Building my very own Megalodon.


On December 6th, 2004 I showed up at Innerspace Systems Corporation for the first day of Meg building.  Leon Scamahorn and Steve Stolen are the CEO and VP of the company, Brian does most of the sewing and Ruby keeps the paperwork flowing.  This is not a huge operation, but the numbers keep creeping up and it wont be long before there will be a need to be in a larger building.  The month of December saw 15 Megs go out the door, pushing the total to around 160 units in service. 

ISC was in the process of earning ISO certification for their manufacturing and as of this writing it has been completed.  The first time they were audited, they passed with an unprecedented 100% perfect rating.  The auditor was very impressed.  Frankly I expected it, when Leon puts his mind to something it will get done.  The care and expertise that goes into the design and build of a Meg rebreather is nothing short of astounding.  In the past months I have spent around 4 weeks at the ISC shop (working on my Meg technician) and have learned plenty about how the units are put together.  An example might be the wiring.  Most places would be satisfied with crimping the tiny wires into Molex pins and then snapping them into the plugs.  These plugs are used on the O2 sensors, the battery packs, and in the handsets, all dry places (excepting the sensors).  ISC assembly instructions specifically require that these wires be measured by ruler, the ends stripped of insulation to specific lengths, crimped to the pins, then hand soldered before being inserted into the plugs.  This extra step of soldering ensures that the connections will remain tight, even though it takes much more time to do it.  I have spent several hours doing exactly that, under magnification.  In building 20 sensor carriages, I cut, stripped, crimped, soldered and clipped 120 pieces of wire.  Every one of them must be perfect, not only was I working on my own rebreather, but other customers units too.  All this time I was under the watchful eyes of Leon and Steve.

  Dutifully hooked up to a static grounding system, I assemble my head plate to the electronics pod and handset cables.  Before touching anything electronic in the shop I had to take a short course in static control.


When Leon told me I was going to spend a whole week building my meg, I had trouble believing him.  I have been building things with my hands all my life, my skills were aplenty, I could solder, use hand and power tools, and knew things about electronics that most never learn.  It still took a week.  By the end of the week I had learned a lot.  Mostly that there are three ways of doing things.  The right way, the wrong way and Leon’s way, which is better.  There is a reason that the Meg is the finest RB on the market, (IMHO) also one of the most expensive.  That reason is summed up in the word “meticulous”.  Even after each Meg is complete, it goes through a 43 point checklist, every function is tested, valve actuated, and button pushed.


  Here I am standing next to my very own meg, rigged and ready for my first pool session.  That pool session lasted 4 hours, it was like a gym circuit course, three of us students swam around the perimeter of a pool, at each corner we preformed a skill, Boom scenario, flood drill, gas loss drill and more.  Buoyancy control was mandatory, and we heard about it if we bumped off of the bottom.


  Steve Stolen, the electronics brain builder, is the father of the Apecs II electronics setpoint controller.  He is retired from Boeing, where he worked on embedded software for airplanes.  The Shearwater electronics system for the Meg was designed by Bruce Partridge and shows up at ISC as assembled boards, ready for testing and potting.  While we are on the subject of electronics, I should mention a bit about ISC philosophy.  Redundancy is the watchword.  The electronics systems used in the Meg consist of a primary system and an secondary system.  The Apecs II has two handsets and an optional HUD, (although almost all units go out with it) the electronics boards are completely separate, although potted into the same physical block, the only commonality is the sensors themselves and even those are electrically isolated.  Two battery packs, separate circuit boards, and separate handsets ensure that even if one handset is destroyed, flooded, or even cut off, the second system will continue to work.  The wire the handsets are connected with costs $16 per foot.  It is military spec wire that will not transmit water through its length, so even if the handset gets flooded, it will not introduce water into the head of the unit.  The Shearwater is designed the same way, but only has one handset and a standard HUD as a secondary.  If the primary system fails (which controls the solenoid) you may still fly the unit manually using the HUD to monitor your PO2 levels.


The HUD is simplicity itself, a single tricolor LED sits in a sealed housing, just in the lower vision of your right eye, attached to the DSV.  It blinks a pattern to let the diver, or his buddy, know what the PO2 is in the loop.  For 1.0 it blinks orange, three times, once for each sensor, then a pause, then three blinks again.  For any value above 1.0 it blinks green, for example, at a 1.1, you would see three green g,g,g,,,g,g,g,,, blinks, for 1.2 you would see three sets of 2 blinks, like this gg,gg,gg,,,gg,gg,gg,,, and so on, at 1.3 it would be ggg,ggg,ggg,,, with the ‘g’s being green flashes and the comma’s being pauses.  This would continue to be true until the PO2 reaches 1.8 where the LED goes solid green, so G,G,G,,,

