Trim issues with steel 12l twins

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absolute_mess

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Location
Melbourne, VIC
# of dives
100 - 199
Hi all,

I've just finished my first weekend of Advanced Nitrox / Decompression Procedures and am having some issues with trim, so I'm hoping for some advice.

The first day of the course, I dived in my Hollis HTS2 harness and wing. I had no problems staying in trim with a set of steel 12 litre twins and an aluminium 6 litre deco bottle. I was then offered an excellent deal on an aluminium backplate and harness, so with my teeth gritted, I pulled out my credit card again to upgrade my kit.

On the second day of the course, I used the BP/W configuration with the same 12 litre twins that I'd been using before and the same deco bottle. This time, I had a huge amount of difficulty staying in trim. Every time I relaxed, I started to tip forward and if I'd let myself go completely, I'm pretty sure I would have flipped upside down, mid-water. This obviously meant that I spent a great deal of energy (and gas), trying to remain in trim and this in turn caused lots of issues holding my (simulated) deco stops. It also created problems for team configuration because I was unable to back-fin properly or to hold my position relative to my team mates because I was too busy trying to stop myself from somersaulting.

I'm finishing off the course next weekend with two 35m dives and a 45m deco dive. I'm really concerned about having similar problems at those depths (the training dives last weekend were only 10m). Does anyone having any advice on how I can improve my trim? Is is just a matter of moving the BP and wing a little higher on the twinset? The valves/manifold were hitting the back of my head while I was diving, so it might just be that I had them up far too high. Any thoughts?

Thanks in advance for your advice!
 
Twin 12L steels make you top heavy, I had the exact same experience. Move the tanks as far down the backplate as they will go and move your wing as high as it will go - this will depend on whether the wing and inflator hose clear your first stages and manifold. You can also loosen the shoulder straps slightly to get the tanks down. You will still need to be able to reach all the valves. Finally you can try some heavier fins, or a trim weight (2-3lb) down low either on the waist strap or in a pouch at the back of the crotch strap just below the plate which is what I do when I dive twin steels in a drysuit.
 
I dive LP85 doubles and am head heavy. In my drysuit I use a 9lb tail weight with my solid rubber fins and I'm in trim. You need to move weight toward your feet.
 
Thanks for the replies guys. I'll try moving the BP and wing up, relative to the twinset. Hopefully I won't need any more weight since I'm diving in a 5mm wetsuit, but it's good to know that it's an option to put some down low if need be when I start diving dry.
 
I had a similar prob during fundies, if i stayed pefectly still, I'd end up with my head resting on the bottom and my feet pointing straight up. Since you are using an ally plate with twins, I'm guessing you are in a wetsuit with no added lead? I ended up ziptying a 3# weight to the bottom tank band and that helped considerably. Once I went dry, The issue went away.

Missed that last post. I was in a 7mm semi dry so was a lot more unbalanced than you. Moving the cylinder bands as far up ast they could go wasn't quite enough in my case.
 
Moving into doubles with a backplate and wing takes a bit of adjustment to get just the right trim. I spent 2 sessions in the pool with a wrench adjusting bands, zip ties and a hand full of soft weights getting just to get the right trim by moving weight around.

I did my doubles configuration as part of getting ready for my cave training and what most people didn't tell me is how much easier it is diving doubles and deco-bottle with a drysuit. You can put air in you're suit and adjust the bubble in the suit to account for being a bit nose heavey or for when you pick up a deco-bottle.

As you progress you should consider looking at moving into drysuit diving. It will become a requirement for secondary flotation as you move to recreation trimix and should be a consideration when ever diving steel doubles.

Hope this is helpful.


T.


Sent from my iPad using Tapatalk HD
 
It probably wasn't the wisest of moves to change your kit mid-course. As others have said, you're probably a bit head heavy. However, if I were you, I'd go back to your original configuration for the rest of the course as you know your comfortable in it. Wait until you've finished before switching, and then take the new kit into the shallows and play around with it until you're comfortable.
 
Hi guys, thanks for all the tips. DM_Tom, I'll definitely look at diving dry at some point in the not-too-distant future. It's just a question of money, as always!

Rivers, yep, point taken - switching mid-course probably wasn't the smartest thing to do but I wasn't anticipating such a difference between the soft harness and a backplate. In any case, I'll try this weekend to shuffle the BP/W around and see if I can get it to work on the first dive. If not, I'll switch back to my HTS2. I may well try ScoobaChef's idea (cheers for that one mate) of attaching a trim weight to the bottom of the plate to keep a bit of weight on my bum. We'll see how it all works out...

At some point in the future, I know I'm going to have to take GUE-F to get all these things sorted out, but like everything else, it's always a question of time and money!
 
At some point in the future, I know I'm going to have to take GUE-F to get all these things sorted out, but like everything else, it's always a question of time and money!

Not true if you can find a mentor or tech diver with good trim to help you out. Another option is a video camera and the shallow end of a pool. That's what worked for me. Good trim is absolutely achievable without a GUE or UTD class.
 

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