If you need to release 50% of your weight in an emergency you are likely overweighted. I need to drop 4 lbs. Maybe 6 at most to stay positive on the surface. That's using 26 lbs of weight with a single tank, dry suit, and BPW.
Looking for Advice on BP/W
- Thread starter jwllorens
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How much weight are you carrying now? Unless you're only carrying 12lbs or so total I can't see a need to ditch 50% of your weight.
Either way, you will need to plan total weighting including the weight of a BP... as that is not ditchable in and of itself. Depending on total weighting, exposure protection, and tank type/size a tall skinny guy can easily get into a spot were there's not much lead to ditch.
As mentioned, I dive steel doubles and even with a drysuit and decent under garments I don't need any lead in saltwater. I need to switch to an aluminum plate in freshwater. Of course I've got a 60lb wing, a drysuit, and a 6ft closed-end SMB for redundant buoyancy on top of my redundant buoyancy.
Interesting. In salt water, at the surface with a jacket BCD and a full 3mm wetsuit I will not sink when the BCD is empty with 14lbs on my weight belt. With 16 lbs, I will sink slowly, and usually fin a little to expedite the process, and once at depth the wetsuit doesn't offer much flotation and I add a breath of air to the BCD and I become neutral. With a BP/W I hear that the backplate offers up to 6lbs of weight, and you have less bouyant fabric, so I would expect to carry 8-10lbs or less. I only have a 6ft sausage with a mouth inflator and no overpressure valve, which I suppose could be used for flotation but would be less optimal than other types of SMBs for redundant buoyancy.
I have never had to drop my weight belt, and even opted not to during the water treading test when I was being certified, with no other gear aside from the weight belt. I hope I never have to. I just assumed that if I had a BC failure and I couldn't inflate it at all then any amount of weight would work against me once I completed a controlled ascent to the surface, especially if I found that after a free ascent from calling off a dive that I was nowhere near the boat (which has happened to me.)
In that particular scenario, my BC was working fine so I inflated it and was able to reach the boat after a bit of a workout. If the BC had not been working, I would have wanted to drop all of my weight. With a drysuit, I assume I could also inflate that for buoyancy, but I will not be using a dry suit for some time until I am more experienced or move to another location. Until then, I am primarily doing boat dives and many of them are far enough from land to where it is not visible. If for some reason I am stranded at the surface, I am counting on my legs and my BC to keep me afloat until I get to the boat or the boat gets to me, so if the BC isn't working I don't want anything making my legs work harder.
But I see what you are saying, at the surface if I only drop 2lbs I would naturally float. I don't think I am over-weighted, it is just the idea of being semi-permanently "attached" to anything designed to pull you below the water seems a little unnerving if you have an equipment failure with your only means of flotation, especially to me since my only "bad experience" while diving was at the surface when flotation was the primary concern. If my BC had not been working I sure as heck wouldn't want any weight on me at all in that situation. In quarry or springs drives, this would obviously be pretty irrelevant.
Is this just an unfounded concern of a novice diver? I know that the circumstances where you would want to drop weight are specific and in many cases rare, especially under water, but I feel like it would not be a bad thing to have the option to drop as much of it as you can especially for boat dives.
Edit: I would also mention that I can't stand diving with a snorkel. It flips around, attempts to rip my mask off, and is just plain uncomfortable. Though I was initially trained to use one when certified as a safety precaution for getting stranded at the surface, I been leaving it in my dive bag as of late and I do not regret it. Without this "surface safety device" I just want to keep my head above the water if I do get stranded. If this is possible with a BP/W with proper weighting and despite a wing failure and few ditchable weights then that settles that in my mind.
Certainly something to be mindful of, but as with anything relative to weighting there is no proper unit of measure equal to "as much of it as you can." Good to be able to ditch "sufficient weight to establish buoyancy" but rare would be the circumstance where you'd need to ditch "as much as you can."
That said... you might be close to the point where "sufficient" and "as much as you can" are almost equal.
If you're weighted properly with 16lbs and a recreational BCD, let's assume you'll need 14lbs with a BP/W (A standard recreational BCD is usually a few lbs buoyant.)
Of the 14lbs, let's go with a steel plate so that's 6lbs of ballast. You've got 8lbs left to play around with. I'm perfectly comfortable diving with no ditch able weight so I'd put 4lbs in two-cam band pockets... but that doesn't mean you should be comfortable doing that. If you were my student I would probably try 2lbs in cam band pouches and 6lbs on a belt or in ditch-able pockets. Perhaps you could get away with only 4 ditchable pounds... but possibly not worth the trouble of moving it around unless putting two lbs elsewhere helped your trim.
cool_hardware52
Contributor
A camband is the 2 inch webbing and Cambuckle that secures the tank to the Plate, typically a BP&W will use a pair of Cambands.
