Loss of Buoyancy from Flooded Drysuit

[knotical]

This is a good test but doesn't take into account the undergarments, although I am not sure if any undergarments out there today are negative. An easy test would be put them in a deep enough container (ex pool) and see if your under garments sink. If they do then you will need to add that into the mix.

Good point. From my thankfully limited experience with sodden undergarments, I believe most of them are fairly close to neutrally buoyant.

 

[eelnoraa]

This is interesting. I once discussed this with AG from UTD, he actually encouraged me to give a flood drysuit a try in a pool, by simply openning the zipper if I don't mind the trouble. Not only I can found out if my 30lb (single) wing is enough or not, but to experience what it feels like in a control environment. I may one day give it a try.

But anyway, here is how we did the estimation.
- In my tropical dive, no shirt, swim trunk only, AL (-2lb) plate, AL80 (+4lb), OMS slip (0lb), weight belt (-4lb). Net -2lb with no suit
- At home with drysuit, SS small plate (-4lb), HP100(-2lb), Jet (-2lb), total lead (-18lb), net -26lb with drysuit & undergarment.

all other gears not listed, ie. reg, canister, backup light, .. remain the same.

So my drysuit should be about 24lb positive. Add 8lb of gas for HP100. So worst flood, I jump in with out zipper open, I will be -2lb with a fully inflated 30lb wing. Something I know I can swim up again. Once on surface, I will ditch my weigh belt which is 12lb.

 

[industrious95]

I dive in a TLS350, and my suit flooded last trip out. I must have really twisted my neck weirdly, because that's where the water came in.

I had several quarts of water in my boots by the time I exited. Not the most pleasing sensation, but no obvious change to my buoyancy. I did a 5 minute safety stop and had no problems maintaining depth.

If your wing can handle your tank and weights, whatever water fills your dry suit won't make a difference.

 

[DaleC]

I disagree.

If your wing could only float your tank and weights, it would mean that with your drysuit alone you can float at neutral buoyancy with the amount of air (squeeze) you usually keep in it. Is anyone neutrally buoyant in their drysuit alone? Not my experience. I cannot freedive in an unweighted drysuit.

I need weight to sink my rig and weight to counteract the buoyancy of the drysuit. In fact, I know I need all my weight to sink the drysuit because I can dive my rig with no weight using a 3/2mm wetsuit.
Part of the weight addresses the buoyancy of the material of the drysuit itself (neoprene/merino wool lining) which does change when flooded (merino wool absorbs a lot of water), and part is the airspace it contains via clothing/creases/bubble etc...

If I bleed all the air out of my suit at depth while comfortably hovering, I will sink. That is because I dive in cold water and keeping a tight squeeze on all the time would defeat the insulating property of the suit and garments. That comfortable zone of inflation is what I weight against.

How about this. Go feet up and what happens? You get floaty and need to get them down or risk a feet first buoyant ascent. What's making you buoyant like that?

Someone said they were neutral jumping in the pool with their undergarments only. That's only half the test. You need to also measure how buoyant you are when you jump in and stay dry.

 

[NAM001]

I may bve stubborn but i cant grasp the concept that a flooded dry suit when flooded is not a problem. I am 2# light. In my dry suit it takes 21# to hold me under water., that extra lift comes form the air space caused by the undergarments. So when you flood that suit you replace the air with water which is 19#. If you ewre neutral before after the folood youare -19# max. To plan for a total flooding you have to be able to deal with the full 19# of lost lift. With my 300g undies, the suit is 38 light the 100g undies im 19 light. i imagine with no undies it may be 5 light, BUT if you dont need undies you dont need a dry suit.

---------- Post added October 7th, 2014 at 10:57 PM ----------

I would think that the resultant lift from adding air to the suit would far out weigh the ability of the air to push the flodded water out of the suit. No matter what anyone says about squeezing out all the aie in the suit it cant be done. get in the water and open the vent to purge all the air and you still have a 1/4 inch layer of air around you because of the undies and the air it contains. You vant get that out and it is all buoyant and floodable .

I know of two cases where people went in off a boat with their drysuit zipper open ... can't get much more flooded than that. In both cases they were able to maintain buoyancy at the surface long enough to get out of the water. It's the getting out part that's hard ... because that's when the water gets really heavy.

I do wonder what would happen if you inverted and hit your drysuit inflator button. This would be functionally similar to clearing your mask, as the air would go directly to the highest point in the suit, which if you were inverted would be your feet. Would it force water to come out your dump valve? Hmmm ... I might have to try this sometime just to see what happens ...

... Bob (Grateful Diver)

---------- Post added October 7th, 2014 at 10:59 PM ----------

Im nor sure but i think you thinking is correct so long as you have ditchable weight and not talking about a shell suit. as long as a shell **** is involved like the tls350 you have a problem if you dont have ditchable weights. Ther more undergarment the mor teh problem becomes in a flood.

I dive in a TLS350, and my suit flooded last trip out. I must have really twisted my neck weirdly, because that's where the water came in.

I had several quarts of water in my boots by the time I exited. Not the most pleasing sensation, but no obvious change to my buoyancy. I did a 5 minute safety stop and had no problems maintaining depth.

If your wing can handle your tank and weights, whatever water fills your dry suit won't make a difference.

 

[ajduplessis]

I once completely flooded my wetsuit...... What a dive.

 

[Bobby]

As has been said the difference in buoyancy will depend on the type of DS & the under garments. I had a complete flood in a shell suit with heavy undergarments in a cave due to a seam failure. It took over 30 minutes to loose the majority of air in the suit however I was over an hour from the exit. Eventually the air I added to the suit simply blew out the neck or the open seam. With my 55 lb lift wing popping the OPV I could not stay off the bottom. Getting out of the water required puncturing the suit at the ankles and slowly raising out of the water and letting the water drain. It was an ugly experience and dive. Towards the very end of the dive as I breathed my stages down I could more easily stay off the bottom as they became more buoyant. It is possible that dumping the stages may have allowed me to maintain buoyancy however until they were breathed down that would have left me with a possible issue of not having enough gas to exit.

I have not had a complete flood like that in my neoprene suits however the buoyancy of the neoprene combined with the much lighter thermals would likely make this much less of an issue. When diving neoprene the suit and thermals add less buoyancy due to the tighter fit and lighter thermals.

From this experience I now check all gear configurations using a compressed neoprene suit, no thermals, and add no gas to the suit. I will drop down to 10 feet and ensure that I can maintain buoyancy with just the wing. It is not that the flooded suit is more negative, it is loosing buoyancy from the suit when it floods. I have had many floods in suits that have completely soaked me however didn't affect my ability to stay neutral.

 

[DaleC]

Yes, exactly. Your suit does not become negative. It just loses the positive buoyancy it once had. How much that is depends on the suit, the clothes and the bubble.