One Long Deco Dive vs Two Shorter Deco Dives with a longer total bottom time?

[Lew Nance]

You are sort of comparing apples to oranges. On the one long dive you you only have around 240cuft (if diving double 120s) or 200cuft (if diving double 100s) compared to around 320cuft (when diving two sets of double 80s). So, of course you will have more bottom time with the 320cuft of available bottom gas... it's more gas!

(i know - tank volumes are only nominal values and only used for the sake of illustration)

 

[Superlyte27]

You are sort of comparing apples to oranges. On the one long dive you you only have around 240cuft (if diving double 120s) or 200cuft (if diving double 100s) compared to around 320cuft (when diving two sets of double 80s). So, of course you will have more bottom time with the 320cuft of available bottom gas... it's more gas!

(i know - tank volumes are only nominal values and only used for the sake of illustration)

unless you have cave filled 104’s

 

[lukeb]

When you say one long dive, how much bottom time are we talking, and what depth/gas are you running it at in multideco?

I was looking at depths of around 120 ft, using EANx30, with 100% O2 for Deco. I would like to do bottom times of up to an hour (exploring wrecks) but without some serious steel doubles it just isn't doable. Hence why I was thinking about two dives to give me more bottom time. Although, I definitely understand the good reasons given by everyone for the single dive (surface conditions etc).

You are sort of comparing apples to oranges. On the one long dive you you only have around 240cuft (if diving double 120s) or 200cuft (if diving double 100s) compared to around 320cuft (when diving two sets of double 80s). So, of course you will have more bottom time with the 320cuft of available bottom gas... it's more gas!

I agree the tank volume really does dictate everything. I think I was just curious to see what most divers are doing for charter profiles as I could see the two options and wondered what direction was preferred.

 

[Heavydpj]

Just stumbled across this. Good stuff.

I’m getting ready to do meg ledge. The operator is offering a 3 tank day, depth is 32m.

With my sidewinder, I can easily do at 111 min BT dive and have enough gas to do a bailout at the end. 162 min RT with about 43 min of deco.

However, to keep in line with the rest of the divers on the boat, I can also do 3 x 60 min runtime dives. Each with about 6,11, and 13 min of deco.

I’m going back and forth about which option to go with and this discussion provided some good perspectives.

 

[VikingDives]

Since I was certified as a deco diver, most of my dives aren't limited by the RT, but by my tolerance for cold (there are other issues too, like my consistent left arm wrist seal leak, but for discussion purposes, let's say cold...). I have a 1.5 to 2-hour drive to the nearest dive site too.

I've consistently opted for a "one and done" approach to deco. My dives aren't generally limited by gas, but there's only so much cold I can tolerate given my preference to exit the water with a GF under 70. That means one long, generally enjoyable dive, followed by a slightly boring, and occasionally terrifying hang.

I spent a stop recently being circled by rec students without an iota of buoyancy control, some of whom were hanging out just below me, threatening to lose control and come rocketing up to the surface.

Last weekend, I started the dive thinking I'd just do back gas deco, as I didn't want to burn my deco gas, but somewhere between my 20-foot stop and my 10-foot stop, I decided that discretion was the better part of valor, so I did a gas switch and exited Dodge because I didn't want to shiver.

All in all though, I'd rather do one long dive than three in-and-outs. . .

 

[RyanT]

Last weekend, I started the dive thinking I'd just do back gas deco, as I didn't want to burn my deco gas,

why?

 

[VikingDives]

why?

Strictly cost/being lazy about getting fills

 

[Troglodyti 4.0]

Two deco dives to say 6 Ata should be spread out to 4 hour surface intervals. If I was paying for the gas, I would use 32%/50% for deco. Runtime 90 minutes or longer a piece. Depending on weather conditions of course. Your dive to 5.5 Ata. Why not use 25% back gas? Take two bottles for deco; let's say you have money to burn. Use 50%, 100%.