Drysuit diving without enough weight. Dangerous !!

[Rimp]

I rented a drysuit on the weekend and my LDS estimated my weight requirements to be approximately 32 lbs. I hadn't dove dry in a while and had no idea what my weight should be. When I got in the water I discovered there was no way for me to submerge with this much weight, even with all the air out of my BC and suit.

My buddy managed to jam enough rocks into my BC pocket (at my suggestion) to get me under.. just barely. Once submerged it didn't seem to be a problem at all since i became negative as depth increased. The one thing we didn't consider was the effect of weight change as air was used from the tank.

I realize this was pretty stupid now..

At the same time, I had a problem with my Octopus that started freeflowing when I reached 50 feet or so.. This resulted in most of my air being expended from my tank very fast, making me positively buoyant and resulting in an uncontrolled ascent to the surface. At the time I thought it was a problem with my suit not venting fast enough, but on later reflection realized it was a problem with weight. Obviously I didn't check my weights correctly and took a huge risk diving with rocks in my pockets and full tanks.

I pulled my suit collar open halfway up the ascent to the surface to reduce the speed considerably, but I didn't have enough weight to remain under the water once my tank air reached a critical level. I had no problems as a result of the uncontrolled ascent luckily. We were in the water about 25 mins.

I did learn a valuable lesson though, so thought I would pass it on here for everyone to read.

When setting up weight for use with a drysuit, be sure to estimate using an empty tank, not a full one, and if your light on weight, don't just add enough to make you negative with a full tank, you need a few extra pounds to compensate.

I wonder what the weight differential is between a full tank and an empty one and how much extra weight is required to compensate?

Lesson learned.

My LDS has offered a free rental as a result of their weight estimation error. They are guessing now I should have gone out with 40 lbs instead of 32.

 

[Dryglove]

I wonder what the weight differential is between a full tank and an empty one and how much extra weight is required to compensate?

Depends on what size of tank you are using. If i remember right a standard aluminum 80 holds about 6lbs of air which means you will be 6lbs heavy at the beginning of your dive and neutral with a near empty tank if you are properly weighted.

Were you using a trilam or neoprene type drysuit. I would think 32lbs would be plenty with a trilam suit.

 

[RiverRat]

Hey, thanks for sharing, glad you made out ok. I recently dove my 7mm wetsuit, steel tank and BP/W setup for the first time (first time with this combo of gear) in salt water. I've since learned that ANYTIME one makes a significant change to gear config that you've got to go right back to the beginning and re-think everything and do a proper weight check (I believe it's in the PADI OW manual...). I too went out light, on a shore dive, and knowing I was a bit light was able to get down and do the dive. Even with the steel tank I underestimated the buoyancy swing of my steel tank and was also amazed at the suit compression of my 7mm. To make a long story short, I had to hold onto a rock to do my safety stop. Not to mention the strong surge from the tide coming in, I was "blown off" the rock while fiddling with my fully flooded mask and was only able to complete half my stop. I should have swam in, got more weight and not have dove until I got it right. I assumed (there's that word again...) that with the steel tank buoyancy swing would not have created an issue. I was wrong of course. I should have known, if I'm light to begin with I'll be lighter as the dive progresses. All the steel tank does is allow one to "need" less weight. One can still go positively buoyant with steel if you're "close" to positive to begin with as there is still a significant buoyancy "swing" with any tank. Dumb move but along the lines of what you did. As you and I both saw, multiple problems can arise and become an unmanageable situation very quickly. In both our cases had we resolved our weighting issues before the dive then that would have been one less issue to add the mix.
Learn...be safe..........

 

[Rimp]

I weigh about 170 lbs. and was using an aluminum 80 tank. I was using a bilam shell suit.

The big difference affecting the buoyancy (I think) was that I was wearing 36 oz fleece under it (Whites Pro undies) and this added alot of bouyancy.

