Universal wing to backplate fit?

[cool_hardware52]

This math is a lot easier to do with wetsuits than drysuits when the buoyancy of the suit theoretically doesn't change based on depth, but is dependent on how much warmth you want from the bubble, but that is a discussion for another day

The math is the same with drysuits / wetsuits / semidry etc. Nearly all exposure suits can lose all the buoyancy they start with. (The possible exception are the suits marketed as neutral, claiming they don't compress)

Neoprene loses buoyancy because it is compressible. At the surface the suit has a given mass, and displaces a given volume.

Soild neoprene has a specific gravity quite close to 1.0 Foamed neoprene (what wetsuits are made of) is buoyant because of the compressible bubbles in the material.

As you compress the foamed neoprene you eventually return to effectively a solid. At that point, (~180-190 FSW) the typical neoprene suit is no longer buoyant, but is neutral (SG 1.0) BC are used to replace the volume your exposure lost. You become negative as you descend in a neo suit not because you gain mass, but because you are losing volume, density being mass/unit volume

Drysuits are in theory a constant volume device. The diver adds gas as they descend and vents the suit on ascents to maintain the same total volume.

But...........

Drysuits can also lose all the buoyancy they started with. A shell Drysuit is buoyant because of the gas in the suit / undergarment , exactly the same way a BC is buoyant if there is gas in it.

If water intrudes into a BC, as it always does, the total lift of the BC is reduced slightly, but as long as the BC can still trap gas it will function as an effective Buoyancy Compensator. OTOH, if one were to rip the fill hose off a BC, and render it incapable of trapping gas the BC would no longer offer any buoyancy.

Drysuits work the same way. A "Flood", i.e. a leak that runs down your crotch or down your leg, is unpleasant, but as long as the Drysuit can trap a bubble the impact on the diver's buoyancy is zero.

But..........

What happens if the Drysuit suffers a total failure, open zipper, badly failed neck seal, or snagged and torn shell, and can no longer trap a bubble, like the BC that lost it's fill hose? The reality is DrySuits don't lose buoyancy because water can get it, but because gas *CAN* get out.

If you are ballasted to offset a Drysuit that is 32lbs positive with minimum gas in it and it suffers a total failure how much wing lift do you need to offset the loss of 32 lbs of positive buoyancy? (Hint you need a "spare" 32 lbs of lift, minimum)

Tobin

 

[Flycaster]

His recommendation for the LCD30 wing is also my personal wing and is quite good

Do you like the Torus wings or would you prefer the zipper?

 

[cool_hardware52]

Do you like the Torus wings or would you prefer the zipper?

Capacity is way more important than Zipper / no zipper or Donut vs Horseshoe.

Tobin

 

[Flycaster]

Capacity is way more important than Zipper / no zipper or Donut vs Horseshoe.

Tobin

Will your LCD line eventually be replaced by zipperless units?

 

[cool_hardware52]

Will your LCD line eventually be replaced by zipperless units?

I have plans to discontinue any of our current offerings. We make what we sell. That makes us unique in the industry. Only one other BP&W brand produces their own inflatable in house, and to the best of my knowledge they don't make their back plates.

We cut and sew, rf weld waterjet cut and finish and forming, and build injection molds and do our own molding and machining.

That is what allows us to offer 9 back plates and IIRC 16+ wings. We aren't bound by the requirements of minimum orders demanded by outside vendors. While I prefer to make reasonable sized batches of goods we can if we need to make a single example. That's helpful when I get an order for an oddball Rebreather wing etc.

IMO there is no clear advantage to horseshoe vs donut or short arc zippered vs zipperless. Both have pros and cons and both offer challenges for fabrication. The sewn shut models require a skilled sewing operator, as the bladder is always just a bit larger than the shell. That means the bladder is trying really hard to creep into the stick path as the wing is closed. Kinda Tricky. OTOH no zipper means no zipper facing or converting 100 yd lengths of zipper into individual pieces.

For divers there are advantages to having the capacity match the application, and that's why we do what we do.


Tobin

 

[JohnN]

. . .

Drysuits are in theory a constant volume device. The diver adds gas as they descend and vents the suit on ascents to maintain the same total volume.

