Steel Vs Alu backplate and ditchable weight for single tank diving

[declan long]

Hi Guys

I have posted this thread here as i am after more tech minded responses as surposed to standard recreational diver answers. Thanks

I am in the process of swithing to bp/w for single tank diving and was wondering about ss plate with no weight or alu plate with weight pockets. I am getting the Xdeep Zeos system. When i dive doubles in a wetsuit i use a ss halcyon plate and no extra weight, ofcourse in tech diving redundancy is key as the direct ascent to the surface is usually not a possibility, but if i was to use a ss plate with no ditchable weight for a single aluminium 11.1 litre tank and i had an emergency then i have nothing to ditch, the primary concern of this i hear is wing failure, to me this is not a problem as the rig is balanced and i have a lifbag anyway always with me underwater.

The problem however, that i do see is, If i had a tank neck o ring blow or an ooa emergency -shouldn't happen i know but it can- then i have nothing to ditch to reach the surface quickly. You may tell me that a bouyant ascent is not a good idea, ofcourse but its better than being underwater with out another breathe.

Thank for your help and responses guys.
Declan Long

 

[MartinL74]

I would prefer to dive with ditchable weight, if possible. Keep in mind that an aluminium plate is lighter on land as well, so carrying your rig to the boat or the shore is easier as well. I currently dive a SS plate with a single steel tank, but I don't really need that extra weight anymore.

 

[fire_diver]

Stop thinking about "ditchable" weight, and start thinking in terms of being properly weighted to start. You have to look at your exposure protection to begin. You dive wet, so how much weight do you need to sink just the wetsuit? The aluminum tank (if the same as our 80CF tanks) will be about 4 pounds positive when empty.

Now look at the weight of your plate in relation to your total weight needs.

For example, I dive a 3/2 wetsuit, AL80 with a 5# SS backplate. That plate takes care of any positive offset of a near empty tank, and I only need 4 pounds for my wetsuit. So I carry 4 pounds (attached to my cam-bands) when I dive. The worst case is that I have a problem at the beginning of the dive while I am only 4-5 pounds negative. I can swim up with no air in my wing without problem.

Now, if you were diving a steel tank that was never +bouyant, a lighter AL plate would make more sense. You have to carry weight, how and where are personal preferences.

 

[GrimSleeper]

Hi Guys

I have posted this thread here as i am after more tech minded responses as surposed to standard recreational diver answers. Thanks
[…]

The problem however, that i do see is, If i had a tank neck o ring blow or an ooa emergency -shouldn't happen i know but it can- then i have nothing to ditch to reach the surface quickly. You may tell me that a bouyant ascent is not a good idea, ofcourse but its better than being underwater with out another breathe.

Thank for your help and responses guys.
Declan Long

My immediate 'tech minded response' is that you're looking at the wrong 'problem'. If you're making plans for having nothing to breathe at depth, the problem is NOT 'how would I get to the surface fast'. The problem is 'how did I come to have nothing to breathe?'.

As you say, "in tech diving redundancy is key". So you have multiple gas sources - twins, double sidemount cylinders, a stage, whatever. Actually, in any halfway properly planned single-tank dive, you still have redundancy - a buddy, or a pony. So if you have a neck o-ring blow (never seen it, but let's go with it) or go OOA, you share with your buddy or you switch to your pony bottle. If your emergency planning consists of ditch and bolt, you need to revisit the way you think about planning.

Also, you say your rig is balanced, so what's the issue? If it truly is balanced, you can swim it to the surface pretty much as easily as you can make a buoyant ascent, with a lot more control.

I really feel I have to add this, because this is the technical diving forum...

If your response, ever, in any form of diving, is to ditch your weights and bolt for the top then you have no business conducting any form of 'technical' diving. Analyse threats beforehand, plan for them, equip for them, and put in the hours underwater to enable you to calmly deal with whatever being underwater throws at you. Ditch and bolt has no place in the technical diving mindset.

 

[decompression]

Well, if you are already tech trained the answers are all ready there, if you're being mentored then look at the "failures". For doubles, Neck o ring failure, nonfixable failure= isolate then receive donated reg and ascend. Wing failure= if balanced rig then controlled ascent or add air to drysuit and ascend. Neither require ditching weight. The idea of an smb as a means of buoyancy has serious drawbacks.

You've asked wrt a single tank and you mention you dive doubles as well. For singles, If there's a catastrophic gas failure or as I like to say "gas temporarily unavailable" then it's an OOA and neutral ascent (balanced rig). If Wing failure then neutral ascent.


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[DogDiver]

Lol love it. When your diving wet and sidemount with steel 120's, primary can lite, half a dozen reels.......etc. I haven't worn a weight belt in 15 years. 180# of gear is more than enough to get me under. And in a cave......what good would ditching weights make. Keep diving safely.


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[Nasser]

Consider the environment for the vast majority of your dives - what exposure protection do you need? what type of cylinders are being used ? (size, material,etc..) and how much weight do you need to dive a balanced rig or to be able to hold a safety/deco stop with very little gas in your wing and about 30 bar in your tank?

You will have to do this every time you go to a new diving environment anyway. Once you've dialed that in... consider how your weight is distributed on your body. Are you going to carry all of it on a weight belt or weight pockets? What about splitting a little so that you have some around your waist and some in trim pockets around your tank? Don't forget to consider accessories that add weight (lights, knives, reels... those are ditchable). That way if you need to ditch, (which if you're diving a balanced rig may not be necessary) then you can ditch just a little to get shallow enough to become buoyant and not dangerously shoot up to the surface in an uncontrolled ascent.

If you find that the vast majority of diving you do does require you to carry additional ballast - even with an SS backplate, then just go for that. If you really dive in very varied conditions with different setups, then consider having both an SS and an AL BP. In my case, I have found that an SS BP has worked 99 % of the time and in only one trip did I feel slightly over weighted... and that was because I was in a 3mm shorty and had to use a heavy 15 l steel tank with an H valve... so I would have preferred an AL BP and maybe a couple of extra kilos instead.

Analyse your environment and conditions... adjust according to your own weight and size and go from there.

cheers,
nasser

 

[rivers]

For single tank stuff, I use an ali backplate. Mainly because I bought my first backplate when I was travelling a lot. I have just purchased a steel backplate, mainly because I was sick of switching back and forth between my single wing and my twinset wing (i'm doing a lot of single tank pool stuff at the moment). In warm water, I don't have any ditchable weight on my single tank set up. Just a couple of kilos on the cam band. My rig is balanced, so in the event of a wing failure, I can swim it up without issue.
So declan, it's really your choice.

 

[lefrogster]

I agree with GrimSleeper above -- ditching weight and bolting uncontrollably to the surface is an awful contingency plan. If there is a catastrophic and unrecoverable failure in your air supply, you should go to your buddy.

That aside, it is much more important to have a balanced rig as being improperly or overly weighted will create a lot more problems.

I dive Xdeep Xeos, SS backplate, SS STA and in a 2.5 mm full, canister light, back up light, I can hold a 6 m stop with 20 bar left for a single ALU tank. If I was sinking (due to BCD failure for instance) I can easily kick this up (I can do it with doubles and 3 deco tanks too), or dump my canister if I need to.

However, in cold water, I dive a 5 mm and need to add trim weights and weight pockets. But at leas the weight you add is minimal, and even if you ditched the weights, you wouldn't shoot to the surface, but just slowly ascend.