Sinlge vs double bladder

[padiscubapro]

madmole once bubbled...
Sorry, It seems to work fine on my double 12's with 2 7l slung stages, and I've used that combo with 8 cylinders strapped to me at 143m (2 of the tanks were stages being postioned for some one else)

Normal UK configuration. We consider it dangerous here to use the BC for buoyancy if you have a drysuit as its task loading. You have to add air in the suit so why add a second thing with air in it into the equation. Then you have 2 things to dump on the way up

We dive dry suits all year round here. ALL have shoulder auto dumps so they vent automatically on surfacing. Much easier than having to physically pull a hose or push a button on a BC

Both techniques work, use what one you are used to

Madmole,
In practice I can't fully agree with you here... First off different dry suits have different buoyancy characteristics.. I find in a shell suit using the dry suit for buoyancy is dangerous and unconfortable, using a neoprene drysuit is much easier..

When diving twin 95s and stages I'm pretty negative the amount of gas required in the suit to make me neutral causes a large buble to move throught the suit, this is very unconfortable and if I go head up I risk the chance of the air escaping through the neck seal..
I dive a DUI cf300 which is a shell suit, even with heavy undergarments its not very bouyant(In mask fins and snorkel I can get below the surface without any weight, I only use 8lbs total with my inspiration), I find its much easier and much more confortable to just add enough gas to eliminate squeeze and control bouyancy with my wing.. I used to dive just using the drysuit but am much happier now.. I also had an experience like mike.. I was ascending up a line and my suit bubbled (I got wet and very negative), That was the lat time I dove it that way.. Besides with minimal air in the suit I can go totally inverted with only minor amounts of gas going into my feet.. I am frequently head down since I lobster hunt alot and air in the feet is not confortable..

If you are using something like a unisuit use the suit for buoyancy is pretty easy until you get deep enough where the suit compression severely comes into play.

Dui suits are pretty common up here in the Northeast so most people use the wings as buoyancy. I do teach the suit as a backup bouyancy device and remind the diver that the attitude in the water column is very important.. The ascent has to be made close to horizontal, Slightly head up.. to level not enough air escapes automatcally to head up you lose gas fast..

 

[madmole]

I do currently dive a membrane (Aerdura) but in the past 3 of my 7 drysuits have been neoprene. Will never have another neoprene (unless its crushed), they are too cold and have too many buoyancy issues. My CF200 dui leaked like a sieve and went back short of my Northern Diver it was one of the worse suits I owned (neoprene seals suck)

Personally I have no problems with just my drysuit for bouyancy. I wear no extra weight with my twins and stages and 6-8 lbs with my inspirstion depending on the stages I wear. Most of my stages are 3L steels ot 7l Alloys. I've been teaching dry suit only for buoyancy since about 1980 when drysuits first come out to amatuers and they've not had any problems either.

If your neck seal is farting then that suggests that a) it doesn't fit or the suit is restrictive and b) you hav'nt discovered the trick of inverting a latex neckseal, which is much more comfortable as well as keeping the air in. Too much air in the feet suggests the suit is too big.

A suit that is too large will definately give you problems with air migration, and one that is too small will not hold enough air and pull on the neck seal when you move.

I'm not saying drysuit is the ONLY way. I'm more opposed to using more than one method at the same time as that can (and I've seen it) lead to task loading on the ascent when there are several buoyancy sources to handle. Add a rebreathers counter lungs into the equation and pop!!!!. Get rid of one of the sources (doesn't really matter which) to make life easier for yourself

Better still stick outo dumps on the drysuit and counter lungs and add a ADV for the inspiration and youre nearly fully automated. Now who's gonna fit a dry suit ADV first????

 

[nickjb]

Have you got any links or more info on ADVs I was looking for something like this for another application (I don't think I'll put one on my drysuit just yet)

 

[padiscubapro]

actually to me any noticable air in the feet is too much! For the last several years I've been using rock boots, so I really dont get air down there anymore..