Tobin

It's a shame you and the US Navy don't align in your words. . of course this must make them wrong:

11‑2.9.2 Variable Volume Dry Suits. Variable volume dry suits provide superior thermal
protection to the surface-supplied or SCUBA diver in the water and on the surface.
They are constructed so the entry zipper or seal and all wrist and neck seals are
waterproof, keeping the interior dry. They can be inflated orally or from a lowpressure
air source via an inlet valve. Air can be exhausted from the suit via a
second valve, allowing excellent buoyancy control. The level of thermal protection
can be varied through careful selection of the type and thickness of long underwear.
However, too much underwear is bulky and can cause overheating, sweating, and
subsequent chilling of the standby diver. Dry suit disadvantages are increased
swimmer fatigue due to suit bulk, possible malfunction of inlet and exhaust
valves, and the need for additional weights for neutral buoyancy. Furthermore,
if the diver is horizontal or deployed with the head below the rest of the body, air
can migrate into the suit lower extremities, causing overinflation and loss of fins
and buoyancy control. A parting seam or zipper could result in a dramatic loss of
buoyancy control and thermal shock. Nevertheless, because of its superior thermal
protection, the dry suit is an essential component of extremely cold water diving.

SS521-AG-PRO-010
0910-LP-106-0957
U.S. Navy Diving Manual Revision 6

 

[tbone1004]

Do you like the Torus wings or would you prefer the zipper?

the zip/no-zip is a difference of opinion that Tobin and I have agreed to disagree on based on my personal diving history which is years of wings getting abused to high heaven in a pool for 6 hours a day, 4 days a week, 40 some odd weeks a year. The bladders usually go before the covers.
That said, I have never actually had to replace/repair a bladder on my personal wings, so I don't actually care about the zipper and having seen a bunch of zips fail, I think the risk:reward on zip vs. no-zip favors the no-zip.
I don't intend on unzipping my LCD wing basically ever and I don't believe Tobin has many Torus wings coming back to him needing him to fix it unless it was blatant operator error *which most pinch flats are*.

I personally prefer donut wings because I dive in a slightly head-down trim and am usually very close to neutrally buoyant so I do have to regularly get all of the air out of my wing. That requires a bit of rotating around which my buddies have told me is funny to watch. I think a small crossover in the bottom is nice to have, but you have to be really careful with them because that is where pinch flats are most apt to show up. I usually dive long tanks so it isn't much of an issue.

I chose the LCD30 because I was concerned the Torus 26 wouldn't be quite enough lift *and I was right based on my specific circumstances for teaching*, and the Torus 35 was going to give me some weird trim issues with the shape that it is because I don't wear a weight belt and that is what the fat bottom is ideal for. If I was not in the specific situation I was in for teaching, I would have chosen the Torus 26 specifically for the crossover. Most divers dive in a slightly head up position anyway, so the crossover is less important, but I do use it all the time in my doubles rig.
In sidemount I prefer a horseshoe because I can more easily pack air in one side of the wing or the other to compensate for lateral trim differences

TLDR-I prefer the Torus wings, but my singles wing is a LCD30 because I needed more lift than the Torus 26 and didn't want the pear shape of the Torus 35. In your situation the reason I didn't want the Torus 35 would likely be mitigated by the use of a weight belt which you will likely be wearing and that is what the shape is specifically tailored for

 

[cool_hardware52]

It's a shame you and the US Navy don't align in your words. . of course this must make them wrong:

Nice try John, however any reasonable reading of my description, OR the Navy Diving Manual section you quoted will see they are in agreement.

Have you nothing better to do than intentionally try to confuse people?

Tobin

 

[tbone1004]

@JohnN you are being a bit pedantic with that argument. @cool_hardware52 's point was that the volume of the suit theoretically stays the same during the dive so you adjust it based on your thermal needs. I.e. if it displaces 2cf of water at the surface, you will adjust it as you descent to maintain 2cf by adding air, and as you ascent, you will dump air to maintain 2cf.
Most suits do not lose volume inherently due to suit compression as they are either pre-compressed, stabilized, or use non-compressible materials.

They are not contradicting each other

 

[JohnN]

@JohnN you are being a bit pedantic with that argument. @cool_hardware52 's point was that the volume of the suit theoretically stays the same during the dive so you adjust it based on your thermal needs. I.e. if it displaces 2cf of water at the surface, you will adjust it as you descent to maintain 2cf by adding air, and as you ascent, you will dump air to maintain 2cf.
Most suits do not lose volume inherently due to suit compression as they are either pre-compressed, stabilized, or use non-compressible materials.

They are not contradicting each other

No. An antonym for Constant is Variable.

If the volume was constant, there would never be run-away ascents and descending without adding gas to the suit would never result in squeeze.

The suit loses (or gains) volume depending on where you are in the water column. You are saying exactly that.