Looking for opinions here...
I understand redundant buoyancy is advised for doubles and its necessary for most if not all of the tech training agencies. I get that and its obvious why redundant buoyancy is needed for sets of big steels.
However is it really necessary for a set of al80's? Would diving wet with a set of al80's and a single blader be as marginal as I am led to believe?
Does anybody here dive doubled up al80's wet and with no redundant buoyancy?
Are you dead yet? :D
H2Andy
May 28th, 2009, 11:00 PM
you can always slip an extra wing behind your plate
as for double AL80's ... you're gonna need A TON of weight to avoid doing the missile breach out of the water at the end of the dive :)
seriously, i don't know ... i don't know anyone who dives double AL80s
scubafanatic
May 28th, 2009, 11:22 PM
actually, twin AL 80's are pretty common 'tech' tanks at lots of dive destinations.....I did a week of cave diving a few yrs ago in Akumal, Mexico and all they had was a TON of AL 80 twinsets and everyone seemed perfectly fine with them.....Mexican caves tend to be shallow so twin AL 80's provided enough bottom time. Also, a fair number of 'tech' liveaboards offer twin Al 80's as the largest capacity gas option. AL 80's are cheap, they don't have the high maintainance/rust issues of steel tanks....and they're weight out of the water is 'reasonable' at something like 80 lbs with tanks/bands/manifold...the 'average' diver these days is in his/her mid-40's, especially the ones with enough income to tech dive AND travel expenses...so the twin AL 80's are a sufficient compromise between cost/weight/capacity.
Personally I like steel tanks (own 9 singles/ plus 2 'small' steel twinsets) but I can't take them on a plane with me, so I can only dive them locally in the lake/quarry...or road trip them down to the coast /TX Flower Gardens.
...with respect to 'redundency' , I'm a big fan of dual-bladder wings, just like I'd rather fly in a plane with 2 engines versus 1 engine....doubles my chances for coming home! The DIR crowd isn't crazy about dual wings, however, they are more 'acceptable' if you leave the back-up (right post) inflator hose disconnected/tucked away and only connect it IF you have a wing failure and need to use it.
H2Andy
May 28th, 2009, 11:30 PM
that's cool
how's the bouyancy at the end of the dive?
specifically, how much weight did you carry?
davetheshoeman
May 29th, 2009, 12:58 AM
As said earlier twin ali 80's are pretty common especially in tropical environments and often its wetsuit rather than drysuit. Your DSMB is a great backup bouyancy devise. Sounds crazy, not really. Its limited in that its an open water (not caves and not inside wrecks) tool. Most DSMB's have a purge valve at the top so you can adjust the amount of gas in it. We are talking a 'last option available' but it can and has been used.
JDMerk
May 29th, 2009, 01:08 AM
Thanks for the replies guys...but what I was getting at was if the redundant buoyancy was really necessary or is it more for good diving practices when moving toward bigger steel doubles.
Based on my calculations i'm anticipating carrying 20lbs of lead. If I lose my wing at depth and have to swim up a set of lets say half full al80's I should have no problem doing it after ditching 20lbs. I might even be so buoyant by dropping all of it that the ascent may become an issue in and of itself. Is there something im not anticipating here? Are my assumptions baseless?
al80 x 2
ss bp
5mm
20lb
scubafanatic
May 29th, 2009, 01:19 AM
...well, if ya gotta do a deco stop/stops after a wing failure, a dual wing sure would make life easier/less effort.
TSandM
May 29th, 2009, 02:10 AM
I dive double Al80's in Mexico with a 5 mil suit and 2 mil hooded vest, with a 6 lb V-weight. Of course, I'm in a cave, so if I had a total wing failure (hard to do, really) I could crawl out :)
H2Andy
May 29th, 2009, 10:32 AM
I dive double Al80's in Mexico with a 5 mil suit and 2 mil hooded vest, with a 6 lb V-weight.
that's not bad at all
JeffG
May 29th, 2009, 11:04 AM
that's not bad at all
Double 80's with a SS plate/Manifold/Regs are close to neutral when empty. So you only need to carry enough lead to sink your suit.
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DA Aquamaster
May 29th, 2009, 12:55 PM
Pretyt much the same thing here - I add an 8 lb v weight if "forced" to dive double AL 80's. I'd rather carry the extra 8 lbs in larger capcity tank weight with tanks that are not as bouyant rather than carry lead - but that leads you full circle to the redundant buyancy requirement.
In my opinion, AL 80's make sense in a lightweight wet suit or other thermal protection that does not have much inherent bouyancy. In that case, all you really have is a pound or tow of weight for the suit and the 10 pounds of swing weight for the gas. if you can swim up 12 pounds, redundant bouyancy is not needed.
rjack321
May 29th, 2009, 02:03 PM
I dive al80s in MX (caves-freshwater), 7mm wetsuit, AL plate (for the plane mostly) and 4-5lbs of lead. I'm not getting so deep that the buoyancy of the wetsuit changes all that much (max 80-90ft).
5mm suit, SS plate and 20lbs sounds like a hell of alot to me, even for saltwater.
