BP/W...please explain what it is!

[CompuDude]

How come? What is the disadvantage of having all your weight, including dump-able on the Rig and only one tank?

It's heavy as hell for one thing.

 

[cool_hardware52]

How come? What is the disadvantage of having all your weight, including dump-able on the Rig and only one tank?

Go and read my post again. I explained exactly why, i.e. having all your ballast on your rig requires a larger wing.

Tobin

 

[AndrewST]

Oh. Ha! You did answer it before I asked it! That is what I get for trying to discuss dinner options with the wife and reading the forum at the same time!

Well, I personally do not like weight belts in the least. I find them to be a pain and will avoid them when possible, at least at this point in my diving.

 

[RJP]

...at least at this point in my diving.

Logged Dives: 0 - 24

 

[cool_hardware52]

Oh. Ha! You did answer it before I asked it! That is what I get for trying to discuss dinner options with the wife and reading the forum at the same time!

Well, I personally do not like weight belts in the least. I find them to be a pain and will avoid them when possible, at least at this point in my diving.

Your goal is a common one, "I hate weight belts!!!!"

Understandable if you have been using heavy 12-18+ lbs belts typical of cold water diving with thick suits and inherently buoyant BC's

OTOH with a SS back plate, and NO inherent buoyancy, the typical BP&W user ends up with 4-6-8 lbs belts. These are easily tolerated by most divers.

It's a mistake to "transfer" the problems posed by conventional BC's to a BP&W.

If you tell me what the most buoyant exposure suit you use, and what cylinders you dive I can make a specific recommendation.

Tobin

 

[munselln8]

Tobin,
As a new BP/w diver I've been wondering about where I should put weights etc, too. Your statement that a wing doesn't need to lift the weight put in a weight belt confuses me. If I am diving a 7mm wetsuit with AL80 in freshwater...well I guess all that detail doesn't matter for the question, which is: Presuming I want to be able to bring my dive belt back to the surface after each dive doesn't my wing need to be able to lift it as well as any harness rigged weight?
for example: I weight myself down and drop to my deepest depth of 100-110 ft. My suit is compressed and I am pretty negative (figuring I will be 6 lbs lighter at the end of my dive I don't worry). Then my 1st stage fails (I don't even know if that is reasonable) and I need to abandon the dive...or maybe my buddy decides it's to freakin cold after two minutes, whatever the reason, I want to surface and bring my weight belt home. See what I am getting at? Is it ridiculous to think that I would ever be that negatively bouyant? (I am open to that possibility as I have lesser experience).
At the same time, If I calculate my wing size (lift capacity) based only on rigged weight, then won't I have a problem staying off the bottom when I add 10lbs of belt to my body?
Like I said...I am confused. I am sure I am missing a crucial piece of knowlege that will make it all make sense
Thanks ahead for any clarification.

 

[cool_hardware52]

Tobin,
As a new BP/w diver I've been wondering about where I should put weights etc, too. Your statement that a wing doesn't need to lift the weight put in a weight belt confuses me.

Any BC needs to do two things:

1) Offer enough lift to float your rig at the surface with a full cylinder.

&

2) Be able to compensate for the maximum possible change in buoyancy of your exposure suit.

Whichever is the larger number dictates the minimum required wing / BC lift

Ballast, by definition, is the sum total of everything you take diving that does not float, lead, backplates regs, empty negative tanks etc.

Minimum ballast is the least amount of ballast required to offset the buoyancy of your exposure suit at your shallow (safety) stop depth when your cylinder is *EMPTY*

If you choose to hang 100% of your ballast on your rig it will have to equal the buoyancy of your exposure when your cylinder is *EMPTY*

Now add back in the weight of your gas, typically 5-8 lbs for most common single cylinders.

If your rig = the buoyancy of your suit with an empty cylinder it will more negative by the weight of the gas when your tank is full.


Example:

7mm suit that is 24 lbs positive, Steel HP 100 tank, weight of gas =~8 lbs.

If this diver configures their rig so it is -16 lbs when their tank is empty and use a 8 lbs weight belt they will have enough ballast, but their rig will only be - 24 lbs when their tank is full.

Here a 26 lbs wing meets both criteria, the suit can't loose more than 24 lbs, and the rig won't be more than 24 lbs negative with a full cylinder.

If the diver ditches the rig the 8 lbs of weight belt stays on the diver, no problem for a diver in a suit that's +24 lbs.

OTOH if the diver places 100% of their ballast on their rig it will be 24 + 8 = 32 lbs negative with a full cylinder.

To float this rig a wing larger than 32 lbs is required, in the DSS lineup that would be a 35 lbs wing.

Tobin

 

[fnfalman]

Tobin,
As a new BP/w diver I've been wondering about where I should put weights etc, too. Your statement that a wing doesn't need to lift the weight put in a weight belt confuses me.

If you're a cold water diver, or wear an exposure suit in general (wetsuit or drysuit), your suit will float the weight belt/weight harness/whatever weight attached to your body instead of on your rig. So your BC will only need enough lift to float the tank and the rig.

That's the advantage of wearing a weight belt. You reduce the size of wing lift.

 

[RicanMedic78]

This tread has been extremely informative

 

[flots am]

I am sure some of you are going But that is fine. I keep seeing talk about a BP/W system instead of a BC and I just can't seem to get what the difference is, or exactly what it is.

BP/W is an abbreviation for "backplate and wing". The backplate is a plate (usually aluminum or steel, but sometimes plastic) with slots for a harness and holes and slots for tank mounting hardware. The wing is a an air-bladder that attaches to the backplate.

Another style, which you've probbaly seen, is a "jacket" BC, which is mostly fabric, with straps to mount the tank and usually some sort of internal plastic frame to help hold the tank.

SCUBABoard has a very vocal BP/W fanclub, however if you're doing recreational dives you won't actually find a lot of BP/Ws out on dive boats, and you'll seldom see them in a dive shop.

There's nothing wrong with it, however unless you need a place to bolt 100+ Lbs of tanks, there's no huge advantage either.

Just like everything else in SCUBA, it's a bag full of compromises, and the only way to know which style you actually prefer is to try both.

flots