Wanted - your wetsuit weight, buoyancy characteristics

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

robzr

ScubaBoard Sponsor
ScubaBoard Sponsor
Messages
252
Reaction score
0
Location
Portland, OR
# of dives
200 - 499
I'm working on a online web page meant for calculating a divers buoyancy characteristics (to predict required weight, required bc capacity). Check it out:

http://cemu.org/scuba/buoycalc.php

The hardest part of this so far has been coming up with wetsuit data... I sent request for information to a variety of manufacturers, and heard nothing back. If any of you could help, it would be much appreciated. Here's what I need:

- Wetsuit brand/model (especially if unique)
- Dry weight
- Size, thickness
- Any large accessories like hoods, vests, would be great as well

And any information on buoyancy characteristics, like how much weight you need to add when changing between suits, or if anyone has measured how many lbs buoyancy a wetsuit has changed under water, that would really help improve the examples.

For anyone who is wondering, here's the approach I'm taking for the calculations:

- Displacement (which can be estimated from the size & thickness)
- Density of gas bubbles (which can be estimated from displacement and weight, as we know solid Neoprene itself is 1.23 g/cm^3) I'm going to forget about any differences in the density of laminates zippers, etc, and just write that off in the margin of error.
- Assumption that the neoprene is fully closed cell

Once we know the displacement and how much of that displacement is gas, we can calculate how much that gas will compress at a given depth, which alters the displacement of the wetsuit, which therefore effects overall buoyancy.

Rob
 
robzr:
I'm working on a online web page meant for calculating a divers buoyancy characteristics (to predict required weight, required bc capacity). Check it out:

http://cemu.org/scuba/buoycalc.php

The hardest part of this so far has been coming up with wetsuit data... I sent request for information to a variety of manufacturers, and heard nothing back. If any of you could help, it would be much appreciated. Here's what I need:

- Wetsuit brand/model (especially if unique)
- Dry weight
- Size, thickness
- Any large accessories like hoods, vests, would be great as well

And any information on buoyancy characteristics, like how much weight you need to add when changing between suits, or if anyone has measured how many lbs buoyancy a wetsuit has changed under water, that would really help improve the examples.

For anyone who is wondering, here's the approach I'm taking for the calculations:

- Displacement (which can be estimated from the size & thickness)
- Density of gas bubbles (which can be estimated from displacement and weight, as we know solid Neoprene itself is 1.23 g/cm^3) I'm going to forget about any differences in the density of laminates zippers, etc, and just write that off in the margin of error.
- Assumption that the neoprene is fully closed cell

Once we know the displacement and how much of that displacement is gas, we can calculate how much that gas will compress at a given depth, which alters the displacement of the wetsuit, which therefore effects overall buoyancy.

Rob


Rob,

I doubt this is an obtainable goal. The variables are just too great.

Neoprene varies widely in density.

Is it a 7 mil suit or a 6.5mm? or a 3 or 4?

How many times has it been crushed? How deep do you dive?

Suit styles and models will vary year to year, if not more often.

Nothing beats testing your own suit.


Tobin
 
cool_hardware52:
Rob,

I doubt this is an obtainable goal. The variables are just too great.

Neoprene varies widely in density.

Is it a 7 mil suit or a 6.5mm? or a 3 or 4?

How many times has it been crushed? How deep do you dive?

Suit styles and models will vary year to year, if not more often.

Nothing beats testing your own suit.

Tobin

Hey Tobin, I agree you can't be more accurate than actually measuring your own suit - but not many folks do that (especially at depth) - if we can make this calculator reasonably accurate (+/- a few lbs; shouldn't be that hard), it can serve as a good starting point. Also, it can serve as a good educational tool for anyone interested enough to spend some time tweaking numbers and seeing what happens. If you check out the calculator, you see there is:

- field for max depth
- field for compressibility (aka density of gas)
- field for displacement (which covers thickness & size)

That should be all we need. Butyl rubber has a density fairly close to that of neoprene, and other parts (outside laminates, velcro, zippers), I think can just be written off in the margin of error.

Rob
 
Rob,

Facinating project. I have a related question for you. Are you aware of a formula for calculating boyancy of the diver? Specifically, an equation that would account for BMI and %Body fat. Let me know if you are aware of one. I would appreciate it.

Flatliner
aka Robert
 
I've measured the bouyancy on all of my and my wife's neoprene. Makes weight changes a snap.

5mm Henderson gold core 1-piece xxl - 13lb
5mm Henderson gold core 1-piece md - 10b
3mm Henderson gold core 1-piece sm - 5lb
3mm Henderson gold core vest sm - 1lb
3/2mm Neosport 1-piece xxl - 7lb
5mm Xcel hooded vest xxl - 5 lb
3mm Seaquest shortie xxl - 4 lb
1/2 mm Scubapro 1-piece xxl - 1lb
 
Flatliner:
Rob,
Facinating project. I have a related question for you. Are you aware of a formula for calculating boyancy of the diver? Specifically, an equation that would account for BMI and %Body fat. Let me know if you are aware of one. I would appreciate it.
Flatliner
aka Robert

Hey Robert... BMI is no good for us (or for anyone really) since it doesn't account for tissue type, it's just a height:weight ratio. For the webpage, I took two formulas used for hydrostatic weighing (which is exactly what we're doing; in reverse), converted units, and solved for %fat. Keep in mind this is done with Residual Volume in lungs (whats left after maximum exhalation), so you will need to add buoyancy for breathing.

$density_brozek = 4.57/($diver_composition * .01 + 4.142) * $freshwater_weight;
$density_siri = 4.95/($diver_composition * .01 + 4.50) * $freshwater_weight;
$density_average = ($density_brozek + $density_siri)/2;
$diver_displacement = $diver_weight/$density_average;
base_buoyancy = ($diver_displacement * $water_weight) - $diver_weight;

Rob
 
https://www.shearwater.com/products/perdix-ai/

Back
Top Bottom