Best way to approach being overweighted?

[Blackcrusader]

It is an amazing feeling that first time you get your buoyancy spot on and you can do the Mission Impossible stop and hover 1 meter off the bottom. Man, I wish I was doing that right now.

I like to take divers with no wetsuits on over fire corals and have them practice trim and buoyancy. After a few coral tattoos I find they learn where all their limbs are

 

[scubaozy]

Agree on reducing weight in smaller increments. Average lung capacity is 6 liters. You can achieve a lot with that. When breathing out to descent, keep them empty until you reach 10-15 feet, by then your suit will be compressed enough, so, you will be *heavier. Common error is to expect immediate descent when breathing out. In reality you need 10+ seconds in that state.

*more negatively buoyant

 

[ontdiver]

Also, good to know that 6lbs is a big difference, DiveClimbRide! I felt crazy when it impacted buoyancy so much, I think I will probably be a bit more successful in smaller increments lol

Proper weighting and buoyancy control are probably two of the biggest challenges for new dives. It takes time to master and needs be adjusted as you shift between different thermal protection; salt vs fresh water; and steel vs alu tanks etc. Keeping a detailed log book will assist you with this so that you can avoid try and error each time you are "shifting".

As already mentioned, you want to make slow, incremental changes to your weight.

Don't be too hard on yourself....

 

[Edward3c]

Hi all - I'm a shiny new diver who is trying to get a good handle on the fundamentals. I'm going out with my buddy this weekend, and I want to use the dives to try and figure out my weighting a bit better.

As was suggested to me in my intro post, I am planning on doing a proper weight check at the end of the first dive, etc etc. But there are a few factors that I'm a little unclear on how to account for.

First of all, I think I'm definitely overweighted right now, using the weight recommended to me by my instructor and the dive shop. I can barely get off the bottom without really inflating my BCD - I'm going through gas like crazy too, which is annoying. But when I tried with 6lbs less, I couldn't descend. That seems like a big difference to me. Is it normal that such a small difference in weight would affect buoyancy like that, or were there maybe other factors at play?

My other question is whether I'm meant to account for the buoyancy of a neoprene drysuit? I know neoprene gets less positively buoyant at depth - is it still correct to just add enough weight to be able to descend at the surface, and I just have to accept the fact that I'll be a bit too heavy underwater?

TIA for the tips!

Hi,

It’s unfortunately common for dive instructors to overweight their students. Also on the first dive with a new operator the same practise is followed. Its costly (falsely) to them to spend the time getting customer’s weighting correct. For instructors in means their student will stay down on the bottom; for operators customers will have shorter dives with little danger of later trips running late.

I dive a neoprene drysuit. I’ve had normal, crushed and compressed neoprene suits. The common theme was there was a bigger buoyancy loss in the first 10m from leaving the surface – its related to Boyle’s Law.

My advice would be to dedicate a dive to getting your buoyancy close, don’t worry too much about getting it spot on in one dive:

• Find somewhere with a clean bottom at 2m (6ft) [you don’t want silt getting in the way].
• Start your buoyancy check with around 50bar (500psi). Use a cylinder from a previous dive then run one down by going on a dive – you might not find the test location or feel like spending the time playing with your weights.
• Place the minimum weight you need on your belt or in the pouches, the remainder should be in 1 or 2kg (2 or 4lb) lumps or bags (if shotweight). Each weight should have a means of attachment so you can easily add or remove to suit your requirement.
• Start the buoyancy check dive with what you think you need, but have the option to remove up to 4kg (9lb), your buddy should carry 4kg (9lb) for you to add if required.
• Either hand off or accept weights from your buddy until you feel close to neutral. The fine adjustment can be made on subsequent dives – you also can use your upper or lower lung capacity for temporary fine tuning.
• Above all have fun.

One possible cause of you not being able to get down at the beginning of a dive is air sticking to your suit. Its possible to have over 1Lt of air in small bubbles which get knocked off during the dive. I’ve noticed the difference between a first and second dive.

Also take a note of the Tare weight of the cylinders your using. My 12Lt steels range from 13.1kg to 17kg, which means I add or remove 4kg depending on which cylinder I’ve using.

It will come with practice.

