Recommended options on new rebreather (Optima CM)

[mdwalter]

Would like to get the experts opinion on which options to get with a new Optima CM. Here are the ones I identified so far:

• Nerd 2 as controller paired with HUD — no cables going to the wrist
• XT1 first stage — rotating turret
• Upgrade the ADV/MAV to a high flow quick disconnect QC-6 fitting —recommended for diving deeper than 40m
• pull dump to replace the bulky drysuit style dump for the counterlung
• Shut off on oxygen line

Do these make sense to you?

Nerd2 - I was given the choice of Nerd or Petrel when I ordered mine. I had never tried a Nerd and was nervous as to whether I would like to have something in my line of sight all the time and whether I would really be able to see it properly with my high prescription (-8) dive mask and my 50+ year old eyes that will soon need bifocals. I already find my arm is too short to see the small print on a wrist mounted computer. Now that I have used the RB for a while with the Petrel, I do find that having to take the Petrel on and off my arm when taking the RB on and off is one of the few annoying things about it. Also, when I side mount my dilout, the cable sometimes gets snagged on the valve of my left tanks depending on how I move my left arm. The up side is the petrel balances well with the Perdix AI on my other arm.

XT1 first stage - I see no need for a turret on the O2 (though I also see little point in having a turret on any other regulator either). The one that comes with it works perfectly and is already detuned for the lower IP required for the solenoid, so just use that.

QC6 for ADV/MAV - Mine came with this upgrade already installed, and at first I thought it was a great deal. But honestly, with how little the ADV needs to run and for as little gas as I need to add when using it as a MAV, I sometimes think I's rather "downgrade" to a normal LP inflator connector. Why? I use my RB with several different OC bailout solutions (BM doubles, SM 2 tanks, and maybe some day single tank BM). That means I needed to buy several more QC6 connectors and regulator hoses for the different regs I use for these OC configs. One QC6 and a reg hose costs more than 4 LP inflator hoses. So I made myself a cheater so I can plug different dil tanks in as needed without paying $125 per reg to add the QC6.

Pull dump - I got both dumps when I bought mine. I much prefer the slimline pull dump over the giant drysuit dump that came preinstalled. It's much easier for dewatering and it's much less obtrusive.

O2 shutoff - at the advice of my instructor, I removed the shutoff on the O2. Instead, I just use the O2 valve knob to shut off the O2 when needed. I still have the shutoff on the ADV, as that really serves a purpose.

 

[mdwalter]

Interesting, I think I would be tempted to run the NERD and strap a Petrel to the back of the unit to pull out if the NERD conks out..

I'm not sure that is a supported config, but if it can be made to work here are some of the issues I see with how you want to do it. If you plug the Petrel into the green control bus and the Nerd into the blue monitor bus, you'll see everything on the Nerd (I think) but you will have to pull the Petrel out every time you want to make a change (CC>BO, .7>1.2, switch dil gas, etc.)
If you plug them in the other way, the Nerd will be in control, and the Petrel will basically just be a high tech HUD you have to dig out and put on your arm to monitor.
Or, it's possible that a Nerd or Petrel plugged into the monitor bus may not work at all. I have not tried it.

 

[LFMarm]

QC6 for ADV/MAV - Mine came with this upgrade already installed, and at first I thought it was a great deal. But honestly, with how little the ADV needs to run and for as little gas as I need to add when using it as a MAV, I sometimes think I's rather "downgrade" to a normal LP inflator connector. Why? I use my RB with several different OC bailout solutions (BM doubles, SM 2 tanks, and maybe some day single tank BM). That means I needed to buy several more QC6 connectors and regulator hoses for the different regs I use for these OC configs. One QC6 and a reg hose costs more than 4 LP inflator hoses. So I made myself a cheater so I can plug different dil tanks in as needed without paying $125 per reg to add the QC6.

What do you mean with a “cheater”?

 

[mdwalter]

What do you mean with a “cheater”?

