Negative Buoyancy Tanks

[watergal]

Foothills,

10% of your body weight.

Problem: there is now a weight restriction on that new bridge, so it looks like you'll have to make 2 trips.

tee hee haw ha ho ho yuk yuk! Sometimes I just crack myself up!

Rest of board: pardon, please--we're buddies (or, at least, we were).eace:

 

[Tavi]

I believe that the 3300 PSI Tank has a DIN valve (anything over 3000 psi does). Is your regulator DIN? If you haven't bought one yet, these are things to keep in mind.
I have a DIN regulator, and a DIN to yoke adapter. I dive steel tanks near home (DIN valves) and use the adapter on vacations (rental aluminum 80's).

So many choices :bonk:

PS. there are no stupid questions :nono:

 

[Bob]

Foothill,
Do you mean the shop beside NLRHS or the one just West of the McCain Park Mall? Yes, have been to both. I certified through Rick's Ski and Scuba, (remember him?) too many years ago. BTW graduated from Bauxite High School, class of 70. Dive Safely.:tree:Bob

PS Now back to weightier issues.

Scuby, Buy steel tanks if you can afford them. You will want to upgrade to them as you gain experience and skill anyhow. The only real advantage Al has over steel is the initial cost. Steel is cheaper in the longterm. Better to have the tanks now, than later. Bob.

 

[large_diver]

Scuby.

A few thoughts and issues when chosing between AL and Steel tanks --

- Steels -- there are high pressure (HP) and low pressure (LP). High pressure tanks usually require a DIN valve....meaning you must have a DIN fitting on the first stage of your regulator.

- Steel tanks tend to be "more negative" in terms of buoyancy than aluminum. HP tanks in general tend to be more negative than LPs of the same volume, although this can vary from mfr. to mfr.

- LPs tend to be heavier (dry land weight) than HPs of the same volume. This can become an issue if you are buying large volume steel tanks and are doing lots of shore diving -- of course, you are able to take some weight off of your belt by using steel tanks (vs. AL), but this may affect your choice of HP vs. LP. For example, an HP120 weighs about 39 pounds empty. An LP 120 weighs about 51 lbs empty.

The first tank I bought last year was an LP 98. My diving is 70% shore/30% boat here in New England (single tank diving). This tank weighs about 39 lbs empty and is about 7-8lbs negative when full and close to neutral when empty. For my next tank I am considering a Pressed Steel HP 120 -- greater volume for about the same dry land weight. Buoyancy is slightly more negative (about -10 lbs when full), but the majority of my weight is still ditchable (I wear about 35 lbs with my current LP 98). For someone who is a smaller human wearing a thinner wetsuit -- a big tank like this might start to represent the MAJORITY of their "weight", which is where Lost Yooper's comments start to come into play -- in a situation like this with a BC failure, the diver might have trouble getting to the surface witout ditching the tank.

Hope these comments are helpful.

 

[foothillsdiver]

Hey watergal, yes I did "set" myself up for that one.

I will never forget an episode on a dive boat
at Looe Key when a new diver asked the DM how much weight he needed and the Dm gave him the same 10% answer. The boy weighed 140 lbs and was diving with no wetsuit, so on the side I offered advice to he and his Dad to try the dive with 4 lbs instead of 14 and the boy did great. Probably could have made the dive with no weights at all. On the same vein I saw a rather large woman on another boat that needed 24 lbs, also no wetsuit. So weighting and tanks can vary widely from diver to diver.
My advice is to try out all the different tanks that you can BEFORE you buy. BTW Scuby, A pool is the best place to practice any new skill before taking it to open water. It may be a lot of hassle but it is worth the time and experience to iron out the mistakes in a pool before finding out you have a problem in the OW.

Lost Yooper: When I started diving doubles I discovered that even with a drysuit and heavy under wear I am overweighted and don't take any weights. So the problem of BC failure could be a very serious one. So I use redundant bladders and also have the drysuit inflation as backups. Should all 3 fail and both air systems fail then It is back to the old Navy term. Ditch/blow/go.
Hope I never have to use that one !!!!

Bob. I lived In Jax AR in 72 and don't remember the shops from that time. Mike owned the Dive Shop in LR in the 90s and he was my Instructor Trainer. At the time He was the Dir of Education for NASDS.
BTW I am originally from Blountstown Fl and started my diving in 63 with the Boy Scouts at places like Camel Pond and Blue springs in Marianna. Did some cave diving there without any awareness of the danger we were in. Live and learn huh.

 

[buff]

The rule shouldn't be "10% of your body weight" but "50% of your body fat".

Every year I have to wear just a little more weight........

 

[watergal]

Buff,
do you know the rate of deterioration of lead? I have the same situation, but I think it must be 'cause the weights are getting lighter.

And neoprene shrinks when left in the closet all winter. Funny thing...

 

[foothillsdiver]

Gee whiz Buff

"The rule shouldn't be "10% of your body weight, but "50% of your body fat".


Let's see now: I weighed 145 when I married, I now weigh 255, so considering 50% of 110 lbs then I guess I need to wear 55 lbs when I dive. sounds about right, I'll try it next time out.

I don't think their is a workable formula. In a former store that I worked with the INST put 16 pounds on everybody in the pool. then added 10 lbs when we did our OW dives in wetsuits.
We had a lot of problems with over weighted and panicky divers.

I rarely put more than 6 lbs for pool and even with full 2 piece 6mil suits only use about 20-24 lbs for any diver.
Myself with a 7mm suit I use 16 lbs.
Weighting is the single most time consuming issue in teaching new divers !

 

[Walter]

There is no quick and easy formula that answers the question, "How much weight do I need?" The only solution is to do a weight check.

Weighting, while time consuming never takes as much time as many other aspects of training. Either you spend a lot more time on weighting or a lot less time on skills.

DSSW,

WWW™

 

[The Chairman]

Originally posted by foothillsdiver
Gee whiz Buff

"The rule shouldn't be "10% of your body weight, but "50% of your body fat".

Which begs the question; just how does one weigh one's head???