Transitioning to doubles...

bamamedic · Oct 1, 2008

This may be an odd question, but...

I've recently picked up a set of LP85 doubles. I've got six dives on them, all under the watchful eye of a fairly experienced doubles diver. I feel I've got my trim and buoyancy under decent control (not nearly as good as when I was diving singles, but not too bad), and I can reach my valves with no problem.

The problem is, due to scheduling issues, my doubles-diving buddy isn't able to go diving as often as I like to (I only live an hour from the local quarry, and like to go diving at least once a week).

Usually I just find a willing local diver on Scubaboard, and that's worked out well so far. More often than not, I wind up diving with fairly new divers (under 25 dives). However, since I'm so new to diving doubles, I'm a little bit concerned about managing the doubles without someone more experienced keeping an eye on me.

Is this something that should be cause for concern, or am I just overthinking things as usual? I guess I'm just worried about forgetting something stupid, and not having anyone more experienced to catch any mistakes. I've thought it through quite a bit, and even came up with a laminated pre-dive "doubles" checklist

so as not to forget anything, but I kind of wanted to see what y'all think about it....

Thanks for your advice

Scared Silly · Oct 1, 2008

I would say while learning, dive your doubles with someone more experienced - does not matter if they are diving singles or doubles. If you have a problem a more experienced diver hopefully will be able to help out. A less experienced diver might not quite react fast enough.

ianr33 · Oct 2, 2008

Go ahead and dive them but keep the dives conservative while you work on trim etc. If you have a problem (freeflow etc) at worst you can share air from your buddy and surface same as you would if you were diving a single.

Just be 100% sure that the isolator is open. (If it is closed pressure will read good but the tank you are breathing from could be empty.)

String · Oct 2, 2008

Not sure a twinset requires a check list - its got 2 knobs more than a single and that's about it.
Although twinsets initially feel a bit different they shouldnt case any problems. Common sense diving while you work on weighting, buoyancy, trim and most importantly valve drills are fine.

You can do a "normal" dive with a single diver and practice valve drills whilst swimming along and so on.

Trace Malinowski · Oct 2, 2008

I don't know what you have on your pre-dive checklist, but one of the most important things to do prior to a dive is to make sure that your isolator knob is open then analyze the oxygen and/or helium content of your gas. Some divers like to analyze their right post side because they will be starting the dive on the long hose primary and wish to verify the gas coming through the regulator they will be breathing during the dive (buying them time if they realize in a flow check that the isolator is closed to abort the dive). Other divers prefer to analyze both posts as a safety check and to make sure they've calibrated the analyzer correctly and get similar results with two attempts at analysis. But, however you analyze, it is essential to check to make sure the isolator is open prior to analysis otherwise you may have a dangerous mix locked in one tank. It is also best to analyze on the same day that you will be diving. Leaving blank duct tape or commercially produced contents lables on the cylinders will remind you to analyze before a dive.

Before diving, a modified valve drill should be adequate to verify the position of the knobs. Right post on. Isolator open. Left post on. Check SPG. Valves open turning towards the left and you may want to do a quarter turn or so to the right to back them off so they don't jam and have more give if you bump them in an overhead environment or protruding object such as a ship's mast. Verify that your back up and primary regulators are delivering gas and working properly by testing them in the water and you are good to go.

When practicing, while GUE procedures call for valve drills before S-drills underwater, if you are diving with single tank divers and want to practice valve drills, explain to them what you will be doing and that you expect them to lifeguard you while you practice. To make sure that the diver is able to donate a regulator to you, you may want to practice an S-drill before doing a valve drill. Conduct your valve drill systematically right to left and then flow check the same as you would do a modified drill. Right on. Isolator open. Left on. SPG check.

Doing a flow check at any time during the dive will give you peace of mind. Practice above water and in the water will create muscle memory. It is easy to verify that your right and left posts are open through the regulators by purging or breathing. The isolator is what gives most beginners trouble. Just remember to open it by turning it counterclockwise.

My brain quickly processes knobs by thinking:
Right post - towards tanks open/towards water column closed
Isolator - towards right ear open/towards left ear closed
Left post - towards water column open/towards tanks closed

When you move into stage diving or deco bottle diving, these tanks also become part of your flow check.

Flowchecks are your best checklist and can be done at any point.

Ed Jewell · Oct 2, 2008

TraceMalin:
I don't know what you have on your pre-dive checklist, but one of the most important things to do prior to a dive is to make sure that your isolator knob is open then analyze the oxygen and/or helium content of your gas. Some divers like to analyze their right post side because they will be starting the dive on the long hose primary and wish to verify the gas coming through the regulator they will be breathing during the dive (buying them time if they realize in a flow check that the isolator is closed to abort the dive). Other divers prefer to analyze both posts as a safety check and to make sure they've calibrated the analyzer correctly and get similar results with two attempts at analysis. But, however you analyze, it is essential to check to make sure the isolator is open prior to analysis otherwise you may have a dangerous mix locked in one tank. It is also best to analyze on the same day that you will be diving. Leaving blank duct tape or commercially produced contents lables on the cylinders will remind you to analyze before a dive.

