Neutral Buoyancy for a safety stop

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Peter Boyd

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Messages
15
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Location
Halifax Nova Scotia
# of dives
200 - 499
Hi, I am having trouble maintaining Neutral Buoyancy for a safety stop. I am diving a waterproof drysuit with winter thermals and a ranger BCD. I have no problem maintaining neutral at depth,but coming up for a safety stop and the last 20 ft I can't seem to bleed off the right amount of air.Does anyone have any tricks or advice?
thanks
 
raise your venting shoulder
a slight up angle will let some sir vent from the legs to the upper body
loosen your rig straps a little

you say you cant bleed off the right amount of air,,, are you capable of venting till you sink? If so you are heavy
verify your shoulder vent is full open so it vents the easiest ,,,, if not all the way open you sill be light

is this an off the shelf ds or a custom and is it a shell suit?
 
Most people are carrying too much lead. This is such a common problem I would start there. Are you making the mistake of using the drysuit for buoyancy? This too can be an issue. The shallower you get the harder buoyancy control becomes - it will improve with time so don't get stressed about it.
 
EDIT: I misread the OP and thought he was in a wet suit, so much of what follows does not apply. Sorry!

You don't provide a lot of information, especially about the thickness of the wet suit, but I am guessing it is a thick one for my response. If you are wearing a thick wet suit during a safety stop, several factors are combining to make your life difficult.

First of all, understand that it is much more difficult to maintain buoyancy during a safety stop than at depth, no matter what you are wearing. The closer you are to the surface, the more the gas spaces in the BCD and wet suit will expand and contract as you rise and sink. At sea level, going from 33 feet to the surface, those spaces will double in size. In the typical range of depths in which divers usually hold a safety stop, those spaces will vary by about 25%. That same range of depth change at about 60 feet will have only about a 10% change in volume.

Next, a thick wet suit makes things more difficult because there is much more expansion and contraction of gases to contend with. The degree to which a thick wet suit expands and contracts with changes of depth can be significant.

A further complication is that a thick wet suit requires you to be overweighted during a dive. That is because you need the weight to descend near the surface, but you don't need as much weight once the wet suit contracts at depth. That means you will have more lead at depth than you need, meaning you must add more air to the BCD to balance it. Even at only 15 feet, that extra amount of air adds to the difficulty of remaining neutral.

Finally, the majority of divers are overweighted regardless of their actual needs, and in my experience, that includes especially divers with thick wet suits. The more anyone is overweighted, the more difficult it is to control buoyancy, and as described above, that problem is amplified at shallow depths. Every extra pound of lead demands about 15 fluid ounces of air to compensate. I have no idea from what you wrote if you are overweighted, but it is possible. I did OW dives in fresh water with a student who had done his pool work with another instructor, and he had done it in a 7mm wet suit so he wold know what his weighting needs were when he did the OW dives. He told me he was certain he needed 22 pounds, and I made him start with about 18. It was way too much, and he could not control his buoyancy on the first dive. When I finally got him down to 10 pounds, he found controlling his buoyancy to be no problem at all.

Ultimately, if you are weighted as best you can be, it all comes down to getting more and more practice.
 
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raise your venting shoulder
a slight up angle will let some sir vent from the legs to the upper body
loosen your rig straps a little

you say you cant bleed off the right amount of air,,, are you capable of venting till you sink? If so you are heavy
verify your shoulder vent is full open so it vents the easiest ,,,, if not all the way open you sill be light

is this an off the shelf ds or a custom and is it a shell suit?
It's an off the shelf d7 pro , I keep the dump valve open. I just switch to a heavy (puffy) undergarment and I might be over weighted. I will remove some weight on my next dive
 
It's an off the shelf d7 pro , I keep the dump valve open. I just switch to a heavy (puffy) undergarment and I might be over weighted. I will remove some weight on my next dive
Under garments are light weight so its the puffyness that counts. If you are light at 20ft then more weight. If heavy then less weight. I was assuming that your safety stops were unstable, heavy one time and light another. I looked it up and it looks like a codura suit. should work like a shell suit in that is is not tight like a wet suit. being codura i would not expect to have air trapped in the legs ect like a wet suit fitting type dry suit. Are you using it for buoyancy or to keep the bite off you and using the wing for buoyancy? I do the latter so the suit does not get control of me or my ascent.
 
I did OW dives in fresh water with a student who had done his pool work with another instructor, and he had done it in a 7mm wet suit so he wold know what his weighting needs were when he did the OW dives. He told me he was certain he needed 22 pounds, and I made him start with about 18. It was way too much, and he could not control his buoyancy on the first dive. When I finally got him down to 10 pounds, he found controlling his buoyancy to be no problem at all.

Ultimately, if you are weighted as best you can be, it all comes down to getting more and more practice.

Must have been a small guy. I keep hearing these stories and when I go diving on vacation I am always told that I am asking for way too much lead and to "try xxx". With my 7mm wetsuit I need ~32lbs. with a steel tank. I guess I should take this as a complement that I don't look as fat as I actually am :rofl3:
 
Ensure you have vented the gas from your suit. Go more heads up and roll so that the exhaust valve is the highest point on the suit. Wait while the air migrates to your shoulder and drains out. Wait some more. I'm always impatient with this, and it bites me at the 10 ft stop.
 
My answer may be woefully inadequate but had the same issue even in a wetsuit. The advice I was given completely solved my issue. Dump all air before starting ascent and once you get to the SS or what ever depth you want to maintain, then bump the inflator as needed to get neutral. This solved my issues with the big pressure swings at the shallower depth causing me to have struggle staying at the desired depth.
 
https://www.shearwater.com/products/swift/

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