Need feedback on 1st BP/W for scientific diving

[RJChen]

Hey all, I'm new around here! Looking to upgrade into a SS BP/W setup from a back inflate BC for scientific work. Currently, I do a fair amount of scientific work in Hawaii and plan to try to get a state or NOAA job next year. I've been perusing the info about BP/W setups and have come up with a configuration, but I would love some feedback on whether or not it's feasible, compatibility issues, and etc.

My primary goal is to build a system that is usable in both cold and warm water and long term durability. Dry weight is also not a concern, since I pack light for travel and I weight lift, so a slightly heavier BC is irrelevant to me. Almost all readily available tanks in Hawaii are Al 80s, so I am not considering Al BPs.

Here's some context about me and my current dive set up:

Anatomy:
- 5'3
- 180 lbs (mostly lean, wetsuits are a pain)
- Almost negative w/ out suit in tropical seawater with a full breath of air

Current BC:
- Medium Zeagle Ranger LTD
- Minimum 6 lbs lead w/ Al80 and 5mm suit
- Generally, 12-14 lbs since most work is done on bottom

Hypothetical Rig:

*Updated* Back Plate: Apeks WTX
- Was Mares XR 6mm, I have been shown the error of my ways about weighting.

Wing: Apeks WTX-D40 PSD
- The Zeagle has 45 lbs lift already anyways, plus it's a pretty flappy horseshoe with just a single. So a 40 lbs doughnut should not be an issue.

Harness: Apeks Deluxe One-Piece Web

Concerns: Resolved. Guess I'm going full Apeks at this point. Just general feedback or pointers about individual components at this point.

A bit long-winded, so thanks for making it through! I nerd out on tech specs, so when I started looking into BP/W setups I went down a rabbit hole.

 

[runsongas]

Mares: makes 6mm backplate, cuts a bunch of holes in it so it only weighs 8.5 lbs. /facepalm

 

[RJChen]

Mares: makes 6mm backplate, cuts a bunch of holes in it so it only weighs 8.5 lbs. /facepalm

Ha, things like this I do not know how to appreciate yet. Judging from your response, I presume 6mm plates are supposed to weight 10 lbs at least? That being said, 10 lbs would be too heavy but the ~5 lbs of the standard doesn't seem like enough for my purposes.

 

[lairdb]

- Almost negative w/ out suit in tropical seawater with a full breath of air

Sigh -- I remember those days.

You mention a "program dive protocol" -- is this an AAUS thing, or local paper rules that aren't actually enforced, or...? If there are specific rules or measuring and approval practices, then random internet strangers won't be as much help.

- It bugs me the Apeks BP is 304 SS and $185 for a 3mm plate when the Mares is 316 SS and $189 for a 6mm plate. I know the diffs between 304 vs 316 are negligible with proper care, but still.
- Compatability issues, I know an Apeks wing should attach to the Mares BP since Mark from Safe Scuba has a WTX D18 attached to an Al Mares XR. Can we talk about how asinine it is that manufacturers don't list the spacing between bolt holes on plates and wings?

Or Piranha's private label is $89, or HOG is $109, or etc. ad infinitum. If you like where the holes are, it's a backplate. (Except, perhaps, Eric's Freedom Contour.)

304 vs 316 really isn't going to matter -- 6 pounds vs. 8 barely will IMO.

Most wing grommets are on 11" centers. Most backplates have slots in one or both positions to accommodate some variation. Yes, it would be nice if everyone posted specs, but they don't. Order from all one mfr if you want guarantees -- or check return policies and take a small risk.

(Wait until you start trying to find spring strap measurements. "WTF does 'medium' mean? Wait, 13.875 from where to where?")

 

[RJChen]

Sigh -- I remember those days.
You mention a "program dive protocol" -- is this an AAUS thing, or local paper rules that aren't actually enforced, or...?

Oh yes, AAUS. Not really set rules, but ya know, best practice standards and such. My train of thought is; if I'm gonna be negative no matter what, may as well make it so I can pack one less weight on my belt or use smaller weights. Also, I can get special rates on Apeks and Hollis gear, which is why I have not really considered alternative BPs. After reduction, they would essentially be the same. Apeks would win out, since compatibility.

 

[johndiver999]

Your "problem" statement is lacking critical information.

If you are potentially going to use steel tanks which are negatively buoyant in warm water (i.e., minimal or thin suit), then you definitely don't want a heavy SS plate. You will be over-weighted all the time and will probably carry zero ditchable lead. If you were a large, obese person you might be able to pull it off, but if your personal buoyancy is as you describe - no.

You can always add some lead here or there, if/when you are diving with a thick suit.

 

[RJChen]

Your "problem" statement is lacking critical information.

Thank's for telling me about the oversight. I forget Hawaii is unique in that almost no one on island has a steel tank. I've only ever seen the old 72 cuft steels here, so Al 80s are almost exclusively used for non tech. Overweighting is ok to a degree since a lot of my work requires me to be on the bottom, in my current set up I am overweighted 6-8 lbs, depending on swell, for scientific work. Also, I'd likely still be negative if I went standard 3mm plate and ditched weights, assuming a semi-full tank.

 

[johndiver999]

Thank's for telling me about the oversight. I forget Hawaii is unique in that almost no one on island has a steel tank. I've only ever seen the old 72 cuft steels here, so Al 80s are almost exclusively used for non tech. Overweighting is ok to a degree since a lot of my work requires me to be on the bottom, in my current set up I am overweighted 6-8 lbs, depending on swell, for scientific work. Also, I'd likely still be negative if I went standard 3mm plate and ditched weights, assuming a semi-full tank.

I'm not sure you are getting the big picture here. Some people will tell you that you should NEVER wear more lead (or ballast) than you need to make a safety stop and if you are diving over weighted, then it is because you have poor diving skills.

However, I know that kind of attitude is wrong and there are often some very good reasons for wearing extra lead so that you can be heavy and accomplish some particular task while working on the bottom.

It is important to be cognizant of the significant compromise in safety which is the result of being (deliberately) overweighted by non-ditchable ballast (e.g. a heavy plate and tank). If you are only familiar with 71.2 steel tanks and aluminum 80's then I understand why you might not fully understand how a heavy steel tank and a heavy plate can pin you on the bottom if the BC fails.

If you are going to over-weight yourself, be smart and make sure you can drop enough lead to allow yourself the ability to swim to the surface with a failed BC. That may not be possible with a heavy plate and big tank. A lighter plate gives you more flexibility.

 

[RJChen]

It is important to be cognizant of the significant compromise in safety which is the result of being (deliberately) overweighted by non-ditchable ballast (e.g. a heavy plate and tank). If you are only familiar with 71.2 steel tanks and aluminum 80's then I understand why you might not fully understand how a heavy steel tank and a heavy plate can pin you on the bottom if the BC fails.
.

Ah, there answers my question. I have dived with that Zeagle and integrated weights for my entire dive career, ~5 years, so weight was just something I chucked into the BC and adjusted as needed. As important as weighting is, as I have found, it seems like it was not sufficienty covered in my rec, commercial, and scientific training. Moving into BPs, that is obviously different with non-ditchable weight.
Considering how I am particularly negative, and how few people seem to have the same issue as I, I couldn't find much info regarding my specific situation. So that's while it boiled down to if I'm gonna be negative no matter what, what's the diff between 5 and 8 lbs plate?

 

[johndiver999]

What's the difference - about 3 lbs . LOL.

How much can you swim up with a failed BC? That is something you have to determine.

Don't kid yourself into thinking your life might not depend on it. Lots of people wear weight belts with BP/W.