Before diving, a modified valve drill should be adequate to verify the position of the knobs. Right post on. Isolator open. Left post on. Check SPG. Valves open turning towards the left and you may want to do a quarter turn or so to the right to back them off so they don't jam and have more give if you bump them in an overhead environment or protruding object such as a ship's mast. Verify that your back up and primary regulators are delivering gas and working properly by testing them in the water and you are good to go.

When practicing, while GUE procedures call for valve drills before S-drills underwater, if you are diving with single tank divers and want to practice valve drills, explain to them what you will be doing and that you expect them to lifeguard you while you practice. To make sure that the diver is able to donate a regulator to you, you may want to practice an S-drill before doing a valve drill. Conduct your valve drill systematically right to left and then flow check the same as you would do a modified drill. Right on. Isolator open. Left on. SPG check.

Doing a flow check at any time during the dive will give you peace of mind. Practice above water and in the water will create muscle memory. It is easy to verify that your right and left posts are open through the regulators by purging or breathing. The isolator is what gives most beginners trouble. Just remember to open it by turning it counterclockwise.

My brain quickly processes knobs by thinking:
Right post - towards tanks open/towards water column closed
Isolator - towards right ear open/towards left ear closed
Left post - towards water column open/towards tanks closed

When you move into stage diving or deco bottle diving, these tanks also become part of your flow check.

Flowchecks are your best checklist and can be done at any point.

:mooner:

piikki · Oct 3, 2008

TraceMalin:
My brain quickly processes knobs by thinking:
Right post - towards tanks open/towards water column closed
Isolator - towards right ear open/towards left ear closed
Left post - towards water column open/towards tanks closed

Way too complicated

I had to come up with something simple, so buddy told me to think of the end of the knob like it's a face of a clock. Thus "clockwise-closed" is the only thing I need to remember now

Ber Rabbit · Oct 3, 2008

bamamedic2.0:
Usually I just find a willing local diver on Scubaboard, and that's worked out well so far. More often than not, I wind up diving with fairly new divers (under 25 dives). However, since I'm so new to diving doubles, I'm a little bit concerned about managing the doubles without someone more experienced keeping an eye on me.

Is this something that should be cause for concern, or am I just overthinking things as usual? I guess I'm just worried about forgetting something stupid, and not having anyone more experienced to catch any mistakes. I've thought it through quite a bit, and even came up with a laminated pre-dive "doubles" checklist so as not to forget anything, but I kind of wanted to see what y'all think about it....

Thanks for your advice

You're right to be thinking about these things but I think you're missing an important issue. Are YOU able to notice and handle an emergency if the other diver gets into trouble? When I first started with my doubles I would only dive them with my experienced buddy who was comfortable functioning as a solo diver or with two buddies. There was no way I could focus on controlling the doubles and be a competent buddy at the same time, for me personally that was too much task loading.

As long as you feel comfortable with your ability to function as a buddy and comfortable with your buddy's emergency handling skills you should be fine without a babysitter for shallow easy dives.

The worst case scenarios is probably going to be OOA; get your buddy's reg and proceed to the surface to sort out the problem just like you would do in a single tank.
Ber :lilbunny:

bamamedic · Oct 5, 2008

Went diving yesterday with two "new" buddies (they were fairly new to diving, and it was the first time I dove with them). I even left the checklist at home, and managed not to forget anything!

Aside from discovering that the local quarry absolutely sucks when it comes to getting doubles to and from the water; everything went well. We had one dive to about 70 feet, and one dive to 40 feet.

The only bad thing I discovered was during a surface swim back to the docks; the amount of lift in my fully inflated wing (42 lb doubles wing paired with LP85 doubles and a drysuit) was just enough to keep my head out of the water (right at about chin level). Is this pretty normal for diving doubles?

I'm used to diving with a single tank, in which even a partially inflated wing keeps my head and even most of my chest clear of the water. I could go up to a 55 lb wing (ugh...another $300) or change out my SS plate for an AL plate (which would let me drop about 4 lbs or so).

I suppose I could have closed my exhaust valve and inflated the drysuit a bit, but if I wind up with a total drysuit failure, I want to make sure I can still keep my head above the water.

Thoughts?

Thanks so much

ae3753 · Oct 5, 2008

A 40# wing is great for LP85s, I wouldn't go larger. In water, you'll appreciate the appropriate size wing.

How's your weighting? For me, LP85s + steel plate in a drysuit, I'd be overweight in freshwater.

What type of wing? The shape will affect how you float out of water.

Transitioning to doubles...

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