Talk me *OUT* of a BP/W setup

[The Chairman]

I simply don't understand how you wouldn't be VERY positively buoyant at the START of the dive with a *full* air tank...?

Air has mass. The more air in a tank, the more it weighs, not the other way around. Tanks at the end of the dive are lighter and thus more buoyant than at the beginning. The max swing will be 4 to 6 pounds, depending on the volume of the tank.

Being over weighted by only six pounds is not that critical. If I am neutral on the bottom of a pool, I can easily breathe another 10 pounds neutral and have picked up as much as 16. In fact, I require all male students to pick up 6 pounds and breathe themselves neutral before they graduate from confined water. Women have to manage at least 4, but many can pick up 10. It's just not that much.

I always am able to ditch some weight and have had to do this once. I was narced, disoriented, cold as hell and that was indeed my parachute. I would do it again today under the same circumstances. If you need a 4 pound weight, it's somewhere at the bottom of Bear Lake in Utah.

If I need weights with a BP&Wing, I use DUI's weight harness. But I rather love integrated weights, which is another reason I like the hybrids like the Express Tech and the Hunter Pack. I only opt for a BP&Wing if I'm diving back mounted doubles. Yeah, it's a rare occasion.

 

[filmguy123]

Ahhh this makes sense.

Stefin - yes! I start tomorrow

This is helping create a hugely beneficial mental map of the territory for me.

Thank you all, fantastic.

 

[Shotmaster]

I have been using a classic forever (30 years), tried other BCD styles including wings. Now I'm waiting for this to finally get to the market.

SCUBAPRO - HYDROS PRO

 

[filmguy123]

Air has mass. The more air in a tank, the more it weighs, not the other way around.

Got it! So if I am understanding... air in the tank, because of density, has mass and will weigh it down. Thus, compressed tank air = negatively buoyant?

Air in the lungs and in the BC or wing, changes the volume (unlike a tank) and has a lower density due to being uncompressed (or less compressed)... thuse creatives positive buoyancy?

 

[filmguy123]

I have been using a classic forever (30 years), tried other BCD styles including wings. Now I'm waiting for this to finally get to the market.

SCUBAPRO - HYDROS PRO

That looks REALLY interesting... interested to hear what people have to say!

 

[doctormike]

Got it! So if I am understanding... air in the tank, because of density, has mass and will weigh it down. Thus, compressed tank air = negatively buoyant?

Air in the lungs and in the BC or wing, changes the volume (unlike a tank) and has a lower density due to being uncompressed (or less compressed)... thuse creatives positive buoyancy?

Things float or sink based on their density relative to water. The air in your tank is at very high density (that's how you can get a volume that would fill up 80 cubic feet at sea level into something the size of a scuba tank). It is higher density than the surrounding water, so it has negative buoyancy (it "sinks"). The air in your lungs and your wing are not compressed to such high density. They are less dense (mass per unit volume) than the surrounding water, so they are positively buoyant (i.e. they "float"),

 

[The Chairman]

Got it! So if I am understanding... air in the tank, because of density, has mass and will weigh it down. Thus, compressed tank air = negatively buoyant?

Bingo! Yahtze! Most tanks are negatively buoyant, but become more so with air in them.

Air in the lungs and in the BC or wing, changes the volume (unlike a tank) and has a lower density due to being uncompressed (or less compressed)... thuse creatives positive buoyancy?

Especially so, since that air spaces are at ambient pressure.

 

[gcarter]

speaking of not matching the gear the others on the cattle boat wear... any problems with compatibility in vacation diving as such?

Will all backplates support either single or twin tanks?

Any disadvantages when doing a lot of travel (vs say a back-inflate travel BC)?

My last trip a careless deck hand managed to give me a pinch flat. This is very hard to do with most BCDs, but easy enough to do with careless handling of a B{/W.

I still would not go back. I had to use a rental BCD while my wing was being repaired and I hated it.

