Weighting question

[LowDrag]

So...can anyone tell me how it is possible to do a dive with 24 lbs get out of the water go have lunch and an SI of 1 hour get back in the water with the same weight/gear and not be able to sink???

My wife and I dove Cove 2 in Seattle yesterday and had this happen to both of us. We wore exactly the same gear after lunch as from before lunch and could not sink. The only difference was that I carried her gear to the water for her on the first dive and she carried her gear to the water on the second dive. We had fish and chips at the Marination Station right there on the pier then walked around and talked to some other divers and then got into our gear for our second dive. Danee was wearing 24 lbs and I had 26 lbs IIRC which worked great for the first dive but both of us had to add extra weight for the second dive.

Any ideas? We are both very curious about what was up rather than down...hehehe

Thanks,
Dave

We are diving this equipment:

Her:

3000 PSI AL80 tank ~3000 PSI per tank
White's Fit dry suit
White's Rock boots
White's zippered hood
Aqualung Lotus i3 back inflate BC
Oceanic 3mm gloves
ScubaPro Mini Spectra mask
ScubaPro Twin Jet split fins
XS Scuba nylon weight belt with weights listed above
One Princeton Tech pistol grip light
Under armor type wicking layer (Paradox brand)
EMT shears stowed in a pocket

Me:

3000 PSI AL80 tank ~3000 PSI per tank
White's Fusion Bullet
White's Rock boots
White's Hood - no zipper
Hollis S38 wing with SS backplate
Oceanic 3mm gloves
Hollis M4 mask
Hollis F1 fins
DUI weight harness with weights listed above
One DRIS 1000 Lumen light on a spring coil bungee
Under Armor wicking layer - Cold weather thickness
One dive knife - forget the brand but it is about 10" in length
EMT shears on my harness

I also carry a very small water proof box in my right pocket for my car/truck key. It is the size of a pack of cigarettes. Oh and a slate in my other pocket.

Nothing changed from dive to dive. As for the trapped air, I would have to question that one. She was in the water for quite a bit moving this way and that trying to squish all the air she could find so I am not sure if that would be a concern. I looked under the surface and I did not see any ballooning of her suit below her weight belt and above water she did not look inflated either.

[Jeff Pack]

get all the air out of BC and drysuit?

[LowDrag]

As far as I know we did. I just added some more info up above. That might answer some questions. I had not had my second cup of coffee yet and forgot to add this info.

[GearHead]

Well, I don't think any of the gear is going to change buoyancy between dives. That leaves the inside of the drysuits, and the insides of yourselves.

When I'm diving with minimal weighting (as in forgot my 8 lb weight belt), I sometimes need to dolphin kick down from the surface, but can remain submerged once at the bottom. The drysuit may end up being a shrink wrap at the end of the dive, but it's surprising how much air can get trapped in the nooks & crannies. Something simple like forgetting ankle weights can make a noticeable difference as well.

[Jeff Pack]

Depending on tank size, if you've removed all air bc/drysuit, and you still have to really kick to get down, you may be underweighted, as with 500psi left in your tank, you've 4+ pounds removed.

[Mortuus]

Two plausible suggestions:

1 - You guys both forgot your weight belts/harnesses at the car

2 - This one actually seems more plausible, but I thought of it second. Do you guys know if you own any neutral Al80s? I am wondering if maybe the first tanks you dove were neutral 80s, and the second ones you dove were just normal 80s. That could probably do it. Luxfer AlN80s are listed as having -5.7 lbs buoyancy when full, whereas a standard Luxfer 80 is listed as having only -1.4 lbs buoyancy when full

[Desert Diver]

And that being said changing from steel to aluminum tanks would certainly do it.

[LowDrag]

Well, I don't think any of the gear is going to change buoyancy between dives. That leaves the inside of the drysuits, and the insides of yourselves.

When I'm diving with minimal weighting (as in forgot my 8 lb weight belt), I sometimes need to dolphin kick down from the surface, but can remain submerged once at the bottom. The drysuit may end up being a shrink wrap at the end of the dive, but it's surprising how much air can get trapped in the nooks & crannies. Something simple like forgetting ankle weights can make a noticeable difference as well.

Definitely did not forget the weights on this dive.

Depending on tank size, if you've removed all air bc/drysuit, and you still have to really kick to get down, you may be underweighted, as with 500psi left in your tank, you've 4+ pounds removed.

We have not done an after dive 500 PSI buoyancy check yet but even with that we were not floating to the surface at the end of the last dive so I think even at 24 & 26 lbs we are a bit on the heavy side. That would just be a guess on my part at this point though. One thing I just remembered is that we ended the first dive with 1200 PSI in her tank and me with 1000 PSI so maybe that explains why we were not floating to the surface on the first dive?

Two plausible suggestions:

1 - You guys both forgot your weight belts/harnesses at the car

Nope.

