Calculated weight for new drysuit seems odd, second opinion needed

[scubazendiver]

Hi,

I ordered a drysuite which should be here by tomorrow and used a calculator to get my balanced rig. But somehow the numbers don´t match my expectations.
Perhaps I had an oversight or keyed in something wrong?
I weighted my wing (entire wing with backplate, webbing, bubble, additional but empty weight pockets around the straps and two backup lights) at 6,5kg.
My regulators (two first and two second stages, plus spg, plus inflator hose) weight is around 2,5kg.
A steel tank of 15L with an empty weight of 18kg has 19,12kg at 60 bar, 21,7kg at 200 bar.
The wing has a max lift capacity of 19kg and is a mono wing.
Counted against are a trilaminat drysuite 5kg, undergarment 200g and 2kg, neoprene hood 1kg (a little higher, just in case, to top up the total amount).
Now it tells me to add 1kg of weight! Seems a little strange to me. I usually add around 3-5kg in my wetsuit.
Btw. I did not count in my fins which are around 1,2kg each, since they are more or less neutral under water.

Thanks!

 

[Alekseolsen]

So, I don't follow above. What would the weight of your harness, backuplights, wing etc. Matter? They for sure are "more or less neutral" aswell.

Have tou tried the "optimal buoyancy calculator" on here?

 

[BlueTrin]

If you can, do a weight check. That’s usually the best way to know how much lead you need.

It’s hard to help unless you give more details about the buoayancy calculator you used and all the inputs.

 

[scubazendiver]

I used a different calculator than the one mentioned by alekseolsen. It is an excel sheet by a guy named Benjamin (balanced rig calculator v1.1)
But you are right, harness, wing should more or less float too, so I don´t have to calculate it in. Lights definitely sink. So have to calculate them in.
Let me check with the calculator you mentioned. Thanks

 

[jborg]

It sounds like you may calculating with the dry weight of things on land (bcd, tank, etc). What you actually need is the buoyancy numbers for how they are in the water, which will be a lot less than their mass.

 

[broncobowsher]

The stuff you are weighing, how much water does it displace?

The 15L tank has 15kg (this is really simple version here) of buoyancy. Weighs 18kg empty. So the in water (15-18= -3) is 3kg of weight.

Fins can be positive or negative buoyancy, if you take it off does it float or sink?

What stuff weighs on land sort of doesn't matter. You have to know what it does in the water.

Undergarments are even more dynamic. They compress. Add air and they fluff up and insulate better, but float more. Let the air out, they compress and are colder, and you float less.

So yes, you did forget to calculate in the water displacement of your gear. You were close to understanding this when you stated the fins weigh 1.2kg but are neutral in the water. That same thing applies to all of your gear.

If you are typically 3-5 kg in a wetsuit, quicky guess is 5-10 kg in a drysuit. When your calculations come out closer to those numbers you will have a better starting point. You will still need to do a buoyancy check when you hit the water.

 

[scubazendiver]

Hm, that makes some kind of sense. I do have some numbers but no specific numbers for my equipment.
For example my first and second stages are an mk22 abyss, heavy steel version which I have no idea of what buoyancy it creates....probably best to find an instructor who can properly check my gear and trim, add or toss weight during a dive until it is correct.

 

[BlueTrin]

Like you said, organise a weight check for your next dive, then you can just write down in the log if you were under or over weighted and you can amend slightly between dives.

 

[Wibble]

Stop overthinking this. You must do a weight check.

Can you dive in a pool or lake?

 

[scubazendiver]

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....