Questions About ScubaPro 109 2nd

[buddhasummer]

You've got my request for 2 sets!

Thought you wanted 1?

 

[buddhasummer]

So as not to take over @Litefoot thread I might start one in the Classifieds to see how much interest in conversion kits

 

[davehicks]

Thought you wanted 1?

No, two sets. I have two old SP109s I want to convert. Another member got the regs, I'll overhaul them and keep one, give him back the other.

 

[Litefoot]

So as not to take over @Litefoot thread I might start one in the Classifieds to see how much interest in conversion kits

Hey, I brought up the conversion kits, so no worries. But I would like some responses on my other questions. How much difference in WOB have you seen after the BA conversion? And how much to you fiddle with the spring adjustment on a dive? Just curious. Thanks!

 

[happy-diver]

Nothing I can ever remember, from dive to dive or gear to gear whether knob fiddling or not it's just diving
not that diving is just anything but with everything elso going on if you tell me there's a difference I will tell

you are Not diving

 

[buddhasummer]

Hey, I brought up the conversion kits, so no worries. But I would like some responses on my other questions. How much difference in WOB have you seen after the BA conversion? And how much to you fiddle with the spring adjustment on a dive? Just curious. Thanks!

Not much in it at all, if anything.

@halocline

 

[Kupu]

I've only used Balanced Adjustable so no experience with diving the 109. But the question has come up before and those that have used both state WOB is comparable between the two with a balanced first stage. If the first stage happens to be unbalanced, then changes in WOB during the dive would be more noticeable with the 109.
The main benefit the BA configuration is related to the lighter spring, lighter pressure on the poppet seat allows longer intervals between service/tuning sessions. For DIYers, the flip side of that point is the higher price for balanced poppet seats vs being able to make the puck style 109 seats at home. (There is an early version of the balanced poppet that can use homemade puck seats, but that is getting into the obscure side of DIY).
New replacement springs are almost impossible to find for the 109, new springs for the BA are going to be available for a long time.

I tune my adjustable second stages to the edge of free flow for easiest possible inhalation effort. With that tuning, the adjustment knob can be used to tighten up the spring during entry and exit which pretty much eliminates second stage free flow on the surface. Once underwater, the adjustment knob is turned back out for easy breathing. During the dive it is hardly ever touched.

 

[Litefoot]

I've only used Balanced Adjustable so no experience with diving the 109. But the question has come up before and those that have used both state WOB is comparable between the two with a balanced first stage. If the first stage happens to be unbalanced, then changes in WOB during the dive would be more noticeable with the 109.
The main benefit the BA configuration is related to the lighter spring, lighter pressure on the poppet seat allows longer intervals between service/tuning sessions. For DIYers, the flip side of that point is the higher price for balanced poppet seats vs being able to make the puck style 109 seats at home. (There is an early version of the balanced poppet that can use homemade puck seats, but that is getting into the obscure side of DIY).
New replacement springs are almost impossible to find for the 109, new springs for the BA are going to be available for a long time.

I tune my adjustable second stages to the edge of free flow for easiest possible inhalation effort. With that tuning, the adjustment knob can be used to tighten up the spring during entry and exit which pretty much eliminates second stage free flow on the surface. Once underwater, the adjustment knob is turned back out for easy breathing. During the dive it is hardly ever touched.

Thanks Dustin! My question came up because as I’m progressing through Peter Wolfinger’s book, he seemed to indicate that there was a significant difference in WOB with the lighter spring in the balanced configuration. I’m sure he was speaking in general terms, not specifically to the 109 conversion to BA.

 

[Nemrod]

With a BA second stage, be it a 109 or a G250 or whatever, it is possible to set the spring force/orifice such that the regulator very slightly leaks with the knob fully out. It is then needed to turn the knob in about a half turn to stop the leak (not free flow, a leak). When the regulator is not being used, turn the knob fully out to save the seat. When in use turn the knob in as needed if it is a primary for easy breathing and if it is a secondary then turn the knob in a little further to prevent free flow during entry. If scootering or working into a strong current, turn the knob in a little more to prevent annoying non-demand flow.

I have encountered some who may think going back to non-adjustable configuration extends seat life and service interval therefore. No, just no. Convert to BA configuration and then set the regulator, after break-in, to just barely leak past the seat. There will be so little force on the seat/poppet in storage with the knob turned out that the seat will not be engraved except by use.

 

[Kupu]

Thanks Dustin! My question came up because as I’m progressing through Peter Wolfinger’s book, he seemed to indicate that there was a significant difference in WOB with the lighter spring in the balanced configuration. I’m sure he was speaking in general terms, not specifically to the 109 conversion to BA.

Over the years I have put a decent number of dives on assorted unbalanced second stages. Always paired with a balanced first stage.
For example, the Sea Hornet Command Air, which I put on par with a balanced SP G250 for ease of breathing. The SP 190, Dive Rite 1200, and Poseidon Cyklon are other unbalanced examples that been very adequate performers.

Which page mentions the lighter balanced spring as it relates to WOB? Maybe putting it into context will help clear things up. I'm wondering if he was making the point about WOB based on a situation where both first and second stages are unbalanced, which would make more sense but still need to take into account variables such as tank pressure and depth.
At a glance I notice on page 60 a sentence that states air balancing helps reduce work of breathing, followed by a paragraph that mentions the importance of stable (balanced) first stage IP as it relates to second stage performance.