Backplate size & style question

[Standingbear56]

Question Everyone,
I notice that between DSS, Halcyon, Oxycheq as well as some of the other Back Plate manufacturers such as HammerHead, there seems to be a question as to one size back plate fits everyone (HH) or that different size ones are needed for correct fit (DSS) Who is correct and why. I also notice that on several brands (Halcyon and HH) there is a curved portion on the bottom of the plate so that it does not dig in. However this isn't on all plates. Again, is this a personal thing, or is it a feature to look for.
Thanks in Advance,
George

 

[cool_hardware52]

Question Everyone,
I notice that between DSS, Halcyon, Oxycheq as well as some of the other Back Plate manufacturers such as HammerHead, there seems to be a question as to one size back plate fits everyone (HH) or that different size ones are needed for correct fit (DSS) Who is correct and why. I also notice that on several brands (Halcyon and HH) there is a curved portion on the bottom of the plate so that it does not dig in. However this isn't on all plates. Again, is this a personal thing, or is it a feature to look for.
Thanks in Advance,
George

George,

We make plates of various lengths for two main reasons:

1) The position of the waist strap relative to the bottom of the rib cage. Too short a plate puts the waist strap across the lower portion of the rib cage.

2) Too long a plate will imped the diver's ability to arch their back.

What is not well understood is a back plate will fit the same diver differently when using single tanks vs doubles. When using doubles the lower corners of the plate don't touch the diver, the cylinders hit the diver in the rear end.

When mounting a single cylinder the plate will contact the diver at the lower corners.

Steeply bent plates with square lower corners can "dig in" when diving singles, and the extra bends are used to reduce this.

DSS plates have a much flatter overall bend, and much larger radius lower corners. This, in combination with proper plate sizing eliminates the problem without any extra bends at the lower corners.

Tobin

 

[Dive-aholic]

There is no such thing as one size fits all. I dive a regular length bp while my wife dives a short bp. I have dived in my wife's short bp and I can definitely feel a difference. It moves the location of the harness and makes it uncomfortable. How tall are you?

 

[Standingbear56]

Hi Everyone,
Tobin, as usual you provide a great in depth answer which is much appreciated. I honestly did not know that a back plate fits people differently if using singles or doubles. I just learned something valuable.
Dive-Aholic, both you and Tobin match my understanding of 1 size fits all. To my knowledge, the "standard" back plate is sized as it is because it (at least in the beginning) allowed the most plates to be produced from a single sheet of metal. Hence the "1 size fits all" concept.
Thanks to both of you.
George

 

[cool_hardware52]

To my knowledge, the "standard" back plate is sized as it is because it (at least in the beginning) allowed the most plates to be produced from a single sheet of metal. Hence the "1 size fits all" concept.

George,

Gauge thickness SS (and aluminum) is most widely available in 48" wide sheets. 48/3 = 16" That's one of the key reasons most "one size fits all" plates are ~15.5" to 15.75" tall.

The second reason is cost of tooling, minimum runs and inventory.

Metal stamping is a low unit cost and efficient way to produce plates, but there are large non reoccurring and reoccurring costs.

Two expensive dies are required to produce a single size of plate, a blanking die and a separate piercing die. A set of these dies can run $25K and up. The costs associated with setting up a 100 ton punch press aren't trivial. These all conspire to make production of a single size via stamping economically attractive.

We don't stamp our plates. We use an abrasive water jet. There s no "hard tooling" involved, changing plate size requires a new Numeric Control (NC) program.

This allows DSS to produce a wide range of plates. The downside is AWJ are ~$350K and are very expensive, ~$150 / hr to operate.

AWJ also allows us to very efficiently use the VERY expensive SS sheet. For example we can cut some LP plates (17.5" tall) and then use the remnant of the sheet to make Small plates.

Nothing wrong with stamped plates, but AWJ is a much more flexible solution for our business model.

Tobin

 

[Standingbear56]

Thank You Tobin. Again, more knowledge gained. Here's another (probably dumb, but I really don't know the answer) question for you. I have a bad back and cannot take the weight of a cylinder on my back. I tried the Poseidon BeSea as it takes the weight off of my shoulders and places it on my hips like a hiking backpack. This helps a lot. Is there anyway a Back Plate can be set up to do the same? I was thinking in terms of one of your tall wide (I'm 320 lbs) so that it goes from the nape of my neck (prominent vertebra) to my waist. (same as the BeSea) I realize this may hinder my arching my back, but it allows me to be relatively pain free, which to me at least is more important.
Thanks in advance,
George

 

[cool_hardware52]

Thank You Tobin. Again, more knowledge gained. Here's another (probably dumb, but I really don't know the answer) question for you. I have a bad back and cannot take the weight of a cylinder on my back. I tried the Poseidon BeSea as it takes the weight off of my shoulders and places it on my hips like a hiking backpack. This helps a lot. Is there anyway a Back Plate can be set up to do the same? I was thinking in terms of one of your tall wide (I'm 320 lbs) so that it goes from the nape of my neck (prominent vertebra) to my waist. (same as the BeSea) I realize this may hinder my arching my back, but it allows me to be relatively pain free, which to me at least is more important.
Thanks in advance,
George

Not that I'm aware of. BP&W's are optimized for in water use, not hiking to the dive site.

For most divers, particularly with a single cylinder, this is not a problem.

I can only suggest limiting your "hiking"

Tobin

 

[Standingbear56]

Wish I could, but the landscape around here makes that impossible. If you do come up with a solution sometime, look me up - I'd really be interested. Till then, I guess I'll be back to good ol side mounting.
Thanks,
George

 

[RTodd]

Wrong forum for this thread.