Pool-to-Open Water Conversion

[Pandie]

I've sifted through a TON of posts this morning but I haven't been able to find the answer to my question (so I'm sorry if it's a repeat -- I really didn't find it!).

I have heard that there's an equation to use to figure out how much weight you'll need out in the ocean if you know how much weight it takes to get underwater in a pool. But I haven't been able to find it yet.

Also, does anyone have any tips on how to reduce the weight you'll need to get down? I know I'm carrying a LOT of weight (20+ lb) and that was the one critique my instructor had for me was to try to shed some of it.

Appreciate any suggestions, but definitely want to try to get ahold of that formula! Thanks heaps!

-Stacy

 

[cdennyb]

I've sifted through a TON of posts this morning but I haven't been able to find the answer to my question (so I'm sorry if it's a repeat -- I really didn't find it!).

I have heard that there's an equation to use to figure out how much weight you'll need out in the ocean if you know how much weight it takes to get underwater in a pool. But I haven't been able to find it yet.

Also, does anyone have any tips on how to reduce the weight you'll need to get down? I know I'm carrying a LOT of weight (20+ lb) and that was the one critique my instructor had for me was to try to shed some of it.

Appreciate any suggestions, but definitely want to try to get ahold of that formula! Thanks heaps!

-Stacy

Well Stacey, I've been diving for 26 years now and taught my kids in our pool and now my two youngest (23 and 15) are ready to assist in some research and recovery projects with the ol' man. (They went to a school locally to get carded but it was more of a formality than an education for them) We have a truck load of gear and suits and compressor so when we go divin', we GO DIVIN'! We use V-Planner software to plan our dives and mix a bunch of strange sounding gasses to breath as well (Donald Duck gas!) containg helium.
To answer your question. 20 pounds is a lot! In my opinion, weigh too much! I weigh in at 127# drippin wet and no gear on. My daughter (the youngest is the same) I teach my kids that every dive trip is going to be a little different, and this weight thing is something you'll have to deal with every time. I get all the gear on (dry or wet suit, BC w/tank combination and extra gear as required (sometimes we need lights, sometimes it's a set of doubles, or maybe a single with camera gear, etc.) then hit the water. I make sure we have about 500-800# of air in the tank(s) and then add weight until I just start to sink (make sure the BC is empty of air). That's what you need in fresh water and add 3% for salt water. That usually ends up being about a 2 or 3# weight in the BC pocket or on the belt that the light cannister goes on, that's all. My total weight for dry suit and set of doubles for a night dive is only 18# and I'm carrying two 80 cu ft tanks of 30/30 trimix, a pony bottle (13 cu ft) of argon (for the dry suit inflation) and my usual gear. (fins/mask)
Hope that answers your weight question. It's always better to be under weighted than over weighted. Remember that for every pound of excess weight you carry, you have to offset that sinking with air in your BC and that air in the BC is subject to expansion and contraction more and more as you change from deeper to shallower water and that makes for problems controlling your neutral buoyancy.
Remember to add enough weight to just start to sink and then throw on maybe a 2 or 3# weight to finish the job.

db

 

[MtnDiver]

This is a topic that should be covered in your briefing before your first OW dive. It depends on several variables such as what type/thickness protection suit you are wearing, fresh/salt water, your body type, etc.

My OW cert. dives were done in fresh water in full 7mm wetsuits. All of our classwork in the pool had been in 3mm shortys. The first thing we did in the water on our first dive was a bouyancy check and adjust.

 

[Mako Mark]

No magic formula stacy,

Jump in the water with a little more to compensate with the salt and do a bouyancy check.

THe human being has the natural instinct to take a big breath before going under watre. You have to over come this and exhale to go down. Otherwise you will end up with extra to compensate for your lung volume.

to reduce the amount you need, slow everything down, breathe with you belly not your chest, breathe slowly and streamline yourself.

the more you struggle and wriggle, the more floaty you will be. The need for lead generally is reduced with the more experience you get in the water.

hope that helps and let us know how you go in the ocean.

.

 

[Pandie]

I appreciate the responses! Yes, we did go over weight in the pool and then weight out in the open water, but I changed gear between the pool and our first open water, and even when I added a bit more weight, I still didn't sink In the pool I needed about 14lb (I've got natural bouyancy compensators built in *wink*), but out in the water, I needed much more it seemed. But then, once I was down to say, 60', I had to fiddle with the BC a bit much to stay neutrally bouyant, so I'm sure I had too much weight on.

Thanks for the tip about the inhale. I know I'm doing that, so I'll try to exhale from everything (BC *and* myself) when I'm trying to get under the water.

I appreciate all the help! I hate being a newbie at this!

 

[GrierHPharmD]

The thing about inhalation is very important. Nobody told me about it in class, either, and I used to go in way overweighted. Making sure that you have all of the air out of your BC when you go down is important too.

If you beach dive with some of us other locals, we'll be glad to help with your bouyancy checks and see if you can drop some of that lead. I weigh 185# and only use 6-8#, depending on whether I use my aluminum or steel tank, to go down when I'm not wearing my wet suit. I used to use 14-20# when I first started, so I know how you feel. Losing that extra weight will make everything a lot easier.

Good luck,
Grier

 

[MSilvia]

3% sounds like a good rule of thumb. I've heard several formulas for figuring it out, but in my experience most of them leave out important little details like what kind of equipment and exposure protection you're using. A diver in a 3mm wetsuit is going to have different requirements from one in a 5mm, 7mm, or dive skin.

Find out the minimum you need to sink with an empty BC and 500psi... that's how much you need.

 

[GrierHPharmD]

Find out the minimum you need to sink with an empty BC and 500psi... that's how much you need.

Excellent advice!

 

[Scuba_John]

3-5% is the best idea for the conversion. And as it has been stated depends alot on the type of wetsuit 3m vs 5m and on. While being a newer diver there is a tendency to breath shallow which by the time you are in the water for a few days and sometime even after the first you will see a change in breathing patterns. Deep and Slow. Another point to look at is the depth has an effect on the wet suit and other cavities that contain air. The deeper you go the more commpressed they become and less weight is needed. What ever weight you end up with remember to add a few for the empty tank which will pull you up towards the end of the dive.

 

[GrierHPharmD]

Here's a nice little discussion of weighting from Rodale's

http://www.scubadiving.com/article/0,7424,3-39-42-78,00.html