Unit doff/don question

[TMHeimer]

I drill my OW students from day one to distribute the weight they are carrying between 2 or more systems based on the amount of lead they are using. And to have the option of only ditching part of it.

Same as the instructors here. With the amount of lead needed here for most, putting it in one place wouldn't be practical anyway. Or maybe using integrated & belt is just always the way it's been done here.
Your method of 2 or more systems, etc.--is that a recommendation by SEI or your own idea? Should all agencies follow this and make it "official"? I would yes. That would be one answer to the guy's question.

Do you teach using 2 systems even if there isn't much lead? In summer in NY I use my shorty wetsuit and 18 pounds all in the BC. Guess I figure my suit is thin with bare arms & legs so not much chance of a runaway ascent should I have to remove the BC.-- Make sense? (also my depths rarely even reach 20 feet in CT anyway....).

 

[Brett Hatch]

I'm not an instructor. When I took my PADI OW course, I used a jacket style BC, AL80 tank, 7mm farmer john, 7mm hood, 5mm booties/gloves, and floaty fins in 50F/10C water. With all that floaty gear, I needed 30 lbs of lead to sink, plus a 2lb weight on each ankle to trim out remotely well.

I found the BCD removal task to be very challenging on the surface. We were taught to remove the BCD, let it float at arms' length or so, then get on top of it to re-don. But the lift on the BCD was insufficient to float the whole rig, so when I removed it, it would sink to the bottom of the pool if I let go, and climbing on top of it to re-don was really hard. Doing it mid-water, around 7-8 feet, was much easier. Maybe because the wetsuit was partially compressed, so me + the rig was overall closer to neutral.

Now I use steel backplate, drysuit, steel tanks, neutral fins (negative fins w/ doubles), and about 14 lbs of lead, which all lives on a weight belt. Doffing and donning the rig is easy on the surface. With a full HP100 tank, the rig is roughly 15 lbs negative so the 30lb lift on the wing is way more than sufficient to float the rig itself. And since 1/2 the ballast is on the rig and 1/2 is on my person, both me and the rig are more-or-less neutral when separated, so removing and replacing the rig mid-water is dramatically easier as well.

Which is all to say, I agree with you Tom that separating it is easier and seems to be safer. I can't comment on whether it should be any agency's universal policy -- but it would have been really helpful if it were at least the policy of my OW instructors. Nobody should be out there diving a rig which cannot be floated by itself, and IMHO that goes hand-in-hand with splitting up your lead in cold water.

By the way, kind of off-topic, but Tom I'm surprised to hear that you are diving with 42 lbs of lead. I found an 8mm semi-dry (aqualung solafx) to be warmer than the 7mm farmer john, and it required less lead overall as well, by something like 8 lbs for me. My drysuit requires a bit more than the 8mm semi-dry, but still less than the 7mm farmer john, and is substantially warmer than either one. I don't know if you are in the market for new exposure gear, but there's some food for thought.

 

[scubadada]

So, this is an interesting question. I dive a Scubapro Knighthawk with integrated weights and dive solo. I very occasionally did doff and don when I would get my dive flag line tangled in my 1st stage. I mostly drift dive in SE FL I would always do this in mid-water and it seemed quite easy. When I did my SDI solo diver in 2013, I had to to doff and don at the bottom and then at mid-water. The latter was so much easier, probably freedom of movement. You may, or may not want to take this into consideration if doff and don comes up for you.

 

[sea_ledford]

Controlling the weight in the BC shouldn't be any different than when doing a weight belt removal and replacement when you have all weight on a belt. It is all about managing your center of gravity and not letting the positive and negative points get too far from the center.

I am teaching a Scientific Diver class this semester and one the the required skills is gear R&R. Most of the students haven't done it since their open water class, so they are not great at it initially. On my first lab of the week, I demoed both neutrally buoyant and horizontal as well as negative and on my knees (only skill I'll allow them to do that way). I will admit my demo of the knees version was a little rougher than my neutral version, because I never do it that way, but every student did it on their knees and they ALL had problems with maintaining control. I should note here that we use longhose regs for scientific, so that adds a few extra steps. After seeing that disaster, on my second lab I just showed them neutral and horizontal. I gave them the option of doing it on their knees, but they all did it neutral(ish). No problems at all. I'm never teaching that skill on the knees again, it is SO much harder! I think when the students are neutral instead of negative, they are just more aware of their COG so it is less of an issue than when they try relate to things with a regular gravity approach. After all when you take of a back pack, your feet don't float up to the ceiling!

