May I pick your brains for a moment?

[doctormike]

Sounds exciting! It also sounds like Zach should have left those amps on the wreck...

 

[Lefty Writer]

Doctormike, we have some realllly old amps from our reference collection. I'm growing up several of these to make antigen for another investigator. Some of these amps were lyophilized in the early 60's, and still grow like crazy once I rehydrate them. They are so old that the labels are just hand written on tape. That's what gave me the seed for this story.

 

[Dish]

Lefty, if this ends up with a creature blowing out of Zach's abdomen and chasing people around the facility, I'm out. Just saying.

 

[Lefty Writer]

LOL......good one, Dish! I might just add that in.

Seriously, though, I want this to be so realistic that the next time one of my fellow divers sees a wreck, they'll wonder if there's some hidden plague lurking in the silt.

 

[Lefty Writer]

Given all the help I've had, I used my omnipotent powers as an author to.......whoosh!.......transform Zach into an experienced tech diver at the beginning of the story. He now has 3 years experience making wreck penetrations with a CCR system and a previous 2 years doing penetrations with doubles. While Zach may be an experienced tech diver, sadly, my magical author powers didn't work on me. I'm still competent to dive in the Caribbean and explore some of the prepared wrecks like the Kittiwake, but that's it. I guess I could hover over the wreck while Zach and Ken do their dive, and take photos of the wreck.

Anyway.....

Could y'all please indulge me with just a few more details? I really want to do this right, and do justice to not only diving in general, but to the tech divers here who have been so generous with their time and knowledge. I even Googled "TriMix dive tables" but they looked even more confusing to me than the RDP on my first night of OW class.

For the story's purposes, I'd like them using rebreathers for a few critical plot points.

The wreck is still the same freighter, in about 140 - 150 feet in the Gulf of Mexico.

From what I've read here, and some online articles, it looks like my characters can safely do a 1 - 2 hour dive at that depth.

How much deco obligation would they have for that time frame? (for plot purposes, this detail could be important)

Is is possible to do this dive profile in the morning, and again in the afternoon? Another reason I thought about limiting their dives to 2 hours max. If not, no big deal, I can keep them on the dive boat overnight. It's a nice liveaboard, and the chef is pretty talented.

Does a CCR system come integrated with its own BCD?

What about the dive computer? Would different CCRs use their own computers, or should my guys use something like a Shearwater Predator? Or is this just total BS and they'd use tables, a bottom timer and SPG configuration?

I think with these last few details I won't have to bug y'all for a while.

Again, THANK YOU! I really appreciate everyone's help!

As thanks, I'll be happy to post the opening chapter for y'all if interested.

 

[rongoodman]

How much deco obligation would they have for that time frame? (for plot purposes, this detail could be important)

Is is possible to do this dive profile in the morning, and again in the afternoon? Another reason I thought about limiting their dives to 2 hours max. If not, no big deal, I can keep them on the dive boat overnight. It's a nice liveaboard, and the chef is pretty talented.

Does a CCR system come integrated with its own BCD?

What about the dive computer? Would different CCRs use their own computers, or should my guys use something like a Shearwater Predator? Or is this just total BS and they'd use tables, a bottom timer and SPG configuration?

I think with these last few details I won't have to bug y'all for a while.

Again, THANK YOU! I really appreciate everyone's help!

As thanks, I'll be happy to post the opening chapter for y'all if interested.

About 1 min deco for each min of bottom time at this depth.

Two dives per day sounds reasonable.

My Prism rides on a standard back plate/wing. Other units may vary.

The CCR's computer has to be connected to the unit so it can monitor the level of oxygen in the loop for deco calculations as well as monitoring the levels for safety. Some units have proprietary computers, some are just hard wired into a standard unit such as a Predator.

 

[doctormike]

Given all the help I've had, I used my omnipotent powers as an author to.......whoosh!.......transform Zach into an experienced tech diver at the beginning of the story. He now has 3 years experience making wreck penetrations with a CCR system and a previous 2 years doing penetrations with doubles. While Zach may be an experienced tech diver, sadly, my magical author powers didn't work on me. I'm still competent to dive in the Caribbean and explore some of the prepared wrecks like the Kittiwake, but that's it. I guess I could hover over the wreck while Zach and Ken do their dive, and take photos of the wreck.

Anyway.....

Could y'all please indulge me with just a few more details? I really want to do this right, and do justice to not only diving in general, but to the tech divers here who have been so generous with their time and knowledge. I even Googled "TriMix dive tables" but they looked even more confusing to me than the RDP on my first night of OW class.

For the story's purposes, I'd like them using rebreathers for a few critical plot points.

The wreck is still the same freighter, in about 140 - 150 feet in the Gulf of Mexico.

From what I've read here, and some online articles, it looks like my characters can safely do a 1 - 2 hour dive at that depth.

