steel buoyancy

[TMHeimer]

I'll do a wt. check next time out. But I'm still fuzzy on the steel buoyancy thing. My BCD takes the 10 pounders that buckle in under the pockets--standard, I assume. So unless I replace them with bullets or square 2 pounders and put these IN the pockets, my only other action would be to take the two 2 pounders out of the shoulder pockets and add them to the belt. Maybe those 4 pounds would make the unit positively buoyant if inflated fully?... but it may screw up my trim. Obviously the BCD is set up to take the 2 ten pounders..... So that still leaves me with a negatively buoyant unit.

 

[Splitlip]

Both my steel 120 and 71.2 tanks are negatively buoyant. I have 24 lbs. (salt water) in the BC. When I'm totally inflated it will sink. This means I can't do the unit removal/replacement skill at the surface. Anyone else have this problem?

Your profile says you have >100 dives. Is that correct?

 

[rstofer]

There are two rules you should consider: First, your rig should be able to float on the surface without being worn. Second, you should be able to float on the surface while wearing some portion of your weight but without the BP/W.

I'm 6'1" 210# and wear a 7/8mm single piece wetsuit. I have an HP 100 tank (-10.5 to -2.5#) with a stainless steel backplate (5#) and 20# of lead in a DUI Weight & Trim Classic.

I could try a different approach to initial buoyancy: float eyeball level with a full tank, empty BC and normal breath. This approach generally results in removing weight equal to the weight of the air - 8#. That implies that I might have to swim down the first few feet and it depends on my wetsuit losing 8# of weight at 15' if I am to make my safety stop. Although this shouldn't be a problem even if I only dive from 0 to 15', as a practical matter, a wetsuit won't re-expand very fast following a deep dive. In other words, there should be no problem making the safety stop with 500psi in the tank.

If this approach works, I could probably get down to about 12-15# of lead. I haven't tried it yet but I will the next time I dive.

Richard

 

[TMHeimer]

Spitlip, 150 exactly.

 

[RonFrank]

Bodies float, without exception!

You sound over-weighted to me.

"When I'm totally inflated it will sink."

Not sure what this means. RU unable to float at the surface that the beginning/end of a dive?

 

[TMHeimer]

Yes, I float easily at the beginning and end of the dive even when the BC is nowhere near fully inflated. In fact, I barely sink at the beginning of a dive indicating I'm at least very close to exact weighting. This is obviously due to the 7 mil farmer john. I swim horizontally always: in fact, I need an effort to not swim horizontally. Hovering is a piece of cake. At the surface when my BCD is totally inflated (to the point that air escapes the the quick dump) my unit will sink. It may have been years before I noticed this negative buoyancy had I not been practising the unit removal prior to the DM course. At our first pool session (weight belt only) the unit was of course very buoyant when BC inflated at the surface and I did the skill, so demonstrating it for students in a pool will not be a problem. But it won't work in the ocean with my current configuration with all that BC weight. Who else has 20+ pounds in the BC and a steel tank and has this problem?

 

[pir8]

I'm sorry but you sound exceptionally over weighted and in desperate need of a buoyancy class/clinic

 

[TMHeimer]

But how do you explain my excellent buoyancy and that I rarely add/release BCD air while on the bottom? And what about the buoyancy of my unit by itself at the surface? Also, I have found that some divers on SB with my same body weight, suit etc. use approx. the same weighting as me....I've found that many divers (in person and on SB) use approx. as much weight as me-34 lbs. with a 7 mil)--though most of those use a little less- like 32 pounds. So I may be a little overweight. But isn't 30-34 pounds the norm for such a set-up?

 

[pir8]

I don't know what you consider excellent buoyancy. You said it sinks by itself. That means your BC has way tooooo much weight in it for its amount of lift!!!

 

[RonFrank]

OK, I *think* I understand what you are saying. You have a 14mm farmer John setup, and all your weight is in on the BC/Tank, 20lbs on the BC, plus the tank weight (5~6lbs full/maybe 1~2 empty). Your bladder is likely in the 30lbs range, and when you remove the BC with all the weight on the BC, and steel tank, it sinks even when fully inflated.

IMO there is NOTHING you can do about that other than to remove some weight from the BC -OR- don't remove your BC.

So those are your choices, outside of purchasing a larger bladder.

If it were me, I'd transfer some weight from the BC to the diver (YOU!) but I have no clue how your weight is setup, and if it's a large bar or something, that may be easier said than done. The only option is a weight belt, or system like the DUI weight and trim.

You could get rid of all that neoprene, and than adjust your weight accordingly. 14mm (7mm+7mm) Farmer Johns work fine, but I feel like I'm in a cast with that much neoprene, and you need enough weight to sink a battleship to go down. They require more than my Drysuit to sink, and that is a LOT of lead! Worst of all, at the end of the day.. .you are wet!

There are those that will tell you that diving steels without redundant buoyancy devices is the Devil's work! I'm not in that camp, I think being able to swim the rig up to the surface is more important that ditch weight, or redundant bladders, so can you?

A drysuit is a great investment, and redundant buoyancy is smart. I picked up a used NexGen many years back for around $350, and have well over 150 dives on it. So drysuits don't have to be horribly expensive, and that suit sells around $600~650 NEW, and has proven VERY durable from my experience.