I never liked the feeling of air moving within the suit so I always dive it with the minimum gas required (just enough to relieve squeeze).. I never had a leaking problem with my cf300, I use latex seals myself.. even diving it with minimum volume is still find it occasionally "burps" from the neck if I'm not paying attention to my positioning.. I do the fold on my neck seal as well.. and the suit fits well.. I think its easier for beginers to control it by suit only especially if its a single tank, but I feel once you start becoming very negative its better to use the wings for what they were designed.. When I used to use thinsulate I was much more buoyant and not really any warmer.. I now only use polartec garments since they are warm and not very buoyant. Unless I am very deep the amount of gas in my suit doesn't concern me, on deeper dives I make sure the gas is venting properly and check it on my deco stops..

I have practiced free ascents many times and other than my first try at it with my RB I haven't had any problems controlling the 3rd air space once I got down the rate I needed to dump the loop while ascending.

 

[jonnythan]

There's definitely something to be said for avoiding the "shopping bag" effect of having a large air bubble in the drysuit. If nothing else, it's uncomfortable and just weird.

 

[madmole]

Details of ADV's can be found on my website Diver Mole "Your Inspiration Buddy" or on Bob Howells Site

So the consensus is use the drysuit if your not too negative and only use the wing if your over heavy. Personally I'd suggest you try allow stages if your combi is that heavy

 

[budgy]

I see lots of dry suit divers are carrying too much ballast, which may account for their large bubble in the back feeling, or an inability for their suit seals to hold enough buoyancy. My experience with ND was a compressed neoprene, bust a gut to get into never dry suit. Some people are happy with theirs I wouldn't buy another one.

 

[Tibbs]

madmole once dribbled...
Thats a supprise, cos most of us dry bag folks use our drysuits as our primary bouyancy compensation on all dives. Controlling the buoyancy in a dry bag is easier than in a wing (just shrug shoulder to vent) and I dont know what drysuits you've seen but my drysuit easily provides probably about 5 times the boyancy of my 55lb lift wing (think Michelin man).

In the UK must people only use the wing/bc for surface support. Its bloody cold in the water so using the suit as your BC also keeps you warmer

Are you sure? I certainly wouldn't say most. From (unrepresentative) polls I have seen, it's nearer to 50-50, possibly with a lean in the direction of BCD. Amongst my contemporaries, none dive soley on Drysuit.

But then again I can't say definitively as I have never seen an independent poll. Do you have one?

Don't tar all of us UK divers with your brush.

Chris

P.S. Be very careful about folding in a latex neckseal. It rests beautifully on your carotid artery - and blowing up the suit will result in pressure on said artery. I've seen a guy pass out on the surface after a dive because of this. Oh, he was using the drysuit as buoyancy as well...

 

[madmole]

All BSAC divers are trained to use dry suit only which are the majority in the UK and as its the biggest dive club in the world must mean a lot of other folks as well

As for folding the neck seal pressing on the carotid artuary, yes, but then so can a normall way up seal if its too tight. With an auto dump its hard to get much above ambient pressure in the suit anyway and you need at least a pressure of 80 mm Hg to stop the flow in an artuary and thats a lot. It would get unconfortable pretty fast with that level of pressure

As an ex paramedic I'm very aware of how hard you have to compress artuaries to stop blood flow

All I saying is that if you are not a ton negative in the water you should be easily able to do you weight control on just one source and not have to involve 2. and as you have to squirt into the drysuit to stop ending up vacuum packed, you might as well need to give it a bit more.

I need approx 8 kg of positive bouyancy at depth (early in dive) to offset my twin set (2x 12.4l aber steels) and stages 2x 7l alloy), now picture that in terms of 4 x 2l coke bottles spread out over your whole body and you'll see why its not an issue (its about a 5mm layer all over you, thinner than your undersuit). If you cant offset your negative buoyancy with just the suit without looking like a michelin man then I suggest your are overweighted or your equipment configuration needs looking at. Remember as the dive progresses you get lighter and need less

 

[MikeFerrara]

madmole,
That's just the point. With my double steel PST 104's (17 liters) and al stages and canaster light and reels I am very neg and the dry suit alone will not work except as an emergency measure. These tanks alone are almost 13 pounds neg each when full. There is little comparison betwen these and what your using. We also teach new drysuit divers to use their suit for buoyancy control. That limits task overload and they should be almost neutral anyway. In our cave rigs we are not neutral, we are neg.

Balancing those heavy tanks on top of a buoyant suit is a real task I asure you.

What kind of technical training does the BSAC provide?