Twin Tanks

[DaleC]

Is diving with twin tanks different from diving with single tank (does it need a course) or it is just the same but more air?

I'm not trying to be rude but how can you be a divemaster with experience deep, cave and wreck diving and not know the answer? I'm curious how you did those dives.

I'd been diving solo in 20-30ft of water in a lake, since I can easily freedive my drysuit to 40. I started reading about solo diving redundant systems, and decided more air and an extra regulator on a twin manifold I had laying around would be a good way to go. It doesn't drive like an SUV as much as it feels like pushing one. A standard fin and kick at a standard pace will move you along at about 6 inches per kick (with no current).

The real beauty is that I'm now exploring places that I'd never seen before, well beyond the horizontal range any other diver would have. Its turning all the old dive spots into new adventures.

I don't have enough experience to be anything close to an expert, but I do have a couple of pieces of advice. Have at least 65lbs of lift for a BC. If your going to be in the current, it better be a drift dive, a crawl dive (extra, extra weight), or aided by a scooter. I've got a scooter in mind that is fast enough to fight the current, but without overdriving the headlights in the murky Puget Sound, make sure the batteries handle longer dives, and you can stay warm for two hours. Chill'n leads to cramp'n, especially when your push'n twins (sounds like childbirth - sorry )

Most divers that die, drown from running out of air. Its nice to have a nearly 1.5 to two hour dive, and return with nearly 1000 PSI. One of the dive shops even filled me up for one tank charge fee, since I had so much left over!

Really think about getting a lot of buoyancy. I'm thinking 85-90lbs of lift on a wing would be better. I want to be able to use the wing like an inner tube and have a chance of swimming back to shore against a light current. Diss the equipment and swim, if your life depends on making back to a boat of shore. A current is going to win against the twin.

Crazy baby!

I dive twins while most of my buddies dive singles and I don't have any problems keeping pace with them. If you are only getting 6" per fin kick you might be doing something wrong (not kicking effectively or gliding in between strokes) or using splits.

A little extra weight on a drift might be ok but not "extra extra" (unless you're a commercial diver maybe). No wonder you need such a large wing. I dive twin Al 80's and twin St 72's and use a 32# wing. This amount of lift floats me just fine even when using a slightly negative camera rig and either a 40 or 80 cuft stage.

Also, think about using that scooter in current. At least have a bailout plan for when it calls it quits at the worst possible moment.

80-90# wing? Don't do it (drop some weight instead). People around here will wonder if you are a salvage diver...

 

[Grant R]

Although I like the idea behind having a redundant system, one thing I've learned is that it's really easy to get carried away with "risk management". Although Murphy's law is great for NASA, I've seen divers so over-complicate their rig that their rig introduces a hazard. Tech diving is a term that has a place, but what one person calls "Tech Diving" (e.g. solo diving in 15 feet of water with twins?) and decompression diving or deep cave penetrations are worlds apart. Even so, I think a lot of Cave and Extended Range divers try to "keep it simple" the last thing they need is having to figure out which of the 8 legs on the octopus is controlling the shut-off to which tank and then which reg will work after you turn off one or the other, doing all this in a collapsed time bubble of narocossis. This is why decompression and deep penetration diving is "Tech diving" and stuff we call Tech Diving is more of an incremental knowledge set that is in the realm of recreational training.

Needless to say, Keep it simple. Don't over-complicate things. I would like to dialogue about real versus imagined hazards on another thread, which can change radically from one dive to the next. Plan the dive, and keep as much in the car as "reasonably practical". With twins, you just need to focus mostly on a huge propulsion defecit and that alone can mean adding weight and playing the "bottom" fish (in current) and of course working out the right speed and kick to manage air consumption. Deeper diving and over-exertion can increase air consumption by 40X! Twins of course give you lots more air, but if your kicking as fast as you can and can't move, you've got the real problem of "getting back" to deal with. Focus on propulsion.

 

[rongoodman]

A standard fin and kick at a standard pace will move you along at about 6 inches per kick (with no current).

Th anything close to an expert, but I do have a couple of pieces of advice. Have at least 65lbs of lift for a BC.

Really think about getting a lot of buoyancy. I'm thinking 85-90lbs of lift on a wing would be better.

It's hard for me to imagine any use for that much lift. 40# is fine for aluminum 80s, maybe 60# for heavy steels and multiple stages.

If you're only getting 6 inches per kick, you need a different "standard fin and kick".

 

[BabyDuck]

I'm not trying to be rude but how can you be a divemaster with experience deep, cave and wreck diving and not know the answer? I'm curious how you did those dives.

he asked 6 years ago, and as he progressed in his diving & changed his profile, this question didn't change.

 

[DaleC]

Ah, that makes perfect sense. I retract my incredulity. I was duped by the ol' "resurrected thread from the dead" ploy!

 

[Grant R]

Dont' be confused, I consider myself a full time student, not a tech diver. People that call diving with twins, 30 feet down in a lake, "tech diving" I think hugely misunderstand how much safer it is than real "tech diving" (my humble opinion) Correct me if I'm wrong, because I simply want to get better.

My most recent mistake with twins was using fins I had bought for barrier reef diving, and late in the dive I decided I had enough air I would hurry back as fast I could (aerobically). I found out later that finning has a sweet spot, and going too slow or too fast is going to give you less distance per tank. I'm thinking I should get a pair of fins like my old extra large Scuba Pro Jet fins.

The problem with a long dive (with twins 2 hours is not unlikely) in the Puget Sound is your going to enter or exit in strong current, since the slack time is shorter than the BT and current can get ripping really fast. That's is why I think a local shop owner/master dive instructor seemed to recommending at least 60 lbs of lift. Many timesI've been in a 4+ knot current and twice I've lost (not dead) two buddies in current, one stalled a ferry he drifted in front of. I take extra weight to crawl in and out. With twins I think its even more necessary. The drag is just too much for stronger current. Any recommendation on fins, affordable dpv?

 

[Paladin]

:cheerleader: JETFINS!!!!:cheerleader:

 

[DevonDiver]

The above post does not appear to be hetrosexual.

 

[stairman]

I cant believe someone answered a 6 year old thread with answers of a 95 lb wing for doubles? And I can get 6 inches kicking with no fins at all with no current. This is all very strange.

 

[AfterDark]

I use a 94# wing with singles or doubles. The most common complaint I hear from other divers is that I swim too fast. Doesn't slow me down any.