2 - This one actually seems more plausible, but I thought of it second. Do you guys know if you own any neutral Al80s? I am wondering if maybe the first tanks you dove were neutral 80s, and the second ones you dove were just normal 80s. That could probably do it. Luxfer AlN80s are listed as having -5.7 lbs buoyancy when full, whereas a standard Luxfer 80 is listed as having only -1.4 lbs buoyancy when full

I have to say I have never heard of that possibility. I will go out check what tanks I rented in a minute or two.

And that being said changing from steel to aluminum tanks would certainly do it.

The tank change out was from aluminum to aluminum. AL80's.

[GearHead]

The neutral vs. standard AL80 is something I didn't think of originally, but is a possibility. The two styles appear identical on the outside. The neutral versions are marked for 3300 PSI and labeled as either C80 or S80 N depending on manufacturer. I have a pair of neutral 80s, and they are about 5 lbs heavier than the standard 80s.

[Mortuus]

2 - This one actually seems more plausible, but I thought of it second. Do you guys know if you own any neutral Al80s? I am wondering if maybe the first tanks you dove were neutral 80s, and the second ones you dove were just normal 80s. That could probably do it. Luxfer AlN80s are listed as having -5.7 lbs buoyancy when full, whereas a standard Luxfer 80 is listed as having only -1.4 lbs buoyancy when full

I have to say I have never heard of that possibility. I will go out check what tanks I rented in a minute or two.

If you don't have a pair of standard 80s and neutral 80s, then I have literally no idea what the problem would be. That's all I can think of if nothing else changed. Hopefully it turns out to be the issue!

[fmerkel]

CYLINDER SPECIFICATIONS
http://www.techdivinglimited.com/pub/tanks.html

I'm wondering how your wife submerges with a standard BC and LESS weight than you. She's somewhere around 8# lighter than you by guesstimate.

Did you have a 'light lunch"?

[LowDrag]

These are the tanks we were using and there is a 3 lb difference in weight. What do guys think? We did our initial weight check with tanks 3 & 4 and then tried to do our second dive with tanks 1 & 2. So...even if we had done a weight check @ 500 PSI we would still have been 3 lbs different right? BUT!!! On our second dive, the tanks would still be heavier than the first two because they were filled to 3000 PSI right even though we ended the first dive with 1200 (her) and 1000 (me)PSI?


#1: Catalina S80 3AL3000 TC -3ALM207 DOT-3AL3000 AS0336533 M4002 03C03 - weight at 500 PSI = 35.6 lbs

#2: Catalina S80 3AL3000 TC -3ALM207 DOT-3AL3000 AS0368361 M4002 03C03 - weight at 500 PSI = 35.6 lbs

#3: CTC DOT -3AL3000 S80 M4002 A45413 - weight @ 500 psi = 38.6 LBS

#4: CTC DOT -3AL3000 S80 M4002 A45460 - weight @ 500 psi = 38.6 LBS

[ljjames]

Did you eat anything at lunch that would give you gas?

[LowDrag]

Did you eat anything at lunch that would give you gas?

Damn Laura...why is everyone asking a variation of that question??? I posted the same question on Scubaboard to get a variety of answers and this very same question came up a couple of times...LOL!!!

Answer: No, we had fish and chips at Marination Station at the pier with ice tea to drink.

[CaptnJack]

Didn't vent your BC after dive1.

[LowDrag]

Didn't vent your BC after dive1.

Nope...I checked that too as well as her DS. NEXT!!!

[Nwbrewer]

It's in your head(s). One of you had trouble descending a little for whatever reason (you're both newish divers right?) Then the other did. It really doesn't take much trapping air in your lungs (not relaxing) to make it hard to drop.

As a new diver I had the same issue a lot. Finally I gave up and started swimming down at the beginning of dives. Keep diving and you'll get to the point where +/- 3 lbs makes no difference whatsoever.

Jake

[LowDrag]

Thank you Sir...we definitely will keep on diving and I will keep in mind to pump as much air out as possible.

[Jeff Pack]

Jake brings up a good point. When I was starting diving again, sometimes with no changes, I had a hard time getting down. In Bob's private class, I went down "ok" and next day couldnt at all.

For the next while, I had to duck dive to get going, nowadays, its sink and away I go. Sometimes your feet are doing the happy dance, and you dont even realize it.

One thing I did to kind of get around the happy feet, is exhaust my air, kick hard straight up, and use that momentum to get down and go horizontal for descent. Just a suggestion to try if your feet might be doing the happy dance.

[Desert Diver]

It's in your head(s). One of you had trouble descending a little for whatever reason (you're both newish divers right?) Then the other did. It really doesn't take much trapping air in your lungs (not relaxing) to make it hard to drop.

As a new diver I had the same issue a lot. Finally I gave up and started swimming down at the beginning of dives. Keep diving and you'll get to the point where +/- 3 lbs makes no difference whatsoever.

