Recently certified - buoyancy a mess. Would PPB help?

[boulderjohn]

I don't think those material is covered in most OW classes. I certainly was never taught how to compute or adjust weight, just told I needed about 28 pounds. The finwr points of distributing it for correct trim I learned from thos board.

You may be right in that it is not taught in a lot of OW classes, but it is supposed to be.

• Doing a weight check has always been a part of the OW class. It is first done in the pool session, and it is supposed to be done (and gradually refined) on every one of the OW checkout dives.
• The PADI OW classes added trim just over a decade ago. The class videos include an instructor adjust a diver's trim by adding weight up high to held with horizontal trim. When those new standards hit, the shop where I worked then added trim pickets to the cam bands of all the instructional BCDs.

However....

• Instructors who still have students do skills, both in the pool and in the OW, while kneeling on the bottom almost have no choice but to avoid teaching proper weighting instruction so that they can overweight students to keep them stable.
• When the new standards were introduced but not yet required, I was allowed to conduct the OW checkout dives on my students who were with me in Mexico. We were using their rental BCDs for the students, and I had them put trim weights on the cam bands using bungee cords. The shop's instructors who were watching were intrigued. Why were we doing that, they wondered. What did that accomplish? I told them what it was for, and I explained it was part of the new standards they would have to be using soon. About six years later we were back at that location, and I saw several OW classes being taught. Nope. No effort to use trim weights. With kneeling students, trim weights are counterproductive to kneeling stability.

 

[Manchz]

I don't think those material is covered in most OW classes. I certainly was never taught how to compute or adjust weight, just told I needed about 28 pounds. The finwr points of distributing it for correct trim I learned from thos board.

That is correct. Because a lot of the knowledge of buoyancy/trim/weight/propulsion is covered in specialty courses, they don't give it away in the OW course - practical or theory. OW is just an intro. Only by making MANY mistakes and asking others (or researching), you learn more facts which makes for more questions and so on.

For example, I only recently learnt from an article posted by someone here that how put your mind to horizontal trim - keep shoulder, bum and knees in a straight line. OW doesn't teach you these little tricks. It also depends on the agency you learn with. I am trained with SSI. Most of my skills were done kneeling. I didn't even know at the time that that wasn't a great idea, until after my certification I started going for real dives and water trickled in my mask and I didn't have the option to kneel. I have figured out now how to clear mask without losing position but this is either through practical experience or from reading/researching.

It's clear to me that initial OW training can be quite subpar but not much I can do about that now. But my instructor, during OW dives, kept me quite light - I wear more weight now for real life diving than she had me on. But she put a bit of focus on fin pivots and weight checks for when I have to adjust these things in future.
However, there is no way I can know the intricacies of trim/weighting/buoyancy this early on (2 months since my OW ticket) as that material is reserved for buoyancy specialties.

But yes agree with the observation above, until my 8th and 9th dive, I have never used trim weights or even knew there were weight pockets on cam bands.

 

[Manchz]

This thread is a good example of why taking a course like GUE fundamentals early on is a good idea. There are many small equipment and setup issues that the OP is struggling with that would be easily fixed by a good instructor. Also learning a proper body position, buoyancy, finning and a proper weight check. There are so many obstacles to gaining comfort in the water if those issues are not addressed, so having more dives before the class would not be much help, and possibly would be a disadvantage because of bad habits formed. I feel lucky to have taken it early on, but I have heard from SO many divers that they wish they would have taken it sooner, because it made diving easier and more enjoyable.

How early on did you take it? After how many dives? So many mixed opinions here. Some say just dive more, don't do GUE. Some say do GUE after a few dives. Some say do GUE sooner than later.

 

[steinbil]

Most of my skills were done kneeling.

But my instructor, during OW dives, kept me quite light - I wear more weight now for real life diving than she had me on.

If you did skills kneeling, you probably were not light. I think it would be quite difficult to be stable on the knees unless you're overweighted. Not speaking from personal experience here, but it's been repeated by many instructors, and it rings true to me. However, you might find that you need less weight as your skills improve. If you are not in trim and kicking your legs, you are constantly swimming upwards, that could trick you into feeling light. Another possible issue is not being able to fully deflate the BC, which would make you more buoyant. Speculation, but that's all we can do on the internet. These are things that a good instructor would help you get right.

How early on did you take it? After how many dives? So many mixed opinions here. Some say just dive more, don't do GUE. Some say do GUE after a few dives. Some say do GUE sooner than later.