For values under 1.0, the LED blinks red for each tenth of a point under 1.0.  So .9 would be r,r,r,,,r,r,r,,,

.8 is rr,rr,rr,,,rr,rr,rr,,, any value below .2 the LED goes solid red, R,R,R,,,R,R,R,,,


I have the Shearwater electronics and I have to say it is a nice bit of kit.  The software works as well as any product I have ever owned, never even a hiccup or weird screen, the setpoint stays right where it belongs and the deco info is very consistent and stays very close to my VR3’s information, even if they cannot agree on stop depths.  I follow the most conservative unit during my dives, which is usually the VR3 because I keep the VR3 setpoint on 1.2, the Meg on 1.2 also, while I fly the unit manually a bit higher, which the Shearwater is aware of and the VR3 isn’t.  Calibrating the unit is very easy and if you trap the O2 into the head, with a dust cap and a cap on the scrubber end, it removes the necessity of flooding the entire loop with O2, thereby saving gas and getting a more solid calibration.


I really like the ability to plumb additional gasses into the Meg, there is an option to add in another gas injection valve and I highly recommend it.  This puts an injection valve in your exhale counterlung where you can plug any cylinder that has a LPI hose into it just like a drysuit valve.  This allows jacking into a sling bottle of trimix, or a buddies off board gas, or even an open circuit divers air supply in a pinch.  For long excursions a diver can change out sling bottles, or change out mixes for different depths of the dive.  The only limitation to length of dive is now thermal, or scrubber size.  The stock scrubber that comes with the Meg is a 4-6 hour unit, depending on how cold the water is.  Recently ISC has signed an agreement with Bill Stone, the inventor of the Cis-Lunar RB, to begin building the famous Cis water tolerant scrubber for use in the Meg.  This is an 8 hour radial unit and Leon is also working on a 10 hour unit for the really serious players.  There are some cave divers who are side mounting two megs with separate loops for total RB redundancy in those really deep penetrations.


Part of my Meg technicians course is oxygen cleaning.  No stranger to O2 cleaning myself, as I do it with all the fill whips I make and the thoroughness that ISC is famous for continues here.  Every fitting is taken completely apart, springs, o-rings, lock circlips, even things that will not come into contact with O2 are ultrasonically cleaned, rinsed with filtered hot water, dried off with “Safeair”, examined under UV light,  put into plastic bags, sealed and labeled until use.  Even the Apeks regulators are taken apart and cleaned before being installed onto a Meg.


Ok, I took a break from writing this and am now back at it, today is 23DEC05 and a few things have changed.  ISC is no longer offering the Shearwater system and only offers the Apecs 2.0.  There were some problems with a few Shearwaters and Leon is taking care of the owners of those units.  Mine is still working ok except a couple dives the depth sensor did some weird stuff, not properly tracking my depth and causing excessive deco compared to my VR3.  It has since been acting fine.  I have also taken a head plate and built a COPI head out of it.  What COPI means is Constant Oxygen Pressure Injection, basically its like the KISS system but replaces the solenoid with an orifice, caps the first stage of the oxygen reg to provide constant IP to the orifice and I built a Meg handset with three Datel millivolt meters in it with a backlight so it reads PO2 of the three sensors in the Meg’s head.  This was built as a backup to my Shearwater head if it ever failed on a trip or expedition.  Since I built that head I met Patti, an open circuit diver who has an interest in CCR’s, I trained her on the Sport Kiss and she was going to dive it for a while until she could afford a Meg.  Well she came into some extra dough and I ended up building her a MiniMeg using the COPI head and now she is diving that, so I guess I need to build another head.   : )


At Innerspace 2005 in Cayman this year I was tasked with showing off the Meg and some new developments as Leon was unable to attend, I was allowed to bring and dive the new 7.5 lb radial scrubber pre prototype (no hydrophobic membrane) and showed off the COPI Head I have been diving and testing.  I also showed off and displayed some of my own goodies like the Draeger Backplate conversion, Fill whips, and CCR Dolphin conversion kit that I still have not put into production (sigh, I just don’t have enough time in my days)


So, in conclusion, I can heartily recommend buying, owning and diving a Meg rebreather, the unit is just solid, well designed and extremely well built, you can make an appointment and go build your own unit, or just have one made for you if you don’t feel that mechanical, its not cheap, but rarely is anything of quality.  There is a wait time involved but it is down around 2 months now, there are 3 more employees at ISC now assembling and testing units so things are happening faster now.  Contact Leon to order your very own Meg.  The website is


 Here is a Picture of Patti with her new MiniMeg COPI.




Ron Micjan