That's a male BC connector screwed into the regulator half of a QC6 so I can unplug my regular (QC6) dil connection, plug thisd thing in, and then connect any other tank that has a LP inflator hose. This is useful for things such as:
1) my regular (sidemount) dilout tank is empty or fails (etc.) so I can plug in the other one using the hose that normally feeds the dry suit
2) I want to switch from bottom gas dil (QC6) to 50% deco dil when I get to 70 ft, but I don't want to buy another $100 QC6 connector for it
3) I decide I'd like to use a different regulator than I normally do (i.e. not the one that already has the QC6) and it already has an extra LP inflator hose.
4) O2 MAV fails, so I can plug O2 into dil MAV instead (this one's a bit far fetched)

 

[LFMarm]

That's a male BC connector screwed into the regulator half of a QC6 so I can unplug my regular (QC6) dil connection, plug thisd thing in, and then connect any other tank that has a LP inflator hose. This is useful for things such as:
1) my regular (sidemount) dilout tank is empty or fails (etc.) so I can plug in the other one using the hose that normally feeds the dry suit
2) I want to switch from bottom gas dil (QC6) to 50% deco dil when I get to 70 ft, but I don't want to buy another $100 QC6 connector for it
3) I decide I'd like to use a different regulator than I normally do (i.e. not the one that already has the QC6) and it already has an extra LP inflator hose.
4) O2 MAV fails, so I can plug O2 into dil MAV instead (this one's a bit far fetched)

It makes a lot of sense. Does anybody know if QC6 is really required over the standard LP inflator hose for diving deeper than 40m/130ft?

 

[grantctobin]

It makes a lot of sense. Does anybody know if QC6 is really required over the standard LP inflator hose for diving deeper than 40m/130ft?

On a BOV yes, on a MAV no. I would say if you’re trying to go open loop at 100+M using a flow restricted inflator hose into a potentially flow restricted inflator valve, you’re going to have a bad time.

 

[LFMarm]

On a BOV yes, on a MAV no. I would say if you’re trying to go open loop at 100+M using a flow restricted inflator hose into a potentially flow restricted inflator valve, you’re going to have a bad time.

Makes sense. Then for my specific need (DSV+MAV), I will not need the QC6 and can keep the flexibility of the LP inflator hose connection.

 

[J-Vo]

Makes sense. Then for my specific need (DSV+MAV), I will not need the QC6 and can keep the flexibility of the LP inflator hose connection.

I use standard inflator hoses. Works fine, but some hoses are more restricted than others. I have had to toss a few as they wouldn't deliver dill as fast as I can inhale.

 

[tbone1004]

Late to the game.

Would like to get the experts opinion on which options to get with a new Optima CM. Here are the ones I identified so far:

• Nerd 2 as controller paired with HUD — no cables going to the wrist
• XT1 first stage — rotating turret
• Upgrade the ADV/MAV to a high flow quick disconnect QC-6 fitting —recommended for diving deeper than 40m
• pull dump to replace the bulky drysuit style dump for the counterlung
• Shut off on oxygen line

Do these make sense to you?

NERD Controller-fine if you like the NERD. With HUD is a lot in your face but if you intend to don/doff the unit in the water it will certainly make things easier

XT1-no strong opinions

MAV to QC-6-who recommended for diving deeper than 40m? If you are diving a high helium mix, which on a CCR you need to be, then the gas density will never exceed 30m. Since flow is based on density of media and pressure there is no need to go to a QC6 because you're going deep. Go to a QC6 if your teammates use QC6 or you intend to use a BOV at some point but there is no need for anything bigger than a BC inflator if you use adequate helium mixes. Exception is if you were taught to open loop breathe on the CCR through the ADV which is possible through the BC inflator hose but you do have to be a bit patient as it can't deal with the initial in-rush flow when you start an inhalation cycle. It's a weird feeling but in practice you basically start inflating as you're finishing your exhale through your nose so there is a bit of a head start. Either way, no need for a QC6 unless you have a BOV or you are putting a second stage on the same LP manifold.

pull dump-personal preference here and it depends on your intended usage. I use mine to dump water more than relieve pressure and the drysuit is better at relieving water than the pull dump.

Shut off on O2-no, just no no no. the bloody O2 tank is about 3 inches farther away than the shutoff would be, just turn the tank off.

Mention of swapping computers-SOLO and OBOE are not interchangeable. You can't just pop a monitor into the controller, they are on different sides of the bus and connect to different boards internally so there is no "swapping". Admittedly you only need the controller to change setpoint so if you aren't planning on changing the setpoint then it doesn't matter which one you "use" but that is something to be aware of. While a controller may be able to plug into a monitor port, a monitor doesn't magically start working as a controller when you plug it into the controller port. RTFM

The solenoids do not require a lower IP, you can use a normal IP in them perfectly well. The reason for the lower IP because there is lower mass flow through the solenoid. Lower mass flow means the solenoid is opened more often which provides a more stable ppO2. They work perfectly fine at 135psi.

 

[mr_v]

@LFMarm - have you used NERD as a controller in an emergency or serious task loaded drills, such as SCR?