Tank to negative for safety?

[DWJ]

Steel HP120 (faber) tanks have a negative buoyancy when full at around 16 lbs. 7 when empty. (numbers are approx but I think pretty close) My son wears 14 lbs on the belt using an AL80 ( he’s 15 yrs old 5’10 and 165lbs wears a 7mil wetsuit) Using the steel tank makes him very negative at the start of the dive even figuring he drops 8 lbs from the belt. I’m concerned that if he needed to dump the 6 lbs at the beginning of the dive, it would have no effect and he would still sink. Now I know I’m thinking worst case like a catastrophic BC failure.
Am I being paranoid here, a too cautious father?
The reason I ask is I just bought a couple of these tanks and didn’t even think of this until I told my kid and said he could now leave his weight belt at home.

Dave

 

[pescador775]

The HP faber is OK for dry suit. However, the largest I would go is 100 cf and not to exceed 100 feet when wet suit diving. BC's are pretty reliable, if the power inflator fails the bladder can be inflated by mouth. Dropping the weight belt should make it easy to swim to the surface anyway. However, the 120 is a heavy monster. I really believe that he should trade the HP120 for a HP100 or LP 100 (overfill a 90?). The PST HP100 would be best for wet suit. Light as a feather. Even so, I should point out that, among the pros, many prefer the negative buoyant tanks. The old PST 94.6, 3300 psi tank sold like hot cakes to instructors. I used them for many years. The buoyancy was similar to Faber HP100.

Steel HP120 (faber) tanks have a negative buoyancy when full at around 16 lbs. 7 when empty. (numbers are approx but I think pretty close) My son wears 14 lbs on the belt using an AL80 ( he’s 15 yrs old 5’10 and 165lbs wears a 7mil wetsuit) Using the steel tank makes him very negative at the start of the dive even figuring he drops 8 lbs from the belt. I’m concerned that if he needed to dump the 6 lbs at the beginning of the dive, it would have no effect and he would still sink. Now I know I’m thinking worst case like a catastrophic BC failure.
Am I being paranoid here, a too cautious father?
The reason I ask is I just bought a couple of these tanks and didn’t even think of this until I told my kid and said he could now leave his weight belt at home.

Dave

 

[MechDiver]

Using the steel tank makes him very negative at the start of the dive even figuring he drops 8 lbs from the belt. I’m concerned that if he needed to dump the 6 lbs at the beginning of the dive, it would have no effect and he would still sink.
Dave

The big problem with wetsuits and steel tanks is not on the surface, but at depth. It he is very negative on the surface, then when the suit compresses at depth he will be that much more negative. I don't seem to remember the Faber HP tanks being that negative, but regardless, you have more issues than just on the surface.

MD

 

[pescador775]

Forget what you remember, it's bad info. The Faber HP is extremely negative. Personally, when using the Faber I just lighten up the weight belt going in and use the BC for ballast at depth (wet suit). I don't worry about failure of the BC. When I started diving (OW) there were no BC's available so never developed the same safety concerns. When I started using a BC then felt almost bulletproof. The Faber has steel walls as thick as an armored vehicle. I suspect their burst pressure is about 8000 psi. I don't believe in entering the water too negative and use less lead than some others. With the Faber I use about 10 pounds with a full wet suit. I don't use heavy accessories like steel plates, amen. If I'm a couple # buoyant at the surface it's no big deal. It can be even helpful for tag line divers who string themselves like balloons during deco.

The big problem with wetsuits and steel tanks is not on the surface, but at depth. It he is very negative on the surface, then when the suit compresses at depth he will be that much more negative. I don't seem to remember the Faber HP tanks being that negative, but regardless, you have more issues than just on the surface.

MD

 

[scubafanatic]

...you might want to consider a dual-bladder wing......I usually dive large singles steels (HP 130, HP 120 or LP 112) or a 'small' steel twinset ( LP 85's )......mostly with a 7mm wetsuit.....and finally decided to buy a Dive Rite Dual Rec Wing ( 51 lbs lift ). The consensus view is diving 'wet' and 'steels' simultaneously is a big 'no-no'.......and a couple weeks ago decided to increase my safety margin and add a dual-bladder-wing to my configuration.

I'd planned to dive this configuration for the 1st time at the Flower Gardens (off the coast of Texas) this weekend, but that trip once again fell victim to bad weather, so that will have to wait for another weekend....sigh.

Karl

 

[fldivenut]

I’m concerned that if he needed to dump the 6 lbs at the beginning of the dive, it would have no effect and he would still sink. Now I know I’m thinking worst case like a catastrophic BC failure.
Am I being paranoid here, a too cautious father?

You are right to think worst case. Especially when you do the think for someone else. You might consider the risks your self and decide to take them. But your son at that age should not.

Get hime a dual bladder wing (or BC jacket) or other tanks. Consider though that the dual bladder need air hook-ups etc. and it is customary to do that from a second regulator, which means a dual outlet H-valve as well.

It is debated if a dual wing should be worn regardless of if you are diving wet or dry when diving heavy steel or doubles. The argument is that a dry suit is not a flotation device.

--A

 

[jimlockNJ]

You seem to have a legitimate concern, but, I think it would depend a great deal on where you are diving. I do a lot of diving in the NE US off wrecks and shore diving in inlets, etc. where the currents are strong. I have had very few instances where I was really scared when diving, and all included coming to the surface too fast, never staying down. In the open ocean, if you ascend uncontrolled because of underweighting or positive buoyancy tanks, you may have big problems. Besides the obvious uncontrolled ascent issues, you may end up VERY far from your boat. As for shore diving, coming up unexpectedly when the current is bad or surf is rough can cause you to make a VERY difficult exit where you did not want to get out. I had to walk 1/2 mile on a beach once because my BC got folded with an air pocket I couldn't empty. The current caught me and I was gone. It was a miserable experience.
If any of these issues is a concern, I would definitely go with steel (or make sure you are weighted properly, neutrally buoyant with empty tanks) and a dual bladder. You can dive a dual bladder with only one inflator hose. In the event of a catastrophe, you manually inflate the 2nd inflator.
You always run the risk of having so much equipment that you can deal with almost any contigency, but you actually create a dangerous environment by diving with too much equipment that may be beyond your skill level, or just takes too much concentration to use easily and ends up confusing you in a panic situation.
Definitely important items to consider though.

 

[rongoodman]

Why is there so much variation in buoyancy among steel tanks? The Worthington HP 130 swings from -2 empty to -11.7 full. Perhaps my question is why would anyone want a tank as heavy as the PST as opposed to the Worthington?

 

[rainman_02]

Why is there so much variation in buoyancy among steel tanks? The Worthington HP 130 swings from -2 empty to -11.7 full. Perhaps my question is why would anyone want a tank as heavy as the PST as opposed to the Worthington?

Buoyancy swing of any tank is a function of the volume of air in the tank. The larger the cubic feet in the tank, the more the buoyancy swing.

Swing:

130 > 120 > 119 > 100 > 95 > 85 > 80 (77.2) > 72 > 63 > 40 > 19 etc.

 

[Leadking]

Negative cylinders have killed more than one diver. They enter the water with their air turned off and cannot get in turned on to adjust their buoyancy (and breath). We lost a diver here because of this (and because he was using a ring to keep his drysuit neck seal open). Make sure to inflate your BC before entering the water, this ensures your air is on and you don't have an uncontrolled descent.

Lee
www.seapearls.com