Swim to surface

[Andy Phillips]

OK,

Dave W, said in a previous thread, as well as other times I have noticed it being mentioned, I have just picked on this one,

Originally Posted by [b

Quote[/b] ]I'm also not overweighted, I've spent a while getting a nicely balanced rig that can be swum to the surface with no air in either the suit or wing and can hold stops at 3m with 30bar.... I carry no weight whatsoever in freshwater but add a small V-weight for salt..

This bit about swiming to the surface with no air in the wing or suit bothers me. Exactly what do you mean??

I admit, I am fighting my rig at the moment, I have just changed suit and it has cost me 5Kg's. I am not happy, this is from a membrane to a hyper compressed super dooper posh O'Three number. I weighted mysef twice in fresh water and I had to add 4Kg's just to sink, tis true ask Mark, I made him dive in Wrasbury.

I don't consider myself to be massivly over weighted, though I am going to fight off some of the extra added. But, when you say you swim off the bottom in full kit, by this I mean twins and two 7L stages, are you honestly saying you dump all your air and swim up. I defy anybody to do this from 65M, or have I missunderstood, am I wrong, I am over weighted, I can't belive it though, I just would not sink, I know the suit was empty, my voice went up an octave or two.

I am genuinly puzzled, not taking the mick - honest.

Please explain,

Andrew - puzzled of Marlow

[Mark]

<font color='#000080'>You would of course be using your drysuit as a redundant buoyancy source when swimming up from the ocean floor with steel tanks. If your stages are steel and quite negatively buoyant it may be a problem so we use neutral-&gt;postitive ali stages to keep 'balanced'.

WetLettuce and I have both recently switched to using ali backplates with our twin 12's as we found we both had to be quite over weighted to keep proper trim when using the standard 6lb s/steel backplate. The problem is that the tanks are pretty top heavy and the s/steel backplate was not helping. Having only the lead you need and having it in exactly the right place is very important. With the ali plates the instant improvement in trim and buoyancy control is very noticable, to say the least! I'm just gutted I didn't get an ali plate to start with.

Regards,

Mark.

[And]

Originally Posted by [b

Quote[/b] (AndyP @ Sep. 29 2003,00:23)]I admit, I am fighting my rig at the moment, I have just changed suit and it has cost me 5Kg's. I am not happy, this is from a membrane to a hyper compressed super dooper posh O'Three number. I weighted mysef twice in fresh water and I had to add 4Kg's just to sink, tis true ask Mark, I made him dive in Wrasbury.

<font color='#0000FF'>Hi

This is the 'balanced rig' question which is often discussed in DIR forums. Its nothing new really, in fact its the same principal which is used on the PADI perfect buoyancy course or whatever, except there are more specifics with types of tanks used with what suits etc.

You and your complete rig should be neutrally buoyant at the surface when your tanks are nearly empty. Discount the stages somewhat as the right stages will be only slightly negative when full and probably about neutral when empty if you count the weight of the reg and rigging etc.

Its important to include all your other kit in this calculation. Torches, argon cylinder, redundant air sources etc.

Therefore, if you get this right the only thing you are swimming up no matter what the depth is the gas in your tanks. Even your Ri OThree suit should not compress at depth and if you use the right undersuit the buoyancy of that doesn't change either. At any depth you should be able to fin up and then as the existing gas in your BC/Drysuit expands you will become positively buoyant.

It does help if some weight is ditchable and for some that ends up being the canister light. For me I have a weightbelt as my canister is only 1kg negative.

I recently changed drysuit and undersuit which meant I had to add 2kg to my weightbelt. Changing to an aluminium BP meant adding another 2kg. I don't really like that much on my belt so I'm going to fit a 2kg tailweight to compensate a little. Mark has the same suit as you and only needs 4kg and that is with an ali backplate rather than steel.

You say you have added 5kg to sink you. How did you do the buoyancy check?

Andy

[Davey Willo]

My Pro 14 is 6lb negative but god forbid I ever had to leave that behind... I'd bawl like a baby.

