Newbie JJ diver advice

[nadwidny]

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?

I've been to Bikini twice. You absolutely do not want to do it on OC. Or deep air. If you aren't able to get some sort of CCR trimix ticket before then, don't go. Re-book. Don't be "That OC Guy That Effs up the Whole Trip for Everyone".

 

[nadwidny]

I would be diving with Dirty Dozen.

I seriously doubt DD would let you dive OC in Bikini.

 

[Heat Miser]

I seriously doubt DD would let you dive OC in Bikini.

no this is wrong I saw DD reel last month saying you can dive it on OC

 

[OTF]

Thanks for this perspective. Out of interest, have you dived Bikini recently? I only asked because I spent quite a lot of time at Truk recently focusing on the deep wrecks (IJN Oite (62m, very moderate penetration), San Francis Maru (57m - light penetration through the aft and forward holds) , Aikoku Maru (56m - moderate penetration) and Amagisan Maru (53m - moderate penetration) as well as a bunch of wrecks in the 40-50m range where we got right into the engine rooms. From what I've read the penetration in the wrecks in Bikini will not be as extensive as what I've experienced at Truk?

I have no desire to climb through wrecks into tight engine rooms at 50m+ on air. In fact, I simply won't be doing that. But if the diving is no more technical than my experiences in Truk then I think I would be better off on air on open circuit where I have experience instead of on a rushed Mod 2 on a unit I only have ~50 hours on.

I would be diving with Dirty Dozen.

• Yes I have dived Bikini recently, on a boat with mostly CCR divers and a couple people on OC trimix. Definitely not air! Our CCR dives were each roughly 2 hour runtimes and we wanted every extra time advantage the units could provide. I don't think the OC people had as much fun. A couple of OC divers had mild DCS symptoms which none of the CCR group experienced.
• Each of the Bikini wrecks are different, some don't offer much penetration at all, some offer longer deeper and sketchier opportunities than Chuuk. Here is a video of some excellent divers (Pink fins is a Master fleet guide) doing the grand tour of the Saratoga interior .
  You do not have to do dives like that to enjoy Bikini though. In fact if you spend your time in there you will miss lots of cool stuff on the outside of the wrecks. One trip isn't enough to see it all so don't worry about doing the hardest interior rooms your first time there. You should be cave trained for the serious penetrations.
• Dirty Dozen runs a good operation.

 

[justinthedeeps]

Definitely ditch the steel backplate and sinking fins unless you're in 7mm+ or drysuit! Standard backplate hole distance.

With carbon plate and ali cylinders I am still not carrying any lead in a 5mm wetsuit and hood

RK3 (lite), Go fins, or Oceanic Accel (or similar small stiff fin) should be plenty for skills circuits.

It's not hard to dive JJ in tropics properly in trim. But yes on an hour+ open bottomless water 6 metre deco hang (typical @ Gili or perhaps Bikini) it becomes clear that there is no bottom to silt....

You can fly the JJ in an ordinary lite shell wheeled suitcase to ease travel, but it will also fit in a wheeled Pelican Air 1606 or similar (partly disassembled) [*head in carry-on]. 316 stainless steel wingnuts can make the stand faster to remove/replace.

~31kg ready-to-dive vs. ~28kg for the rEvo micro (have weighed)

 

[KBlack]

I dive a JJ-CCR in Thailand's tropical waters. And Thailands not so warm caves and mines.
Stock standard as it comes from the factory with no modifications.
I dive a drysuit

It trims out just fine. I have students who do there course in 3mm wetsuits and they can still trim it out nicely. It is when you start changing backplates for carbon fibre and cylinders for either aluminium or carbon that the weight distribution gets all wrong.

Fins make a difference. I dive Scubapro Jetfins with the drysuit and Hollis F2's with a wetsuit

Kiwidiver_Kevin
Tech Instructor Trainer | CCR Instructor Trainer

Tech Dive Asia - Thailands most experienced technical diving team

Based in Phuket but diving all over Thailand and South East Asia, The Tech Dive Asia team of Instructors, Trainers and explorers are always busy with diving adventures.

techdiveasia.com

 

[rsingler]

Post in thread 'Flying with a JJ' Flying with a JJ

 

[bipolarbear]

I've just finished my Mod 1 Helitrox and wanted to share my thoughts given all the helpful advice received.

1. The unit is certainly tail heavy. I swapped my Jet Fins for Deep 6 Eddys which helped a lot, although there was still some fin sculling involved to trim out on deco stops.

2. I dived with aluminium cylinders. I ended up quite liking the standard harness and kept the stock steel plate instead of swapping it out for my Halcyon plate. I figured this makes sense from a trim perspective, because while the carbon plate would make the overall unit lighter, it could potentially exacerbate the tail heavy nature of the unit when diving wet.

3. I hate the stock SPGs. Swapping them out for transmitters tomorrow morning now that I've finished the course. I haven't yet made a decision on the gag strap. I kind of hate it but in the grand scheme of things it's not that much of a hassle.

4. I found the course really quite challenging, particularly when doing high SP ascents in the 9-6m range when you're juggling the reel/DSMB, the wing and the counter lungs while the solenoid is continuously firing. I need to learn to just vent the loop entirely and pump it full of 02.

5. Blue Marlin on Gili T was great, with good fills and a clean tech room. My instructor was Chris Gamlin, who was superb, and who I plan to take my Mod 2 with sometimes next year once I get more hours on the unit.

 

[KBlack]

I've just finished my Mod 1 Helitrox and wanted to share my thoughts given all the helpful advice received.

1. The unit is certainly tail heavy. I swapped my Jet Fins for Deep 6 Eddys which helped a lot, although there was still some fin sculling involved to trim out on deco stops.

2. I dived with aluminium cylinders. I ended up quite liking the standard harness and kept the stock steel plate instead of swapping it out for my Halcyon plate. I figured this makes sense from a trim perspective, because while the carbon plate would make the overall unit lighter, it could potentially exacerbate the tail heavy nature of the unit when diving wet.

3. I hate the stock SPGs. Swapping them out for transmitters tomorrow morning now that I've finished the course. I haven't yet made a decision on the gag strap. I kind of hate it but in the grand scheme of things it's not that much of a hassle.

4. I found the course really quite challenging, particularly when doing high SP ascents in the 9-6m range when you're juggling the reel/DSMB, the wing and the counter lungs while the solenoid is continuously firing. I need to learn to just vent the loop entirely and pump it full of 02.

5. Blue Marlin on Gili T was great, with good fills and a clean tech room. My instructor was Chris Gamlin, who was superb, and who I plan to take my Mod 2 with sometimes next year once I get more hours on the unit.

I dived a unit with Aluminium backplate. Definitely noticed the unit was lighter but noticed no effect on trim. I plan to put aluminium backplates on all my units.
High setpoint accents do take a lot of practice but practice regularly until it gets easier.
I have dived at Blue Marlin and agree it is an excellent training facility, Big with a lot going on but well set up. I have never seen so many JJ's in one place as was there during our trip. I have dived with Chris and he is a sound instructor.