Talk me *OUT* of a BP/W setup

[Shotmaster]

I guess it depends on whether you want a BCD or a life raft attached to your back.

Scubapro is just another overpriced distributor.

LOL, that was funny! I see your point, I hope you never have to see mine.

 

[DiverDownD3]

As one of the inexperienced divers on this board, I'm curious to what happened in your dive scenarios where you needed the extra lift?

Note: I'm not trying to be a smartass, I'm seriously curious. I guess I just invision that as you come up the water column your exposure suit expands providing you even more lift. Just thinking out luod

 

[kr2y5]

The single most important factor in determining required lift is the buoyancy of the exposure suit.

It is a personal preference, but many people believe in the idea of being able to float their entire rig on the surface, e.g., in case they need to get out of it, and if you subscribe to that idea, I think the weight of the rig becomes the dominant factor (as compared to the loss of suit buoyancy, e.g., due to a flooded drysuit, which many people seem to believe is generally only partial, not total).

 

[stuartv]

As part of the Rescue Diver course, I was taught to take off my own BCD in some scenarios. If I ever need to do that, I sure hope it will stay on the surface, so I can get it back later!

Also, some boat scenarios are easier if you don or doff your BCD in the water.

Being able to float your rig seems like a good idea to me.

 

[rivers]

A 40lb wing will easily float a set of HP100s, with torches, regs, v-weights and various other bits attached. Easily floats me with 2 stages attached as well. Quite a few of my friends will use a 40lb wing with 3 stages.

 

[cool_hardware52]

My comment was addressing everyone

Then don't quote me. I said nothing about small wings.

Tobin

 

[cool_hardware52]

It is a personal preference, but many people believe in the idea of being able to float their entire rig on the surface, e.g., in case they need to get out of it, and if you subscribe to that idea, I think the weight of the rig becomes the dominant factor (as compared to the loss of suit buoyancy, e.g., due to a flooded drysuit, which many people seem to believe is generally only partial, not total).

Suit buoyancy is what needs to be compensated for, and it is routinely ignored.

Lets look at two divers, both using 2 x hp 100's.

The first is diving in a drysuit with a thin undergarment, and his suit with minimum gas in it is 18 lbs positive

The second is diving in a drysuit with a high loft undergarment and his suit with minimum gas in it is 32 lbs positive.

Both are using the *same* cylinders

Which needs the larger capacity wing?

Why?

Tobin

 

[Stoo]

I take my wing (a single one and adapter) when I fly, if it's someplace where I am diving dry (like BC, which is an annual trip). In that case, I have two 50# bags, plus a camera case and a backpack. Kinda ridiculous.

When I am heading somewhere warm, odds are, Mrs. Stoo is coming with me... We have a bag of gear each, plus a smaller clothing bag... although I sneak some of my gear into her bag. We tend to travel to remote places, so take a certain amount of "spare" gear since rental stuff isn't readily available.

I intend to take up badminton in my next life. I have never gone on a vacation that didn't involve hauling tons of either dive gear or skiing equipment. I long for the life of a "carry-on" vacationer at times... Although I think I'd be bored silly.

 

[kr2y5]

Suit buoyancy is what needs to be compensated for, and it is routinely ignored.

Lets look at two divers, both using 2 x hp 100's.

The first is diving in a drysuit with a thin undergarment, and his suit with minimum gas in it is 18 lbs positive

The second is diving in a drysuit with a high loft undergarment and his suit with minimum gas in it is 32 lbs positive.

Both are using the *same* cylinders

Which needs the larger capacity wing?

Why?

Tobin

I wasn't suggesting that it should be ignored, my point was that we do need to take the weight of the rig into account, and that it could be just as large, and maybe even a bigger factor than the possible loss of suit buoyancy that you were alluding to earlier in the thread.

Let's take my example. My body is somewhere around neutral. I then put on undergarments, suit, hood and fins, and I end up with +X of positive buoyancy that prevents me from sinking even if my suit is shrink wrapped. To be fair, that positive buoyancy is X = Y - Z, where Y is contributed by all the air trapped that can get flooded, and Z is the negative buoyancy of my fins, and the likes. So at least in theory, the total loss of buoyancy in my suit could be Y > X, possibly even more than it takes to bring me back to neutral. But, my fins are not that negative, and I wear something like a trash bag for exposure protection, so presumably Z is on the order of a few pounds or so.

I then put on my rig: a pair of HP100 doubles, backplate, and regulators, and like most people, I realize that's not enough to sink me or to hold a safety stop, so I end up compensating for it by strapping some V-weight to my rig. I end up with a rig that is 30-something pounds negative in the water. For easy math, let's assume that's about 35 lbs. Since I not only manage to sink in the end, but I have also taken precaution to be able to hold a safety stop, I know that my rig, with all the weight strapped to it, weighs X + Z', where X is what it took to get me back to neutral, and Z' is all the extra, again presumably on the order of a few pounds.

So, in the end, it looks like the negative weight of my rig floating on the surface is Y + (Z' - Z), roughly comparable to the total theoretical maximum loss of all buoyancy Y in my suit, the difference (Z' - Z) being presumably close to 0. But, I'm not expecting the suit to lose all of its buoyancy. I've seen people claiming that I should expect maybe a third of the suit to become flooded. In any case, it sounds like it's really the rig, not the loss of suit buoyancy, that's the dominant factor.

Now, let's take out that 6lbs V-weight I have on my plate, and swap my tanks for another pair that's 10lbs heavier. Then, let's add some stages. We've now presumably crossed the line to a point where the weight of the rig is quite a bit more than the total theoretical loss of the suit buoyancy...

I could be wrong.

 

[cool_hardware52]

I wasn't suggesting that it should be ignored,

I never suggest rig weight *should* be ignored either.

I can however cite numerous, current examples of wings being marketed based only on the cylinders used, with no mention of the buoyancy of the diver's exposure suit.

Minimum wing lift for doubles is: Weight of the divers back gas (the gas not the tanks) + the Buoyancy of the exposure suit + 2-3 lbs (assuming a dry suit)

Minimum ballast is the buoyancy of the divers suit +2-3 lbs with empty back gas tanks.

Play with these numbers a bit and see if a pattern doesn't become apparent.

BTW, the 100's and 100's of posts I've made regarding wing lift I have always noted that wings need to be able to:

Float your rig at the surface with full tanks.
&
Compensate for the maximum possible change in buoyancy of your exposure suit.

Tobin