 

[bruce o]

Was air in the suit that you expelled from the neck seal on the way up from expansion or did you have a low pressure hose hooked to the suit? I had trouble when first using neoprene drysuits w/ not enough neg buoyancy, too. switching from suit inflator back to BC inflator helped a lot because once the air was out on the way down it's easier to control, and keeps the feet down too. I've tried the rocks also. Not so dense as lead for their size and wear throuh pockets quickly. Also the thinnest clothing that's warm enough holds less air. Sound like you had a bad day. Good luck.

 

[Rimp]

I had added a tiny blast of air into the suit to reduce some squeeze just before the great fly away occured. This is how the whole thing started.

I was having trouble venting from the rental suit because it was a rear entry model and the exhaust valve was almost in my armpit area. Not a very smart place to put an exhaust valve IMO.

The air I let out of my suit was partly a result of doing this, and it expanded on the way up as expected. I just couldn't vent it fast enough using conventional methods.. especially since I was travelling faster than air by this time.. ;-) Octopus was freeflowing, air was shooting out of tank, tank was getting lighter and I was fooked. ;-)

I can tell you it was an odd feeling.. kinda fun actually (of course, not safe).

Things I have to do as a result of this include;

- fix octopus to prevent freeflow, or replace it entirely.
- increase weight to 40 lbs. test with nearly empty tank.
- ankle weights to keep feet down.
- accept some squeeze rather than risk floating off to never never land.
- use BC for buoyancy control
- use a drysuit with an exhaust valve in a semi intelligent location.

 

[String]

40lbs sounds an incredible amount of weight.

 

[opiniongirl]

I had added a tiny blast of air into the suit to reduce some squeeze just before the great fly away occured. This is how the whole thing started.

I was having trouble venting from the rental suit because it was a rear entry model and the exhaust valve was almost in my armpit area. Not a very smart place to put an exhaust valve IMO.

The air I let out of my suit was partly a result of doing this, and it expanded on the way up as expected. I just couldn't vent it fast enough using conventional methods.. especially since I was travelling faster than air by this time.. ;-) Octopus was freeflowing, air was shooting out of tank, tank was getting lighter and I was fooked. ;-)

I can tell you it was an odd feeling.. kinda fun actually (of course, not safe).

Things I have to do as a result of this include;

- fix octopus to prevent freeflow, or replace it entirely.
- increase weight to 40 lbs. test with nearly empty tank.
- ankle weights to keep feet down.
- accept some squeeze rather than risk floating off to never never land.
- use BC for buoyancy control
- use a drysuit with an exhaust valve in a semi intelligent location.

Gotta say,

The service you received (especially if you rented your regs too) sounds especially like a notorious store in Vancouver...on 4th...was it?

Common calculation for BC dives is 10% of body weight plus 20 lbs, come down as necessary with more experience...

 

[Night Diver]

Like maybe going to a steel tank, among other things. 40 lbs. really is an incredible amount of weight, and while I hardly subscribe to the popular "everyone is overweighted" theme, if you're diving with 40 lbs. ditchable if you ever lose it you'll go airborne!

I dive dry with a 300g undergarment and an E8-130 with 20 lbs. ditchable, even if I assume a 6-8 lb. swing for the aluminum tank I'd be OK with 26-28 lbs. And I am roughly your weight (OK, 20 lbs. more, not sure if that part is muscle or fat).

Anyway, just my opinion.

 

[s7595]

rimp
please read this carefully .I have been through every thing you have had except free flow.you do not need that weight.when I bought my dry suit the instrutor said I need more weight and taught the proper setting for my exhaust valve.with sweat pants and pinnacle underware I could not get down with 32lbs,so I added more weight to 38lbs.then after posting on here and haveing trouble with bounyancy ,I new I needed to drop weight.did a dive with a dm and he opened my exhaust valve all way open,I droped like a stone .now I have dropped my weight down to 28lbs ,I weight 170lbs too.I burp suit and enter water and slowly sink at about 10' I add a little air ,then as I go deeper i ad more. I still were shirt ,shorts and pinnacle underware .my dry suit is a tri-lame pinnacle manufature.last point my exhaust valve is at my bi-cept ,so at dept I close half way .hope info helps you