Northwest Dive Club

So i just got ow 2 months ago. Been waiting for my new gear to come in. Decided $55 for 3 days (including 1 full tank so what an hour)
Every time i wanted to go out was gonna be to much. So i picked up everything from blake yesterday and he hands me a heavy bag of weights and says "get yourself adjusted". So go to the albany rest stop. 8-15 feet of water. No worries. No wet suit.

Got my weights, new gear (no wetsuit warm enough) and a 80steel tank.
In ow i had to use a 25lb weight belt.
Yellow house 36lbs
Got in the water with the steel and and empty bcd. Loaded myself up 20lbs of soft weights. Reg on mouth step off rock BAM bottom. inhale nothing. Ok

Get out drop to the 2 5s and 2 3s
Step off bam. Almost no lift with a full breath. So much for eye level.

Get down to 4 lbs in each side of my bcd
Start to go up and stay level at 8lbs only?

So point of all this. Is a drop from 25(didnt use a wetsuit in the pool) to 8 lbs with a steel tank normal? How much more do i add for when the air is empty?

Thanks
That was my first time away from an instructor diving.

Short answer - yes, steel tanks can make a huge difference.

Check out the table at this link. Pay particular attention to the last two columns relating to buoyancy when full and empty. Now compare the specifics between the aluminum and steel tanks. You can see how an AL80 can be positively buoyant by 4+lbs when empty, whereas a similarly sized steel tank can be as much as 7+lbs negative when empty. You have to match what make/model of tanks you used to be able to compare them accurately.

The buoyancy when empty specifications are the ones you're going to rely on when determining what your weighting needs are when switching to a different model of tank (once you have better idea what you need). The buoyancy when full specs come in handy when determining how much additional weight you'll need to add if you do your neutral buoyancy test with a full tank.

Sounds like you're using different gear than what you used during your OW class. You'll come to realize that every time you change your equipment configuration (even just a single item), your weighting requirements may change. Your new BCD may be less buoyant than the one you used in class, for example.

The negative buoyancy of steel tanks is what makes them attractive to us cold water divers.

You need to do a weight check with a near empty tank. You will need 6 or 7 lb more when empty. There is about 5 or 6 lb difference between an AL80 and a 3442 steel.

I only drop 2# from my aluminum 80 to my steel 80.

Echo wrote:I only drop 2# from my aluminum 80 to my steel 80.

You are either overweighted on the steel 80 or underweighted on the AL80. Depends on the tank(s) but the "empty with valve" difference is usually about 5 to 7 lbs. +4 on the AL80 and -1 to -3 on the steel 80.
http://www.huronscuba.com/equipment/scu ... ation.html

I think the main point that is being missed here is what are you wearing? are you wearing a drysuit if so what kind of drysuit are you wearing? Type.. Make... also what are you wearing for undergarments how thick are your undergarments? these are all going to play a key factor in how much weight you need

CaptnJack wrote:

Echo wrote:I only drop 2# from my aluminum 80 to my steel 80.

You are either overweighted on the steel 80 or underweighted on the AL80. Depends on the tank(s) but the "empty with valve" difference is usually about 5 to 7 lbs. +4 on the AL80 and -1 to -3 on the steel 80.
http://www.huronscuba.com/equipment/scu ... ation.html

My S80 is a HP Sherwood. Al is a LP Catalina. I use the same weight with my S72s.

Echo wrote:

CaptnJack wrote:

Echo wrote:I only drop 2# from my aluminum 80 to my steel 80.

You are either overweighted on the steel 80 or underweighted on the AL80. Depends on the tank(s) but the "empty with valve" difference is usually about 5 to 7 lbs. +4 on the AL80 and -1 to -3 on the steel 80.
http://www.huronscuba.com/equipment/scu ... ation.html

My S80 is a HP Sherwood. Al is a LP Catalina. I use the same weight with my S72s.

Did you even look at the chart? There's no way these are all the same weighting.

Sherwood (genesis) Hp80 3500psi = -3 empty
Catalina al80 = +4 empty
That's 7 lbs difference when empty, not 2#

I don't know what a "S72" is. Is that an 2250+ steel 72 or a 3000psi AL72?

I use 16# for my al80 and it's perfect, 14 and it's too light. I drop 2# for the 72 and the HP 80 is a newer tank for me. I rarely use it and use the weights that I have instead of buying more for the 1X/month that I do use it.

2# less between an al80 and lp72 is about right. Lp72s aren't on that chart since they haven't been made in 3 decades.

Erika, try dropping 6 lbs and diving the hp steel 80. Should be pretty close.

I used my hp 80 last night and took another 2# off. I was fine. Thanks for bringing the weight difference to my attention.

Awesome.

CaptnJack wrote:2# less between an al80 and lp72 is about right. Lp72s aren't on that chart since they haven't been made in 3 decades.

My LP72's seem to be about neutral when "emtpy", vs the 80's I had that were 4lbs positive. YMMV on LP72's though as there is a bit of variability depending on who made them.

Jake

I think mine are about 1# positive. Its hard to tell for salt as I only use them in freshwater where they are for sure about -2#.