Buoyancy and thick wetsuits

[dumpsterDiver]

10 -12 lbs of lead with a full 3 mm suit and aluminum tank is about what I wear. For a 7 mm suit similar to yours I wear around 26-28 lbs. So my GUESS is that you are a little heavy with 36 lbs.

However, if you can not control your bouyancy at 15-20 feet (and no air in the BC) then you simply need more lead. We can estimate all we want, but you need to wear whatever it takes to allow you to do your stop safely.

 

[bajashack]

With out seeing you in the water I would think you are not relaxing enough at the surface which is why you need so much weight. Then once you get under way you relax more and then have to deal with the extra weight. If you are using an aluminum tank try using a steal. You should be able to take off at least 4lbs.

I used to were 30lb 10 years ago I am 6'5 then I was 210lb. Now I am 245. I use the same 7mm farmer John then as I do today, but use only steel tanks 100 cf. I use 20lb of lead.

 

[Eric Sedletzky]

One thing I have to add:

The reason it is so effortless and easy to hold a stop at 15 feet with a completely empty BC is because there's no air to expand and contract in the bladder. Between 10 to 20 feet is a critical area with the most pressure changes happening, so if you have to have air in your BC to hold a stop and you descend a few feet the air in your bc will compress and you'll get heavy fast, if you ascend a few feet then the air in the bladder expands and you get really light fast so what you end up doing is filling and dumping constantly to try and hold a stop. If the swells are running this problem is even worse because you've got the crest and trough of the swell adding or subtracting depth on you when you're trying to hold a stop.

With a completely empty bc you just sit at 15 feet and breathe normal and nothing then really affects your ability to just sit still and enjoy your stop.

 

[bisugo767]

It seems you have a lot of lead ....

What is your weight, height and sex?
What tank?

I could check your configuration with our simulator

Regards,

I_AM

Height: 6-ft, 2-in.
Weight: 195-lbs.
Sex: Male
Tank: Al 80

I appreciate the offer. The simulator result will help me know where to start before I do a bouyancy check.

Phil

 

[bisugo767]

10 -12 lbs of lead with a full 3 mm suit and aluminum tank is about what I wear. For a 7 mm suit similar to yours I wear around 26-28 lbs. So my GUESS is that you are a little heavy with 36 lbs.

However, if you can not control your bouyancy at 15-20 feet (and no air in the BC) then you simply need more lead. We can estimate all we want, but you need to wear whatever it takes to allow you to do your stop safely.

I wear a 7mm John + 7mm Vest + 7mm Hood + 5mm Glove. A full 7mm up here in Vancouver won't do even in Summer.

Phil (bisugo767)

 

[bisugo767]

Start diving in Florida and your problem is solved.

So far, for the last three years, I have been diving in Mexico where I spend my vacation. I would like to try Florida Keys someday.

 

[AndrewJD]

You say you've been diving wet during the summer months. Does this mean you dive dry during the winter months or not at all?

If you do have a drysuit, then I suggest you dive dry all the time and vary your undergarments during the summer. Assuming you have a shell drysuit that won't compress at depth, then your issue will be solved. Your BC will have the necessary lift you need.

If you don't have a drysuit, then I'd recommend investing in one. Thick wetsuits are not your friend.

Jonathan

P.S. Of course you'll need to add gas to your drysuit to maintain loft like Pete says... Thank you Pete.

 

[spectrum]

bisugo767,

Why do we use a BC? It's to compensate for the change in buoyancy in our gear as we dive. That change comes from 2 main sources. Our neoprene become less buoyant with depth and our cylinder becomes more buoyant as we dive. If it serves that purpose we should be golden at the surface since at that time our neoprene is fully buoyant.

Regarding your weighting a common number (and it's only that) Dumpster Diver mentioned 26 pounds and I also use 26 with a steel cylinder in the ocean while wearing similar neoprene. Adjusted for for an AL-80 I would need 33 pounds. So you being you it's possible that you are not over weighted.

Below 30 feet you should more or less drop like a rock and need to add air to your BC.

Getting back to why we use a BC now you said you were fully inflated at 60 feet and still negative. Something is wrong with this picture because there is no way you lost 46 pounds of buoyancy from neoprene compression. So what is wrong? I see 2 possibilities.

1. You are getting a tremendous amount of water into your BC (or not draining it) robbing it of it's advertised lift capacity. (There is also an outside chance that you have a wimpy OPV that prevent full inflation)
an/or
2. You are grossly over weighted. Perhaps your lung volume is varying widely causing you to find yourself buoyant in the shallows.