Jake

Plus or minus 3 lb won't make a difference unless it is minus. When your drysuit is empty, your bcd is empty, your tank is low and you are breathing shallow you are going up unless you swim down and I hate having to swim down on a safety stop.

[Nwbrewer]

It's in your head(s). One of you had trouble descending a little for whatever reason (you're both newish divers right?) Then the other did. It really doesn't take much trapping air in your lungs (not relaxing) to make it hard to drop.

As a new diver I had the same issue a lot. Finally I gave up and started swimming down at the beginning of dives. Keep diving and you'll get to the point where +/- 3 lbs makes no difference whatsoever.

Jake

Plus or minus 3 lb won't make a difference unless it is minus. When your drysuit is empty, your bcd is empty, your tank is low and you are breathing shallow you are going up unless you swim down and I hate having to swim down on a safety stop.

From my "happy weight" I can deal with losing 3 lbs of lead buy diving a little squeezed at the end. I should have added that caveat, my advice is based on drysuit diving where you're typically comfortably lofted with an empty BC and 500psi.

[Desert Diver]

It's in your head(s). One of you had trouble descending a little for whatever reason (you're both newish divers right?) Then the other did. It really doesn't take much trapping air in your lungs (not relaxing) to make it hard to drop.

As a new diver I had the same issue a lot. Finally I gave up and started swimming down at the beginning of dives. Keep diving and you'll get to the point where +/- 3 lbs makes no difference whatsoever.

Jake

Plus or minus 3 lb won't make a difference unless it is minus. When your drysuit is empty, your bcd is empty, your tank is low and you are breathing shallow you are going up unless you swim down and I hate having to swim down on a safety stop.

From my "happy weight" I can deal with losing 3 lbs of lead buy diving a little squeezed at the end. I should have added that caveat, my advice is based on drysuit diving where you're typically comfortably lofted with an empty BC and 500psi.

I agree completely. To deal with 3 pounds underweight you need to find about 3 pints of air to exhaust when your tank gets low on air. Sometimes hard to do coming up, but should be easy going down with a full tank.

[ljjames]

Sometimes you can trap gas in odd places in your suit. especially when putting on gear, cinching up belts, etc... I make a point of doing what we affectionately call the "Bob" maneuver (after my fundies instructor Bob Sherwood) where i lay flat, face down in the water, and put air in my drysuit, filling up my legs. I then do a silly dance stretching each leg out and making sure the crotch of my drysuit is up where its supposed to be and my droopy drawers from excessive pocket contents and/or weight of wet drysuit is remedied. Next up I do a stretch kind of like you used to do in highschool track when you got a side stitch. Streeeetch that arm above and across over my head (still laying flat in the water - i did say silly dance didn't i) This pulls extra material that might be bunched around my waist up to where it needs to be to allow maximal shoulder flexibility. Then i stand up and am always amazed at how much 'better' my drysuit fits and easier it is to vent air from it

It could be that just putting your wet gear on you did something different like tighten a strap a bit too much (easier when the gear is wet) and are trapping a little bit of extra gas in there. It could be that you both felt a little cold after the first dive with lunch being digested, so left a bit of extra gas in your suit to stay warmer.

Strange to me that it happened to both of you... therefor I'll go out on a bit of a stalk of kelp.

IT could be (and this is a bit of a zebra) that the tide changed and was now pushing back the river, so on the first dive you had more fresh water on the surface (do you remember any visibility change, a temperature change and/or pearly water in the top 4'?) and therefor gained just enough negative to slip past that "noob with gas in suit or trapped in BC" stage on the first dive but didn't have that benefit on the second dive...

[LowDrag]

Strange to me that it happened to both of you... therefor I'll go out on a bit of a stalk of kelp.

IT could be (and this is a bit of a zebra) that the tide changed and was now pushing back the river, so on the first dive you had more fresh water on the surface (do you remember any visibility change, a temperature change and/or pearly water in the top 4'?) and therefor gained just enough negative to slip past that "noob with gas in suit or trapped in BC" stage on the first dive but didn't have that benefit on the second dive...

Only one problem with that thought Laura...we were in Cove 2, there wasn't any fresh water river to push back in with the tide change.

As for your funkie dance...Danee and I would like to see that...hehehe

[LowDrag]

Jeff Pack, NWbrewer and Desertdiver...I totally get the "happy feet" thing, only thing I would have to question about that is that we were walking in and then leaning forward to drop under the surface. We did not swim out and then descend so kicking while descending would be out I would think.

We were talking about the different answers that we are getting here and Danee is thinking that maybe she wasn't letting go of the air her lungs as well as she should have. I know I squeezed all the air out of her BC and when I looked at her suit under water it sure looked like it was vacuum packed around her.

These are all great things to keep in mind for our next dive(s) and I will definitely be reporting back. Our next set of dives will be in a high altitude lake over next weekend.

Thanks all,
Dave