Newbie JJ diver advice

[bipolarbear]

Background: OC TDI Adv Trimix, Adv Wreck etc diver. I am an entry level diver with around 250 total dives, but ~175 of those have been accelerated deco dives, and ~100 at the 50-90m range. I've been diving for 4 years.

I just bought myself a JJ and will be doing my MOD1 / Helitrox in the Gili Islands. I had a couple of questions I was hoping to get some feedback on:

1. I almost exclusively dive 'tropical', even for 2hr+ hypoxic trimix level dives with doubles + 3 decos/travel gas. What can I expect trim wise from switching to the JJ at the Mod1 level? I dive t-shirt, tech shorts and heavy jet fins. I understand the JJ can be hard to trim out in this configuration.
2. It's been almost a year since I did proper technical diving. I will have 5 days in HK where I can get in the water with doubles and stages if necessary to get back up to speed. Aside from being comfortable with bailout / gas switches, is there anything in particular I should focus on prior to beginning my JJ training?
3. I have a spot on a Bikini Atoll trip booked in late September (3 months from now). I have no work commitments until then and can conceivably dive twice a day on the JJ and work up to Mod 2. Any thoughts on whether I should just dive OC (deep air, unfortunately) in Bikini or take the JJ as a very fresh mod 2 diver?

 

[nickbutcher]

Background: OC TDI Adv Trimix, Adv Wreck etc diver. I am an entry level diver with around 250 total dives, but ~175 of those have been accelerated deco dives, and ~100 at the 50-90m range. I've been diving for 4 years.

I just bought myself a JJ and will be doing my MOD1 / Helitrox in the Gili Islands. I had a couple of questions I was hoping to get some feedback on:

1. I almost exclusively dive 'tropical', even for 2hr+ hypoxic trimix level dives with doubles + 3 decos/travel gas. What can I expect trim wise from switching to the JJ at the Mod1 level? I dive t-shirt, tech shorts and heavy jet fins. I understand the JJ can be hard to trim out in this configuration.
2. It's been almost a year since I did proper technical diving. I will have 5 days in HK where I can get in the water with doubles and stages if necessary to get back up to speed. Aside from being comfortable with bailout / gas switches, is there anything in particular I should focus on prior to beginning my JJ training?
3. I have a spot on a Bikini Atoll trip booked in late September (3 months from now). I have no work commitments until then and can conceivably dive twice a day on the JJ and work up to Mod 2. Any thoughts on whether I should just dive OC (deep air, unfortunately) in Bikini or take the JJ as a very fresh mod 2 diver?

You will almost certainly be tail heavy. In tropical water with a Fourth Element Thermocline - similar to Sharkskin and neutrally buoyant - I had to ditch jet fins and even with Mares Quattros my feet would sink when I stopped finning.

I don't do this kind of diving often enough to try to find a solution but you could try fitting some of that foam the togs use with their camera rigs to the top of your fins if you find it annoying.

Bikini is easy enough diving and much more enjoyable with some helium in the mix if you want to remember a trip of a lifetime. I was a fairly fresh MOD 2 JJ diver the first time I did it.

 

[Rayk]

1. JJ Sucks big time in warm weather wet diving. I use carbon backplate, aluminum cylinders and travel stand and deep6 Eddy fins to mitigate the issue. Like stated above, seahorse trim is kinda unavoidable.
2. I am coming from backmount doubles and stages background too, and at MOD1/Tec1 level that’s pretty straightforward. However it starts getting complicated at Normoxic and Hypoxic level pretty quick and that depends how do you want to carry bailout, if you want to stick with stages, be prepared to do lots juggling and carrying tanks on the leash. I sidemount my bailouts and that makes life much easier in few aspects.
3. Air travel with JJ is discouraging, specially if you have to fly economy. Level of discouragement depends on you, to me it was discouraging enough to buy second CCR for travel.

I hope it helps and welcome to the club.

 

[Heat Miser]

Congrats on moving to the silent side.

Are you saying your going to do Mod 1 Helitrox (45m) soon and hope to knock off Mod 2 within 2 months of that? It seems ambitious to me. I don't know Will personally, but I know some very good divers that he has told to go away and come back when they had practiced more (i.e. a year)

I was also told recently, that MOD 1 now has a maximum deco time, so whilst Bikini isn't a heck of a lot deeper than a MOD 1 cert on average (say 50m) it clearly is a lot more deco.