How much deco obligation would they have for that time frame? (for plot purposes, this detail could be important)

Is is possible to do this dive profile in the morning, and again in the afternoon? Another reason I thought about limiting their dives to 2 hours max. If not, no big deal, I can keep them on the dive boat overnight. It's a nice liveaboard, and the chef is pretty talented.

Does a CCR system come integrated with its own BCD?

What about the dive computer? Would different CCRs use their own computers, or should my guys use something like a Shearwater Predator? Or is this just total BS and they'd use tables, a bottom timer and SPG configuration?

I think with these last few details I won't have to bug y'all for a while.

Again, THANK YOU! I really appreciate everyone's help!

As thanks, I'll be happy to post the opening chapter for y'all if interested.

I’m an open circuit tech diver, but on CCR I’m just mod 1 (no deco, no trimix), so you are probably better getting dive planning information from someone else. The considerations would be deco obligation, O2 exposure, and bailout requirements.

I dive a JJ, so my answers are for that unit. Other units have different configurations.

Most technical divers do not use the typical recreational diver’s jacket BCD. Rather, a backplate and wing is used which is a modular device that serves the functions of holding the tanks, holding the rig to the diver, providing lift to compensate for the extra negative buoyancy of gas weight and exposure suit compression at the beginning of the dive, and providing positive buoyancy on the surface. All CCRs have to have those functions; the JJ has a standard backplate, harness, and wing to provide this (although the buoyancy issue is a bit more complicated).

The JJ comes stock with a modified Shearwater Petrel dive computer connected to the rebreather by a cable. This calculates decompression information, and also serves as a controller to add oxygen to the “loop” to keep the partial pressure of oxygen (PPO2) at a predetermined set point based on the reading from three O2 sensors. In addition, many divers have a backup decompression computer - typically a stand alone Petrel on the other wrist. There is a heads up display that provides redundant PPO2 information in front of the diver’s mask. I have replaced the HUD with a NERD, which is essentially a Petrel with a heads up display in front of the mask, that provides PPO2 and decompression information (so I don’t have the second Petrel any more). Other CCRs have separate controllers and deco computers.

The problem with using regular tables is that you aren’t calculating for a given mix and depth, but rather for a fixed PPO2 over a range of depths. There are CCR dive tables for constant PPO2 diving, but I don’t know many people who use them.

 

[Jerome O'Neil]

1. Would it be plausible if my character was trained on rebreathers instead of doubles? If so, what would be a suitable beginner rig? Something like the Poseidon Seven?

2. Regardless of system, would this be done with TriMix? I looked at my nitrox MOD table, and saw that Nx 25 might work. Yes? No?

3. Given this is in the Gulf of Mexico, would a dry suit be necessary, or could he get by with a 5 or 7 mil? He's a native born Texan, and dives primarily in the Caribbean. He's warm natured, and is generally tolerant of cooler water. Since I've only done safety stops (and a "deep stop" diving the O), a 3/2 was adequate for me. I have no basis for comparison for doing a long deco stop.

Keep that level of detail out of the story. No1currr.... Even Tom Clancy got old with that crap.

Describe the scene instead... "...the quiet hum of the re-breather..."

4. Anything obvious I'm missing?

Your audience? Don't write a Popular Mechanics article. Tell a compelling story. Stories are about people.

 

[Lefty Writer]

This is all fantastic info.....thank you! My biggest challenge is balancing the technical parts of the story with the overall narrative. I realize that Joe Schmuckatelli in Idaho might not be a diver, and not care a whit about what breathing contraption Zach is using, and just wants to enjoy reading a thriller. That's totally cool with me. I'd hate for one of y'all, though, to read even a single sentence involving diving and roll your eyes at how ridiculously I wrote it.

Ideally, if I can describe the scene accurately, yet have my readers be able to smell the wet neoprene, hear the seagulls flitting about the dive boat, and taste the slice of pineapple that Zach is eating then I'll be a happy camper.

One reason I'm so uptight about accuracy is that I read a book and enjoyed it right up until the point where the author described an air strike being launched off a carrier.....with F-16s.

 

[doctormike]

This is all fantastic info.....thank you! My biggest challenge is balancing the technical parts of the story with the overall narrative. I realize that Joe Schmuckatelli in Idaho might not be a diver, and not care a whit about what breathing contraption Zach is using, and just wants to enjoy reading a thriller. That's totally cool with me. I'd hate for one of y'all, though, to read even a single sentence involving diving and roll your eyes at how ridiculously I wrote it.

Ideally, if I can describe the scene accurately, yet have my readers be able to smell the wet neoprene, hear the seagulls flitting about the dive boat, and taste the slice of pineapple that Zach is eating then I'll be a happy camper.

One reason I'm so uptight about accuracy is that I read a book and enjoyed it right up until the point where the author described an air strike being launched off a carrier.....with F-16s.

I don't think that accuracy and attention to detail is incompatible with good story telling. Not sure why you wouldn't want the background tapestry to be as well done as the main characters. Don't go overboard with technical details, but what you include should ring true! You are to be commended for taking the time to do this right...