DIR Explorers - View Single Post

*Fredrik Taule* · March 25th, 2008, 08:32 PM

Quote: (Originally Posted by chucklindsey)

All,
Well im sitting here scratching my head. Recently read an IANTD course curriculum that stated the use of an SMB for redundant bouyancy source. Can anyone GUE certified touch on this, pros cons etc?

Also, pros/cons on a dual bladder system. Thanks in advance!

Chuck
Deep-Descent

Assuming the diver is properly weighted and dives a balanced rig, under what kind of circumstances are you seeing a need for redundant bouyancy?

Though the drysuit is not regarded as a bouyancy control device per se, it can undeniably provide additional lift in order to help the diver remain neutrally bouyant in case there is a leak from the wing (as demonstrated by the vast number of 'too much lead carrying' recreational divers who are using the drysuit as their only bouyancy control device).
Keep in mind that provided the diver is properly weighted, with a membrane suit he's only compensating for the weight of gas in his cylinder(s).
The discussion on drysuit being a 'back up' source of bouyancy or not is a pretty long and nuanced discussion, and I hope that I'm not causing any confusion by cutting it short.

I want to say that it's completely unlikely that all gas will be lost from a failing wing, but I'm sure someone will arrest me on that if I put it that way

So, it's highly unlikely that all gass will escape from a failing wing. We sometimes 'steal' eachothers wing OPV if things get too boring. Most divers don't notice any shift in bouyancy or realize that it's gone before they need to vent gas from the wing. Depending on where the leak is, shifting ones trim will help save gas in a leaking wing.

Speaking from my own experience I've managed to pull off my inflator going up a fissure crack at nintyish meter with +/- 2 hour decompression and a kilometer exit from the cave left to do. I can't say that really changed anything except for not finding the inflator when trying to reach for it the first 15 mins after it was gone. Considering the above, if I someone can steal my OPV at the bottom of my wing or loosing the inflator from the upper part of the wing without impacting the rest of my dive in any signifficant way, that provides the comfort I need with regards to having satisfactorily means to controll my bouyancy.

If loss of bouyancy due to suit compression in a neopren wetsuit is signifficant enough to cause problems, I'm guessing that more often than not a membrane suit with appropriate undergarment will be a preferred solution.

Weighing that against dual bladders, inflators, hoses, failure modes and procedures for managing the extra kit I find it difficult to see how dual bladder systems can be benefitial.

Hope that makes some sense to you!

Best,
Fredrik

March 25th, 2008, 08:32 PM	#4 (permalink)
Fredrik Taule(Offline) GUE Instructor Join Date: Oct 2006 Location: Oslo, Norway Posts: 60	Quote: (Originally Posted by chucklindsey) All, Well im sitting here scratching my head. Recently read an IANTD course curriculum that stated the use of an SMB for redundant bouyancy source. Can anyone GUE certified touch on this, pros cons etc? Also, pros/cons on a dual bladder system. Thanks in advance! Chuck Deep-Descent Assuming the diver is properly weighted and dives a balanced rig, under what kind of circumstances are you seeing a need for redundant bouyancy? Though the drysuit is not regarded as a bouyancy control device per se, it can undeniably provide additional lift in order to help the diver remain neutrally bouyant in case there is a leak from the wing (as demonstrated by the vast number of 'too much lead carrying' recreational divers who are using the drysuit as their only bouyancy control device). Keep in mind that provided the diver is properly weighted, with a membrane suit he's only compensating for the weight of gas in his cylinder(s). The discussion on drysuit being a 'back up' source of bouyancy or not is a pretty long and nuanced discussion, and I hope that I'm not causing any confusion by cutting it short. I want to say that it's completely unlikely that all gas will be lost from a failing wing, but I'm sure someone will arrest me on that if I put it that way So, it's highly unlikely that all gass will escape from a failing wing. We sometimes 'steal' eachothers wing OPV if things get too boring. Most divers don't notice any shift in bouyancy or realize that it's gone before they need to vent gas from the wing. Depending on where the leak is, shifting ones trim will help save gas in a leaking wing. Speaking from my own experience I've managed to pull off my inflator going up a fissure crack at nintyish meter with +/- 2 hour decompression and a kilometer exit from the cave left to do. I can't say that really changed anything except for not finding the inflator when trying to reach for it the first 15 mins after it was gone. Considering the above, if I someone can steal my OPV at the bottom of my wing or loosing the inflator from the upper part of the wing without impacting the rest of my dive in any signifficant way, that provides the comfort I need with regards to having satisfactorily means to controll my bouyancy. If loss of bouyancy due to suit compression in a neopren wetsuit is signifficant enough to cause problems, I'm guessing that more often than not a membrane suit with appropriate undergarment will be a preferred solution. Weighing that against dual bladders, inflators, hoses, failure modes and procedures for managing the extra kit I find it difficult to see how dual bladder systems can be benefitial. Hope that makes some sense to you! Best, Fredrik __________________ Oceanic Tech, Fue.no - www.fue.no Last edited by Fredrik Taule; March 25th, 2008 at 10:41 PM.