Pros/cons on backplate/wings vs wraparound BC.

[Lorenzoid]

At the risk of opening a can of worms (since it's been the topic of entire threads), remind me what is the implication of having no dumpable weight on a BP/W rig? Personally, I don't mind a weight belt at all, and the idea of having some dumpable weight somehow seems comforting. But am I overlooking something?

 

[Eff]

At the risk of opening a can of worms (since it's been the topic of entire threads), remind me what is the implication of having no dumpable weight on a BP/W rig? Personally, I don't mind a weight belt at all, and the idea of having some dumpable weight somehow seems comforting. But am I overlooking something?

A very good question!
After all, a BPW or any BCD for that matter could fail...


When diving a setup without ditch-able weights, proper weighting in the water is even more important.
If you're too heavy and experience a BCD/wing failure, you'll have trouble ascending, and trouble staying at the surface!

So, here's how to to make sure you stay awesome:


When shallow:
With nearly-empty main tank(s) (often 500 psi but sometimes lower), no extra gear (cameras, lights, stage/deco/slung pony bottles or just empty), a diver in the water should be neutrally buoyant at ~10-15ft and able to hold a stop with everything deflated (BCD, Drysuit, etc).
Anything more, and the general consensus is that you have too much weight.
Caveat #1: If diving a drysuit in cold water, one often elects to add a couple extra pounds of weight in order to add a bit more than the minimum required gas to the drysuit for insulation.
Caveat #2: Quite a few divers have a preference to be neutrally buoyant with the above setup (low gas) not at 10-15 feet, but at the surface, so they could possibly submerge again if a boat is headed at them (high-traffic areas mainly). If thick neoprene exposure protection is being worn, this may require a significant addition of weight due to neoprene compression effects relating to buoyancy.

When at depth:
With FULL tanks and ALL gear carried for the dive, one should be able to ascend from the bottom depth by swimming up with BCD deflated and a compressed wetsuit.

***Anyways, if you're diving non-deco and can meet the above criteria for both shallow and deep waters, you're probably fine as-is without ditch-able weight. An SMB is still highly recommended at least so you can have something to lay/grab onto once you're surfaced. ***


If you're wearing a drysuit or are carrying a lot of gear, see below....





Redundant buoyancy:

Because I wear a set of heavy doubles, carry stage & deco bottles, sometimes survey equipment, video cameras, etc, I would have quite a rough time ascending if my BCD/wing failed and had no redundant buoyancy compensation!
After all, when I set myself to be neutral on low gas at my last stop, that's not including the stage or deco bottles, camera, or even lights.
Which means that on the bottom, with all the extra gear, I'd be quite heavy if my wing catastrophically failed.

But I DO have redundant buoyancy! My lovely drysuit.
Because I can't swim up with all that gear if I were in a compressed wetsuit and failed wing, and because the water where I am is quite cold, it works out wonderfully. I don't even have to add all that much gas.

But what if the drysuit fails and the wing is good? My wing is sized to lift (just barely) me with all my gear in full doubles, stages, deco, etc, in a flooded drysuit. So take that into account for your wing size calculations.

For cases where both drysuit and BCD have completely failed (a really bad day... thermal concerns will likely become just as deadly as breathing gas concerns), well, that's why I carry a lift bag & SMB... Shoot the bag and wind my way up! One could also ride the bag up, controlling the ascent via venting the bag, but watch out for the higher potential of a runaway ascent. If using braided nylon "cave line" (I do), although quite strong, you may not get enough grip on it or leverage on the spool/reel, and have to ride the bag up after all. Try it in a pool with a safety diver and see. It sucks.

In the end, it's a really bad scenario, and your buddy/team would hopefully be helping you out a LOT. But don't plan for that.

I would highly recommend practicing the failed wing, flooded drysuit, and mix of both scenarios in the pool.


Where it gets weird/scientific diving:

If you're wearing a wetsuit due to temp/whatever reasons and MUST be overweighted due to expedition/survey/gear/large steel doubles requirements, if you still need weight you want to make it ditch-able. Or at least have a source of redundant buoyancy immediately available, such as a double-bladder wing. Adds some clutter and requires specific procedures to use safely.
If the requirements for the dive are that specific, well, things get complicated fast and I'll stay out of that rabbit hole for now.