Best wishes ... you'll need alot of ascent and stop work, belting up and down an ascent line very GUE Fundies esk, to practice bouancy and minimum loop volume.

 

[kensuf]

Congrats on moving to the silent side.

Are you saying your going to do Mod 1 Helitrox (45m) soon and hope to knock off Mod 2 within 2 months of that? It seems ambitious to me. I don't know Will personally, but I know some very good divers that he has told to go away and come back when they had practiced more (i.e. a year)

I was also told recently, that MOD 1 now has a maximum deco time, so whilst Bikini isn't a heck of a lot deeper than a MOD 1 cert on average (say 50m) it clearly is a lot more deco.

Best wishes ... you'll need alot of ascent and stop work, belting up and down an ascent line very GUE Fundies esk, to practice bouancy and minimum loop volume.

The maximum deco time is just during training.

 

[Heat Miser]

The maximum deco time is just during training.

I'm not an instructor and I know you are a good one but someone needs to inform SSI instructors of that rule:

SSI CCR Diver / CCR Extended Range - JJ​

The CCR Extended Range program qualifies you to dive to a depth of 40 meters using air, or up to 45 meters using trimix as a diluent with a maximum decompression time of 25 minutes.

 

[kensuf]

Standards

xkcd.com

 

[Heat Miser]

@kensuf
I was wrong here is what the SSI standards say:

XI. Certification
Upon completion of all academic and in-water requirements, the SSI Professional may issue the program’s digital certification card.
The SSI CCR Extended Range certification entitles the holder to dive autonomously:

• In environments similar to those of the diver’s training and experience,
• With the equipment configuration used during training,
• To a maximum depth of 40 meters,
• Using an air diluent,
• For a maximum accumulated decompression time of 10 minutes,
• With an equally- or more-qualified dive buddy.

In addition, the SSI CCR Extended Range Trimix certification entitles the holder to dive autonomously:

• To a maximum depth of 45 meters,
• Using trimix breathing gases

 

[kensuf]

Yeah, I've never been certified for a single thing through SSI so I don't know what to tell you about their standards.

In training, no instructor with an agency following ISO standards is allowed to go beyond 10 minutes of decompression. My understanding is that ISO Standard 24805 does not specify that this 10 minute rule is in place once the person is certified. Different agencies may have different approaches to how they handle it.

 

[bipolarbear]

1. JJ Sucks big time in warm weather wet diving. I use carbon backplate, aluminum cylinders and travel stand and deep6 Eddy fins to mitigate the issue. Like stated above, seahorse trim is kinda unavoidable.
2. I am coming from backmount doubles and stages background too, and at MOD1/Tec1 level that’s pretty straightforward. However it starts getting complicated at Normoxic and Hypoxic level pretty quick and that depends how do you want to carry bailout, if you want to stick with stages, be prepared to do lots juggling and carrying tanks on the leash. I sidemount my bailouts and that makes life much easier in few aspects.
3. Air travel with JJ is discouraging, specially if you have to fly economy. Level of discouragement depends on you, to me it was discouraging enough to buy second CCR for travel.

I hope it helps and welcome to the club.

Thanks for the helpful input. I have a halcyon carbon backplate that I'm assuming I can swap out with the stock JJ model without issue? And it seems like it might be a good idea to swap my jet fins out for something a bit lighter.

I'll need to work to get this dialled in as I'm currently not a dry-suit diver and probably won't be for at least a couple of years. I enjoy the challenge of deep open water technical diving as well as wreck penetration, but I am fortunate enough to always dive in very warm waters.

On your point re bailouts, is it the case that they can't be carried the same way as we do with doubles? For 2 bottle ~60m level dives with doubles I usually sling an AL80 of 50% on the left shoulder and hip d-rings, along with an AL40 of 02 just clipped off to my hip d-ring. I'm guessing things might get a little more complicated once deep bailout is taken into account and the deco time begins to rack up.

Lastly, I note your point re air travel. I will often fly economy but I always have heaps of luggage allowance (80+ kg) due to status. Would you recommend just getting a pelican case for the JJ and, if so, which one?

Thank you!