Trim with 3 deco cylinders?

[stuartv]

I dived on Sunday with 3 deco cylinders for the first time ever. I was practicing (in a shallow, local lake) for an upcoming class.

My config:

- drysuit with moderately thick undies
- double steel 120s
- SS back plate
- 1 x AL80 on left
- 1 x AL80 on right
- 1 x AL40 on right

I was very head heavy. It was hard work to stay level. I added a 3# tail weight and was better. Changed to a 5# tail weight and was pretty stable. That was a single lead weight attached to my crotch strap, between the BP and the butt D-ring.

I did not like the overall config at all, because of how it cluttered up my right side. Also, I realized after the fact that I probably would have been even better if I kept the tail weight and changed from my SS BP to my Kydex BP. When I had no tail weight, I was still very negative.

I have now changed all my rigging and regs so that I can carry 2 cylinders slung on the left and one on a leash from the left waist D-ring, over my left thigh, to between my legs. I.e. GUE/ISE style.

My question is: With the 40 moved to the leash and behind me/between my legs, is that really going to make a difference to my trim, compared to when I had all 3 slung from my chest/waist? When I do a bottle rotation to put the travel gas at the back and the 40 up front, will that make any real difference?

I'm thinking it won't really and, for my next time in the water, I should stick with the plan to use my Kydex BP and the 5# tail weight. Meaning, I expect the differences to be small enough that I should stick with the plan and I can compensate for the differences without needing to change weighting or trim weight position.

For the class, the 2 80s will have TX21/30 and TX50/10. O2 in the 40. When I dived them last weekend, none of them had any helium in them. Will that affect any of this?

Thanks!

 

[tbone1004]

why not carry two on the leash and one slung?

 

[stuartv]

In my research of how different people/agencies teach it, I have not found anyone that recommends that. And I do seem to recall a video from the ISE guy that specifically mentioned swimming with 2 on the leash is annoying (my interpretation - not his wording).

I have swam (swimmed? swum?) 2 on the left before and I'm okay with that. Also, I talked to my instructor and we both agree that we don't want to switch to bottom gas in between deco mixes. So, once I get on my first deco gas, I want to switch to the next one directly from the first one, and so forth. Which means having 2 "up front" anyway, at least during gas switches.

 

[grantctobin]

Why not switch to backgas between bottles? Two hoses (plus your long hose) around your neck at the same time with three different gasses is a ginormous cluster. Strongly disagree with how PADI and TDI teach it in this manner. There shouldn't ever be multiple non-stowed hoses on one person at one time.

Edit: how the TDI and Padi standards are written for this procedure. Also, 21/35 rides nicer than 32% or similar. Luxfer>Catalina.

 

[cerich]

What does your instructor say? If you trust scubaboard more than your instr... Change instructors.

Plus, what is up with that gas mix,?

 

[rjack321]

The 80s are going to be lighter by 30% from the helium but... The heavy bit is the valve and reg, having the tail float up is not going to help much with your head heavy-ness.

This whole configuration (including the gas choices) sounds like a total mess to me. What class has you carrying doubles 120s (what mix in those?), 2x al80s of 21/30 and only a single al40 of 50% nitrox for deco?

Not going to backgas between deco gases is a major clustereff in the making and I don't like your instructor at all for that alone (nevermind the bizarre gas choices) and the bottles on the right parts.

Also 50/10 is ridiculous at your level.

(edit mixed up the gas - bottle combo on first reading, but this is still a mess)

 

[rddvet]

I’m not hypoxiC trained. What is 50/10 used for that 50% isn’t.

 

[rjack321]

I’m not hypoxiC trained. What is 50/10 used for that 50% isn’t.

Its makes the bottle slightly lighter - that's it. But 50/25 would be the more common variant as 10% helium is doing nothing substantive. Helium in your 50% gas pretty much obligates you to have O2 along as your last deco gas.

I can't tell if the 21/30 is a bottom mix or a deco mix. Either way this is a mess. I'm guessing there's probably some IBCD prevention silliness behind the gas choices.

 

[Boston Breakwater]

Hey, Stuart. Double Steel 120's?????????????????????? You're a man after my own heart.
Cheers.

 

[RyanT]

Gonna agree with a lot of what's already been said here. Just put the 3rd bottle on a leash. Also agree, the gas choices are a bit odd.