Not knowing much about your exposure suit and cylinders I am making a few assumptions, but I talk with a lot of divers moving from a BC to a BP&W, and quite a few are adamant about not using a weight belt. That's understandable with 12-18 lbs in a belt, not fun.
Once you get rid of your current floaty BC and add the ~ 6 lbs of plate and harness a BP&W typically provides you may find the resulting weight belt of ~ 4-8 lbs to be easily tolerated. Most divers do.
There are some benefits in terms of required wing capacity of having some of your ballast on your person vs having 100% of it on your "rig"
Not sure where your require to be able to ditch 50% of your ballast springs from, but I'd be happy to walk you through how I prefer to rig ballast and under what (limited) conditions I might consider dropping weight.
Tobin
I use a 3mm long wetsuit. I dove in cozumel with it on every dive in bathtub-warm water a month back, and more recently I did a quarry dive. My buddy and I quickly discovered that 40ft in the quarry was our limit due to the temperature but we managed a 35 minute dive at 50F-56F no problem. I like using this suit even in warm water because the neoprene on my legs seems to help with trim.
I dive with aluminum 80s primarily, and I drop a lb or two if I end up with a steel tank. Another lb or two if diving in fresh water. I would love to dive with doubles eventually but as I mentioned before I am mostly just going on as many trips as I can with the local training facility to gain experience (and because the instructors and other divers are great) so all my dives now and in the foreseeable future are going to mostly be with aluminum 80s in warmer water with the 3mm wetsuit.
I dive with aluminum 80s primarily, and I drop a lb or two if I end up with a steel tank. Another lb or two if diving in fresh water. I would love to dive with doubles eventually but as I mentioned before I am mostly just going on as many trips as I can with the local training facility to gain experience (and because the instructors and other divers are great) so all my dives now and in the foreseeable future are going to mostly be with aluminum 80s in warmer water with the 3mm wetsuit.
cool_hardware52
Contributor
A couple quick thoughts; most common steel tanks are ~6 lbs more negative empty than an aluminum 80. There are exceptions, but steels are ~-2 lbs empty vs +4 for al 80's. That suggests that you should be able to drop 6 lbs when moving from an al 80 to a steel tank.
The quick and dirty rule of thumb for salt water vs fresh is 2.5% or 1 lbs of ballast for every 40 lbs of diver and gear. I may have missed it but I haven't seen your weight. If I assume your are ~180 lbs and are wearing 60 lbs of dive gear for a total of 240 lbs the change in ballast from fresh to salt should be about 240 / 40 = 6 lbs.
Your comment suggest a careful weight check could be beneficial.
If we assume that you are neutral in your swim trunks (most reasonably fit people are, given that we are made out of slightly salty water) then any ballast you carry is needed to offset the buoyancy of 1) Your exposure suit, 2) Your current padded and floaty BC 3) a buoyant al 80.
14 lbs + 2 lbs of regulator = 16 lbs of things that don't float. A 3mm suit on a person of normal stature will be ~3-5 lbs positive. And empty al 80 is +4 lbs 16- 4 -4 = 8. Very few BC's are * lbs positive . 3-5 lbs is not uncommon, but 8 is on the very high end of the known range. That suggest you may be a bit over weighted.
Lets look at a typical BP&W with a SS plate for warm water.
The plate and harness will provide about 6 lbs of ballast and your reg will provide ~2 lbs for a total of 8 lbs of things that don't float. Your 3mm suit is ~+4 and your empty al 80 is +4 lbs 8 lbs of things that don't float vs 8 lbs of thing that do. Bingo! Many diver in warm water with thin suit and buoyant tanks use nothing but their plate, harness and reg for ballast. Very streamlined.
Of course they have no "ditchable" ballast other than their rig, but adding ballast just to have something to drop isn't really a solution. These divers will never be very negative, at the start of the dive they are -4~5 lbs and suit compression may add another 2-3 lbs.
As they breathe down their cylinder their max negative drops.
Fit divers in thin suits using a BP&W have little need for additional ballast. If you plan on warm water only you need very little wing, 20lbs or less.
If your range of applications includes other cylinder and thicker suits for cold water wing selection becomes a bit more of a compromise.
Gotta run, dinners on. There are a number of ways to approach a given application, but I have found an interactive conversation is the most productive. I'm around the office most days. 626-799-5078
Tobin
VsubT
Contributor
The DUI weight & trim harness system that TSandM mentioned above addresses both of these issues directly. It's a great piece of gear for those of us with the wrong hip configuration to hold a belt in place. I picked one up a while back, and I'm really happy with it.
Lance
cool_hardware52
Contributor
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