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I am a person NOT a number
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Discussion Starter · #1 ·
Last time I dived my twin 12 Fabers (last year) I was using bowstone weight harness and I have since gone onto a shot weight belt. Yesterday I dusted the twins down and took them for a play in Capernwray.

I didnt use my normal weight belt as I would have been too heavy (8kgs) I used 2 x 3 kgs in a pouch weight belt to check the weight (the idea is to get another shot weight belt for when diving with twins). At 1.6 metres and 130 bar in both tanks I was struggling to stay down, am I asking too much? How much more shot do i need?

I am rubbish at physics.
 

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Likes rummaging in rust
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If 8kg in the harness was OK then I would guess 8kg
in the shot belt would do the same thing.
I dive twin L Fabers in a compressed neoprene
suit with a SS backplate and use 12lb (5.5kg)
 

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Diving happy
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As much as you need. It is your body/equipment mass.

Generally a steel 12 will be posatively buoyant when empty; so two of them will mean you are more posatively buoyant! Thats one of the things about twins...

Compared to my 300bar twin-7s (which are negatively buoyant when empty), my 232 steel twin-12 is 5kg more posative - i.e. I have to put on 5kg of lead when I swap from the 7s to the 12s.

You can add weight on the backplate/cylinders - tail weights, V-weights etc. You can add something like 4-6kg easy that way and not burden your belt (just makes em even fecking heavier to shift out the boot of the car!).

http://www.divingniknaks.com/scuba_P_weights_V_weights.php
 

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I am a person NOT a number
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Discussion Starter · #5 ·
If 8kg in the harness was OK then I would guess 8kg
in the shot belt would do the same thing.
I dive twin L Fabers in a compressed neoprene
suit with a SS backplate and use 12lb (5.5kg)
Sorry I didnt make it clear. I use 8kg of shot for when diving single 15.

As much as you need. It is your body/equipment mass.

Generally a steel 12 will be posatively buoyant when empty; so two of them will mean you are more posatively buoyant! Thats one of the things about twins...

Compared to my 300bar twin-7s (which are negatively buoyant when empty), my 232 steel twin-12 is 5kg more posative - i.e. I have to put on 5kg of lead when I swap from the 7s to the 12s.

You can add weight on the backplate/cylinders - tail weights, V-weights etc. You can add something like 4-6kg easy that way and not burden your belt (just makes em even fecking heavier to shift out the boot of the car!).

P weights and V weights, Tailweights at divingniknaks
I struggle lifting the twins in and out the boot of my SEAT Leon so I dont really want to add extra weight. Will probably do my next dive with 7 kgs in the belt to see if i can hold my stop at 1.6 metres next time.
 

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Yaz,

I have a set of Faber twin 12s that I used at the weekend. I had a 6kg V weight and had no problem holding a stop with 100bar in them. Have you got all of the air out of your suit and/or wing?

Having said that, I agree with the others. 8kg on a weight belt == 8kg in a harness == 8kg as V weights == 8kg stashed around the body in various pockets == 8kg swallowed as a large pill ;)*


* Please don't try this at home. It's not big or clever.
 

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If you go playing with your twinset again, take a little too much then at the end of the dive you can adjust your weight to get that superbness state of buoyancy.

Try taking some ankle weights and clip them onto your harness, then you can alter it by 1 kg.

or if you can get at a weight pouch r in a pocket or somewhere like that.

You will know its not an exact science you just need enough, not too much.

Have fun
 

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I used to use 8kg with a single 15, and now use 2kg in twin 12's.

You need what weight you need, but 8kg seems an awful lot if you were having difficulty staying down.

This may seem obvious, but, were you on your way up, and therefore having gas expanding that was having difficulty escaping? So many people automatically go for 'I can't hold a stop therefore I am underweighted' without going the other way, and seeing how little weight they need to sink.

:)
 

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Nigel Hewitt
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130 bar in 24L is 3.9Kgs.

So that needs to go on the belt to just to get back to 'struggling to stay down' on empty.

2Kgs is the difference between possible and comfortable for me so I'd say add 6Kgs and expect to feel a bit light.
With that you can dive and tweak for comfort later.
 

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I am a person NOT a number
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Discussion Starter · #10 ·
I used to use 8kg with a single 15, and now use 2kg in twin 12's.

You need what weight you need, but 8kg seems an awful lot if you were having difficulty staying down.

This may seem obvious, but, were you on your way up, and therefore having gas expanding that was having difficulty escaping? So many people automatically go for 'I can't hold a stop therefore I am underweighted' without going the other way, and seeing how little weight they need to sink.

:)
I had 6kgs on with the twin 12's and wouldnt normally be spending so much time at 1.6 metres playing with the fish as once my computer had cleared me of stops then I normally ascend the last 6 metres. Yesterday I was experimenting with buoyancy and I had no air in suit or wing.

130 bar in 24L is 3.9Kgs.

So that needs to go on the belt to just to get back to 'struggling to stay down' on empty.

2Kgs is the difference between possible and comfortable for me so I'd say add 6Kgs and expect to feel a bit light.
With that you can dive and tweak for comfort later.
So my 6kgs was roughly right?
 

