LP45/50s in cave diving

[lunaire]

For those of you sidemounting these lovely tanks in the caves - Do you usually carry stage tanks, or are they for short, specific dives only?

 

[inquis]

I typically see them used as bailout with a rebreather. For OC, I would sidemount LP85s instead of LP50s+stage: more gas, less hassle, and lower profile.

 

[Marie13]

For those of you sidemounting these lovely tanks in the caves - Do you usually carry stage tanks, or are they for short, specific dives only?

My cave/CCR instructor said 50s are too small for even OC intro level cave dives (I asked right before I took my class). For OC SM, I use 85s. It’s too bad as 50s are lovely to dive. I use 50s for CCR dil/BO (Kiss Spirit) on open water dives (mod 1 right now) and I’ll use them for shorter cave dives when I get to that point (not enough hours yet). I do see plenty of people using 50s for CCR BO, especially with Kiss units or Choptima.

 

[grantctobin]

For those of you sidemounting these lovely tanks in the caves - Do you usually carry stage tanks, or are they for short, specific dives only?

Most people (and especially cave divers) have rib cages that are far thicker than 45s and 50s, so their use is generally overblown. Most people are also lying to themselves about the ability for bailout 50s to get them out of a cave safely and it's pretty alpinistic, especially when the cave is 20m+ deep and penetration is 500m or more without backup scooters

That said, at 3600psi of 32% they're roughly 65cf of 32% each. They're particularly useful in sumps, some shallow FL river cave, and places like the below:


They also work great in a rack for open water diving with a CCR.

 

[divingx]

I only use 50s as bailout/dilout for rebreather in caves. Cave diving with OC 50s doesn’t make sense to me. If I need more bailout for further penetration, I would change to 85s before adding stages.

 

[crofrog]

I only use 50s as bailout/dilout for rebreather in caves. Cave diving with OC 50s doesn’t make sense to me. If I need more bailout for further penetration, I would change to 85s before adding stages.

How far and at what depth do you feel comfortable swimming out with the 50s?

 

[divingx]

How far and at what depth do you feel comfortable swimming out with the 50s?

It’s a tricky question. There are a few factors to consider: with/without flow, main/side passage, how familiar with the cave, etc.

I don’t factor in flow in my calculation. Flow is my extra conservatism. I use 9 meters/30 feet per minute as my exit speed, which is fairly slow. Of course I need to adjust the number if I’m diving in a syphon. If I know I’m going to some small side passages which could end up with no vis on the way out, I’ll use a slower exit speed depends on the situation. And main passages usually have stronger flow than side passages.

As an example, I’m very comfortable to swim out from 1600ft from Ginnie main passages with two cave filled 50s.

 

[billgraham]

I have used them for a small cave with a squishy entrance and a max depth around 45 feet, and they were nice to dive!

 

[lostsheep]

I saw a YouTube video once of a guy using lp50s to bailout from a 220’ deep cave dive so clearly they are perfect cave cylinders

 

[grantctobin]

I saw a YouTube video once of a guy using lp50s to bailout from a 220’ deep cave dive so clearly they are perfect cave cylinders

Iirc the sac rate of the diver with the aforementioned video is something in the 30+L/min range. #supergoodenough #oneaironenotenoughhelium