 

[bergersau]

Ok, ok. Here's some questions and a summary of what I am hearing:

QUESTIONS:

Break this down for me in "minutes" of setup time, plus ideal gear AND cost? Be realistic and assume I'm a little slower than you, and only dive 50-60 dives a year. Required Setup time for each + ideal gear/cost when swapping parts (ie different BP or W):

1. I've been diving cold freshwater in Oregon lakes with a 7mm wetsuit and singles, but need to switch to a cold saltwater deep dive in drysuit with doubles.
2. I've been diving cold saltwater in Puget sound with a drysuit and DOUBLES, but now want to switch to board shorts and a single for a warm water tropical dive in Bonaire.
3. I've been diving tropical warm water in Bonaire, and now will go to Alaska fresh lake cold water where I will dive deep fresh coldwater in drysuit + doubles.

How many minutes will each task take for a non-pro, and what gear ideally shall I swap out (multiple backplates, STA, different wings, etc.?)

My next question relates to being REALISTIC about what I want to invest in for my setup. There's a lot of talk about BP/W works for everything! It's cheap! But as I was starting to gather and one post pointed out, less talk about what sort of gear investment I really need to make it work for these scenarios.

Very true on the "someday I will dive the Doria" scenario - no need to plan for future contingencies. But my most common scenarios, and those which I predict immediately and all within the next 18 months include:

Cold freshwater and cold saltwater, in both drysuit and wetsuit, in both singles and doubles. Puget sound, Crater Lake, Alaska.
Warm and mid tropics: Maui, Bonaire, Puerto Vallarta, Indonesia, Thailand

Even split between them all, and even split between local and travel. I fully anticipate hitting all of these in the next 18 months or so.

^^
REALISTIC KIT NEEDS FOR THIS?

Do I need multiple size wings? Say a 30 for Bonaire warm, and a 40 for drysuit doubles? I don't mean "you could maybe sort of technically squeeze by on a 30 for both" because let's be real, guys who dive BP/W don't strike me as the type to be cool with "maybe sorta technically squeezing by"?

Do I need multiple backplates? One setup for singles, one setup for doubles, and a lighter weight and higher weight option?



SO, hit me!

That's a lot to ask of a single rig.

For what it's worth if I was in your position.
I'd suggest you might be best off with two wings and two plates+harnesses might be optimal. - Please bear in mind that I don't dive doubles.

Having two harnesses means you won't need to re-thread the harness every time you swap plates.

A single tank wing in the 30lb lift ballpark.
A twin tank wing - unsure of size, that would depend on the size and style of tanks and exposure protection..
The take away point for this conversation is that because twin tank wings are considerably wider than singles you'd want one of each if you dive with both single tank and with twins.

A light-weight Aluminium plate and harness.
A Stainless steel plate and harness.

Having each plate set up with it's own harness takes the pain out of changing the rigs to suit the upcoming dives.

Use the aluminium plate for travel or tropical dives in light exposure suit with a single tank.
Use the Stainless plate for cold water singles diving locally (drysuit or thick wetsuit) . Less lead on the belt = more comfort and better trim.

Use whichever plate is appropriate to get correct weighting and trim with the twin set and exposure protection you'll be using.

Changing a wing from single to double or from one plate to another is about as easy as changing tanks on a normal BCD.
Whilst moving a one piece harness from one plate to another is about a 10-15 minute task. Adjusting the length of the shoulder straps only takes a minute at the start of the first day (Especially if you mark the correct lengths on the straps once you've dialed them in correct for each exposure suit. )

Getting two 'mix n match' plates and harness ,and two wings seems to me to give the best of all options.
Given the cost of travel, accommodation, boat charters, drysuits etc, having two of each is a relatively small incremental cost.

The advantage will be consistent placement of D rings, buckles, and most other gear and you'll find you're reaching in the correct places for D rings and dump valves regardless of which combination you're currently diving.

 

[gcarter]

A good back-inflate integrated BCD gives you all the same things.

My first 100 odd dives were on my SeaQuest balance, a back inflate weight integrated BCD. I was quite happy with it.

I am happier with the BP/W. The big difference is the lack of extraneous "stuff". Comparatively speaking, you always know the BCD is there. A properly adjusted BP/W "disappears".