Backplate/Wing selection & Use Questions

[Doctor Rig]

I’m interested in learning more about BP/W BCDs. From my reading, steel & aluminum back plates are typically selected on the basis of their difference in weight alone.

Why wouldn’t the optimum back plate be the aluminum backplate with or without the addition of a P-weight of the desired amount? Wouldn’t this approach give the diver the most flexibility in use? What am I missing?

In use, are there any structural &/or durability characteristic pros & cons for back plates, as a function of plate material &/or plate thickness that could/should be considered?

Another general back plate question..... Do BP/W divers ever experience problems with their lower back plate edge impacting and breaking or damaging a wing bottom dump valve or creating a pinch leak in their wing. I can visualize this possibly happening when dropping a BP/W tank into a tank well on a dive boat.

 

[dorsal]

The weight of the plate offsets any needed additional lead. Many like steel for ocean diving as it weighs more. Plus it’s better distributed weight. But traveling might mean an aluminum plate and just use more lead.

Personally I travel To the ocean with aluminum and add 6 pounds of lead as my bag gets heavy. Same setup in fresh is zero lead.

 

[Marie13]

You're in the Mitten State. Do you dive local?

Diving the Great Lakes in a dry suit, heavy undies, and steel tanks, I still want more weight. So, steel BP.

Aluminum seems to be the thing for tropical divers or those who don't need the extra weight of a steel BP with steel doubles.

You need to be careful with pinch flats when you have short tanks and a longer wing. I dive HP80s and my Halcyon single tank 40lb wing is long. I just watch it.

 

[Bowers]

When i dive single tank i dont use a sta so v weight is out. But that would be a fine choice if you prefer the option. With most of my students, an aluminum bp and steel 72 on their back still requires about 6-8lbs of lead on average (i teach a lot of stocky firefighters). So anyone of that build would be fine diving steel plates even in thin wetsuits but especially if living in colder climates (like near me) where 5mm suits or drysuits are used year round by guys diving single tanks.
My students can be hard on equipment and thus far no damage like what you describe. The webbing does wear out at the shoulders after a while. Webbing protecters help a lot. And after a few years it only costs about $20 to buy new webbing and rethread the harness.

 

[Doctor Rig]

I’m interested in learning more about BP/W BCDs. From my reading, steel & aluminum back plates are typically selected on the basis of their difference in weight alone.

Why wouldn’t the optimum back plate be the aluminum backplate with or without the addition of a P-weight of the desired amount? Wouldn’t this approach give the diver the most flexibility in use? What am I missing?

In use, are there any structural &/or durability characteristic pros & cons for back plates, as a function of plate material &/or plate thickness that could/should be considered?

Another general back plate question..... Do BP/W divers ever experience problems with their lower back plate edge impacting and breaking or damaging a wing bottom dump valve or creating a pinch leak in their wing. I can visualize this possibly happening when dropping a BP/W tank into a tank well on a dive boat.

 

[runsongas]

aluminum is not as durable as steel. you can round out the holes on an aluminum plate over time if you use them with heavy doubles and shore dive.

the extra thick 6mm steel plates are an option for extra weight instead of a weighted sta or p/v weight.

finish (matte vs brushed vs electropolish) and material (304 vs 316) sort of matter if you want the plate to look nice even after some usage.

 

[Doctor Rig]

The weight of the plate offsets any needed additional lead. Many like steel for ocean diving as it weighs more. Plus it’s better distributed weight. But traveling might mean an aluminum plate and just use more lead.

Personally I travel To the ocean with aluminum and add 6 pounds of lead as my bag gets heavy. Same setup in fresh is zero lead.

@dorsal As an example, the only difference in the DGX aluminum and their SS back plate is three pounds. A three pound P-weight bolted to an aluminum backplate would make them equal. Easily done and out of the way. While adding three, it’s would be just as easy to add more.

Why would think the distribution be better on a SS back plate. I’d think the P-weight directly over your spine would be ideal.

 

[Bowers]

@dorsal As an example, the only difference in the DGX aluminum and their SS back plate is three pounds. A three pound P-weight bolted to an aluminum backplate would make them equal. Easily done and out of the way. While adding three, it’s would be just as easy to add more.

Why would think the distribution be better on a SS back plate. I’d think the P-weight directly over your spine would be ideal.

And that does work fine. But personally i dont like that it would bring my center of gravity further off my back. The steel plate is just distributed closer to my back.

 

[CuriousRambler]

@dorsal As an example, the only difference in the DGX aluminum and their SS back plate is three pounds. A three pound P-weight bolted to an aluminum backplate would make them equal. Easily done and out of the way. While adding three, it’s would be just as easy to add more.

Why would think the distribution be better on a SS back plate. I’d think the P-weight directly over your spine would be ideal.

The stainless plate essentially spreads 6lb of weight over the entire area of your back, no more than a fraction of an inch away from your back. An STA weight creates a line centered over your spine, and an inch or so off your back. You can think of it as comparable to a keel weight on a sail boat, but you're now balancing it on top.

An STA is also required for an STA weight, moving the tank farther out from your back and adding to the same issue.

I dive a stainless plate with a single aluminum 80 and an STA. No STA weight, but frankly I can't imagine the "keel weight" issue ever actually being a real problem for anyone, but that's the concept of better distribution of weight. When I dive tropical (yes I fly with my SS plate) I add 4lb of trim weight to my bottom cam band. In swim trunks, I trim out well but could afford to shave a little more weight off if I really wanted to minimize. An STA weight would almost certainly leave me head-heavy in the same configuration. I also pretty much hate the STA, and will never buy another single tank wing that utilizes one.

All my fresh water diving has been cold, low 50s max. Wearing a wetsuit, I still have to add weight with the stainless plate.

I bought a used Dive Rite aluminum plate and put a new harness on it probably a decade ago, so I had all the bases covered. It's never been off the hanger it went on ten years ago. I've just never found a need for an aluminum plate, and I've never felt like my SS was a compromise in any way.

Getting into HP100 doubles, I've got those set up on an aluminum plate because they're so inherently heavy.

I'm sure there are plenty of situations an aluminum plate makes sense. I've never found myself in one, so an STA weight is just another piece to deal with.

Edit: I do take my wing off the BP when traveling to avoid pinch flats. Other than that, I'm just mindful of my equipment and have had no issues, but I also don't dive charters.

 

[Zef]

Here are some thoughts in an attempt to answer your questions:

A steel plate spreads the weight out over one's center of mass a bit more than an aluminum plate with a p-weight.

Depending on one's weight requirements, such as when diving a drysuit, they may need the weight a steel plate has to offer plus the added weight of a p-weight.

If one is going to do a lot of work in a pool the chlorine can attack an aluminum plate, particularly anywhere there are scratches in the anodized coating.

Generally speaking, if one is going to do a lot of traveling the recommendation would be an aluminum plate and if one is primarily diving locally the recommendation can go either way depending on how much weight one needs.

I try to mount my wing so that my dump valve clears the plate edge...whether that is important is a matter of opinion, when diving I don't think it is an issue but in transit it could be.

Pinch damage typically happen if the wing is pegged between the plate and the a hard surface and the scenario you describe with a tank well on boat is a common cause. Coated nylon wing bladders tend to be less prone to pinch damage than urethane bladders.

-Z