxygen rebreather. As soon as the counterlung is flat, the valve is activated and adds diluent. The valve is very smooth and well hidden.

In the scrubber lid electronics and the battery compartments have been installed. The battery compartments are placed in separate pressure proof houses. The electronics work on various battery types, but have to be soldered.(The Inspiration has a sealed battery compartment. Two independent circuits with easy change, readily available batteries.)

The electronics are placed in the so-called ‘POD’.

The stainless steel Snap-Tite solenoid has been placed nicely onto the scrubber lid. The connection to the oxygen supply has been equipped with a quick lock connector whereas the Inspiration uses a SCUBA standard ( oxygen clean) 2nd stage hose so could be more easily replaced when required. Point of discussion could be the risk of accidentally disconnect the supply..

Over all the unit looks very solid and robust. The three oxygen cells have been placed in axial directions in relation to the gas flow and are placed in a simple removable core. The cell holder is kept in place by a stainless steel locking system and can be de-assembled without any tools. An absorbent cloth is present.

The housing of the scrubber is anodized aluminium and in my opinion indestructible. The locking devices that hold the scrubber lid have been put on the housing by Tig welding.  The scrubber itself has been made from transparent polyethylene and an ingenious spring-loaded system keeps the sofnolime in place.

The axial functioning scrubber has almost the same dimensions as the Inspiration scrubber. The contents of the sofnolime is equal. Striking detail: the advised using time is 4 hours for the Megalodon against 3 hours for the Inspiration. Question is, are the testing conditions for this measurement the same….

( The scrubber time is 3,5 hours or 3 hours at 0 degree Celsius, this information has been supplied later)

The Megalodon cylinders have been built onto the scrubber by means of a Tiger Gear quick release system. Because of the heavy construction of the Megadolon it is easy to use larger diving cylinders. A rebreather housing is not present. Therefore, configuration with other cylinders is easier, however, it makes the unit look less streamlined.

At around two o’clock in the afternoon we slid into the water without problems and had a bubble check at 6 meters. Both units functioned without any problems and we dove 45 minutes to 30 meters. The stability in the water, the balancing and above all the absence of bubbles proved that the Megalodon is at the top of available closed circuit rebreathers.

After previous handsets with or without integrated decompression software, the current Apecs 2.01 offers software without an integrated decompression program and a decent and reliable control. The future 3.0 version will be featured with deco software and a pressure sensor will be present in the scrubber lid.

The Megalodon has made a very robust and reliable impression. On a small number of points improvement is possible. I would consider a redundant control system of the solenoid as an improvement. By diving with Johan Duits I have established that ISC has made a high quality product.

I would like to thank Johan Duits for the nice dive and kind cooperation to let me review this rebreather.

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