Drysuit Diving Buoyancy as it relates to your BCD

[Ulfhedinn]

From what I understood in an AOW Dry suit dive that I use the dry suit for buoyancy and not the BCD. Is this correct?

As I played around with the dry suit and BCD in the water I felt that as long as I kept enough air in the suit so it didn't squeeze the life from me I preferred to still use the BCD for better buoyancy control. Was that wrong of me?

This even seems more correct when using something like a Whites bullet suit due to fit?

 

[Tigerman]

You can use the suit or you can use the bcd, none of them is "wrong"
However, if you're properly weighed removing the squeeze from the suits makes you very near neutral so you wont need to use the bcd.

Providing you're diving single tanks

 

[coldwaterdufus]

You will probably get answers on both sides of the fence, ie suit versus BCD. I was told during my drysuit course to use drysuit for buoyancy and bcd only on the surface. I struggled with this for prob 40 dives. I then took a peak buoyancy course and the first thing the tech diver / instructor said to me was don't do that. Use suit to eliminate squeeze only and bcd for bouyancy. This made a huge difference for me. I always had trouble venting my suit and using the suit for buoyancy always caused me lots of problems. Live is a lot easier for me now.

 

[300bar]

From what I understood in an AOW Dry suit dive that I use the dry suit for buoyancy and not the BCD. Is this correct?

For a PADI AOW, yes it's correct

As I played around with the dry suit and BCD in the water I felt that as long as I kept enough air in the suit so it didn't squeeze the life from me I preferred to still use the BCD for better buoyancy control. Was that wrong of me?

If you still need air in your BCD (assuming you're diving single tank) you need to get rid of some weights.
I'm diving dry year round and never use my BCD during the dive.

just my 2 (euro)cts.

 

[Scuba_Noob]

PADI teaches you to only use your BCD at the surface and use your drysuit throughout the dive (so you don't have to load your mind with both the BCD and the drysuit). However, people have personal preferences.

I prefer using the BCD for buoyancy and using the suit only to counteract the squeeze (and I know many experienced divers who do the same). Generally once I descend past 20fsw, I close my drysuit valve; then I open it once I ascend higher than 30fsw.

I don't think it's wrong to have a personal preference.

 

[TSandM]

The reason given for teaching the sole use of the dry suit for buoyancy is that it minimizes task loading on the diver. It's felt that it's too difficult (and risky) to expect a relatively novice diver to remember to manage two different air chambers.

However, if you use the inflator hose for venting your BC, the motion you use (lifting with the left hand, and rolling slightly to the right) will also vent the dry suit.

It was my experience, as with quite a few folks here, I think, that keeping less gas in the suit and more in the BC made buoyancy control much easier and safer when I was first learning. Eventually, with facility, you put the air where you want it, depending on the dive you are doing. If the water's very cold, I run as much gas in the suit as I can manage; if I'm having to assume "unusual attitudes" (as in the caves), I run the suit as tight as I retain adequate mobility, and use the BC for buoyancy control.

 

[Rainer]

In a single cylinder, as Tigerman notes, and assuming you're properly weighted, simply filling the drysuit first to relieve the depth-induced squeeze will often result in neutral buoyancy. If not, then add gas from the BCD. Your goal is a comfortable amount of gas in the suit (taking off the squeeze and maximizing warmth, without making the suit difficult to dive).

In doubles, you still start with the suit to relieve squeeze, but you'll need to add a substantial amount of gas to the BCD.

Basically, if properly weighted in a drysuit, you're only negative the weight of the backgas (in a wetsuit, you're also negative the loss of suit buoyancy with depth).

With experience (and in cold water), I've found myself putting more gas in the suit whenever possible for increased warmth. When I first learned to dive dry, it was easier to keep a good portion in the BCD.

 

[tylerinflorida]

I hate using my drysuit for buoyancy control. I keep just enough gas in it to prevent squeeze. BCD is much easier for me to use for that purpose, maybe because it's second nature.

 

[NAM001]

I am sure there are probably reasons for this ... but when I tried to use the suit for bouyancy i would get light feet. When in Good trim with proper body posture, feet are the high point. The center of mass and weight is not the feet, the legs are functioning as a lever. Using the bcd for bouyancy seams right. lift where the center of moment/mass is and not at the lever end that primarily controls trim angle. When trim is controled by head movement and feet tucking or extending (equivilant of .1 lb changes in weighting at the feet area), shifting a couple of lb's of lift to the feet is overkill and counter productive. I use the suit air to counter suit squeeze, and the bcd for bouyancy for the center of mass that equally lifts both the head and feet without changing aspect in the water. I would guess that there are very few that have dry suits that have legs so snug that it precludes an air volumn from migrating to the feet. There are those that are strapped such that it retards greatly the movement of air to the feet. I look at the suit as a exposure suit and not a bouyancy device. The dry suit besides providing exposure protection also provides a BACKUP bouyancy function. So dry or wet the purpose of the bcd does not change. The only changes are the price you pay for the selected type of exposure protection. Wet= changing bouyancy and brrrr in coldwater and dry = toasty warm but you have to counter the increased overall bouyancy fo the suit with weight. Granted every time you put air in or vent air you are geting the effects of the bcd nature, however what little air you put in for squeeze comtrol is only restoring the baseline bouyancy of the suit. Another thing is that if i want some lift i want it from the tank area not the body area where it will (by phisics) try to roll you belly up when the suit is used. normally this effect is so minimal it either doesnt count or is well within you ability to compensate for it. the auto rlief valve in the suit when properly set is there to minimize the air volumn in the suit, and as such minimize the suit as a bouyancy device. One last thing to think about. Your bcd is about say 20" long. your dry suit is about 6 feet long. air moves along the full leignth of the air vessel. soooooo, take a slight up angle and the air rises by ging to the highest end. in the suit it is a 2-4 ft shift in center of lift. in the bcd it is much less than a foot. One other thing. Another poster said that if you are probperly ballasted you wont need the bcd. you still have the weight shift of air consumption, say 6-8 lbs. if the tank changes then the cpmpensation of the weight should be limited to the same area as the change ie the tank and therelies the bcd.

 

[Tigerman]

Although your feet is the highest point doesnt mean the air flows there.. The knees can be the lowest while the feet is the highest