Calculated weight for new drysuit seems odd, second opinion needed

[BlueTrin]

I have free access to an indoor pool around 3,5m depth, a giant water tank around 12m depth and 45m wide and several lakes around 10m depth. That should not be the problem. I just thought it could be calculated pre diving....

It can be done, you just have to measure the weight and volume (water displaced) for every bits including yourself. (To be exact in your case you’d have to measure yourself with the drysuit and undersuit with the correct amount of gas and the valve closed)

This will give you the total weight and volume of your system, then you need to add enough weights to bring it to the same density to than the water you are diving in.

You can use scales and large buckets to measure the water displaced and weights if you have that around … will be tricky for the drysuit though

I never used the calculator from scubaboard, but people here say it’s quite accurate, maybe you can try it and compare the results?

Also if you do a weight check in a pool, write down the delta to go to the sea in your log.

 

[Wibble]

I have free access to an indoor pool around 3,5m depth, a giant water tank around 12m depth and 45m wide and several lakes around 10m depth. That should not be the problem. I just thought it could be calculated pre diving....

There's no real calculation about it. Too many variables.

If it's the first time you've dived with a drysuit and that config you really won't have any idea what you'll need until you do the weight check. You can sort of guess by looking at others, but it's just a wild guess.

Fresh to Salt water is about 2% of your weight, so 2kg/5lbs to 4kg/10lbs. Again you really would be better off with a weight check.

(This isn't being harsh, it's just the reality )

I once did a deep freshwater dive and overthought everything. Ended up jumping in grossly overweighted. Was horrible. Incredible how much gas I consumed. That was an invaluable lesson learned!

N.B. being a little overweighted is fine as it gives you a little leeway. Nothing worse than being extremely light and having to dump everything as you do your stops; squeezed and cold, not nice.

 

[broncobowsher]

When you first enter the water you will be extremely floaty. The air in the suit will be excessive and take a little bit to find its way to the exhaust valve. Since you have great water access, use it.

When I first started I would enter the water, couldn't get down, add weight. The suit would find its home and I would dive very overweighted. Get to the end of the dive, I could shed many pounds of lead and still get neutral. Eventually learned how little lead it actually takes, know that I will bob around on the surface for a minute or two as the suit forms to me and the excess air leaves, and a happy dive.

As for trying to figure the buoyance factor of your brass regs, don't bother. They are so dense that they are heavy in both air and water. That would be like trying to figure the buoyancy of the lead and factor that into what you need. Measure with micrometer, mark with chalk, cut with ax. Skip the micrometer, you will never find the exact correct weight. Each time you inhale the numbers will all change.

 

[Ayisha]

Whatever weight you normally wear without the drysuit and moderate undergarments, add 2.5 - 3 kgs or about 6 lbs. That should be a pretty good starting point all things being equal.

The best way to know your weighting though is to do a weighting check.

 

[Robert H. Diver]

I have free access to an indoor pool around 3,5m depth, a giant water tank around 12m depth and 45m wide and several lakes around 10m depth. That should not be the problem. I just thought it could be calculated pre diving....

Those calculators are pretty much always wrong, just do a weight check and be done with it.

 

[scubazendiver]

Thank you very much guys. Unfortunately I have never done any weight checks so far. My instructor never asked me to and never taught me. I never thought about it. Recently I got in touch with some technical things and wanted to go into that direction. That´s how I found this balanced rig calculator and read about how important it is to be properly equipped with suitable weights.

 

[lexvil]

Thank you very much guys. Unfortunately I have never done any weight checks so far. My instructor never asked me to and never taught me. I never thought about it. Recently I got in touch with some technical things and wanted to go into that direction. That´s how I found this balanced rig calculator and read about how important it is to be properly equipped with suitable weights.

This one is not bad

Estimated Diving Weight Calculator | DiveBuddy.com

This scuba diving calculator determines the estimated diving weight needed for proper buoyancy.

www.divebuddy.com

it can get you close if you are honest with it and afterward do a weight check to dial it in.

 

[admikar]

Weight check: get into water that you plan to dive in (fresh/salt) with planned configuration, empty wing, suit and exhale. Can't sink? Add weight. Repeat. Now you can sink? Great. Now add more weight to offset gas you will expend (easy to calculate in metric system). Weight check complete.
Note: doing cold water dives with absolute minimum gas in your drysuit sucks big time. Add few pounds for warmth.

 

[edwin71]

I have received my first dry suit last Saturday, in my point of view the only thing that changes is the suit. So I asked around among my buddies how much weight they added for their dry suit. My conclusion was to ad 4kg. So with my double 7mm wet suit i dive with 2 kg additional lead in my pockets, with my dry suit i took 6 kg and that work fine. At the end of the dive i had 50 bar in my tank and floated perfectly at 3m depth with suit and wing empty. So for now i wil be diving with the 6 kg.
extra info i'm 1.76m and 80 kg

 

[admikar]

extra info i'm 1.76m and 80 kg

And that is absolutely irelevant, unless we know exactly what rig and undergarments you have and how well does your suit fits you.
Why do people overthink this? Weight check is weight check. Take enough weights with you and keep adding until you sink. Forget about trim, that can be sorted later. Same for balanced rig.