Why Steel Doubles?

[Kern]

Even though you're positive with empty tanks your tanks are still negative by themselves, you just wear a weight belt to make yourself more negative. All your weight is neither on the tanks or on you therefore if you seperate yourself from the tanks you will indeed still be positive. Let's break it down using 130s as an example:

130's - -2lbs each empty
regs- -4
BP AL or SS (-2 to -6)
Bands/manifold -5
Can light -3

That makes -18 to -22 depending on what your plate is made of.

Personally my undergarmets are 25lbs positive in the drysuit alone. I wear an additional 4lbs in a tailweight to remain neutral at the end of the dive. Does this make sense?

Edit:

I'm sure you know this, I'm at work and I'm tired and I think I read the previous couple posts wrong. Sorry if this is useless, hopefully it'll at least help someone else

As I said, I'v not actually done this (& it'll be a desperate day that I try), so you may be right.

As I dive temperate waters I doubt my undies are even half as buoyant as yours though. I also use different size & make of tanks. I have 9lb on my weight belt.

Actually, now that I'm more comfortable diving dry I want to recheck my weighting in the near future. I think I may try an experiment.

 

[GeorgeC]

......If you diving doubles your not in a shorty most times. And even a full 3mm suit will need a few lbs of lead.

I dive a 3mm full suit with a Steel HP 100, a Dive Rite Transpac, no extra weight and I am negative. If I dive a 5 mm full suit with double HP100's I sink like a rock! I have to rely on another form of lift should my BC fail.

 

[StreetDoctor]

I dive a 3mm full suit with a Steel HP 100, a Dive Rite Transpac, no extra weight and I am negative. If I dive a 5 mm full suit with double HP100's I sink like a rock! I have to rely on another form of lift should my BC fail.

You should not be diving steel doubles with a wetsuit. If you want to dive a wetsuit you should stick to double AL80's.

 

[Kern]

I dive a 3mm full suit with a Steel HP 100, a Dive Rite Transpac, no extra weight and I am negative. If I dive a 5 mm full suit with double HP100's I sink like a rock! I have to rely on another form of lift should my BC fail.

I'v never dived double 100's in a 5mm steamer. When they're empty, do you still sink like a rock?

 

[GeorgeC]

You should not be diving steel doubles with a wetsuit. If you want to dive a wetsuit you should stick to double AL80's.

II have to disagree with not being able to dive Steel 100 doubles with a wet suit. Albeit it requires a little more planning i.e. double bladder air cell or backup lift bag/smb for a wing failure.

I will agree diving double steel in a wetsuit is not optimal and something that requires planning. I tried it once in the warm waters of Florida on a training dive and had difficulty swimming the rig to the surface with a fully deflated BC.

However, I do dive a single Steel 100 on a regular basis with a wetsuit.

 

[ScubaInChicago]

I have no problem swimming up my steel HP100 to the surface with a fully deflated BC. I have to disagree with not being able to dive Steel 100 with a wet suit. What is the reasoning behind this? If I dive a 7mm full wetsuit I have to add lead to sink. Why must I dive Aluminum with a wetsuit?

People are truly scared, very concerned for your safety, and think you will DIE.

 

[StreetDoctor]

I have no problem swimming up my steel HP100 to the surface with a fully deflated BC. I have to disagree with not being able to dive Steel 100 with a wet suit. What is the reasoning behind this? If I dive a 7mm full wetsuit I have to add lead to sink. Why must I dive Aluminum with a wetsuit?

I said doubles. Most people can swim up 10lbs from depth... So let's do the math.

Double HP100's -4 empty -20 full
Regs -4
Manifold/Bands -5
Let's assume AL BP -2/-3
and you've ditched your cannister light

That's -15 to -16 with empty tanks or -31 to -32 with full tanks. At depth your wetsuit compresses and looses the majority of it's buoyancy that it provides at the surface, so if it provides +10 on the surface it won't be anywhere near that at depth.

In a single setup you're looking at having a rig that's about -8lbs empty or -16 with a full tank not accounting for the compressed wetsuit at depth. Most likely you're only swimming up around -5lbs with the compressed wetsuit and an empty tank. Of course the shallower you get the more buoyant your suit will become.

 

[GeorgeC]

Sorry miss read the question and edited my response above!

 

[StreetDoctor]

No problem, a lot of people will tell you the double bladder wings are not very safe either. The best bet is to go dry if you're going to dive steel doubles.

 

[GeorgeC]

People are truly scared, very concerned for your safety, and think you will DIE.

A little dramatic. Wetsuit with a single steel tank = you will die?