I originally wanted to take a GUE rec 1 class, which is GUEs version of the OW class. For practical reasons that didn't work out, so I ended up taking a private PADI OW class with two GUE divers in a twinset. So I completed all the PADI drills and the basic GUE skills right away. Then I continued with a GUE fundamentals class after 21 dives, and learned even more. I feel very lucky to have gotten such a good start to my diving and avoiding having to unlearn bad habits.

So I would advise anyone to do it sooner rather than later. It's much easier than unlearning old habits. And it makes diving more comfortable and fun! In any case, reach out to a local GUE instructor. They can help answer any question you might have, the ones I have been in touch with have been very welcoming and helpful. And then you can decide what route to take.

PS
Feel free to shoot me a DM if you have any questions

 

[FreqFlier]

Some say do GUE after a few dives

IMHO GUE course is a much better program than SSI or PADI or NAUI (some will strongly disagree, but that's my personal humble opinion). All of those certification agencies have own pros and cons though.
If you feel strongly about learning how to become a better diver - GUE fundies is what you want at this point (includes answers to most of your questions and then some). Some say get a few dives in first is because GUE course is very extensive and time consuming (and $$$ too). I'd say do it as soon as you realize you actually WANT to be underwater.
On the other hand there's plenty of really good instructors out there (agency affiliation doesn't really matter much, experience and skillful teaching is what you're after) that will help you with your progress without GUE. Sometimes it's tricky to find a good one though.
You can get tons of advice here on SB, but the problem is - you don't know what you don't know yet. Hence a course awaiting to be taken.

 

[jellycatsdad]

So I’ve struggled with buoyancy too - and it’s taken me a while to get a grip on it as a new diver. One thing - don’t wail down on the BC inflator button and/or treat it as an elevator - press it for a quick “hit”, breathe and see what happens. If you’re crashing to the ocean/sea floor still, add another hit of air. What worked for me was switching to a BPW(backplate/wing) BCD setup. That allowed me to carry part of my weight on the tank cam bands, and especially on the upper one and it encourages proper trim in the water. I also decided to dive steel tanks as well to avoid the buoyancy swings from aluminum when you breathe them down. On my last few dives, I’ve gotten to know my gear better and finally had no decent issues. Not all BCDs have their weight in “optimal” positions - I still use a weight belt since weight pockets with my BPW setup don’t allow me to have it “secure” on my body.

Also, once you get your buoyancy in control, you can start to work on different finning techniques and keeping your hands close to your body - the nice thing about nailing down buoyancy is less air use. Sounds like you were overweighted. I like do a weighting check at the end of my dive once I breathed down my tank.

 

[inquis]

I also decided to dive steel tanks as well to avoid the buoyancy swings from aluminum when you breathe them down.

A buoyancy swing is a property of all cylinders, as that is caused by the gas being consumed. In fact, the swing of a steel tank is often larger than AL.

The fact an AL80 becomes positively buoyant in isolation means nothing when it's rigidly attached to a BCD, a bunch of lead, a regulator, etc. The goal of being correctly weighted is for the ensemble (including you & any exposure suit) to be slightly negative when nearly empty.

 

[boulderjohn]

I also decided to dive steel tanks as well to avoid the buoyancy swings from aluminum when you breathe them down.

The swing in tank buoyancy is determined by the weight of the gas lost during the dive. The composition of the tank does not matter.

 

[lowwall]

I also decided to dive steel tanks as well to avoid the buoyancy swings from aluminum when you breathe them down.

The swing in tank buoyancy is determined by the weight of the gas lost during the dive. The composition of the tank does not matter.

I think this oft repeated nugget about AL tanks refers to trim changes rather than total buoyancy. I'm not sure how much it actually matters, but a positively buoyant tank held on by a tank band above its center of balance will torque your lower body forward/up slightly if you are horizontal.

Here's the image of a "Recreational scuba diver" from Wikipedia.

Sure it's only roughly 3 pounds positive (at 500psi) over the whole length of the tank. But that's a decent size lever on single tank band BCDs like this.

If I'm visualizing the forces correctly, changes in negative buoyancy have much less effect because either the plate or the tank itself will have additional contact points lower on the body which greatly shortens the lever arm.

BTW, can we get a better example photo? That's just embarrassing. Here's the entry: Scuba diving - Wikipedia

 

[inquis]

If I'm visualizing the forces correctly, changes in negative buoyancy have much less effect because either the plate or the tank itself will have additional contact points lower on the body which greatly shortens the lever arm.

The lever arm is the horizontal distance between centers of buoyancy and mass. The physical attachment points are actually immaterial. Applying this concept elsewhere: