BP magic

[kathydee]

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.

Agreed, it's much nicer to dive when some of the weight is distributed next to your back rather than out on a cam band.

The bp/w offers more options for weight distribution. For example I dove my single rig yesterday, and experimented with additional weight plates that are screw onto the SS back plate (which allowed me to unload some of the weight from my weight belt).

Somehow the weight just seems lighter when distributed on the bp and the bp/w setup certainly helps with good trim. My instructor says that removing some of the weight from your weight belt helps gas efficiently migrate within the drysuit. But as others have said, it's important to leave enough weight on the belt - so that if needed you can ditch and have the strength to kick up to the surface.

Streamline is another magical function about the bp. Less bulk = less resistance in the water. This is especially true if you follow configuration to efficiently stow hoses, lights, spg, etc.

 

[LeadTurn_SD]

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.

I remember reading tests in a dive magazine (Scuba Diver?) a few years back, that listed the inherent buoyancy of several BC's, and it seemed that the average was about 3 lbs positive (due to padding).

Many folks will find that they can remove around 5-8 lbs from their weightbelt because their old BC was 3 lbs positive, and the BP/W can be around 5 pounds negative... so a total of 8 pounds can be removed.

Best wishes.

 

[Divedoggie]

Even if his favorite tool is a Makita cordless drill, a carpenter uses many different tools to build a cabinet.
Divers use many different tools to swim around underwater.
A backplate and wing rig is a favorite tool of drysuit divers, manifolded doubles divers, and a number of other divers, but its just a tool.
It is not the most effective tool for every situation. For example some of our dive center open water classes are taught in a 65 foot deep hotspring wearing only swimsuits. Most people don't need any weight on belts or BCD, but usually bring 2 lbs. A bcd is light, very comfortable on bare skin and with all hoses and gauges configured effeciently, its plenty streamlined.


Perhaps I'm playing devil's advocate because I enjoy diving with my bp/w and I enjoy diving with my Ranger, and I enjoy diving with a rental vest style BCD.
Maybe its lucky to be in a position where I can try many types of equipment and configurations.
I enjoy a long hose, bungied 2nd as well as a traditional recreational 36" octo stowed on a chest D-ring as well as an integrated octo.
I have used a HUD mask, and own a wireless wrist computer, as well as an air integrated console and a couple additional wrist and watch style computers with brass n glass spgs. They are all good!

 

[Akimbo]

I remember reading tests in a dive magazine (Scuba Diver?) a few years back, that listed the inherent buoyancy of several BC's, and it seemed that the average was about 3 lbs positive (due to padding).

Many folks will find that they can remove around 5-8 lbs from their weightbelt because their old BC was 3 lbs positive, and the BP/W can be around 5 pounds negative... so a total of 8 pounds can be removed.

Best wishes.

As parzdiver mentioned, there are a few back packs (as opposed to metal back plates) with padding also. Are there any wings, excluding intergraded back-inflate BCs, that aren't neutral by more than 1 Lb with all the air sucked out? I suppose all that padding might make sense in a 3mm wetsuit or less.

Is the 5 Lb negative estimate for the wing only or does that include a metal back plate? I suppose the right answer requires looking at each product combination for the net buoyancy change.

 

[cool_hardware52]

As parzdiver mentioned, there are a few back packs (as opposed to metal back plates) with padding also. Are there any wings, excluding intergraded back-inflate BCs, that aren't neutral by more than 1 Lb with all the air sucked out? I suppose all that padding might make sense in a 3mm wetsuit or less.

Is the 5 Lb negative estimate for the wing only or does that include a metal back plate? I suppose the right answer requires looking at each product combination for the net buoyancy change.

The typical SS plate is about 5 lbs negative, the SS in the harness can be another ~1 lbs. if heavy duty buckle(s) are used.

Our wings are made of:

Woven nylon fabric (Specific Gravity ~1.15)

Urethane film (Specific Gravity ~1.1)

Injection molded delrin fittings (Specific Gravity ~1.40)

Thermoplastic hose (Specific gravity ~1.0)

Misc metal springs, valves, grommets, hose disconnects etc. (Specific gravity ~6-7)

None of these items float, and most are just slightly negative. A typical wing with no gas in the bladder will sink, but usually be less than 1 lbs negative.

Tobin

 

[cool_hardware52]

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.

It's very common for new BP&W users to remove 10 lbs or more from their weight belt.

There are a few reasons for this:

The ballast provided by the SS plate and harness (~6 lbs for a SS plate)

The absence of inherent buoyancy typically 3-4 lbs or more for many "full featured" jacket BCs'.

Often New BP&W users are motivated to focus on weighting and find they were over weighted before, often to overcome hard to vent BC's.

Tobin

 

[Akimbo]

The typical SS plate is about 5 lbs negative, the SS in the harness can be another ~1 lbs. if heavy duty buckle(s) are used.

Our wings are made of:

Woven nylon fabric (Specific Gravity ~1.15)

Urethane film (Specific Gravity ~1.1)

Injection molded delrin fittings (Specific Gravity ~1.40)

Thermoplastic hose (Specific gravity ~1.0)

Misc metal springs, valves, grommets, hose disconnects etc. (Specific gravity ~6-7)

None of these items float, and most are just slightly negative. A typical wing with no gas in the bladder will sink, but usually be less than 1 lbs negative.

Tobin

That's fully consistent with my experience. Some of the posts led me to think that there are some wings, exclusive of back plates, on the market that were significantly more negative or positive. Perhaps it is just my impression.

 

[Akimbo]

...Often New BP&W users are motivated to focus on weighting and find they were over weighted before, often to overcome hard to vent BC's...

Good point. I guess the OP (Original Poster) has to ensure the comparisons are apples to apples. I am always suspicious of blanket statements like the OP's questions are based on without a little dissection. I haven't found any magic that escapes Archimedes Principal yet.

 

[ZzzKing]

I thought this thread was going to be about some magic that British Petroleum had found to restore the gulf...

 

[Divedoggie]

It's very common for new BP&W users to remove 10 lbs or more from their weight belt.

Tobin

Even a minimalist BC will have a bit more positive buoyancy than a bp/w, but the combined weight of the backplate, webbing and hardware, wing and inflator, and any add ons like a can light combine to nearly equal the weight that came off the belt.
And as the OP suggested, now they are carrying the weight on their shoulders instead of their hips.

If people are overweighted and then shed some lead because they focus on proper weighting due to a switch to a bp/w, then thats great. Its still going to take a specific amount of weight to sink someone who is wearing a 7mm wetsuit and is positively buoyant.

Assume a person is properly weighted with a belt and BCD and then weighs himself on a scale, then switches to a bp/w and removes 10 lbs from the weightbelt and then weighs himself on the same scale, he should weigh about the same, maybe slightly less to counter the tiny amount of positive buoyancy inherent in the bcd.
As mentioned by Akimbo, you can't fool Archimedes.