DIR- GUE Balanced rig with a thick wetsuit - mathematically impossible?

[johndiver999]

It does not "depend"

If its "thick" by which I mean 6+mm its got air in it - which is how it provides insulation in the first place. No amount of magically $$$ neoprene is going to keep those gas bubbles from smushing to a 2mm thickness (or less) at 30m+

There is some pretty big differences in the actual weight of a unit of neoprene. Some suits, even thick ones are pretty light while others are noticeably heavier in your hand. It stands to reason, that if the suit starts the dive much heavier, it is going to stay heavier during the dive. It also seems reasonable that it will compress less at depth and be less thermally efficient at shallow depths.

 

[Ayisha]

Actually this post made me think: if you ditch weight and become positive so you cannot hold a stop, would you be then not diving a balanced rig?

I don’t think ditchable weights were mentioned during my Fundies.

The potential of having ditchable/removable weight is still mentioned in some of the GUE materials, so that's interesting that they might not have been mentioned in your Fundies. It's definitely not the focus or goal, though.

Under the older system, if a catastrophic wing failure happened at the beginning of a dive, and you couldn't swim up your rig (which means you're not balanced), then you could ditch just enough weight to be able to begin to swim up. That might be just 2.2 lbs/1 kg. You just began the dive, so you have most of the 6 - 12 lbs/2.7 - 5.5 kg or more of gas in your tank as leeway to still be neutral at your last stop.

In other words, if you already determined whether you could swim up your rig as the GUE materials stated, and couldn't for whatever (pre-determined) reason, you would need ditchable/removable weight to make the rig balanced. The amount of ballast that you would make available to ditch should be no more than the gas you're carrying, to allow you to begin the ascent, but still do your last stop and ascend safely.

Personally, I have always preferred, in the last 13 years anyway, to achieve a balanced rig without ditchable weight, so I don't have any. I can swim up my rig from depth, so I've never needed any, even back when ditchable weight was common. As long as you could swim it up, it was balanced.

 

[BlueTrin]

The potential of having ditchable/removable weight is still mentioned in some of the GUE materials, so that's interesting that they might not have been mentioned in your Fundies. It's definitely not the focus or goal, though.

Under the older system, if a catastrophic wing failure happened at the beginning of a dive, and you couldn't swim up your rig (which means you're not balanced), then you could ditch just enough weight to be able to begin to swim up. That might be just 2.2 lbs/1 kg. You just began the dive, so you have most of the 6 - 12 lbs/2.7 - 5.5 kg or more of gas in your tank as leeway to still be neutral at your last stop.

In other words, if you already determined whether you could swim up your rig as the GUE materials stated, and couldn't for whatever (pre-determined) reason, you would need ditchable/removable weight to make the rig balanced. The amount of ballast that you would make available to ditch should be no more than the gas you're carrying, to allow you to begin the ascent, but still do your last stop and ascend safely.

Personally, I have always preferred, in the last 13 years anyway, to achieve a balanced rig without ditchable weight, so I don't have any. I can swim up my rig from depth, so I've never needed any, even back when ditchable weight was common. As long as you could swim it up, it was balanced.

Thanks for the explanation, that’s the no more than the gas weight I was missing.

That allows you to safely ascend then, and is consistent with being neutrallish at the end of the dive during stops.

 

[Angelo Farina]

The potential of having ditchable/removable weight is still mentioned in some of the GUE materials, so that's interesting that they might not have been mentioned in your Fundies. It's definitely not the focus or goal, though.

Under the older system, if a catastrophic wing failure happened at the beginning of a dive, and you couldn't swim up your rig (which means you're not balanced), then you could ditch just enough weight to be able to begin to swim up. That might be just 2.2 lbs/1 kg. You just began the dive, so you have most of the 6 - 12 lbs/2.7 - 5.5 kg or more of gas in your tank as leeway to still be neutral at your last stop.

In other words, if you already determined whether you could swim up your rig as the GUE materials stated, and couldn't for whatever (pre-determined) reason, you would need ditchable/removable weight to make the rig balanced. The amount of ballast that you would make available to ditch should be no more than the gas you're carrying, to allow you to begin the ascent, but still do your last stop and ascend safely.