[Mark]

Originally Posted by [b

Quote[/b] (Dave Williamson @ Sep. 29 2003,11:20)]My Pro 14 is 6lb negative but god forbid I ever had to leave that behind... I'd bawl like a baby.

<font color='#000080'>Dave,

I think you could attach it to your reel (if you had time) so you could wind it back in when safe.

Regards,

Mark.

[Mark Chase]

Ali stages is a bit of an American thing isnt it?

UK ali stages are heavy due to increased wall thickness to meet UK safety standards and get CE mark. I think Amreicans use burst disks so have a lower tolerance on cylinder wall thickness.

That said there isnt a whole heap of diferance. Check out the Faber site and the Luxfor specification and see what I meen:

Luxfor Aluminium &nbsp;7ltr Stage &nbsp;48 cu ft. &nbsp;Full -2.4Kg Empty +1.3

Fabor light Weight 7ltr Stage Steel &nbsp;Full - 1.8kg Empty +0.00

Catalina Aluminium 6ltr 40 cu ft. Full - 1.1 empty +1.9Kg

Empty the ali stages are positive so you have to carry extra weight to compensate for this. At a glance you would think the Steel stages were the best choice as they are only 1.8kg negitave when full and neutrol when empty. All alluminium stages are positive when empty and the Luxfor are only .5kg lighter when full. The Catalina is 1.3 kg lighter when full but you have to wear nearley 2kg to compensate for the empty weight so that makes the rig 0.7kg heavier than the steel.

I have never understood the argument concerning Aluminium cylinders perhaps someone could explain it to me.

PS: I wouldent like to try finning up from 50+ M and hope I never have to try. I am not sure it would be possable in a tech rig. Surley it is a mute point. If you have to fin up you have lost all gas and BCD options, by virtue of which surley your dead any way. &nbsp;

ATB

Mark Chase

[And]

<font color='#0000FF'>Hi

Originally Posted by [b

Quote[/b] ]Empty the ali stages are positive so you have to carry extra weight to compensate for this. At a glance you would think the Steel stages were the best choice as they are only 1.8kg negitave when full and neutrol when empty. All alluminium stages are positive when empty and the Luxfor are only .5kg lighter when full. The Catalina is 1.3 kg lighter when full but you have to wear nearley 2kg to compensate for the empty weight so that makes the rig 0.7kg heavier than the steel.

Add on the valve, first stage, SPG, and rigging, boltsnaps etc. the ali will be neutral, the steel negative.

I hope thats explained it for you.

Andy

[Andy Phillips]

OK,

I'll give you a clue as to the size of the problem I am currently faced with, ignoring the ali / steel arguament as I feel this is a mute point, I know my stages are neutral from around half full.

I have 3Kg clipped to the rh tank, an argon bottle on the lh one, 4Kg.s on the harness at the front / sides and a further 2 to 4Kg's on the belt. Before I changed suit I had 2Kg's on the tank and 4Kg's on the belt, nothing on the harness. There is no way on this planet I would use an ali back plate, I don't like them.

The suit does not compress at depth, that is the whole purpose in it's design, it is not an RI the material is absolutly brand new, I have also gone from a weezle to a thinner under suit.

SO WHY ON GOD's GREEN EARTH HAVE I HAD TO ADD WEIGHT.

The swimming up bit was a red herring, to be honest, once again it is just common sense to dive a rig that is neutral to when empty.

If anybody has some bright ideas, help, I hate lead with a passion, it gives me back ache.

Andrew - still puzzled of Marlow

[Scuba1]

<font color='#000080'>Well Andrew a Compressed Neoprene suit has more bouancy than a membrane i use on myself in the winter and need 2 kg more than in a 7mm semidry.

Hope that helps

Michael

[Andy Phillips]

Originally Posted by [b

Quote[/b] ]Compressed Neoprene suit has more bouancy than a membrane

I know, I know, but 5Kg's, don't forget the change of undersuit and it is a fitted suit, much smaller air space.

Andrew