Twinset weighting

[TheRedDarren]

Hi all,
thanks so far for all the info, I'm going to be buying the Scubapro Xtek pure and Euro 12 cylinders to go with it.
I'm just adding everything up and writing my shopping list...

Should I also buy the Xtek weight system (intergrated weights)? I don't actually own a weight belt as I dive with intergrated weight on my BCD, so if I need weight I won't have a way of attaching any to me!
I know this is a 'how long is a piece of string' question but how much weight (after a weights check) do you use on your twin 12's?

[TheRedDarren]

Should have said, steel backplate!

[drmwc]

Twin 12s tend to be quite negative. I use a 1K v-weight, which goes between the cylinders and the plate. Then I need no addition weight for freshwater; and add 2k on a belt for salt. This is with an O3 RI2-100 drysuit, and too much bioprene.

Of course, the most important thing is to do a weight check with near-empty cylinders (40 bar or so). There is quite a lot of gas in 12s, (I think around 6k) ,so buoyancy changes quite a lot between full and empty. V-weights or tail weights can help with trim - you may be head or feet heavy.

[jturner]

Do a weight check to find out how much you need but for what it's worth, I doubt you'll need any weight; maybe just the odd kilo, which is best attached as a tail weight or the like on the twinset itself. To give you an idea, with all the same suit and thermals, with a steel plate, wing and single steel 15L cylinder I might need 12kg. With the twin euro 12ls with flat bottoms, I need ~1kg.

I don't like the idea of ditchable weights for so-called technical diving anyway. They take up precious harness space, add bulk, get in the way of attaching stages and losing the ditchable weights would be... regrettable.

[Steve Clark]

As shot in the dark :
Fat person, fresh water - steel plate + 4 kilos. +3 more kilos for the sea.
Thin person, thinner undersuit - steelplate + 0 kilos. +2-3 more kilos for the sea.

Cylinders vary at lot. I've seen D12 Euros at 12.2kg and I own some that weigh 14.4kg. That's +/- 4kgs on a set.

[PhilPage]

Should I also buy the Xtek weight system (intergrated weights)? I don't actually own a weight belt as I dive with intergrated weight on my BCD, so if I need weight I won't have a way of attaching any to me!
I know this is a 'how long is a piece of string' question but how much weight (after a weights check) do you use on your twin 12's?

The xtek weight system is pretty bulky on the harness. I don't use mine, as I don't need the ditchable weight - I only need a couple of kilos which I carry in trim pockets at the bottom of my nose-heavy cylinders.

Buy your set without them & do a proper weight check. If you end up needing lots of extra lead, then you can buy mine

If you want help with your weight check, I'd be happy to come buddy you @ chepstow - I just got a new drysuit which needs weight checking...

[Energy58]

As shot in the dark :
Fat person, fresh water - steel plate + 4 kilos. +3 more kilos for the sea.
Thin person, thinner undersuit - steelplate + 0 kilos. +2-3 more kilos for the sea.

Cylinders vary at lot. I've seen D12 Euros at 12.2kg and I own some that weigh 14.4kg. That's +/- 4kgs on a set.

Middling fat git (90kg 5'11") - ali backplate, 2 kg V weight to sort trim out (otherwise I am driven head first into the bottom as I have to have the cylinders mounted high cos of limited mobility in my right shoulder) + 4kg for the sea has me able to hold a stop with nearly empty cylinders. Steel backplate would let you lose about 2kg of that. Dont forget you are carrying more than 7kg of gas at the start of your dive which you wont be at the end so you need to start heavy.

On a somewhat related topic I did some testing with a luggage scale in the pool the other day - a full 80cu ft ali stage fully rigged (APEKS 1st and 2nd stages) is -2kg and more or less neutral with 50 bar in it

[nigel hewitt]

Don't forget to weight yourself for neutral on empty.
Flat, 0 bar, nothing left, empty.
Deco diving it is no excuse, when you're hanging off your buddies long hose with a blown something, to drag him up because you can't hold that stop you both need.

I usually just weighted myself for what I had, checked the SPG, worked out the weight of the gas in the tank and added that as lead too.

[Wrecked_Diver]

Sorry to hijack a little but it kinda follows on from this question....

How much weight would you typically need to add to carry a 7l ali stage? I think I'm right in saying they are roughly 1.5kg positive when empty so I was going to add 2kg on top of my standard twinset weight. Is this the right kind of ball park to get me started?


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[jturner]

Sorry to hijack a little but it kinda follows on from this question....

How much weight would you typically need to add to carry a 7l ali stage? I think I'm right in saying they are roughly 1.5kg positive when empty so I was going to add 2kg on top of my standard twinset weight. Is this the right kind of ball park to get me started?

I guess YMMV and all that but I don't account for the stage in my weighting; I don't plan on ever emptying my stage (so it will end up as about neutral as the gas usage calculation will leave it about with extra gas left inside) and if it was empty, I'd send the thing up the DSMB line and be done with it. No point in carrying it around if it is empty. Needless to say if you are diving in a cave, this won't apply!

