Needle valve spreadsheet?

[rjack321]

Download the Pelagian DCCCR manual off rebreatherlab.com. There's a chart on page 65 that's basically a flow table, and it's got some math on it that might help.

Ok this helps a lot, thank you

 

[JohnnyC]

That's no different than if you were diving a KISS or rEvo. They also use blocked first stages.

Dive a KISS or a rEvo?! Ugh, I think I just threw up in my mouth a little.....

You give up your SF2?

For sure it's not a huge issue, I just don't find the necessity of tweaking the needle valve once or twice more often to be too much of an issue that a blocked first stage would be advantageous.

After a couple hours on a needle valve, your familiarity with how much adjustment you need to make is pretty automatic. It's just another one of those things that you do, like adding gas to your wing on descent, it just happens and then you realize you've done it, maybe.

 

[rjack321]

After a couple hours on a needle valve, your familiarity with how much adjustment you need to make is pretty automatic. It's just another one of those things that you do, like adding gas to your wing on descent, it just happens and then you realize you've done it, maybe.

Do you have the fathom one or chris kennedy one? (unless there's another I don't know about)

I'm bringing my kiss (sidewinder) unit on a extended trip next spring/summer so I wanted to get the needle valve this winter to get some hours on it beforehand.

 

[kensuf]

He's got a pelagian, which uses a needle valve too.

I've still got the SF2. There are pro's and con's to both the SF2 and the Fathom, but for some of the dives I want to do the Fathom wins out so that's what I'm spending my time on right now.

 

[JohnnyC]

I have a Pelagian one on my Pelagian, and I have a Chris Kennedy custom one as well that's going on my SF2 eventually. I've seen the Fathom in person, it's a nice MAV, and I like the recessed O2 add. It's a nice feature. Overall the whole unit is just a Pelagian if it was built in the US instead of some garage in Thailand. The cell-face clearing, the needle valve, the limited electronics are all things that the Pelagian did years ago (not saying Andy invented any of the concepts), and all are very useful features. The larger tube, the removable radial scrubber, the nice head attachment design, and counterlungs that aren't made out of scooter innertubes taken from Chinese knock-offs of Ural motorcycles are all things that Fathom did that make it a much better unit in terms of overall construction. To be perfectly honest I'd rather have a Fathom than a Pelagian. Unblocked of course....

As far as the adds themselves, personally IMO they're all a block of delrin with a spinny thingy and a button that goes psssshhhh. In the case of these three, one has an unprotected button (Pelagian), one has a protected button (Fathom), and one has an unprotected button and a QC on the bottom (Chris Kennedy). All three protect the needle valve by placing it in between the O2 hoses. Andy wants stupid money for the Pelagian ones separately, the only benefit is that it's tiny. The Chris Kennedy ones are super nice, but they're in Australia, and I'd like to see the Fathom ones readily available on the market for a reasonable cost to purchase separately, as I think needle valves are the way to go regardless of the unit you dive. Unless you have a specific need for a tiny MAV or a custom one, the Fathom is the most attractive in my mind.

 

[rjack321]

I know Charlie is offering the Fathom one separate and seeing how he's the only one in the states, I was leaning pretty hard that way already. Its quite a bit larger than my stock kiss add though. If the kiss mav had someway to exchange the orifice down I would just do that for budget and simplistic reasons. I have seen a Kiss needle valve prototype so I am waiting until after DEMA to confirm there isn't something else available shortly.

 

[kensuf]

You can put a smaller orifice in pretty easily. I had the 0.0025 one from tecme (Kiss Rebreather Parts) and you can get a stiffer spring from them too.

 

[rjack321]

You can put a smaller orifice in pretty easily. I had the 0.0025 one from tecme (Kiss Rebreather Parts) and you can get a stiffer spring from them too.

Jeesh Kim told me there was no smaller orifice available...
Now I don't know whether to swap to a smaller one or splurge on the needle valve. My consumption does vary a fair amount between FL (69F) and WA (45 to 52F) waters.

 

[JohnnyC]

Get the needle valve! Even if you do the blocked first stage thing and the needle valve, get the needle valve!

 

[rjack321]

Charlie's sending me an invoice, not sure if he has them on the shelf or not. Do they have an integrated filter? Or do I have to add that?

I also ordered a dwyer flow gauge so I can experiment a bit on the surface to depth flow conversions. Or at least have a more educated guess to start