Drysuit vs Wetsuit

[Gareth J]

Since a drysuit with catastrophic failure would have no inherent buoyancy, someone like me probably couldn't ditch enough weight to be buoyant if that happened, after the weight of a BP/W and tank. In a swimsuit in the pool, with a jacket BCD and AL80, I can't remember if I sank with no weights or just a few pounds of weight. So with a BP/W I'd definitely be pretty negatively buoyant without a wetsuit, and the wing would have to sized to be big enough to make me positively buoyant, correct?

Its an old wives tale that you don't have buoyancy in a flooded drysuit. Whilst you are in the water the effect is negligible (other than the discomfort).

My Girlfriend had a catastrophic failure of her drysuit bout 6 years ago. The zip failed totally.
She had no issue in the water, the ascent, and decompression stops where no problem at all. The only problem she had was getting back on the boat with a suit full of water up to here waist.
If the boat had been one of the ones we normally use with a lift, even this would not have been a problem.

It also would have helped if we all weren't rolling around the deck in fits of laughter at her struggling and looking like the Mitchelin Man. We had to tip her upside down to get the water and her out of the suit. British divers are such sympathetic individuals. Luckily it was August, so she wasn't too cold, just missed out on her last dive.

Gareth

 

[stuartv]

My Girlfriend had a catastrophic failure of her drysuit bout 6 years ago. The zip failed totally.
She had no issue in the water, the ascent, and decompression stops where no problem at all.

So, you're saying her wing had adequate lift to compensate for the buoyancy she lost. Okay...?

 

[Gareth J]

Yes, no issue at all.

Remember, there is no 'additional' weight, from the water in the suit . Just the effect of the loss of bouyancy, which is minimal if you are correctly weighted.

Gareth

 

[Storker]

British divers are such sympathetic individuals

Yeah, I have the impression that they're at least as nice as Scandinavians...

 

[jseyfert3]

Yes, no issue at all.

Remember, there is no 'additional' weight, from the water in the suit . Just the effect of the loss of bouyancy, which is minimal if you are correctly weighted.

Gareth

Yes, no additional weight, but as I mentioned before, I could sink with just an AL80 in an jacket BCD with no extra weight during my pool dives. So a total loss of bouyancy of a drysuit would end with me negatively buoyant with an empty wing.

 

[tbone1004]

Yes, no additional weight, but as I mentioned before, I could sink with just an AL80 in an jacket BCD with no extra weight during my pool dives. So a total loss of bouyancy of a drysuit would end with me negatively buoyant with an empty wing.

which is fine because remember what a wing has to do. Float your rig at the beginning of a dive with you not in it, so negative buoyancy of the tank plus all of the stuff on it. If your rig is more than 30lbs negative, you did something wrong imho. The second is to compensate for exhaled gas, which in a single tank will never exceed about 12lbs for an exceptionally large tank. With something like the LCD30, it gives you call it 20lbs of weight to sink your drysuit assuming you don't want to ditch any lead. 20lbs isn't a whole lot for a drysuit in cold water, but the odds of a true catastrophic drysuit flood are pretty minimal. Neckseal breaks, just stay head down, zipper breaks, same thing, you'll still get some air in the legs/feet. If a foot gets ripped, the other one will still hold air and you can go head up to keep some air in there, etc. etc. Best to just plan on the ability to drop lead if you have to, which is highly unlikely.

Keep the lead on your rig to the point where you aren't going to overweight the rig, and you'll be ok. If you go with DSS, which you should because of the length, you'll be in a long pattern plate. With the weight plates *which I would also highly recommend if diving dry*, your backplate alone will be roughly 16lbs negative. A PST104 which is one of the more negatively buoyant tanks, when overfilled with a valve and regulator, will be around 15lbs negative at the surface, so the LCD30 is cutting it pretty close, but that is an extremely heavy cylinder and if filled 3k instead of the 3600 we fill to in cave country, the LCD30 will be fine. That gives you a total of around 20lbs negative ballast against your drysuit with the ability to get to the surface without ditching any lead. Anything else should be on a weight belt so you can drop it if you have to, but you shouldn't have much lead on there unless you are ice diving...

 

[Gareth J]

Yes, no additional weight, but as I mentioned before, I could sink with just an AL80 in an jacket BCD with no extra weight during my pool dives. So a total loss of bouyancy of a drysuit would end with me negatively buoyant with an empty wing.

I don't think you are unique, I am the same. I start to float again when I take the set off. Which makes a full inwater dekit and rekit challenging in shallow water.

The point is that you need minimal additional bouyancy when a dry suit floods, to maintain neutral bouyancy. There is more than enough in the BC/wing. If you actually wear a weight belt, the probability is that if you where to dump it you would actually be positive[1].

Gareth

[1] A lot of us use V weights, which are integral to the twin-set, so to drop the weight you need to drop the twin-set - unlikely!

 

[Captain Swoop]

I've had a drysuit flood. I just squirt enough gas in to it to stop it squeezing, all I needed to do was put a squirt in to my BCD to compensate, nothing dramatic.
As already noted in the thread, getting back aboard is the hardest bit.