Question about drysuit weighting

[Sebs]

For wetsuit diving, we were taught (for recreational diving) to have the cylinder completely full, have the suit completely flooded (i.e., no trapped air bubbles), and have the BC completely empty. Inhale, and float, hanging vertical, at eye level. This is for Midwest diving in a full two-piece 1/4" (6.5mm) wetsuit with hood and gloves, and a old-school steel 72 or an Al 80.

Am I the only one who has always been underweighted at the end of the dive by doing this type of weight check? Even in a 5mm at the end of the dive I couldnt hold a stop, much less in a 7mm.

 

[Roy_W]

Am I the only one who has always been underweighted at the end of the dive by doing this type of weight check? Even

Which kind of tanks do you use , Steel, Alu or Carbone Fibre ?

Alu or Carbon Fibre might make you underweighted at the end of the dive as they are extremely buyoant when they are nearing empty . ( If we consider that 50 bar is nearing empty)

 

[lexvil]

You’ve got a lot of good advice so for, just remember it takes the weight it takes no more and no less, easier to compensate for slightly more than slightly less.

 

[rx7diver]

Am I the only one who has always been underweighted at the end of the dive by doing this type of weight check? Even in a 5mm at the end of the dive I couldnt hold a stop, much less in a 7mm.

@Sebs,

With this approach, everything except your (hooded) head above your eyes is submerged, while you're holding a full breath. If using a steel 72 or an Al 80, for example, you're talking about a weight change of only about 6 lbs (5.7 = 0.08 * 71.2 or 6.2 = 0.08 * 77.4) from full to *completely* empty.

In fresh water, even with only 200 psig (say) in either of these cylinders, a 15 ffw safety stop should be easily held.

However, being able to hold a 15 ffw safety stop isn't the motivation for this approach. The motivation for this approach is to provide some protection for a diver who has an emergency at the surface, with a completely full cylinder, and a completely empty BC. Even breathing a snorkel, the diver, being slightly negatively buoyant, will sink if he/she is not finning/sculling. This approach will hopefully keep the diver near the surface long enough to allow him/her (or a rescuer) to drop the diver's weightbelt and establish positive buoyancy either by orally inflating his/her BC, or jettisoning his/her kit.

I, myself, dive a bit lighter than this, because I prefer to use a competent surface dive to get down from the surface at the start of a dive--which allows me to dive with a bit less air in my BC at depth.

ETA: If, after using this approach to weighting, you discover that you need more weight, then add more weight.

rx7diver

 

[inquis]

Am I the only one who has always been underweighted at the end of the dive by doing this type of weight check?

You likely did not have had enough breath. You need at least 2.3 liters above normal end-of-exhale to offset the 5 lb of non-reserve air (assuming an AL80 tank). Obviously that inhale is difficult to gauge, so with a full tank I prefer to first weight to be eye level at the end of a normal exhale (as that's easy to gauge) then add 5 lbs lead (AL80), 7 lbs (HP100), etc.

 

[Sebs]

Which kind of tanks do you use , Steel, Alu or Carbone Fibre ?

Now steel but every other time I was told that this was how you weighted yourself, it was alu80s.

 

[Caversluis]

Here is another view. Adding a bit extra weight, may add a bit of safety. Let me explain. Let’s say you are struggling with floaty feet at the end of the dive. You know the manoeuvres you need to make to rectify this. However, most of them are easier if you have enough weight to stay buoyant.

You must make sure that your BCD has enough lift to make you float at the beginning of the dive (with the weight of the air in a full tank).

Here is another tip. There is an easy way to check whether you are correctly weighted. At the end of your dive, let’s say at your safety stop, reach back for your BCD and feel whether there is still air left or whether it is fully empty. If it is empty, you are correctly weighted. If there is lots of air left, your are overweighted. If there is some air left, this might be your reasonable safety margin - just until you get fully proficient.

 

[boulderjohn]

Which kind of tanks do you use , Steel, Alu or Carbone Fibre ?

Alu or Carbon Fibre might make you underweighted at the end of the dive as they are extremely buyoant when they are nearing empty . ( If we consider that 50 bar is nearing empty)

I missed this thread when it first came out, otherwise I would have commented on this.

Aluminum and carbon fiber tanks (and I don't know anyone who uses carbon fiber tanks) are more buoyant than steel tanks, but they are equally more buoyant than steel tanks at the beginning, middle, and end of a dive. It will take additional weight because of that, but you will need that additional weight at the beginning, middle, and end of the dive.

The fact that an aluminum tank is by itself buoyant at the end of a dive is irrelevant. Your buoyancy in the water is determined by the buoyancy of you and all your gear together, and no one piece of equipment is the determining factor. If you breathe 6 pounds of air during a dive, you will be 6 pounds more buoyant at the end of the dive, and that will be true whether your tanks are made of steel, aluminum, carbon fiber, or balsa wood.

 

[passeparici]

Which kind of tanks do you use , Steel, Alu or Carbone Fibre ?

Alu or Carbon Fibre might make you underweighted at the end of the dive as they are extremely buyoant when they are nearing empty . ( If we consider that 50 bar is nearing empty)

Steel tank or aluminium tank are the same : what is important is not that the aluminium tank is buyoant at the end of the dive, what counts is the difference between the begining of the dive and the end...

 

[Landau]

If I attempt the classic wet suit weighting test floating vertically in a dry suit I can't possibly tell if I have the right amount of air (for comfort and warmth) in the suit. My feet are squeezed and I have an excess of air at my shoulders slowly escaping from my latex neck seal.

Similar to others above I do the test hovering horizontally in shallow water with 500-1000 PSI left in the tank. This also helps students realize that they do have enough weight to stay down and any floaty issues during the dive were from too much air in suit or BCD and not insufficient lead.