Should I switch to BP/W?

[GreenDiverDown]

or... an Al plate with a can light!

 

[JeffG]

or... an Al plate with a can light!

I doubt I would take a can light to any warm water trips these days. I'll probably just use my scouts that have LED upgrades instead.

 

[-hh]

Bob, we can either continue to poke each other with sticks and massage bruised egos, or we can get back to the crux of the disagreement, which is the protocol.

I'm don't want the former. Let's get back on track.

At no point did you ask me to explain my teaching methods. If you had, I would have answered the question.

I had thought that I had already made such a request, so but fine:

"Please consider this to be the request for you to explain your teaching methods, (relevent to weightbelt over/under)."


I merely want to understand what your rationale is for advocating WB under, either for yourself or others, and what your claimed benefits are for the trade-off that your choice represents.


Since by your claim this apparently includes your teaching to students, then this request also should include these elements as part of your response too. Please make sure to include what student levels and environmental conditions it applies to, as my impression is that it includes down to no-deco OW-I.


Finally, please note that I don't dispute that from a risk tolerence standpoint that there can be some instances where WB Under is acceptable: my concern is with what I consider to be the baseline default for the mainstream diver who's typically OW, diving no-deco profiles and who probably is diving wet instead of dry, so their rig lacks buoyancy redundency.

Granted, things may be different for you in the PNW, but that should then be documented as relevant local conditions that affect your risk management rationale.


....Aside....

FWIW, I'll note the potential the traditional fallacy of "most victims were PADI" template that might also be present here too...

Here you are once again introducing something into the conversation that has no relevence ... to what end?

Because both of these statements are true:
"Most divers who die were PADI trained."
"Most divers who die were wearing Jacket BCD's".

Stating such facts implies a causality - - which is false; a fallacy.

My statement was intended to proactively expose this fallacy, to prevent it from being malicuously used.


-hh

 

[-hh]

An assertion was made earlier that a drysuit looses its inherent buoyancy upon compression. This is not exactly correct, however. One of the advantages of a drysuit... aside from its superior thermal protection... is that it can maintain its buoyancy throughout the dive... One could also add that the drysuit can function as a redundant source of lift.

There's essentially three drysuit technolgies in the marketplace: membrane, crushed neoprene and neoprene. The first two don't have buoyancy variation with depth issues like the third, which is the same (IMO often worse!) as a wetsuit.

They do, however, all have in common the air bubble inside the drysuit which as Stephen points out, is a redundant source of lift/buoyancy. It is through the use of this redundency that a drysuit tends to be able to "net to zero" regardless of its constrution type, in a fashion unlike a wetsuit.

This applies to our discussion in that when trying to achieve a balanced rig in cold water, dives with ceilings, or prolonged exposure situations, a drysuit may be required. It also brings up another thought on the weightbelt/crotch strap deal... specifically... weight belt under when dry, over when wet.

Agreed - I personally see this as a reasonably acceptable trade-off. For me, its more because of the buoyancy redundency of the drysuit than because its construction may be of non-crushable materials (FWIW, my old Unisuit isn't).

Do you think that this would apply to team diving where there is no need for the "emergency buoyant ascent"?

It can depend on a lot of factors. For example, a compromise from diving on a snaggy wreck or something - - is the team willing and equipped to literally tie themselves together, so as to prevent human strength/fatigue from causing a buddy separation? A lot of this comes down to the question of time. For example, if I'm recalling the values from the USN DCS Risk Study correctly, their estimated risk of a DCS hit from 60 minutes @ 100fsw is only around 5%. As such, the degree of hazard of an EBA may not necessarily be as great as being physically unable to hold onto -30lbs of slippery wet buddy for a ~5 minute ascent, plus 3-10 minutes safety/deco; YMMV.


-hh

 

[-hh]

or you can use an Alum plate with a couple of trim pockets to hold weights and keep the weight of your luggage down.

This is what I'd do, since I have ~28lbs worth of UW camera gear that eats up airline weight allowances.

...and the modeling lights inside dual Ikelite SS-200's tends to obviate the need for me to carry a hefty primary light...my old UK1200 buglight has been gathering dust, along with those heavy rubber fins that are back in style these days.


-hh

 

[MXGratefulDiver]

Bob, we can either continue to poke each other with sticks and massage bruised egos, or we can get back to the crux of the disagreement, which is the protocol.

I'm don't want the former. Let's get back on track.

I had thought that I had already made such a request, so but fine:

"Please consider this to be the request for you to explain your teaching methods, (relevent to weightbelt over/under)."

