UTD's New Sidemount Configuration

[John C. Ratliff]

Pure strokery. I would not/could not dive that configuration. How many points of failure are there in this setup?

Wow, just when I felt technical diving couldn't get more complex, this comes along. I have several other questions about this setup

--The regulator first stage appears to connect to the second stage via a presta valve. Has anyone looked at the performance through this valve?

--There are a lot of turns to the flow of the air from the first stage through to the second stage. Has there been an evaluation of performance loss due to all these changes in direction. If you will remember back to the 1980s, Scubapro decided to place an outlet on the top of their Mark V first stage because coming out the sides cause preformance losses (their less expensive first stage out-performed the Mark V).

--Lastly, the block which changes which tanks are used is behind the neck; anyone looked into whether there would be diver errors in determining which to turn off?

Now, I have a setup that meets the DIR requirements for a long hose, but they may not like it. It is an original Calypso regulator with a long hose and a second generation Calypso as the safe second.

 

[tursiops]

Just remembered another one.

I believe they have refered to using He rather than O2 to displace nitrogen and reduce decompression load. So 21/11 has the same NDL as 32%.

At least it has a deeper MOD than 32%.

 

[J-Vo]

--The regulator first stage appears to connect to the second stage via a presta valve. Has anyone looked at the performance through this valve?

They are using a QC6 witch shouldn't have any flow issues. The rest of your points are completely valid.

 

[L13]

Just remembered another one.

I believe they have refered to using He rather than O2 to displace nitrogen and reduce decompression load. So 21/11 has the same NDL as 32%.

That probably actually works for NDL dives. The nitrogen will behave as 32%, and the He won't have enough time to build up from zero and become a factor during an NDL dive.

 

[Gone for diving]

--There are a lot of turns to the flow of the air from the first stage through to the second stage. Has there been an evaluation of performance loss due to all these changes in direction.

Perhaps on the short hose.
I can't 100% prove it, but a long hose should be better in theory.

Your long hose holds at least 2 breaths of air, and it allows the 1st stage not to supply all the air in larger volumes, and let's it open less for longer. Lowering the chance for freezing and should help performance.

 

[ginti]

That probably actually works for NDL dives. The nitrogen will behave as 32%, and the He won't have enough time to build up from zero and become a factor during an NDL dive.

I don't follow you. Dives that are within NDL with nx32 might require deco with 21/11. For example, dives between 25 and 30min at 30m would not require any deco with nx32, but require some minimal deco with 21/11 - we are speaking of 5/10 minutes, but still something. Why do you think He shouldn't have enough time to build up?

 

[J-Vo]

I expect the He would absorb faster due to higher partial pressure differential as you are starting with none in your tissues. The idea that He doesn't absorb into tissues is laughable.

 

[Robert H. Diver]

I don't follow you. Dives that are within NDL with nx32 might require deco with 21/11. For example, dives between 25 and 30min at 30m would not require any deco with nx32, but require some minimal deco with 21/11 - we are speaking of 5/10 minutes, but still something. Why do you think He shouldn't have enough time to build up?

Yea quite a difference when diving the same profile but with those 2 different gasses. Not to mention the gas bill $$$.

 

[L13]

I don't follow you. Dives that are within NDL with nx32 might require deco with 21/11. For example, dives between 25 and 30min at 30m would not require any deco with nx32, but require some minimal deco with 21/11 - we are speaking of 5/10 minutes, but still something. Why do you think He shouldn't have enough time to build up?

I didn't actually run the profiles or do the math, just back of the envelope estimates.

fraction N2 = 68% in both cases. same profile --> same N2 loading throughout the profile.

fraction He = 11%, so saturation at 30m is only 0.44 ATA. the 5min compartment will be close to that but clear quickly, the 27min compartment will be about 1/2 that. doesn't seem significant.

BUT I FORGOT that bubble formation is driven by total pressure supersaturation for all gases, not partial pressure supersaturation by individual gases. Adding ~0.4 ATA to the N2 supersaturation of the leading compartment WOULD BE A PROBLEM. This would be true for any amount of any inert gas, so they (and I) were completely wrong for any length or depth of dive with any combination of inert gasses.

More detail: The leading compartment would probably be ~13min Tissue. With an N2 satuation of ~2.2ATA (~2 half times at ~2.7 ATA starting from ~.7 ATA saturation). This means that the He would add ~17% supersaturation (2.6 ATA, vs 2.2 ATA),which would be significant.

In Short: I was wrong.

 

[Mobulai]

This whole thread was a delight — a great distraction from some heartache over a missed dive