Dry Suit bouyancy check?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Scott M

Contributor
Messages
894
Reaction score
2
Location
Upstate NY - Lake Champlain
# of dives
100 - 199
Tobin,

I have a couple of questions: If I am doing a buoyancy check for my dry suit I would want to have on just my U/G and dry suit with no air in it, will this include, fins/gloves/hood/mask also. I would assume so since they effect buoyancy but would like to know for sure. I am looking for eye level with a full breath? Sink when I exhale?

Once I have that number I would subtract out the negative weight of my rig? correct?
For me that is a -6lb SS plate, -6lb STA, and I typically use an HP100 so -3 when empty and -2 for my regs. So what ever number I come up with it will be less 17lbs? Is this correct so far?

Ok, if that is all correct or assuming you will correct where I have made a mistake, once I have obtained this neutrally buoyant rig at the end of the dive my question would be how much do add for air to be used in the Dry suit, if any? And does this change depending on the under garment being used?

Thanks in advance for your assistance
 
Tobin,

I have a couple of questions: If I am doing a buoyancy check for my dry suit I would want to have on just my U/G and dry suit with no air in it, will this include, fins/gloves/hood/mask also. I would assume so since they effect buoyancy but would like to know for sure. I am looking for eye level with a full breath? Sink when I exhale?

I like 1/2 a breath. Gives me a little room either way for my built in BC.

Leave the fins and mask off. These don't compress. We are trying to determine the buoyancy of things that can change. If you hood and gloves are significantly buoyant wear them.

Once I have that number I would subtract out the negative weight of my rig? correct?
For me that is a -6lb SS plate, -6lb STA, and I typically use an HP100 so -3 when empty and -2 for my regs. So what ever number I come up with it will be less 17lbs? Is this correct so far?

I'm not sure what you are referring to. Try not to make this more complicated than it needs to be.

Once you know the buoyancy of your exposure suit at the surface you also "know" how much total ballast you need.

This ballast can be any combination of back plate, STA (if you are using one) regs, empty negative tanks, can lights, H-Valves, P weights, weight plates, weight belts, etc. etc. etc.

In short all the things you are taking with you that DON'T FLOAT should = the things that DO FLOAT, i.e. your exposure suit.

Ok, if that is all correct or assuming you will correct where I have made a mistake, once I have obtained this neutrally buoyant rig at the end of the dive my question would be how much do add for air to be used in the Dry suit, if any?

If you are diving singles (with a STA I hope so) I am assuming NDL dives with a ~3 shallow stop. I am assuming you can tolerate 3 minutes shrink wrapped in your suit. Your suit will be actually less buoyant when shrink wrapped at ~15 ft than it was at the surface.

If you were in doubles the assumptions would be different.

And does this change depending on the under garment being used?

Different undergarments will provide different amounts of buoyancy. That's why I like to see divers actually test their own gear.

Tobin
 
Tobin,

That all makes sense to me now. Yes all my dives are NDL dives on a single HP100 (AL80 if I can't make it to the fill station before I use up my HP100's. I hate the AL's with the Dry suit). I do have STA's on both of my rigs. My Dry suit rig's is weighted. Once I get the bouyancy check done I may look to put some more weight on the rig itself so will possibly be ordering some weight plates. I don't like carrying a lot of ditchable weight.

I have been doing my safety stop with a completely dumped suit. The squeeze of the Fusions suit is minimal anyway so it's no problem there.

One last question, I am doing all this for fresh water right now but will be diving salt also with this rig. How would my weight be effected going to saltwater with the same exact set-up?

In the near future I am going to be setting one more rig for my place in Florida so I can just leave it there. That is going to be set up to dive NDL, single AL80 tank with a 5mm wetsuit so I will be looking for some advise to a suitable rig for that. I was thinking basic harness, ss plate and a 30lb wing but will have to take a bouyancy check of the suit first.

Thanks again.
 
One last question, I am doing all this for fresh water right now but will be diving salt also with this rig. How would my weight be effected going to saltwater with the same exact set-up?

Rule of thumb: 1 lbs of ballast for every 40 lbs of diver and gear. Add when moving from fresh water to salt, remove when moving from salt to fresh water.

Tobin
 
Rule of thumb: 1 lbs of ballast for every 40 lbs of diver and gear. Add when moving from fresh water to salt, remove when moving from salt to fresh water.

Tobin
Perfect, thank you Tobin.
 
Perfect, thank you Tobin.

The reason Tobin is saying 1 lb of weight for every 40 lbs of diver & equipment is because salt water is 2.5% denser than fresh water.

1 / 40 = .025 or 2.5%
 

Back
Top Bottom