SM Boat diving, Gas switching block

[MichaelMc]

Don't (ETA: some) high end full face masks use a half mask scheme where the bottom reg portion comes out? Less dead air space and all. Where you can remove the bottom half and replace it with a normal reg with mouth piece in an emergency? Could you not just have two of the removable lower parts? One on each sidemount tank? Presumably you would need to clear the FFM after swapping, but that seems a normal FFM issue. It might get really annoying to do that 3 or 4 times per dive, but you would get really proficient at your FFM.

Talking underwater is cool and all, but ditching the FFM seems a reasonable plan.

E.g. the Kirby Morgan. I used a FFM with a removable pod in the pool, but not the Kirby Morgan.

ETA: Added (some) and removed 'upgraded' from 'your (upgraded) FFM' above, from tbones point.

 

[afmiller]

Don't the high end full face masks use a half mask scheme where the bottom reg portion comes out? Less dead air space and all. Where you can remove the bottom half and replace it with a normal reg with mouth piece in an emergency? Could you not just have two of the removable lower parts? One on each sidemount tank? Presumably you would need to clear the FFM after swapping, but that seems a normal FFM issue. It might get really annoying to do that 3 or 4 times per dive, but you would get really proficient at your (upgraded) FFM.

Talking underwater is cool and all, but ditching the FFM seems a reasonable plan.

OTS has the Spectum, but you can only use 1 Second Stage
Kirby Morgan has The MOD-1 which will support the dual Second Stages as seperate bottom parts, just purge as you swap them out. Was talking to the Dive shop, The MOD-1 looks like it might support CCR as well. Im not sure if the MOD-1 has air flow to the eye part to prevent fogging. I know it has the nose and mouth part for the hookup

I've considered either one as a future purchase, the less deadspace is nice

 

[tbone1004]

@MichaelMc it's not a feature of "high end" FFM's, it's just a couple specific ones that do it. They are high end masks, but they aren't the standard use FFMs. Kirby Morgan M-48 Mod 1 is the one you're thinking about. IIRC you lose comms when you swap those out and it's not a system I would ever plan on using for regulator changes.

 

[JohnnyC]

This is just a hot mess waiting to happen. And since you've decided you're already going to go down the tech path, and already decided that you're going to change your configuration for AN/DP, you're far better off ditching the FFM for anything sidemount. There's really no good way to deal with it, even with a switch block or RSV, etc.

My recommendation, sidemount like normal. I hate sidemounting off boats, but if you're gonna do it, do it with a normal configuration all the time. For rec diving, just dive single tank backmount and sling a pony. It's a rec dive. Keep your FFM if you must, and donate off whatever you've got slung.

If your goal is technical diving off boats, do it in backmount.

My FFM is dedicated to my IWR rig, with an RSV and QC6's for gas switching solely for air breaks. I'd hate to use it for anything else.

 

[rjack321]

This is just a hot mess waiting to happen. And since you've decided you're already going to go down the tech path, and already decided that you're going to change your configuration for AN/DP, you're far better off ditching the FFM for anything sidemount. There's really no good way to deal with it, even with a switch block or RSV, etc.

My recommendation, sidemount like normal. I hate sidemounting off boats, but if you're gonna do it, do it with a normal configuration all the time. For rec diving, just dive single tank backmount and sling a pony. It's a rec dive. Keep your FFM if you must, and donate off whatever you've got slung.

If your goal is technical diving off boats, do it in backmount.

My FFM is dedicated to my IWR rig, with an RSV and QC6's for gas switching solely for air breaks. I'd hate to use it for anything else.

Wut he said ^^^

 

[WarrenZ]

My vote goes to ditching the ffm on sidemount. My concern is more about the gas switching than connecting the tanks on the boat I think that adding gas blocks or zsystem manifolds etc is just adding complexity without value.

When you go through a good tec course you will see the value of good, simple, bullet proof rigs and at least in my case I ditched several pieces of flashy gear that served a purpose but that purpose was better served with a better simpler piece of gear.

My opinion on sidemount from a boat is this it is a reasonable expectation for you to be able to enter the water fully kitted up and ready to dive both tanks in place. By the way you should be able to reboard the same way. Some boats may pass up stages/tanks due to the style of boat but unless everyone is tossing their gear in the water and putting it on then you probably shouldn't expect to have the crew passing tanks to you while everyone else waits.

I was the talk of Cozumel when I was diving with Aldora and their steel 120s sidemount it is very doable from a boat. The captains eyes went wide when I climbed the ladder with both tanks on to see how it worked reboarding that way.

 

[MichaelMc]

So again, why FFM? Given the complexity of staying with it. Why are you using it? You mentioned a) spent lots on it, b) cold, c) wife likes it.

a) is a sunk cost... nothing to do there but maybe move on.
b) cold. Sure, but a well fitting hood and mask should cover most of that.
c) wife likes. So, how much, and why? How new is she to diving? How much is it a comfort thing for her, that you can both talk. Are you worried that if you can not talk, she may not be comfortable?

What or why you do is up to you. Just knowing why might help integrate the base reason into your new exploration of sidemount and later tech.

 

[tbone1004]

@WarrenZ many if not most of the boats along the east coast of the US, including where the OP leaves do not allow you to get on the boat fully kitted up. MAYBE off, but not easily. The gates are barely big enough to get onboard with doubles and an AL40 deco bottle. It's not like the Florida/caribbean boats that have wide open transoms. Gearing up in the water is pretty much required, which sucks since the seas in those areas are also not exactly flat which is why the transoms aren't wide open....

 

[rjack321]

There are other problems that SM poses on boats when gearing up or de-gearing in the water too. In cold water you either have dry gloves or numb hands or both. Clipping stuff off and being *sure* you won't drop it is an art.

If you get in or out of the boat without your tanks you often have considerable lead on, but no power inflator or suit gas. Yes you can orally inflate, but not with a FFM. And if you are sinking by surprise oral inflation is too late. So the FFM compounds the issues posed by SM in another way.

I really doubt you are going to find a good deco diving instructor to teach you in FFM as well. There's no redundancy on the FFM second stage unless you use a pod and I guess put it on a necklace? But that's bulky. If you use I pod and its necklaced, how would you donate if I'm OOG? There's a very good reason deco divers donate what you're breathing and you basically can't do that from a FFM. If you don't use a pod style FFM you have to have a switch block which is a terrible way to reliably switch breathing gasses. The list of problems and issue with this combination is the reason it's not done this way.

Commercial divers in hard hats (and comms) dive surface supplied - so any gas switches are not controlled by them in the water unless its to go to their bailout bottle. And there's a backup valve on the hat and several procedures specifically created to manage failures in this kind of diving. The FFM doesn't allow those commercial procedures nor for conventional OC recreational deco procedures which were developed over the course of time from the bad and fatal experiences of earlier generations. Do you really want to be the FFM deco guinea pig? It could cost you your life "working things out".

 

[AJ]

I really doubt you are going to find a good deco diving instructor to teach you in FFM as well.

That's one issue, but how about finding a buddy to dive with? I sure won't do a deep dive with someone who has this config. To complicated and too alien for my taste. Maybe a shallow one, but not a serious deep dive.