Question about weighting in a thick suit

[TexasKaren68]

Well, after playing around trying to get my weighting right in a 3mm shorty, a 3mm full, and then a 5mm full, I find myself off to complete AOW in a cold fresh water lake wearing a 7mm full with a 7mm hooded vest over the top.

Am I going to need 50 pounds to get me under

It took 22 pounds to keep me down in salt water wearing the 5mm (and my guess is I should have started with 4 extra pounds to compensate for air usage).

I know fresh water will give me a little bit of a break, and I may have to try a couple different configurations to get it worked out, but what do y'all think would be a good starting weight to try? I do have a bit of "natural buoyancy". I weigh 160 or so at 5'6".

 

[Bubble_Boy]

I'd guess more or less 30 pounds. If you put on 50 pounds, you'll sink like a stone

 

[xyrandomyx]

If I estimate using the guidelines in the PADI AOW book, I'd say you'd need 25--27 lbs wearing a 7mm wetsuit with hood and gloves, plus the 4 lbs to compensate for an empty cylinder.

 

[TexasKaren68]

I'd guess more or less 30 pounds. If you put on 50 pounds, you'll sink like a stone

The 50 pounds comment was a joke - hence all the smilies. I know 50 pounds is too much but I don't have anything to tell me how to compensate for that extra hooded vest.

If I estimate using the guidelines in the PADI AOW book, I'd say you'd need 25--27 lbs wearing a 7mm wetsuit with hood and gloves, plus the 4 lbs to compensate for an empty cylinder.

So I'll probably need even a bit more than that because the hood comes attached to what amounts to a shorty (a step-in hooded vest).

I wonder if I'll even be able to walk.

 

[Selchie in LB]

Hi Texas Karen,

You need to know the buoyancy of your cylinder when empty (~500 psi) to more accurately guesstimate your weight. For example a steel 72 will be ~-4 lbs and an X7 100, HP100 will be ~-2 lbs. However, an Aluminum 80 will be +2 lbs, so would need to add an additional 2 lbs to compensate for the additional buoyancy at the end of a dive. The mass change between empty and 500 psi maybe about the same, I didn't look this up or try to calculate it here so ~- 5 lbs.

The general rule is 10% of your body weight and then about 4-6 pounds for 7mm in salt water. But remember the tank weight! The best way to determine this is to perform the actual check after a dive with 500 psi. There are plenty of threads here that review this problem of weighting. Have a buddy or instructor help you by estimating the correct weight and they can add weight to get you to the proper mass.

Good Luck I takes some of us including me several trial and errors to get this down.

 

[Blue Sparkle]

You need to know the buoyancy of your cylinder when empty (~500 psi) to more accurately guesstimate your weight. For example a steel 72 will be ~-4 lbs and an X7 100, HP100 will be ~-2 lbs. However, an Aluminum 80 will be +2 lbs, so would need to add an additional 2 lbs to compensate for the additional buoyancy at the end of a dive.

Is this true? I may be wrong (not an expert!), but wouldn't one just figure out their buoyancy/weighting for themselves with full tanks, and then add weight to compensate for the weight of the gas breathed by the end of the dive (which would be the same in any tank for a given volume)? I don't see why one would add more for a tank that went positive at the end of a dive vs. one that stayed negative, given that you first get your weight "right" and then add for weight of used gas (for the end of the dive).

Am I off base?

I'm thinking of my own (limited) experience in a 5mm suit and either an AL63 or an LP95. In both cases I figured out the right weight for me to dive in, and then added weight to compensate for lost gas (about 4# for the AL63 and 6# for the LP95). But my calculations didn't change due to the AL63 being positive when empty (+2.6#) vs. the LP95 staying negative (-1.6#)

 

[surfinusa555]

Is this true? I may be wrong (not an expert!), but wouldn't one just figure out their buoyancy/weighting for themselves with full tanks, and then add weight to compensate for the weight of the gas breathed by the end of the dive (which would be the same in any tank for a given volume)? I don't see why one would add more for a tank that went positive at the end of a dive vs. one that stayed negative, given that you first get your weight "right" and then add for weight of used gas (for the end of the dive).

Am I off base?

I'm thinking of my own (limited) experience in a 5mm suit and either an AL63 or an LP95. In both cases I figured out the right weight for me to dive in, and then added weight to compensate for lost gas (about 4# for the AL63 and 6# for the LP95). But my calculations didn't change due to the AL63 being positive when empty (+2.6#) vs. the LP95 staying negative (-1.6#)

From what you described, and my also limited experience, I would think you have that backwards. You should need less lead with the lp 95 than the al 63.