Have you ever tried to do something like this as a weight check?

Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.

You can make the same test pre-dive with a full cylinder and add 5 pounds to compensate for the buoyancy gain you will experience as you breathe the tank down. Be sure to repeat at the end since you are apt to have some stowaway buoyancy (trapped air) in your gear early in the dive. You are safer being two pounds heavy than 2 pounds light.

What you are wearing for a wetsuit is nothing exceptional, something is wrong. I would not proceeded with the drysuit until you understand what's happening with your buoyancy. Adding the drysuit to the equation when 46 pounds of lift is not getting the job done could create an unpredictable situation.

Pete

Hi, I live in the Vancouver BC and I have been diving wet during the summer months. Ever since I got certified years ago, I have been struggling with bouyancy issues when diving with a 7mm vest, 7mm john, and 7mm hood. I use a Sequest ProQD BCD with 46-lbs of lift and around 38-lbs to 40-lbs of lead. My bouyancy is OK at around 15 to 30-ft. but I sink like a rock on deeper dives. At one time at 60-ft., my buddy noticed that I have already pumped the max air into my BC but I was still too heavy. If I reduce my wieght to 36-lbs., I become too light at shallow depths and just a tad heavy in deeper water. I know the thick suit plays a big part with this bouyancy problem. I have since acquired a Sequest Black Diamond BC with around 50-lbs. of lift. Do you think this will solve my bouyancy issue? I believe if my BC has enough lift, I will be able to properly compensate for drastic bouyancy changes due to wetsuit compression at depth. I would like to hear from other divers out there who wear the same set-up and find out how you dealt with this bouyancy issue.

My weight: 195-lbs.
My Height: 6-ft. 2-in.

 

[spectrum]

You say you've been diving wet during the summer months. Does this mean you dive dry during the winter months or not at all?

If you do have a drysuit, then I suggest you dive dry all the time and vary your undergarments during the summer. Assuming you have a shell drysuit that won't compress at depth, then your issue will be solved. Your BC will have the necessary lift you need.

If you don't have a drysuit, then I'd recommend investing in one. Thick wetsuits are not your friend.

Jonathan

A cold water undergarment however will have very significant compression that needs to be counteracted to some extent with suit air just to maintain warmth. It's hardly a steady state.

Pete

 

[nagel]

There is something definately "goofy" going on - I too have a problem with the farmer johns - hate them. I wear a full 7mm and avoid the farmer john. But, really what is bothering me is a previous quote from you:

"Anyway, I will take all your bouyancy check tips and apply them when I do my next dive. ZKY, Steve_Dives, I will make sure I follow your Bouyancy Check tips. These are things that you only learn through experience. I have not read or heard of the 15-foot zero bouyancy thing but it does make perfect sense to make sure that you are neutrally bouyant at that depth at the end of a dive."

Not trying to be an @ss here, but what am I missing? You have not heard of a 15-foot zero bouyancy thing? Did they not talk about safety stops in your class? Absolutely, you have to be able to control your bouyancy especially at 15 feet.

My guess here is that you are not relaxed when you start the dive. Yes, you have a thick suit on. Apparently, it is what you need for your dive conditions. The suit is constricting;which, causes your heart rate to increase along with your breathing. Additionally, the bodies own defense is to keep some air in your lungs even though you think you have exhaled everything. The water is cold; therefore, your body is unconciously trying to get you out of it and also keeping air in your lungs (what happens when somebody throws cold water on you at the surface - you immediately inhale). You may be finning up a little and not realize it. You may be suffereing from something I did for many dives, once my head was under water, I tended to panic a little and had to work on calming down. My breathing increased until I calmed down - all this was a huge fight with the initial descent. Are you sure you are getting all the air out of the bc. Just dumping from the inflater hose may be leaving an air bubble. Try dipping your right shoulder and using your right arm squeeze the side of your bc. This should push any air bubble out of your bc.

Here is what helped me tremendously (I learned this from this forum). Most people will tell you blow out all your air from your lungs as you start your descent. This is totally wrong for me because once my head got under water I wanted to take a breath; which, caused me to bob back up. What I do is I lift my inflater hose and start dumping air. I take a deep breath right before my head starts go down. Once my head starts to break the surface I exhale - walla I start sinking. Play with this and it should help.

S. Nagel