I merely want to understand what your rationale is for advocating WB under, either for yourself or others, and what your claimed benefits are for the trade-off that your choice represents.

Since by your claim this apparently includes your teaching to students, then this request also should include these elements as part of your response too. Please make sure to include what student levels and environmental conditions it applies to, as my impression is that it includes down to no-deco OW-I.

Finally, please note that I don't dispute that from a risk tolerence standpoint that there can be some instances where WB Under is acceptable: my concern is with what I consider to be the baseline default for the mainstream diver who's typically OW, diving no-deco profiles and who probably is diving wet instead of dry, so their rig lacks buoyancy redundency.

Granted, things may be different for you in the PNW, but that should then be documented as relevant local conditions that affect your risk management rationale.

OK ... what I teach depends on the gear the student is wearing.

Backplate/drysuit = weightbelt under ... in the event of a wing failure, use your drysuit for buoyancy control. The consideration here is that the procedure reduces the offsetting risk of accidental loss of weightbelt, which would result in an unwanted buoyant ascent.

Backplate/wetsuit = weighbbelt over ... you don't have the backup BC, therefore you live with the risk for accidental weighbelt loss.

normal BCD = N/A ... in most cases you won't have a crotch strap, so it's a non-issue

integrated weight BCD = N/A ... in some cases you won't use a weight belt. In those where you distribute weights, it won't matter anyway since you have ditchable ballast in your weight pockets and you go for those first.

In all cases, I teach my students to dive as a team ... this starts on the first pool session and is ingrained in their diving style from the outset. This means there should not ever be a need for an emergency buoyancy ascent, except in the most dire, and remotely possible, set of circumstances.

I also teach those students who will be diving a rig that uses weighbelt under the crotch strap how to release and remove that weightbelt. It really isn't all that difficult ... and in fact, the more practical reason to teach it is because when diving froma small boat, you need to do so in order to dekit ... remove weightbelt first, then rig. This is a practical skill, and gets practiced ... ON THE SURFACE ... where weightbelt removal is a far more likely consideration than at depth.

Put the above in the context of my prior statements and you will see that you made some interesting leaps of logic between what I said and what you interpreted in my comments. If you recall, the thread is about backplates ... BACKPLATES ... which does not include how most of the world dives.

In the PNW, almost everyone dives in a drysuit.

....Aside....

Because both of these statements are true:
"Most divers who die were PADI trained."
"Most divers who die were wearing Jacket BCD's".

Stating such facts implies a causality - - which is false; a fallacy.

My statement was intended to proactively expose this fallacy, to prevent it from being malicuously used.

-hh

The implication being ... what?

If you read this board ... and my posts on it ... regularly, you will know that I do not bash agencies.

Furthermore, if you read what I initially wrote to you in this thread, the above "logic" merely supports what I was trying to tell you ... consider ALL the facts, then consider what those facts are really telling you. People can cherry-pick "facts" to support any claim they happen to believe in. But if you wish to learn from history, you need to look at the bigger picture, because "facts" can lead you to some amazingly misleading conclusions.

I.E. ... your earlier statements about the statistics of "dead divers with their weighs in place" does not say anything about the underlying causes of those deaths, or whether any protocol was relevent to their death. Therefore, it lends nothing useful to the conversation ...

... Bob (Grateful Diver)

 

[halocline]

or you can use an Alum plate with a couple of trim pockets to hold weights and keep the weight of your luggage down.

Sure, but this takes the weight off your back where it really belongs and puts it on your belt, taking away from the great trim characteristics of a SS plate. Most people wearing any sort of wetsuit will need a few pounds in pockets or on a belt anyway. The real reason for an alum plate IMO is to use with heavy steel tanks, where there's already alot of weight on your back. Ideally you'd want weight and buoyancy sources to be as close together as possible, right near your lungs; this way small changes in buoyancy affect trim less.

It probably doesn't make much of a difference...but what the hell, if I can't go diving today, might as well spend sometime arguing about diving!

 

[GreenDiverDown]

Sure, but this takes the weight off your back where it really belongs and puts it on your belt, taking away from the great trim characteristics of a SS plate.

Not at all... well... not if you use cam band trim pockets.

 

[webediving]

You will also find that using a Bp/w will give you a better posture and flotability. Much more nicer and less restrictive (movements). Get it you will love it!
Hapy Diving
T

 

[webediving]

You will also find that using a Bp/w will give you a better posture and flotability. Much more nicer and less restrictive (movements). Get it you will love it!
Hapy Diving
T