Bismark
May 29th, 2009, 10:31 PM
double al 80's, ss plate, 3mm suit, no weight. It's a sweet set of gear.
Meng_Tze
May 30th, 2009, 09:40 AM
double al 80's, ss plate, 3mm suit, no weight. It's a sweet set of gear.
Indeed that is! Dove same rig for a long time too. It was always funny to see the frowns of the DM's : 'this guy is going diving with no weights....'
ianr33
May 30th, 2009, 11:02 AM
double al 80's, ss plate, 3mm suit, no weight. It's a sweet set of gear.
Yep,done lots of local dives like that. In saltwater I need to add around 4 lbs weight. When I first got my doubles I went to about 60 feet in the local lake and dumped all my air.Found I could swim them up without a huge amount of effort.
Colliam7
May 30th, 2009, 01:00 PM
However is it really necessary for a set of al80's? Would diving wet with a set of al80's and a single blader be as marginal as I am led to believe? Does anybody here dive doubled up al80's wet and with no redundant buoyancy? Are you dead yet? I have, from time to time, used double AL80s, a SS BP, a 3mm wetsuit, and no redundant buoyancy and gone deep that way (130ft SW) a couple of times. I am not dead yet, at least I don't believe I am (friends and acquaintances are free to differ, of course). The ONLY reason I did it was that I was using a single bladder wing (an Oxycheq Signature 50 is really quite nice with AL80s) and failed to bring a lift bag. I usually try to have a lift bag and/or SMB with me these days because, even though the probability of buoyancy failure is small, why take a chance?
double al 80's, ss plate, 3mm suit, no weight. It's a sweet set of gear.YES!!!
JDMerk
May 30th, 2009, 02:45 PM
I dive al80s in MX (caves-freshwater), 7mm wetsuit, AL plate (for the plane mostly) and 4-5lbs of lead. I'm not getting so deep that the buoyancy of the wetsuit changes all that much (max 80-90ft).
5mm suit, SS plate and 20lbs sounds like a hell of alot to me, even for saltwater.
Your right...i did my math wrong. I thought that sounded a little much myself so my new estimate is 13lbs. That's not counting the manifold and bands, also my initial numbers may be 1-2lb overweight so that number could possibly drop by 4lbs or so once I get the gear assembled and do a final buoyancy check.
ivobj
June 21st, 2009, 12:49 AM
Basically with single AL80 in warm water (wetsuit) I have no problem diving without redundant buoyancy, with my setup (SS BP, weighted STA, trim weight in STA rigs pockets) I can ditch the weight in the pockets (usually 3 kilos, little more than 6 lbls) and swim up with the rest without any problem (specially because with a single AL80 I will be in shallow waters).
I used double AL80s only once in Japan, Okinawa, with SS BP and 3 kilos V-weight, but at that time although water was warm I used redundant buoyancy (TLS 350 trilaminate drysuit), but changed the undergarnment for shorts and a long sleeve T-shirt because of water temperature
deepstops
June 21st, 2009, 12:56 AM
double al 80's, ss plate, 3mm suit, no weight. It's a sweet set of gear.
Ditto, the perfect rig for 120-170' IMO.
Web Monkey
June 21st, 2009, 01:52 AM
Looking for opinions here...
I understand redundant buoyancy is advised for doubles and its necessary for most if not all of the tech training agencies. I get that and its obvious why redundant buoyancy is needed for sets of big steels.
However is it really necessary for a set of al80's? Would diving wet with a set of al80's and a single blader be as marginal as I am led to believe?
Does anybody here dive doubled up al80's wet and with no redundant buoyancy?
Your wetsuit becomes less buoyant as you go deeper, and you'll be overweighted by at least the weight of your gas at the beginning of the dive, so the question is really "Can you swim back to the surface, do any required stops on the way up, and stay there when you're 25 pounds negative?" (12.9 lbs for the gas and maybe 12lbs for the wetsuit).
Terry
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Mayor
June 21st, 2009, 09:39 AM
last Wednesday I spoke with a GUE instructor and he mentioned with a wet suit double 80s would be a nice rig. I'm thinking of setting up a pair.
Rick Inman
June 21st, 2009, 10:19 AM
I did the dbl 80's, 3mm wetsuit no weight thing in Hawaii a couple of years back, and it was a sweet rig. I had the usual pre-rigged ss in my pocket and a 50# bag rolled and stored on the butt of my PB. This last year I took my Fusion drysuit, an al BP and added (as I remember) a 3# V weight, and I liked that even better.
Flightlead
June 21st, 2009, 11:35 AM
I'm a big fan of dual-bladder wings, just like I'd rather fly in a plane with 2 engines versus 1 engine....doubles my chances for coming home! The DIR crowd isn't crazy about dual wings, however, they are more 'acceptable' if you leave the back-up (right post) inflator hose disconnected/tucked away and only connect it IF you have a wing failure and need to use it.
heh heh actually it doesn't. statistically you have a higher likelihood of a fatal off airport "landing" with a single engine out in a twin than an engine out in a single engine aircraft.