 

[boulderjohn]

The last two posts illustrate what I believe is a problem with getting instructors to move to neutrally buoyant instruction--they assume that the skills must be harder that way, and they refuse to believe it when people tell them that many of the skills are easier when neutrally buoyant. They use their assumption as a reason not to make the change. Here is a story to illustrate.

If you see the PADI article from a decade ago that introduced the idea to PADI instructors, you will see pictures of me doing skills both neutrally and on the knees. I needed to have a good photographer with high quality gear to get the quality shots that PADI needed, and the shop instructor who fit that description was a confirmed on-the-knees instructor. (By the time we got the article published, I had been experimenting for 2 years and most of the other instructors had joined me and co-signed the article.) After we took the pictures, he asked some questions, and we talked about the doff and don. He said that it had to be so much harder to do it in mid water that he doubted he would even be able to do it himself to demonstrate it. We were still in the pool, so I pointed to the deep end and asked, "Why not give it a try?" He did it beautifully on his first attempt. What do you know?

 

[TMHeimer]

Brett: Yes, I agree that separate weights systems seems safer. Not sure at what point that would matter regarding how much weight you use-- ie. 18 pounds OK all integrated, 19 not OK? I do think there should be some sort of universal standard recommendation, which seems to be what the person was asking in the article.
Re the 42 pounds needed (an old SB topic for me). My instructor when taking the MSD program as astounded that I need that much. But it is what it is. Only $ I have for scuba is for a new BC at Xmas.

scubadada: Good advice. But how much weight are you wearing in SE FL? Would it work up north with tons of weight?

sea_ledfrod: I really like your point about managing your center of gravity and not letting the positive and negative points get too far from the center. Such as what I think Boulderjohn said back there-- do things intelligently, etc.

John: Yeah I know you're probably right that doff & don is easier midwater than on the bottom. No reason for me to try it at this point...But either way, neutral or not, my question to all is again--

Should there be a agency universal standard regarding weight systems should you ever need to doff & don?

Paging tursiops---- I'm too lazy to look it up-- What does PADI standards have to say about this?

 

[CT-Rich]

I learned the on the bottom version (at the time buoyancy control wasn’t yet a thing). The two times I felt the need to do it in the wild, it was on the bottom and I swung the tank around and braced it between my knees while cutting line and then flipped it over my head so I was sure the hoses went where I wanted them. I always split my weights.

Personally, I find doing anything at the surface more stressful than at depth because everything is on the same plain, lines and gear are floating around. Much happier de-screwificating gear before getting in or on the bottom. Fixing gear before decent is done as a necessary evil...

 

[boulderjohn]

I'm too lazy to look it up-- What does PADI standards have to say about this?

CW Dive #4 Requirements

Underwater:
1. Remove, replace, adjust and secure the scuba kit
with minimal assistance in water too deep in which
to stand, without losing control of buoyancy, body
position and depth.

 

[TMHeimer]

CW Dive #4 Requirements

Underwater:
1. Remove, replace, adjust and secure the scuba kit
with minimal assistance in water too deep in which
to stand, without losing control of buoyancy, body
position and depth.

Yes I'm familiar with this. So there is nothing about recommending splitting weight systems, or at what amount of weight you should do this, should you have to remove the scuba unit.

 

[boulderjohn]

Yes I'm familiar with this. So there is nothing about recommending splitting weight systems, or at what amount of weight you should do this, should you have to remove the scuba unit.

No, and that would not be in the standards anyway. Standards are strict rules that must be followed, not recommendations. PADI has a teaching guide that provides recommendations, but those are not requirements.

PADI's standards are written in such a way that pretty much any of a variety of approaches can be used. For example, their standards for alternative air sources allow for the traditional "golden triangle," bundeed necklace with long hose, Air II--pretty much anything you have ever heard of. They allow for primary donate, secondary donate, and secondary take.