Suggested BP/W setup for possible convert?
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DwainT
Contributor
cool_hardware52
Contributor
I often talk to diver's that dive locally, i.e. at home in moderate to cold water and travel to warmer vacation destinations.
What one set up will best best for both?
Wings must be sized for the most buoyant exposure suit, and cold water diving involves substantial ballast.
My recommendation is to use a SS back plate, and to carefully select a wing that is large enough for the cold water application without being over sized.
A typical cold water diver may use a SS plate, steel tank and weight belt to offset the ~20 lbs of positive buoyancy a 7 mm wetsuit will provide.
That means the diver will need a wing in the 20-30 lbs range, maybe a bit more if they are wearing a lot of neoprene.
How will this gear perform in warm water? With a 3mm suit (~+4) and a buoyant al tanks (~+4 lbs empty) the diver will need about 8 lbs of total ballast. A typical SS plate and harness provides about 6 lbs and a regulator provides about 2 lbs.
If is quite common for divers using thin wetsuits and al 80's to dive with only a SS plate and regulator for ballast.
My recommendation for those who dive in cold and warm water is to start with a rig that will serve them in their cold water diving, and to take that same gear on their next warm water trip. See how it works, see if the ~3-4 lbs weight difference is meaningful in terms of travel weight. For some travel weight is key, others find a BP&W, even with a SS plate, is already lighter weight than the jacket BC is replaces.
IMO, most divers find the SS plate and "right sized" cold water wing is ok in warm water.
There is of course a place for lightweight plates and tiny wings. Great for diver who needs to cut their toothbrush in half to get under weight restrictions, and small wings are fun to dive in warm water. Unfortunately tiny wings are not useful in cold water diving.
Tobin
That rig is small enough that, since you have no other weight than the weight of your backplate, it shouldn't be too tough to swim the rig up. Once on the surface, simply take it off... something you'd probably do with any rig, in the event of a wing failure, unless you have some other way of floating it.
Remember, "ditchable weight" is really intended to be ditched only at the surface, else you risk becoming a missile as gas expands and you go shooting up. Ditching at depth is really a worst case scenario where you can't swim the rig up for whatever reason. A wing failure is not the same as OOA, so there shouldn't be quite the same urgency.
MSilvia
Contributor
What would you do if this happened WITH ditchable weights? Hopefully "plan A" isn't to make an uncontrolled buoyant ascent from 120'...
My plans are:
a) Add gas to my drysuit to assist with any loss of wing buoyancy.
b) Use a lift bag, SMB, or safety sausage to provide additional buoyancy for the ascent and surface flotation.
c) Have my buddy assist me in getting to the surface.
d) Swim to the surface.
e) Remove my harness, orient the wing so the hole is at the lowest point, purge some gas into it, and ascend with the assistance of whatever gas the wing will hold while keeping the hole as low as possible.
f) Start coming up with creative alternatives, like purging air into my wetsuit, climbing the anchor rode until I regain enough buoyancy to ascend, etc.
z) Ditch my heavy gear at depth and rocket to the surface without making a stop, then spend some quality time in the recompression chamber.
Just looking for the proper procedure. Here's a scenario that just happened two weeks ago on a shore dive: 300-400 yds out, about the descent point, a group member popped the filler hose seal on his BC (filler hose on the top of the shoulder). He started to descend. Popped his reg in his mouth (mask still around neckline) and dumped his weights at about 8-10 feet or so. He popped back up. Buddy retrieved his weight sacks and excorted him back to shore.
Just wondering what that would look like wihtout ditchable weights. Just kick and kick and hope you can get everything off before sinking??
a) Add gas to my drysuit to assist with any loss of wing buoyancy.
.....Nope. Dive a wetsuit
b) Use a lift bag, SMB, or safety sausage to provide additional buoyancy for the ascent and surface flotation.
....Sausage? For maybe 2# lift? No lift bag or SMB.
c) Have my buddy assist me in getting to the surface.
.....Yes but I prefer a more solid process
d) Swim to the surface.
....Of course but...see above
e) Remove my harness, orient the wing so the hole is at the lowest point, purge some gas into it, and ascend with the assistance of whatever gas the wing will hold while keeping the hole as low as possible.
.....Sounds like you're gonna die
f) Start coming up with creative alternatives, like purging air into my wetsuit, climbing the anchor rode until I regain enough buoyancy to ascend, etc.
.....I'm an engineer and a data geek
. I need solid processes to save my life. I'll keep the creativity for the kitchen
z) Ditch my heavy gear at depth and rocket to the surface without making a stop, then spend some quality time in the recompression chamber.[/
.....Don't have heavy gear. What to ditch is the whole question.
Plan a: So basically it's down to swim hard, hope your buddy is close, keep your reg in your mouth and breath easily while you dof your gear hoping you don't descend too far.
Plan B: Or, think it through a bit more smartly and have your gear light enough to require at least 6#-8# ditchable weight that would allow self-rescue to be much, much easier and far more likely
I go for plan B.
cool_hardware52
Contributor
For local dives here in so cal on can expect a fairly buoyant exposure suit, typical 7mm suit will be about 20 lbs positive at the surface.
How buoyant will it be at 15 ft? Most would agree that it will be less buoyant at 15 ft, as the pressure is doubling in the first 33 ft.
It's typical that a 20 lbs buoyant wetsuit will be 6-7-8 lbs less buoyant at 15 ft. This is easy to confirm. On the start of the next dive descend to 15 ft and try to hover without adding any gas to your bc.
Why should we care? Simple 6-8 lbs equals or exceeds the weight of the gas in a typical single cylinder. That means we can start a dive in a heavy wetsuit weighted so we are eyelevel at the surface with no gas in our wing and a full tank.
At the end of the dive we will be lighter by the gas consumed, i.e. ~5-6 lbs and we will be able to hold our safety stop due to the loss of buoyancy of our compressed wetsuit.
Pretty neat.
What other implications are there of being weighted as I describe? In the event of a buoyancy failure, even with a full bottle the diver can stay at the surface without dropping any ballast.
That makes a wetsuit wearing single tank diver pretty safe. If he has a buoyancy failure at depth he might be a bit negative, but this improves as he swims up until he reaches the surface, where the he will remain without effort.
Sounds to me like the diver in your example was overweighted.
Tobin
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