Got my first ever DH reg

[Underwater Tourist]

He height is close to right... The distance the backplate and STA space it from your back is the problem you'll have. Like I said above, pool test it and you'll see the difference in breathing characteristics... With DH regs body position in the water will always effect it, but that large gap off your back will make it more pronounced.

Which one has a greater effect on wob, distance to the body or the height?

 

[rx7diver]

How does it matter ...

@Nemrod,

For my single-hose regulator, I have my standard-length cylinder (either 25" old-school U.S. Divers/PST 72, or 26" Luxfer Al 80) set so that I can relatively easily reach over my right shoulder with my right hand to grab and manipulate my cylinder valve. This allows me to relatively easily recover my 2nd stage, too (by reaching back to where its IP hose connects to the 1st stage). The single-hose regulators I typically dive are my Scubapro Mk 10 + D400/G250/BA, with the turret turned down and the IP hose exiting the side of the 1st stage.

For my double-hose regulator, I have my cylinder located relatively low on my back. It is so low, in fact, that I cannot easily reach my cylinder valve. In fact, I prefer to use my OMS (Faber) LP 66 with my PRAM, because it is a couple of inches shorter than my 72 (my otherwise favorite cylinder).

The cylinder position does NOT stay the same for the two rigs. The cylinder is much higher up my back when I am using a single-hose regulator.

I wear my Freedom Plate much higher up my back than I wear my VDH Classic double-hose Plate.

rx7diver

 

[James79]

Which one has a greater effect on wob, distance to the body or the height?

I'm at work at the moment, and can't go deep into it. Short answer is "yes", lol. And it's not a WOB thing, strictly speaking, it's a characteristics thing.
More to follow at a weird hour of the night when I get off work.

 

[Nemrod]

@rx7diver, no worries, I was just curious, asking why, not so much what. I am not sure why it more important to reach the valve with a single hose than a dh reg but, meh, whatever. I can reach my valve if I need to for whatever reason I might need to. I wear my shoulder harness very loose, I just kick the tank over. I pretty much wear my cylinders low always and altering it for one or the other just ruins my trim. But do what you need to. I do not find repositioning the VDH style plate difficult and only takes a few seconds to adjust the hang loop, for me.

Did you have or have a RX7?

 

[Nemrod]

Which one has a greater effect on wob, distance to the body or the height?

Both are equally bad and both together are horrible. Not to repeat, but, hey, old people get to repeat things , you will not be able to find DH joy with a bent doubles plate nor most BCs. Just to try it out in a pool, go for it.

 

[Nemrod]

Oh, just go for it, jump in. It will not be worse than sucking on a vacuum cleaner . Gotta start somewhere. Devolving into DH thinking, especially for divers who did not learn or grow up with them, is a process.

 

[rx7diver]

@rx7diver, no worries, I was just curious, asking why, not so much what. I am not sure why it more important to reach the valve with a single hose than a dh reg but, meh, whatever. I can reach my valve if I need to for whatever reason I might need to. I wear my shoulder harness very loose, I just kick the tank over. I pretty much wear my cylinders low always and altering it for one or the other just ruins my trim. But do what you need to. I do not find repositioning the VDH style plate difficult and only takes a few seconds to adjust the hang loop, for me.

Did you have or have a RX7?

It is important for me to be able to reach my cylinder valve when I dive my PRAM, too. I simply can't easily do it.

Same with my HP80 + single-hose regulator. For things to balance out for me, I need to wear my HP80 quite low on my back. In either case (PRAM or HP80), if I absolutely have to, I can reach my valve, but it's not pretty, not effortless: Loosen the appropriate strap(s), reach under the cylinder with my left hand and push the cylinder "up" enough so that the valve is within reach of my right hand. Not anything that I would want anyone videoing. Love the HP80, otherwise. (My very first cylinders, purchased new in 1988, when they were introduced to the market.) Well, they're too negatively buoyant (for me) in fresh water when wearing no or a very thin wetsuit. So, there's that, too.

NOTE: This (reaching my valve(s) when using my PRAM) is not an issue whatsoever when I wear my baby doubles (Faber LP50's), since the PRAM sits "below" the valve ("below" the manifold) rather then "on top of" the valve. I wear these 25" double cylinders at approximatley the same height whether I am using my PRAM (with my VDH Classic Plate and single-outlet, solid-bar, J-valve manifold) or using a pair of Scubapro Mk 10's (with my old aluminum Dive Rite doubles plate and old OMS isolator manifold). Neat!

Yes, I still have my 1993 FD (3rd gen) RX-7. Bought it new in 1993. I seldom drive it now, but I still love it when I do. It's in the shop right now getting a new fuel pump and fuel filter. (RX-7's don't like not being driven!)

rx7diver

 

[James79]

Work of breathing comes in 2 parts, inhale and exhale. There is also a difference in objective and subjective WOB. The actual total work of breathing shouldn't change too much, but the perceived WOB will in a big way.... If the mouthpiece is above the reg, it will feel like it's trying to feed you air and puff your cheeks out (mouth is higher in the water column) and the exhale will feel like you're having to force it out. But the actual effort of the inhale/exhale is determined by reg position relative to your lungs. If the reg is higher in the water column than the mouthpiece, it will feel the opposite (easy exhale, but hard inhale).
The better the reg placement, the less that effect is... But it is always there. The way I wear mine, the most balanced subjective WOB is when I am about 5 degrees head up from horizontal trim.

Respectfully,

James

 

[Nemrod]

Here is an old illustration of regulator postion considerations:




Some Krakens have been modified with a diaphragm stop to prevent the exhaust valve from being pulled out by the diaphragm. The exhaust valve can vacuum seal like a stopper to the diaphragm. Another mod a few Krakens have is an extended mouthpiece vane. Had the Krakens continued in production and there had been a series III, I bet these mods in some form would have been included in the design.

As to WOB, the three aspects thereof, cracking force, inhalation Venturi, exhalation, the Kraken and DH regs in general have a very low exhalation effort. As well, it is possible to have a stable adjustment of cracking force below 1.0 inches of water, for example around .6 on my Magnehelic. But, inhalation, that is where the adventure begins and DH regs are particularly sensitive to position. The Kraken has a powerful and adjustable Venturi to assist inhalation once the valve cracks. Most/many Kraken divers have one HPR bleed port fully blocked and the opposite partial (half) blocked. With the improved mouthpiece vane it is possible to fully block both bleed (anti-Venturi) ports.

See that slotted screw there. It adjusts the height of the second stage orifice/knife edge. Leave that set center and flush to the body. Messing with that screw can cause unintended consequences.

 

[Underwater Tourist]

Tried it in the pool for the first time and my plate really wasn't set up correctly. When swimming in trim with the usual slightly arched back, there was a big gap between the plate and my back. So for next time I will move it higher.

WOB was pretty poo poo for me also in trim, but in the seahorse position it got much better. Again probably user error and more tweaks are required

On the bright side, $77usd UTD knock off fins that are sold under a different brand name on amazon were amazing. They are also slightly shorter than other jetfin variations, and i loved that as well