Weighting methodologies

[Spratman]

Greetings Scubaboarders!

I've done a search on this and cannot really find information that I'm looking for. My question is regarding weighting and neutral bouancy.

Should the weighting be done with a full kit, so you know how much weight you need? Or should you start with all your rubber on and get that amount and start adding the rest of your stuff? The first seems the easiest, the latter the most definitive.

Since I did most of my cert. in warm water, I know have to try to load it on for a full set of gear. I'm trying to get this sorted out, before buying 35lbs of weight and finding that I need more or less. I think if I could get a good pool session with someone knowledgable to get the weighting and trim set, I'll be good to go.

Also, is it better to get two tens rather than four fives? I think I would rather do a belt and BC weights, rather than strictly integrated. Another 35 pounds is a lot to hoist out of the water....

Jack

 

[Walter]

Should the weighting be done with a full kit, so you know how much weight you need? Or should you start with all your rubber on and get that amount and start adding the rest of your stuff?

I have absolutely no idea what you are trying to say here.

With 500 PSI or less in your tank, get your weighting while wearing everything you'll have on a dive. Any change (different type tank, different suit, etc.) will require weighting with that configuration.

 

[jonnythan]

You need to be weighted so that you can maintain any depth with an almost empty tank. It's virtually impossible to tell someone how much weight they need without getting in the water with all your gear and 500 psi in their tank and going through trial and error. Once you figure out how much you need, you can move weights around and so forth so that your trim works out well. I'd distribute the weight as much as possible.. but if you're shoving lots of weight in your BC, make sure you have enough that's dump-able and that your BC has enough flotation so that it doesn't sink when you're not in it.

 

[Jason B]

Also, is it better to get two tens rather than four fives?

four 5 pounders will give you more options than two 10 pounders.

Jason

 

[Charlie99]

Should the weighting be done with a full kit, so you know how much weight you need? Or should you start with all your rubber on and get that amount and start adding the rest of your stuff? The first seems the easiest, the latter the most definitive.

Also, is it better to get two tens rather than four fives? I think I would rather do a belt and BC weights, rather than strictly integrated. Another 35 pounds is a lot to hoist out of the water....

While in theory you can figure out your personal buoyancy and the buoyancy of each piece of gear and add it all up, in practice that will just get into the ballpark. It would give you an idea of how much lead to go out and buy, but you really need to do a weight check with all your gear.

35 pound is an awful lot to try and put into integrated pockets. The more you put in pockets, the more likely you are to have them fall out by accident. Spreading the weight between both a belt and pockets is a good idea, and even for weight on a belt it is generally better to break it up into more than 2 weight blocks.

It sounds like you are making the transition from warm water to cold for the first time. Hopefully you can find a good buddy to help you with your introduction to your local conditions. He will probably have some extra lead around

 

[Stirling]

Greetings Scubaboarders!

Should the weighting be done with a full kit, so you know how much weight you need? Or should you start with all your rubber on and get that amount and start adding the rest of your stuff? The first seems the easiest, the latter the most definitive.
Jack

If I'm understanding that part of your question correctly, you should do it all at once. Don't bother to put on some of your stuff and add weight, and then add other stuff and add more weight (or have to remove weight), and then more stuff and more or less weight, etc. There's no reason to go through any of that. You're going to dive with all of the stuff at once, and so you should determine the total amount of weight you need for all of the stuff at once.

Once you get that figured out for *the total package* of the equipment that you expect to be using most of the time, you may want to go back and figure out how your weight needs change if you *change* the equipment you are diving - if you go from a 3mm to a 5mm or 7mm suit, or from aluminum to steel tanks, or carry or don't carry a camera or a big light, etc. - by changing one of those variables at a time and seeing what it does to your buoyancy.

But start from a baseline that is determined by the combination of all the equipment that you expect to be using most of the time, and a tank (also of the material and size you expect to use most of the time) that is low on air (@ 500 psi or thereabouts). It's no good to be neutral at the beginning of a dive if you can't maintain neutral buoyancy from the middle to the end of the dive, as the air is consumed and you become more positive.

 

[matt_unique]

Do a shallow (15') shore dive wearing all the gear you plan to use in the water you plan to dive with 500 psi in a tank. Have a buddy with you with extra lead and a way to hold lead if you have brought too much. With all air carefully vented from your BC, no movement of fins/hands/etc., exhale all the air from your lungs. Add or remove lead as necessary for you to sink without having to swim down. Note the weight and gear used and apply this the next time you dive. Keeping in mind you should sink a little faster with a full tank assuming you are diving alum 80's.

--Matt

 

[Charlie99]

The weight of air is very predictable and never changes, so it is quite reasonable to do your weighting with more air than 500psi, then add a correction for the extra air.

For example, with a 3000psi, 80 cubic foot tank, each 500psi is pretty close to 1 pound. For example, if you follow Matt Unique's procedure above, but have 1500psi in an AL80, then you need to add 2 or 3 more pounds of lead.

You can also get pretty close by checking your weighting in a fresh water pool, then adjusting for saltwater by adding another pound of lead for each 40 pounds of total dive weight (weight of all gear including tank and lead, plus your body weight).

 

[Spratman]

Thanks to all for your input and suggestions. I really don't have a dive buddy yet. My best friend from HS is a diver and asked me to go out. Only problem is that some of his escapades makes me question his diving abilities.

That is why I was just hoping to get someone from a dive shop to spend an hour or two one on one helping me get weighted properly. I reckon I'll check the dive shop and see if I can get someone willing to assist me with this. Other than a light, I don't think I'll be carrying anything additional until I do the AOW.

I'm sure I was overweighted when doing the SW dives. I was carrying 18lbs, so I used the BC more than necessary.

Sorry about the confusion, Walter.

I'm glad I found this board! You guys are a great help!

Jack

 

[mrjake]

The weight of air is very predictable and never changes, so it is quite reasonable to do your weighting with more air than 500psi, then add a correction for the extra air.

For example, with a 3000psi, 80 cubic foot tank, each 500psi is pretty close to 1 pound. For example, if you follow Matt Unique's procedure above, but have 1500psi in an AL80, then you need to add 2 or 3 more pounds of lead.

You can also get pretty close by checking your weighting in a fresh water pool, then adjusting for saltwater by adding another pound of lead for each 40 pounds of total dive weight (weight of all gear including tank and lead, plus your body weight).

Does anyone know a quick reference for how much weight to subtract when using a thinner wetsuit? I am planning to dive Bonne Terre Mine next weekend (April 1 & 2 anyone want to come?) and I normally dive an Aquaflite 7mm full suit with a 7mm shorty (they call it a jacket) over the top when diving the local quarries (45 deg temps). Bonne Terre is supposed to be around 58 deg and I don't think I will use my jacket, just a hood. If I remove the extra 7mm how much weight can I leave behind. It takes about 35lbs with both layers on. I weigh 270 and am 6' tall.

Thanks,
Bob J