BP magic

[Crush]

This is not a troll - I am looking for honest advice. However, if you must, flame away.

I have read several posts indicating that when the poster went to a BP/w (from a vest BC) they were able to drop several pounds off their weight belt. The fact that this reduction in weight belt weight is seen as positive is perplexing to me - what am I missing?

Does somehow the total weight (i.e., all gear, including all weights) carried by the diver drop if using a BP/w? If so, are vest-style BC really that buoyant? Assuming that vest-style BCs are not that inherently buoyant, there seems to be some kind of BP magic going on here...

If you drop 4# from your belt but have an extra 4# on your BP (as part of what it is made of, assuming a 6# SS BP), why is this an advantage? Your total weight is unchanged, and for those with bad backs, it is better to carry the weight on your hips rather than on your back. Sure, having the weight over your shoulders may help to trim you out, but the same effect can be achieved by taking weights off your belt and putting them on the top cam strap of your vest-style BC.

 

[Jimmer]

Yes, vest style BC's are actually that buoyant. Toss a vest BC into the water with no tank on it and no air in the bladder and see what happens. Toss a BP and wing into the water with no tank or air in the bladder, and you will be doing a recovery dive later.

I personally disagree with you that having the weight on your back is worse than your hips, if you have a bad back. I have a bad back myself, but I can very comfortably move my double 130's around if I have them on the backplate.

I'm not one of those guys who believe that a BP/W is the be all and end all, but for me, after having dove extensively in both setups, I will never go back to a vest style BC. I dropped 8 pounds off my belt when I bought my first BP setup and did a weight check on it, and I would MUCH rather have less physical weight to lug around on shore and have the same net buoyancy in the water.

Cheers,
Jim

 

[ringmod65]

Some people (myself included) don't like to carry ditchable weight. A weight belt is one more piece of gear to deal with (and potentially overlook). However, before foregoing the ditchable weight I made sure that my rig was balanced: Able to swim up from depth with no air in wing or dry suit; and, able to hold a stop at 10' with 300psi.

ATB.

 

[fnfalman]

A 4-lbs jacket BC is 4-lbs of nothing that helps the diver - wasted weight. A 4-lbs BPW is 4-lbs of dive weight.

With the jacket, not only you have to carry the weight of the BC but also the weight in lead that is needed to sink the BC.

 

[Crush]

Jimmer, ringmod65, and fnfalman,

Thank you for your replies.

I dropped 8 pounds off my belt when I bought my first BP setup and did a weight check on it, and I would MUCH rather have less physical weight to lug around on shore and have the same net buoyancy in the water.

The clarification helps. The above quote (emphasis added) is typical of what I see on SB. I keep thinking - what's the catch? If you take the weight off your belt, are you just putting it somewhere else? Apparently not, or at least not all of it.

While it doesn't make sense to me intuitively that a BC should be that buoyant, I have not carried out the experiment proposed by Jimmer so I can't argue the fact.

 

[Jax]

My BCD, with my flashlight, knife, etc in the pockets, weighs 8.3 lbs. In my 7mm, I carried 20 lbs on a weight belt, in salt.

My SS BPW, with all my crap on it, weighs 8.2 lbs. In salt, I carried 10 lbs but wore a 3-5 hooded vest . . . could have done 8 lbs without the vest, I think.

So I lost 8 lbs of buoyance by swapping to a BPW.

 

[Scared Silly]

It is quite surprising how much buoyancy is in a BCD but it is there. There are some nice travel BCDs that besides being light weight are not very buoyant. Also the overall bulk of BCDs compared to a BP is also quite remarkable.

 

[Divedoggie]

Compare apples to apples. Put 6 lbs in your BC/vest and toss that in. Then toss your 6lb backplate in. Both will sink.

As an avid backpacker, it definitely makes sense to carry weight on the hips while its balanced by the shoulders. Obviously scubagear has a different use than a backpack, but we do spend time walking with heavy gear on our backs.

When I teach I tend to use my Ranger BCD, when I dive for pleasure or dive doubles its usually with bp/w. I switch back and forth all of the time for various reasons, and find the total weight of each kit to be about the same.
In warm water, I prefer the BCD largely because the bp/w weighs too much, and I don't have an aluminum or plastic bp.

While proper fitting equipment, proper weighting, and certain gear configurations can help fine tune trim and buoyancy, only knowledge, practice and experience can combine to make a skilled diver.

 

[parzdiver]

As others have stated, the jacket BC's tend to have padding that will make them buoyant. You can get similar padding on a backplate configuration that will add some inherent buoyancy, but for the most part, you don't have the extra padding and material that floats.

Shift the weight to the backplate is more effective than just putting weight on a cam strap due to the face the weight is evenly distributed across the back between your lungs and the wing (your two sources of lift). That distribution gives the diver a great start in their quest for good trim.

 

[Akimbo]

… I have read several posts indicating that when the poster went to a BP/w (from a vest BC) they were able to drop several pounds off their weight belt. The fact that this reduction in weight belt weight is seen as positive is perplexing to me - what am I missing? …

The geometry of some jacket BCs are more difficult to vent all the air out at the surface, which may account for some or all of the discrepancy. You also, have to consider that most BP/Wing users have metal back plates in the 2-5 Lbs range, effectively transferring weight off their belt.

If you evacuate all of the air out of any bladder, and provide enough time for air between the bladder and protective fabric jacket to escape, there should be no difference between wing or jacket BCs. I personally prefer wings, but I can't see how this as a blanket statement is a valid factor.