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comfortable

I was diving with 6kgs in salt and 4 kg in freash water (All in V;weights) with my twin 12 euros and could just hold a stop when down to below 30 bar, This year I have upped this by 2 kg and found that it has helped alot, in the grand scheme of things with twins 2 kg is not really a huge percentage and i haven't really noticed it during the dive but not having to completely dump the air from my suit makes ascents a lot more controlable and comfortable.

Mind you now I have changed from a neo to membrane I am back to square 1 again, dived with 6kg at vobby yesterday ok on the stop with 130 bar but took an age to dump the suit.
 

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Se mi havus multe da mono mi acxetus novan biciklo
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When I had a compressed neoprene suit I was happy with 9kg in sea water and 7kg in fresh, with twin 12.2L Fabers. But the suit leaked like a sieve. My nice new 5mm O'Three (and O'Three base layers to replace a threadbare thinsulate) keeps me nice and warm but is quite a bit more buoyant. I put an extra kilo on in Scapa, but now suspect I was light, but getting away with it because the cylinders were topped up before every dive. 24.4L x 230Bar = 7kg of air, all of which counts because I'd rather empty the cylinders than miss a stop.

My 12.2L (internal volume) cyls weigh 13.8kg each, so they are almost positively buoyant when empty.
 

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I used to use 8kg with a single 15, and now use 2kg in twin 12's.

You need what weight you need, but 8kg seems an awful lot if you were having difficulty staying down.

This may seem obvious, but, were you on your way up, and therefore having gas expanding that was having difficulty escaping? So many people automatically go for 'I can't hold a stop therefore I am underweighted' without going the other way, and seeing how little weight they need to sink.

:)
yup and the more weight you add the more air you put in and the harder it gets for the gas to escape and we have a nasty triangle , sorry viscious circle.
 

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Nigel Hewitt
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Burnley!! Add another 6kgs? I wont be able to walk!
Physics is physics.

You said you had 130 bar in 24 litres of cylinder. That's 3.9Kgs.

You said you were "struggling to stay down" and that's got to be 2Kgs minimum.

It will probably turn out to be 7Kgs.
When you can hold a stop on empty your weighting is right.

Also...
Kids these days...
I can walk with 12Kgs on my belt and a 300bar twinset on my back, did it a couple of weeks ago, and I'm 60 this year.
 

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What drysuit, undersuit(s), what cylinders (ie Faber etc), how much do the cylinders weigh, how much bioprene you carrying Yaz? :D

Sound like a lot of weight to me. With Fabers - I dive 3kg in fresh, 6kg in salt and I'm 17 stone and a big lad.

Having a bit of air trapped in a suit or wing is going to be fooling all the calculations - so's a difficult or slightly runaway ascent?

Too much weight will make buoyancy and trim a nightmare - but that said - you need what you need
 

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What drysuit, undersuit(s), what cylinders (ie Faber etc), how much do the cylinders weigh, how much bioprene you carrying Yaz? :D

Sound like a lot of weight to me. With Fabers - I dive 3kg in fresh, 6kg in salt and I'm 17 stone and a big lady boy.

Too much weight will make buoyancy and trim a nightmare
I am just under 18 stone ( and bult like a front row )and dive a neoprene drysuit with a CD backplate on which twin 12s are mounted ( fabers) and i need 8kg. and 10kg in the sea.

if that helps with comparisons
 

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I am a person NOT a number
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Discussion Starter · #19 ·
What drysuit, undersuit(s), what cylinders (ie Faber etc), how much do the cylinders weigh, how much bioprene you carrying Yaz? :D

Sound like a lot of weight to me. With Fabers - I dive 3kg in fresh, 6kg in salt and I'm 17 stone and a big lad.

Having a bit of air trapped in a suit or wing is going to be fooling all the calculations - so's a difficult or slightly runaway ascent?

Too much weight will make buoyancy and trim a nightmare - but that said - you need what you need
My backplate isnt the heavy duty type hence another reason for needing weights. I dont have a problem with buoyancy and I trim out horizontal. Yesterday I was just enjoying playing with my buoyancy at very shallow depths. And yes I have some winter bioprene on and also carry 2 SMB's size large :D

Physics is physics.

You said you had 130 bar in 24 litres of cylinder. That's 3.9Kgs.

You said you were "struggling to stay down" and that's got to be 2Kgs minimum.

It will probably turn out to be 7Kgs.
When you can hold a stop on empty your weighting is right.

Also...
Kids these days...
I can walk with 12Kgs on my belt and a 300bar twinset on my back, did it a couple of weeks ago, and I'm 60 this year.
Ahhhhh now i get you Nigel. Kids? Yay I aint been called a kid for many years........erm since I was a kid really. This 52 year old 5ft 1 inch granny is gonna tell her kids shes been called a kid :)

I am just under 18 stone ( and bult like a front row )and dive a neoprene drysuit with a CD backplate on which twin 12s are mounted ( fabers) and i need 8kg. and 10kg in the sea.

if that helps with comparisons
OI I look nothing like you Steve ! :redface:
 
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