 

[Lorenzoid]

But Eff, isn't weighting for neutral bouyancy with nearly empty tank at the surface the same as what one is supposed to do (well, by what PADI and I assume other agencies teach) with a jacket-style BC? A jacket-style BC implies ditchable weights--either integrated or a weight belt. When we learned to dive with the venerable jacket-style BC, we were taught the importance of being able to ditch weights at the surface in case of emergency--I dunno, maybe the diver is entangled in kelp on the surface or something and wants extra buoyancy. Also, in the Rescue Diver course we were taught to ditch the weights of an unconscious diver. How can any of these emergency procedures be done with a BP/W and no extra ditchable weight? Again, what am I missing in my thinking here?

 

[halocline]

The short and simple answer about ditchable weights is that how important it is depends on the circumstance. For most warm water recreational diving it's simply not necessary. PADI seems to be obsessed with dumping weights, but I believe that's because many new OW divers, especially students, have a hard time managing the surface. Often that's because they're so overweighted to begin with. There is almost no scenario I can think of when a properly weighted warm-water diver would need or even want to ditch weights at depth; its really a surface issue.

In colder water where divers are offsetting thick wetsuits or drysuits with lots of weight, it's thought to be important to have some of that weight ditchable....really IMO (I'm not very experienced with cold water) probably more important to have the weight separated so that some of it is on your rig and some on your body. That way both the rig and diver could be somewhere near neutral at depth.

If you are carrying so much ballast that you could not swim to the surface in the event of a BC failure, the safest thing is to have some redundant buoyancy source, and maybe some ditchable weight. Don't forget, though, any substantial weight-dump at depth is likely to mean a rapid ascent. There is a trade off.

I carry any ballast I need in pockets on my waistbelt and/or on the cambands. I don't like quick-release weights at all; while I've almost never seen a certified diver unable to stay afloat at the surface, I've seen plenty unable to stay down because a quick-release weight fell off their BC. But again this is in warm water; cold water is somewhat different.

 

[Lorenzoid]

Thanks, halocline. I suspected it might be just that. "PADI seems to be obsessed with dumping weights ..." is an interesting way to put it.

Though you've pretty much answered my question, another thing occurred to me in this regard. I have on occasion taken my weight belt off and handed it to someone on the boat so I could climb the ladder without having to haul an extra 10 lbs. up along with myself and my rig. I guess if I plan to switch to BP/W, I better do some more squats at the gym.

 

[rhwestfall]

I have on occasion taken my weight belt off and handed it to someone on the boat so I could climb the ladder without having to haul an extra 10 lbs. up along with myself and my rig. I guess if I plan to switch to BP/W, I better do some more squats at the gym.

If you really need 10#, you likely will have to find a place for 4# +/- (belt, or cam band pockets, etc), so you may still need that belt and be able to hand it off.....

 

[Johanan]

Pros/cons regarding balance & buoyancy?
... anything else you guys can think of.
Thanks. John

To the OP: If it helps, recently I did the switch from a jacket BC to a BP&W and I like it. Sorry that I can't really compare the trim and buoyancy of both systems because I started to dive dry at the same time and had to learn these skills anew. My most obvious "Pros" for the BP&W are not very sophisticated, yet. 1) After a jacket BC, to rinse and dry a wing is a pure joy; 2) I felt a clear decrease of drag, I can swim with less effort now; 3) I like that the harness is so simple and clean - no mess or confusion and everything is at hand. 4) it packs much more compact. The only "Cons" I can think of is the "conflict" between the weight belt and crotch strap, but there is a way around it - either by more practising, or by buying weight pockets. So far I do only recreational dives but I like the idea that if I move on to the technical and cave diving, I can just build up the same BC.

 

[TheQuintessentialMan]

Guys, thanks for all the info, advice, and ideas; it's been helpful. Had to put the quest on hold for a few weeks, but hopefully get it going again soon after some things blow over.

John