Drysuit bouyancy issues

[Mel.B]

Hi,

I got a shell suit for Christmas last year and have done maybe 30 - 40 dives in it since (I don't keep a log, but have done around 350dives). Of those dives, probably about 10 have been between 10 - 25m with nothing deeper. I have recently picked up new drysuit undergarments (paragon/oceanic fleecy 200g weight). Before getting the undergarments I was just wearing tracksuit pants and jumper and had no trouble with managing my bouyancy, particulary on the ascent. This weekend, I went away and did a couple of dives in the 20 - 25m range. One the first dive my safety stop was all over the place but I managed to hold it. The next day, I was a lot more conscious about air in the suit and made a number of efforts to ensure I didn't have trapped air in the suit - even righting myself a couple of times, putting my arm in the highest position and getting rid of all the air (or so I thought). The last time I did this I was at probably 12m. I then start my ascent and the next thing, all this air comes gushing out of the vent and of course I start heading for the surface. I manage to grab the anchor line at around 3m and was able to hang there for a minute but then I was off again. Obviously I'm not very happy about the whole scenerio. I had previously done two dives in the 20m range with these undergarments and had managed to do open water ascents with no references safely so I'm not sure what went wrong this weekend.

A couple of questions - undergarments act by holding/trapping air...correct? Do some undergarments hold/trap more air than others? Is there any way to reduce the amount of air they will trap (obviously this means I will loose warmth, but I'm prepared to wear a layer of thermals). I think getting a pair of gaitors will also help things - I feel like the boots are about half a size too big and I know air gets down there. How have others gone with gaitors?

For reference, I was wearing 15pd of lead on the first dive, 12pd on the second (still able to descend easily but felt I needed to concentrate more on my bouyancy the second dive, may also be why I lost it on the ascent on the second dive). Shell suit, super steel tank (100cf).

Thanks,
Mel.b

 

[spectrum]

The fit and finish of the garment should be such that it will not plug the vent. Sometimes the garment can get sucked up against the vent stopping the flow.

Does you garment have any vent gromets in the vent area or in the underarms? Sometimes those are included to provide a direct air passage.

Pete

 

[Mel.B]

Hi Pete,

No it doesn't and I must admit I'm a bit paranoid about the garment 'plugging' the vent. I might try wrapping some tape around and over the top of the garment where the vent is to stop this from happening (although it might look a bit strange!)

Thanks,
Mel.b

 

[bolantej]

tape might cause it's own set of problems. Maybe layer something over the garment that won't block the airflow?

 

[KazooDiver]

your right that some types of garments trap air more (they are usually warmer). When I dive in my dry suit I try to minimize the amount of air I put in the suit. I have found that the first 20 feet are the toughest to maintain boyancy.

 

[S. starfish]

After a while you may be left with a nice sticky residue on you rundergarmet and the inside of your suit if you use tape - rubber bands or something of the like may work better.

 

[FishDiver]

What type of fabrics tend to block the exhaust vent?

 

[Mel.B]

I don't know if any fabrics 'do' actually block the vent, but I'm just paranoid about it actually happening (saying that though, I've never heard of it happening)

 

[spectrum]

What type of fabrics tend to block the exhaust vent?

I'd worry about garments that don't fit closely and have very loose supple shells like a nylon outer layer.

 

[TSandM]

There are anecdotal reports of the nylon taffeta originally used on Weezles getting sucked into a particular type of dump valve and blocking it. I believe they changed the fabric, but some people using Weezles still put duct tape over the arm near the dump valve (I've seen people using the DUI Thinsulate garment do this, too, although I don't know if it's really necessary). Fleece, because it's so porous and irregular, shouldn't be able to do the same thing.

But fleece does hold a lot more air, which is why it's warmer. You have to anticipate your buoyancy changes a lot more when you use heavier undergarments.

I never used gaiters, but I am a great believer in finkeepers. They are rubber straps that fit around your dry suit boots and collapse them around your feet. They prevent kicking the boots off if they get too much air in them. I've found them very helpful.