 

[inquis]

I can barely get off the bottom without really inflating my BCD

Just wanted to add a little bit of an overview: your ideal weight is that such that you can be neutral at the safety stop (SS) in the middle of a normal breath with empty BCD at reserve pressure (commonly 500 psi if using an AL80 tank) and enough air in the DS to avoid a squeeze. Consequently, at all other phases, you will need to compensate. Upon your initial descent to the bottom, you have 1) about 5 lb more air (assuming AL80 tank) and 2) lost buoyancy due to neoprene compression (not sure how much is in your DS+hood+gloves+boots, but more than zero). Guessing 6-7 lbs total, that would require 3 LITERS of additional expansion/buoyancy to compensate.

In other words, you will still need to add a fair bit of air to your BCD during the beginning of your dive even when correctly weighted. The litmus test will be during the safety stop with near-reserve pressure. (You can purge your regulator to get to that pressure if necessary.) Cross your legs to prevent kicking (don't worry about trim during this), empty your BCD, and just see what you have to do to maintain depth with breathing alone. Hand off weight to your buddy in small increments (e.g., 1 lbs) if possible, otherwise just take less on the next dive. You already know losing 6 lbs is too much, so you should have it dialed within one or two more dives. Lastly, different undergarments change things, so keep notes!

After you figure out the total amount you need, then you can deal with distributing it so you don't rotate when you stop kicking. Best of luck!

 

[napDiver]

What tank your using? What's your exposure protection? Drysuit type and undergarments?

It is common for new cold water divers to struggle with getting down from the surface. You may need to swim down the first 10-15ft. Are you sure you are dumping all the air from the bcd and drysuit?

 

[wetb4igetinthewater]

when I went in to rent gear, the dive shop employees just asked what drysuit I was using and gave me weight...., but I figured they probably knew what they were doing.l

We all make the same mistake In assuming that dive shop employees know what they are doing. But when they are paid peanuts, expect monkeys. Doesn’t matter if they’ve been doing it for years, many people have e done the same profession for decades poorly.

Moving on. It is simple formulas on the correct weight. But it is contingent on you being as relaxed when determining the weight as you are in open water as people stressed don’t fully exhale.

 

[TMHeimer]

I was never told or read about doing anything regarding the buoyancy of your wetsuit.
Do the proper weight check and let us know how diving after that feels. Are the concerns you mention (like needing to inflate to rise from the bottom) fixed? Don't forget to add 5-6 pounds after doing the weight check to account for the tank getting lighter as you breathe it down-- so then of course you are 5 pounds heavy to begin with. It can never really be perfect.

 

[nolatom]

Diving with no line or objects to hold on to if you're too light or too heavy, is a challenge. You can meet that challenge in time, but..
With a patient buddy to hover near you, pick a boat dive where you "have to" descend and ascend on the anchor line. Then work at being neutral as you descend, and again as you ascend. The anchor line is your training wheels. After a while, you'll be riding the bike by yourself ;-)

And don't get discouraged if you have trouble getting and staying neutral once you're shallower than 15 or 20 feet. We all do, it's just more of a challenge because each foot of movement up or down has so much more effect on your "neutrality" than when you're at say 100 feet, for a nice round number. Ascend to 90. Easy, huh? Very little or even no BC or inhale/exhale adjustment needed, it's only a ten percent of your total depth.

Try to ascent that same from 15 feet, and you want to level off at 5 feet?? Really difficult, hard to avoid involuntarily surfacing and being mad at yourself. We've all done it, so don't feel bad. That ten feet was 67 percent of your beginning depth. That's a huge difference. Which is why it is nice to have an anchor line to help you stop, readjust, and collect your thoughts.

Later on, you'll get so good you can do a free ascent, and a safety stop at 15 feet, then slowly ascend to the surface, in control all the way. That's Graduate School ;-)

 

[lowwall]

Later on, you'll get so good you can do a free ascent, and a safety stop at 15 feet, then slowly ascend to the surface, in control all the way. That's Graduate School ;-)

And here is where we get into moaning about the state of typical dive training. This shouldn't be Graduate School, it should be something everyone can do before being handed their OW card.

To the OP,

As others have said, focus on your safety stop. If you empty your BCD and stay absolutely still with half a breath, do you sink? If so, you need to shed some weight. OTOH, if you have to kick down to stay at your stop, you need to add some.