Am I overweighted

[MauiScubaSteve]

... BTW, NAUI is now teaching the 15 foot empty BCD with empty tank rule which one NAUI instructor is calling Naui's "new" way of weighting.
I hate to tell him, but weighting light for 15 to 20 foot neutral buoyancy has been around since diving started. It had to be, they didn't have BC's to help people fake it.

Seems to me that "15 foot empty BCD with empty tank" is just a little lighter than my "surface empty BCD with empty tank" but probably still just a little heavier than your "hold a 15 foot stop empty BCD"

NAUI seems to almost be the worry wart "your gonna die" poster I was typing about.

You are at 15 feet with an empty tank and you are still neutral, as long as you are "only" normally breathing your buddies alternate.

 

[boulderjohn]

My thinking on minimal weighting has changed over the years. I used to advocate the traditional approach of having the very least amount of lead possible, leading to the empty BCD at the safety stop concept. I have changed my thinking based on several reasons.

One was just mentioned by Halemano. I want to be able to hold a stop comfortably in an air sharing situation with a buddy who might not be totally composed.

The second was born of my technical diving training. I learned to achieve proper trim while very much overweighted with steel tanks and loads of gas that would be used up during the dive. I realized that, at least for me, while recreational diving with a single tank and a BCD (back inflate), a proper distribution of weights was more important than the amount of weight itself. With the BCD I was using then, if I distributed the available weight evenly, diving was really, really easy. I could just hang motionless with the fishes while in good, comfortable trim and enjoy the scenery. Since I could not control the sizes of the weights available on commercial dive boats, the amount of weight I dived with varied, but I always came as close as possible to that even distribution ideal, even if it meant overweighting.

I finally decided that I preferred to be a couple of pounds overweighted. As the air in the tank goes away, it is much nicer not having to twist and turn to find route last tiny bubble of air to a vent.

 

[rgiles]

DevonDiver - Just want to say thanks for the blog. I personally believe that buoyancy is the MOST important skill and I work on it everytime I dive. It's nice to read your blog an pick up on the finer techniques that have passed me by.
Rich

Losing 1/2 your weight, and still being able to easily re-descend, does indicate that you are over-weighted.

At what stage in the dive did you lose the weights? More relevant: how much air remained in your cylinder at that time, and at what depth were you?

Whether you cylinder was full, or empty, would make a difference to the impact of losing the weight.. as the air in your tank has a weight value. Likewise, the depth is a factor, as this will determine the relevant buoyancy provided by your exposure suit.

The cast-iron test for weighting is whether you can maintain a hovering safety stop, with minimum reserve air in your cylinder. This means that your exposure suit is at its most buoyant and your cylinder weighs the least. If you can maintain the stop, then you have enough air. On that stop, assess how much air you have in your BCD. You shouldn't really need any air in that scenario. If you have air in your BCD, then remove weights from your rig, until you reach the limit at which you can comfortably maintain your hover. That will be perfect weighting.

Problems with descent, in novice divers, are often linked with either; failure to fully deflate the BCD, anxiety causing heavier breathing (inflated lungs add buoyancy), not fully exhaling and/or subconsious movement of the feet (fining, whilst vertical) which provides upwards thrust.

I'm in the middle of writing a series of blog articles on buoyancy and weighting at the moment; you may find them useful:

Scuba Buoyancy Masterclass 4of9 - Assessing Your Weight Requirements

 

[Eric Sedletzky]

There are a couple reasons for having no air in your BC at 15 feet.

First, 15 feet is the most critical depth for gasses to expand and contract. With not having any air in your bc to expand and contract it makes holding a stop that much easier. Many times divers have to do stops in larger swells that constantly change the depth while the diver is trying to do a stop. If the diver is overweighted then air has to be kept in the BC to maintain a stop and is subject to expansion and contraction as the depth constantly changes. This can become annoying because constant inflation and deflation of the BC has to be done to hold position.
Helping a diver out of air would only add one more thing to an already problematic situation. So in that respect tuning your weights to be neutral at 15 feet with empty BC would be better. Breath control can easily be used to fine tune buoyancy a few feet either way.

The second reason for shedding as much weight as possible is because who wants to lug around extra weight if it's not necessary? Not only is that miserable for shore diving but it's also miserable underwater. Light, fast and free is my motto.
It must be from freediving.
Not to mention the savings in money at 2 or 3 bucks a pound for lead.

 

[brucetrinity]

This is one of those threads that is full of good information but starts to drift to the "I can dive lighter than you" mentality. If someone on the boat can dive with hardly any weight I really don't care. I wear what makes me feel comfortable at a safety stop without worrying about drifting to the surface even if my tank is near empty. That amount changes depending on configuration and dive location (yes, I add 2 lb if I'm cruising around in 10 feet of water) .... that's why I take notes and refer to them before diving.

I'm not questioning any of the methodologies ... but no one should allow themselves to be convinced to shed weight if it makes them uncomfortable.

 

[TSandM]

I'm with Boulderjohn. Massively overweighted is horrible, especially for new divers; the expansion of the BC bubble in the shallows is really problematic. But those of us who do technical diving learn to tolerate being "overweighted", because the gas you bring down weighs so much, and you can NEVER be lighter than the gas. As a result, I've learned to manage a larger amount of compensatory air in the BC and dry suit, and I LIKE being warm. Therefore, even though the weight penalty for diving Puget Sound with four inch thick undergarments is substantial, I do not try to parse my weights as closely as possible. A couple of extra pounds means a warmer diver, a much warmer deco (I don't have to try to get ALL the gas out of my suit in the shallow water) and a safety margin if something delays me at depth (been there, did that).

 

[Antagonist]

So what I got from all the post is to do a proper weight check at 15 ft. Having enough weight to control my depth with my breathing.

 

[MauiScubaSteve]

perfect