JJCCR and wetsuit diving

[GF99/99]

Honestly as I mentioned in my first reply befor you go crazy and start overthinking everything you just need to get hours on the unit. But that being said technically steel tanks would trim out better as they would lay horizontal better S19’s will be valve heavy.

Like I said earlier the trim on a CCR in general is not something you will be able to read about and it’s really hard to describe in words. It is something were you will just need to spend hours underwater on the unit and you will “learn” how to stay in trim over time. Especially since everyone has a totally different body types.

But I will say that as @doctormike mentioned your couterlungs have 2 holes and stock JJ backplate has 3 holes and they actually do make a difference where you locate them. This is very often overlooked in the JJ setup.

Who was your instructor? Reason I ask is some instructors will spend more time on setup than others.

If you located in the Philippines check out Jong Moon Lee. Might be worth getting in contact with him and explain your trim issues and see if you can setup some one on one hours with him.

 

[doctormike]

@doctormike



For the past 5-6 years I have almost exclusively dove S19 ali tanks on my JJ unless I just can’t get them where I travel. I personally like ali tanks over steel. I am naturally very negative (even in salt water) with two 3L steel onboards and four S80 bailouts I need to have the wing fully inflated plus my suit inflated to the point where my neck seal keeps burping out gas just to stay afloat on the surface. Now if I had four 3L steels plus four S80 bailouts I can’t even image how negative I would be.

RIght, but that's clearly not a MOD 1 configuration!

And of course, I don't mean to imply that everyone has the same weighting characteristics. You use what works. I was just saying that the stock JJ design is clearly 3L steel tanks.

Maybe that's just best for Denmark and New Jersey, but I also found it perfect weighting (without the tube weights) in a 3 mm shorty wetsuit in Bonaire.

 

[rsingler]

Yes, start with that top C/L grommet.
Realize that with full JJ C/L's you'll get more buoyancy in your shoulders, affecting trim.

Maintaining optimal C/L volume will be a key task as you build hours. Generally, less is better, except that with the JJ, you need a bit more C/L volume when head-down vertical. But C/L volume will not be your major focus in MOD1 compared to neutral buoyancy, so don't sweat it for now.

 

[justinthedeeps]

1.) stick to original config as it is in my class. Steel 3L Tanks.

Are you strapping the tanks up such that the regs are nearly touching up against the bottom of the can? I don't expect much difference in trim with steel vs. alum honestly. Plenty of experience here. 2L steels feel the same too.

2.) use lighter backplate? i do have an aluminum lying around.... carbon if it works...
3.) 3mm wetsuit for the moment.... although im planning on dry in the future., it's really not much of an option over here unless diving long hours on tech. maybe will do with ccr diving. OC Tech is like 90mins max. 3mm is still ok...

5mm suit and booties is probably better. If hot, keep it wet. A used 3mm turns into like 1mm at depth

How much air is in your wing? Tune rig and suit thickness/type so that it's not much, or none. Air in wing can pool toward your head, exacerbating trim issues.

so far? is everyone ok with this?

Great point elsewhere about re-checking for minimum loop volume. Keep ADV unlocked and vent gas until you sense the ADV triggering on inhale, repeat regularly. (Ps. closing ADV slider is a lazy act w.r.t. loop management and serious hazard to inexperienced or overwhelmed divers)

 

[Fat old english bloke]

I believe Tecline produce a wing with increased volume towards the bottom, which is aimed at CCR users with this problem - might be worth looking into?

I ended up biasing the gas ratio in my suit/wing heavily towards the suit, obviously not an option if diving in a wetsuit.

I’ll be diving my JJ for the first time in years this weekend, so I’m sure I’ve all this fun to go through again.

 

[Rayk]

I believe Tecline produce a wing with increased volume towards the bottom, which is aimed at CCR users with this problem - might be worth looking into?

I ended up biasing the gas ratio in my suit/wing heavily towards the suit, obviously not an option if diving in a wetsuit.

I’ll be diving my JJ for the first time in years this weekend, so I’m sure I’ve all this fun to go through again.

I use Tecline with JJ and it is much more comfortable than stock JJ wing.

As mentioned before, JJ is heavy beast even for Drysuit (I never used SS backplate), for wet diving I have got carbon fiber backplate and aluminum tanks, however I couldn’t try them yet.