Preferred DSMB length and width

[USMC CPL.]

I think drysuit itself is a redundancy. Do you need another one ontop of drysuit?

I am not going to be using a dry suit. So I still need the other backup as required.

 

[KenGordon]

You need a DSMB regardless of this backup buoyancy argument. Depending on how negative you are with a twinset, what suit you are wearing and so forth it may be enough for a lost wing scenario. To compensate for backgas you will need up to 7 or 8kg. Beyond that it is suit crush. If that can be more that 10kg I suggest just using a dry suit.

You will want a backup SMB too. I use a smaller CO2 one for that, and a crack bottle AP one as a main. I guess I have 30kg available there. I am never 30kg negative.

If you find you are negative with the empty twinset at your last stop and no weight then I suggest making serious efforts with backplate and cylinder materials or choices to get it 'balanced'. Otherwise you will have much more work to do controlling your buoyancy and it will be less fun.

 

[divezonescuba]

I am not going to be using a dry suit. So I still need the other backup as required.

Padi 45 and 50 require something such a redundant bladder with a wetsuit. You cannot use an bag or dsmb for that. The diverite rec model in either exp or xt material has 45 lb lift and is available with a 25 lb redundant bladder.

During TEC 40, with doubles, I had to prove I had a balanced rig as well by swimming up from the bottom with no air in the bladder and with all weight.

In TEC 45 or 50, you will have to demonstrate bouyancy control with all the air suddenly dumped from your primary bladder, midwater.

 

[packrat12]

During TEC 40, with doubles, I had to prove I had a balanced rig as well by swimming up from the bottom with no air in the bladder and with all weight.

In TEC 45 or 50, you will have to demonstrate bouyancy control with all the air suddenly dumped from your primary bladder, midwater.

Good luck swimming up with a 5mm or thicker wetsuit even with a balanced rig. My 5mm requires offset of ~12 lbs. Assuming compression at the bottom will reduce the offset by at least 6 lbs, there is no way I am going to swim through my deco obligations in a 5mm let alone a 7mm without alternate lift. When I wear a 3mm, there are no issues but then the 4-6 lbs offset is not so bad to swim through deco with the 2 - 3 lbs of negative!

As for the loss of buoyancy demo - It is easier mid water then deep bottom. Your wet suit compression is less and your weight offset is less. Near the 20', it is almost gone, which is where I suspect you may have done it!

 

[JohnnyC]

I seem to remember @Wookie posting something about which was best for his divers to use from a captain's standpoint but my search-fu is weak right now. He'd be an excellent subject matter expert to ping considering his extensive background keeping eyes on floating bits and bobs with divers hanging below them.

 

[divezonescuba]

Everything was done in a 3mm. In my case loss or gain in bouyancy due to depth was minimal.

On TEC 45 dive three with a minimum depth of 60 ft, the primary bcd failure occurs on the ascent at 30 ft. You establish bouyancy control for your deco stops by deploying your redundant bladder. You have to also do a gas switch at 20 ft and valve shutdown drill at 15 ft with the redundant bladder.

I wouldn't want to be finning or holding onto a bag or dsmb while doing all that.

 

[PfcAJ]

You're going to swim up in doubles, hold your deco stops? USMC's thought is consistent with what I was taught in TDI's Helitrox class.

You're only swimming against the weight of the gas which is barely anything with trimix (and getting to be less and less with each breath), and if its shallow enough to do on nitrox why bother doing deco at all and adding that extra risk when you could do 2x no deco dives instead?

 

[eelnoraa]

Good luck swimming up with a 5mm or thicker wetsuit even with a balanced rig. My 5mm requires offset of ~12 lbs.

By definitely, that is not a balanced rig. Balance include the choice of tanks, suit, placement of weight (ditchable vs not), wing size ...

I think one way to make the rig balanced with wet suit and double is to use lighter tanks, like AL80s, and wear ditchable weight. But when the suit get to 5mm and above, it become hairy. To OP, do you really want to do your 30 minutes deco in a thick wetsuit? you are not moving much at deco. It can get cold fast. Cold bodies don't dece efficiently.

 

[Tom Winters]

I carry the OMS 9'7" orange sausage. It's long enough to bend into a triangle which makes it way easier for the dive boat to see if they're downsun from you. I've also been rescued at sea off Florida and Hawaii, so I carry a Nautilus as well. Nothing like surfacing and seeing nothing else on the horizon.

 

[Coop42]

Big enough to be seen, and compact enough to bring along. I bring one on every dive as a habit.

It's 2 metres x 15cm, with two stripes of retro reflective tape across the top.