[PhilPage]

Sorry to hijack a little but it kinda follows on from this question....

How much weight would you typically need to add to carry a 7l ali stage? I think I'm right in saying they are roughly 1.5kg positive when empty so I was going to add 2kg on top of my standard twinset weight. Is this the right kind of ball park to get me started?

Not really - a stage is ditchable in an emergency (i.e. if you've sucked it dry and it's making you positive, you can just unclip it).

As to how positive it would be depends on the cylinder in question (wall thickness, etc.). If it's still positive when full, I'd weight the cylinder itself to get it neutral at half full.

[Energy58]

Not really - a stage is ditchable in an emergency (i.e. if you've sucked it dry and it's making you positive, you can just unclip it).

As to how positive it would be depends on the cylinder in question (wall thickness, etc.). If it's still positive when full, I'd weight the cylinder itself to get it neutral at half full.

An 80 cu ft ali stage fully rigged is -2kg negative full so almost exactly neutral more or less empty. So I would expect an 7l to be slightly negative when empty as the regs weigh the same and the volume/weight ratio is slightly worse so I'd add nothing particularly as if shit really happens you can always ditch it!

[Ian_6301]

From experience, an Al80 will float when empty. Not by a lot, say 1kg? Don't forget you have the weight of the rigging and the reg on it too.

Al7 232 bar is a bare smidgen positive in fresh when empty, so again less than 1kg in the sea.

Al40 is spot on neutral at empty in fresh.

All based on a standard DIR type rigging with no mahoosive p clips or anything and a Ds4/xtx40 reg.

BUT cylinders do vary.

Best advice would be to cart a bunch of almost empty stages along to pool night and go monkey diving! That's how I checked mine out. If floaty, try clipping 1kg weights on to the rigging and seeing how they fare.

Ultimately, for my tins, worst case scenario is that I am maybe 1kg light. I know that my weighting is approx 1kg more than absolute minimum, for comfort purposes. without a stage and with zero back gas, I can have a drained wing and a normal amount of suit gas for comfort and warmth. With an empty stage, I'd be shrink wrapped to hell, pinch and cold, but not floating.

More than one empty stage is a really bad day at the office. As above, once one is empty, send it up the line.

With a bottom stage (which you intentionally empty, or almost empty), it doesn't become an issue unless/until you also run out of back gas. Again, by this point, you're on ascent, with a DSMB up before it really becomes an issue, so just clip it off and away it goes.

Get your weight right for empty twins, with torch etc, but no stages. Then pick the right stages.

Nothing wrong with steel stages by the way, but again do your weight check without them. If they then make you negative, great. But don't remove lead, because sod's law says the day you go out if back gas, you will have left the stages on the boat or in the wreck/cave.

If diving steel stages though, DO consider your max buoyancy requirements. You may need a bigger wing if carting nitrox about in them. Probably not needed, but just check.

[PhilPage]

Get your weight right for empty twins, with torch etc, but no stages. Then pick the right stages.

That's the money shot right there

[Wrecked_Diver]

From experience, an Al80 will float when empty. Not by a lot, say 1kg? Don't forget you have the weight of the rigging and the reg on it too.

Al7 232 bar is a bare smidgen positive in fresh when empty, so again less than 1kg in the sea.

Al40 is spot on neutral at empty in fresh.

All based on a standard DIR type rigging with no mahoosive p clips or anything and a Ds4/xtx40 reg.

BUT cylinders do vary.

Best advice would be to cart a bunch of almost empty stages along to pool night and go monkey diving! That's how I checked mine out. If floaty, try clipping 1kg weights on to the rigging and seeing how they fare.

Ultimately, for my tins, worst case scenario is that I am maybe 1kg light. I know that my weighting is approx 1kg more than absolute minimum, for comfort purposes. without a stage and with zero back gas, I can have a drained wing and a normal amount of suit gas for comfort and warmth. With an empty stage, I'd be shrink wrapped to hell, pinch and cold, but not floating.

More than one empty stage is a really bad day at the office. As above, once one is empty, send it up the line.

With a bottom stage (which you intentionally empty, or almost empty), it doesn't become an issue unless/until you also run out of back gas. Again, by this point, you're on ascent, with a DSMB up before it really becomes an issue, so just clip it off and away it goes.

Get your weight right for empty twins, with torch etc, but no stages. Then pick the right stages.

Nothing wrong with steel stages by the way, but again do your weight check without them. If they then make you negative, great. But don't remove lead, because sod's law says the day you go out if back gas, you will have left the stages on the boat or in the wreck/cave.

If diving steel stages though, DO consider your max buoyancy requirements. You may need a bigger wing if carting nitrox about in them. Probably not needed, but just check.

Thanks ever so much for the advice everyone. Much appreciated. That gives me somewhere to start. I'll have a go in the pool and a quarry, get it all spot on then venture out for some proper diving!


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