Personally, I have always preferred, in the last 13 years anyway, to achieve a balanced rig without ditchable weight, so I don't have any. I can swim up my rig from depth, so I've never needed any, even back when ditchable weight was common. As long as you could swim it up, it was balanced.

I agree on ditching "just enough" weight.
But if you ascend early with tank yet full there is no need of a safety stop at 3 or 5 meters: you can ascend directly to the surface. And you should do that, as ditching weight and anticipated ascent means that something bad happened, so there is no reason to loose 3 minutes in an unneeded safety stop.
If by error you ditch too much weight and you become positive at 3m, this is substantially no problem.
It is actually a good thing, when you surface, to be slightly positive: your BCD failed and being positive at the surface is a very good and safe thing...

 

[rjack321]

There is some pretty big differences in the actual weight of a unit of neoprene. Some suits, even thick ones are pretty light while others are noticeably heavier in your hand. It stands to reason, that if the suit starts the dive much heavier, it is going to stay heavier during the dive. It also seems reasonable that it will compress less at depth and be less thermally efficient at shallow depths.

Weight on dry land is virtually meaningless and is at most tangentially related to the density of the material.

This has been a ridiculously overthought thread already, so feel free to start measuring the density of neoprene materials.

 

[Angelo Farina]

Weight on dry land is virtually meaningless and is at most tangentially related to the density of the material.

This has been a ridiculously overthought thread already, so feel free to start measuring the density of neoprene materials.

Density of closed-cell expanded neoprene varies wildly.
This manufacturer provides sheets of different thickness and with density varying between 140 and 1900 kg/m3. The latter, of course, is basically without any air cells...

Closed Cell Neoprene Sponge Rubber

Our neoprene sponge rubber is a high-quality, closed cell material that combines excellent UV, Ozone and Oil resistance with good physical properties

therubbercompany.com

For shallow depth free diving also open-cell neoprene foam is used, which is even lighter and more compressible.

For dry suits, instead, "crushed" neoprene foam can be used as an alternative to trilaminate.

The buoyancy and thermal properties of those different materials vary strongly with depth for some of them, and vary much less for others.

 

[Celt]

This mornings dive in the Elios wetsuit I was a little too warm but the water temperature around Ireland is warmer than usual. Obviously there’s a huge difference in suits including dry suits. A badly made bag dry suit would fit everyone on the boat as would a badly fitting wetsuit of soft neoprene. The main buoyancy shift in a HD neoprene wetsuit happens in the first 30 feet and very little as you go deep. For a wet suit to keep you warm it has to be a close fit allowing only a thin layer of water on the skin that stays there. The problem for manufacturers of wet suits is it’s the first suit a new diver encounters and it has to feel soft, comfortable and fit a large cohort of different shape divers. A custom HD neoprene suit will only fit the diver it was built for. The price is another thing people get wrong. A scubapro novascotia 7.5 mm is €580 off the peg. Stefano at Elios Sub built my suit for €460

 

[rongoodman]

I want to know more about this MTM you speak of.

I assume he means Made to Measure, i.e., a custom fit.

 

[jadairiii]

It’s obvious you know nothing about neoprenes and the many different densities available.

Boyle's law applies regardless of the quality of the material. Higher end neoprene will "survive" longer over time and retain its thickness(?), and that is what you are paying for. Cheap neoprene will crush down pretty quick. A cheap 7 mil suit after a year of heavy use will be a 3 mil. But in the end, to quote the Clash, they all go the same way - through the kitchen.

 

[johndiver999]

Weight on dry land is virtually meaningless and is at most tangentially related to the density of the material.

This has been a ridiculously overthought thread already, so feel free to start measuring the density of neoprene materials.

If we are looking at neoprene of the same thickness, I am not sure how you have surmised that density and weight are (at most) "tangentially related"? Mathematically they are directly correlated, with small variations possible due to the lining inside and out.