Your weight belt

[Mike Veitch]

Here we go again...

AL 80 with Jacket BC and brand spanking 7 mm, 6 pounds....3# in each of the trim pockets on the back of the BC, no belt, i hate belts
Currently i have a 6 month old suit so i use 4# but sometimes have to give that away...
No suit. No weight
I'm 170 and not skinny....

In other words it all goes to show, there is no one answer. I believe this is the single most important thing in improving someones skill. Proper weighting and therefore proper trim.

A good instructor will continue to work with you until its all good, unfortunately a lot just put you through the drills with a ton of lead so you stay on the bottom. THis leads to a large percentage of people being overweighted from day one and therefore using it as a crutch or teddy bear ("don't take my weight, i need it...")

Thankfully, most people do listen and take out 2# per day over a week when we suggest it to them. Its great to watch them improve their skills, buoyancy, and of course air consumption as the week progresses...

 

[DTB1981]

what is the differance in weight going from a al80 to a steel 100

 

[H2Andy]

well, it depends on the tank. for example, the Luxfer aluminum 80 weights 32 lbs or
so, empty, and is 4.4 lbs positive. when full, it is 1.4 lbs negative.

a Faber steel 100 weights 39 lbs when empty, but it stays negative
at around 7 lbs negative when empty and about 15 lbs negative when full.

 

[String]

a Faber steel 100 weights 39 lbs when empty, but it stays negative
at around 15 lbs negative when empty and about 7 lbs negative when full.

Err surely being a steel tank its more negative when full and less negative when empty.

Try here:

http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi

Example my 15l steel is 3.3kg (7lb) negative when full and 0.7kg negative when empty (1.5lbs).

Obviously weight wise its heavier on land when full.

 

[H2Andy]

ooops... got those backwards

thanks

(long day)

 

[spectrum]

what is the differance in weight going from a al80 to a steel 100

Weight as in how heavy is it walking across the beach? Or Bouyancy as in how will it effect what I carry for Ballast? Those are 2 very different questions.

For the sake of discussion all starting and ending air volumes are the same.

As mentioned an AL-80 has 4.4 pounds of positive bouyancy when empty. Meanwhile a PST E7-80 will be 2.5 pounds negative.
4.4+2.5 = 6.9, call it 7 pounds of difference in bouyancy.
The aluminum tank is a liability since you need to add weight to hold it down at the end of the dive. The steel tank contributes to keeping you and your exposure suit down.

Now when you go to walk across the beach...
A Catalina S80 weighs 31.6 empty less the valve so add about 2 LB = 33.6 pounds
A PST E7-80 weighs 28 pounds empty including the valve.
Again both are filled with apoximately the same air volume. Also remember the AL-80 diver gets short sheeted with only 77.4 CF in a nominal fill but that's trivial in terms of weight.
33.6 - 28 = 5.6 pounds heavier on land

So now the AL-80 diver has a tank that's 5.6 pounds heavier and he's wearing 7 pounds of extra weight to sink the thing making him 12.6 pouinds heavier hiking across the beach. He also has that much more mass he's pushing through the water etc, etc.

Reference:
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

So there you have it, in my eyes the great AL-80 hoax, a cruel joke the industry played on the diving community.

I recognize that there are some applications like doubles and stages where these properties can work as an advantage but for the single tank diver I think it's a shame.

As long as you stay with 80CF the cost difference is not that dramatic.

Pete

 

[DTB1981]

ooops... got those backwards

thanks

(long day)

You have it right, he said the same thing you did when it was in kg they are more negative when full

 

[DTB1981]

The total weight differance of the scuba unit on land the steel 80 is 12 lbs lighter and the steel 100s total weight is 6 lbs lighter, but the 120s 3 lbs heavier. It sounds like steel is the way to go if you can afford it.

:monkeydan

 

[m3830431]

I think the created the hoax as a safety margin so that you are not to negative at the end of a dive.

 

[Rookie_J]

The 10% thing is just rubbish.

I wear 26lbs in full drysuit/thermals, 12lb in a 5mm semi dry and 8lbs in a 3mm full wetsuit (all steel tanks).

Not one of those comes anywhere near my 10% body weight which is roughly 175lbs.

doesn't a steel tank allow you to drop about 6lbs off your belt?


hood, boots, gloves, AL80, lycra and 2 piece farmer john, i wear 22-24.. I'm 5'-6" 180.. with only the farmer John no hood/gloves i can get by with 14-16 (depending on my anxiety level).