 

[Blue Sparkle]

From what you described, and my also limited experience, I would think you have that backwards. You should need less lead with the lp 95 than the al 63.

Yes, less added lead overall because the tank is less bouyant and therefore "counts" as some of my weight. But what I was describing was the "extra" added to compensate for the weight of breathed gas. I was saying that I didn't add more or less lead due to the tanks "going positive" or staying negative; rather it was based on the weight of the gas I would breathe during the dive.

In other words, whether I had an aluminum 80 or a steel 80 (maybe a better example since there would be the same weight of gas in each one), I would add the same amount of weight for each (after I had my weighting figured out for the dive) to compensate for the weight of breathed gas.

 

[diveprof]

Well, after playing around trying to get my weighting right in a 3mm shorty, a 3mm full, and then a 5mm full, I find myself off to complete AOW in a cold fresh water lake wearing a 7mm full with a 7mm hooded vest over the top.

Am I going to need 50 pounds to get me under

It took 22 pounds to keep me down in salt water wearing the 5mm (and my guess is I should have started with 4 extra pounds to compensate for air usage).

I know fresh water will give me a little bit of a break, and I may have to try a couple different configurations to get it worked out, but what do y'all think would be a good starting weight to try? I do have a bit of "natural buoyancy". I weigh 160 or so at 5'6".

Wait a minute everybody 30 pounds, 27 pounds - she is talking about doing her AOW in freshwater with a 7mm full suit with hooded vest using an AL 80. I would estimate 20 pounds max, most likely less. The weighting tables in the PADI AOW are a bit excessive from my experience. When I teach AOW my students are generally several pounds below the table estimates when they finish the course (when wearing 7mm suits). I usually recommend the Peak Performance Bouyancy elective as the first dive - get the weighting right and understand the mechanics and zen of bouyancy control. However, we reassess as we move forward with the dives. The more you dive and get comfortable with your gear the less weight you need and may be able to reduce further. I would strongly suggest you take few minutes before beginning your first dive to get your weighting right. A good instructor who knows you haven't dove in heavy suits/cold water before will do this with you anyway. It will make life easier for him too. Take some smaller weights (ie 2lb weights) so you can adjust up or down. At the end of the dive when you are down to 500-700psi and are doing your safety stop, do you have much air in your BC? If so, you can likely drop more weight. Get the lead out. Nothing screws with bouyancy control and air consumption more than being overweighted. Currently I am diving my 8/7 semidry in freshwater with a steel 100 (takes 4lb off my weighting) with just the 5lb backplate - and I do have a bit of bioprene

 

[xyrandomyx]

Wait a minute everybody 30 pounds, 27 pounds - she is talking about doing her AOW in freshwater with a 7mm full suit with hooded vest using an AL 80. I would estimate 20 pounds max, most likely less. The weighting tables in the PADI AOW are a bit excessive from my experience. When I teach AOW my students are generally several pounds below the table estimates when they finish the course (when wearing 7mm suits). I usually recommend the Peak Performance Bouyancy elective as the first dive - get the weighting right and understand the mechanics and zen of bouyancy control. However, we reassess as we move forward with the dives. The more you dive and get comfortable with your gear the less weight you need and may be able to reduce further. I would strongly suggest you take few minutes before beginning your first dive to get your weighting right. A good instructor who knows you haven't dove in heavy suits/cold water before will do this with you anyway. It will make life easier for him too. Take some smaller weights (ie 2lb weights) so you can adjust up or down. At the end of the dive when you are down to 500-700psi and are doing your safety stop, do you have much air in your BC? If so, you can likely drop more weight. Get the lead out. Nothing screws with bouyancy control and air consumption more than being overweighted. Currently I am diving my 8/7 semidry in freshwater with a steel 100 (takes 4lb off my weighting) with just the 5lb backplate - and I do have a bit of bioprene

It sounded like a lot to me too (though I'm only a beginner, so certainly no expert). I personally only use 15 lbs of weight, but my bodyweight is a little less than hers. However, she did say that she did a weight check in a 5mm wetsuit and needed 22 lbs -- if that's accurate, she's clearly going to need more than 22 lbs in a 7mm wetsuit with hood.