The "other" end of the DIR question

[IndigoBlue]

"Halcyon's" harnesses are not Halcyon's at all. It's 15 feet or so of weight belt webbing and standard keepers and D-rings. And what's wrong with their manifolds?

Jonnythan, there is nothing "wrong" with Halcyon's manifolds. I simply compared Halcyon's, Sherwood's, and OMS's manifolds, and I "like" OMS's better.

I also do not like "webbing" in place of a B/C. I prefer OMS's and Zeagle's B/Cs to "webbing." I love Halcyon's wings, and I plan to replace my Zeagle wing on my Zeagle B/C with a Halcyon wing, next.

 

[fishnchips]

A Spare Air won't get the average diver to the surface from 80 feet unless that diver exceeds a safe ascent rate.

I've seen the math in here before ... but basically considering that the type of person who's likely to carry a Spare Air is going to be relatively inexperienced, and with a relatively high SAC rate, it's safe to say that in an emergency their SAC could easily exceed 1 CF per minute. At a rate of 30 fpm, and coming up from 80 feet, they're going to run out of air at somewhere around 50 feet.

... Bob (Grateful Diver)

I am really curious, and eager to learn.... I could not come to a conclusion that there is a particular "TYPE" of person that carry Spare Air. BUt You know for sure the type of person who's likely to carry a Spare Air is going to be relatively inexperienced, and with a relatively high SAC rate, and it's safe for you to say that in an emergency their SAC could easily exceed 1 CF per minute? Really? Incredible!! WOW!! :dropmouth You can come to this conclusion just by seeing someone carrying spare air? :god: How do you do that? Please please please teach me. Is there a book I can read or meditation or just plain silly hitting my head with a hammer over and over and over..... :bonk:

I like this board...... always learn something new! :wave-smil

 

[DennisS]

"Halcyon's" harnesses are not Halcyon's at all. It's 15 feet or so of weight belt webbing and standard keepers and D-rings. QUOTE]

what do all the Hs stand for?

http://www.halcyon.net/

 

[jhelmuth]

I am really curious, and eager to learn.... I could not come to a conclusion that there is a particular "TYPE" of person that carry Spare Air. BUt You know for sure the type of person who's likely to carry a Spare Air is going to be relatively inexperienced, and with a relatively high SAC rate, and it's safe for you to say that in an emergency their SAC could easily exceed 1 CF per minute? Really? Incredible!! WOW!! :dropmouth You can come to this conclusion just by seeing someone carrying spare air? :god: How do you do that? Please please please teach me. Is there a book I can read or meditation or just plain silly hitting my head with a hammer over and over and over..... :bonk:

I like this board...... always learn something new! :wave-smil

I'm going to agree with Bob on this one (not always though). You should keep in mind that he is making a generalization, and he is correct in assuming ~ 1 cf/min in an emergency. In an OOA situation, you can't count on a "clean" shot to the surface (although it would likely be in most circumstances). A pecimistic point of view, and good advanced thinking and preperation, will always be more likely to keep you from death. If a better SAC rate than expected happens, excellent! What you can infer from his post is that inexperience (or really just the lack of forethought) is why the "spare air" sells as well as it does. I would call it a marginably safe option to OOA at no more than 50 fsw (and better than nothing) - which is where most OW divers are at. If that is your "floor", then OK - but I would seriously consider a 13 cf pony a better choice, as it would give a better margin for workload and/or additional depth. Yes, it's more expensive - but is that why one would choose the spare air over a legit pony (not wise IMO)?

Assume a 1 cf/min SAC and calculate the floor for a 13 cf
pony using a normal assent rate and safe stop at 15-20 fsw...
13 cf / 1 cf/min = 13 min - 3 min safety = 10 min * 30 ft / min = 300' floor. Using a pesimistic view of having 2x the requirements for a greater margin of safety, that would make the floor 150'. (anyway, that's my thinking)

I'd advocate proper buddy practice myself, but if you're going to have a second source, why cheap-out?

 

[bwerb]

Assume a 1 cf/min SAC and calculate the floor for a 13 cf
pony using a normal assent rate and safe stop at 15-20 fsw...
13 cf / 1 cf/min = 13 min - 3 min safety = 10 min * 30 ft / min = 300' floor. Using a pesimistic view of having 2x the requirements for a greater margin of safety, that would make the floor 150'. (anyway, that's my thinking)

And the original question has faded into oblivion...

Just wanted to point out one little tiny problem with your calculation...you forgot to account for the fact that for every ATM, your actual gas consumption increases. Assuming your 1CFM SAC; 2CFM @ 33 feet, 3CFM at 66 feet and lo and behold...6CFM at 99 feet...hmm...don't think I'd try an ascent from 300' on a 13...I'd die...

 

[jonnythan]

And the original question has faded into oblivion...

Just wanted to point out one little tiny problem with your calculation...you forgot to account for the fact that for every ATM, your actual gas consumption increases. Assuming your 1CFM SAC; 2CFM @ 33 feet, 3CFM at 66 feet and lo and behold...6CFM at 99 feet...hmm...don't think I'd try an ascent from 300' on a 13...I'd die...

From 300' to 200', at an SAC of 1 and a 30 fpm ascent, you'll use 28.6 cubic feet.

That's from 300' to 200' alone.

The total ascent, excluding any deco or safety stops (!) would use over 55 cubic feet.

Using the formula (depth / 66 + 1)(depth/30) to calculate how much gas you'll need for an ascent from a given depth, the max depth you could ascend from with a 13 cf tank is 130 feet. This is, of course, excluding any safety stops or emergencies or any time at all at depth. Obviously quite different from 300.

If you assume you'll spend 30 seconds at depth figuring things out and preparing for the ascent, this gives us the formula (depth/33 + 1)*.5 + (depth / 66 + 1)(depth/30) you get a max depth of 116 feet.

Now if you tack on a 3 minute safety stop at 15 feet, you get (depth/33 + 1)*.5 + (depth / 66 + 1)(depth/30) + 15/33*3 for a max depth of 108 feet.

 

[jonnythan]

For comparison, a 3 cf Spare Air will get you up from 50 feet at an SAC of 1 and ascent rate of 30 fpm, or 80 feet at an ascent rate of 60 fpm. Again, assuming you begin your ascent immediately.

It's 50 feet with a 60 fpm ascent rate if you spend 30 seconds at depth, and 30 feet if you plan on doing a safety stop.

 

[The Chairman]

Too funny... usually a thread about a certain configuration or technique will degenerate into a DIR/Anti-DIR debate. Now we have jus tthe opposite. This board rocks!

 

[pipedope]

I have to agree with PIPEDOPE.

That is a heck-of-a name you gave yourself. I'm guessing you are a steamfitter?

Working in stormwater drain pipes, retention ponds and other interesting places in central FL until my body forced me to retire.

Typical working dive (the most common type);
1. Get to job site.
2. Check the layout of the system and what needs to be done.
3. Check for hazards. In FL you have to be ready for aligators but they are rarely a problem.
4. Setup dive station and gear up.
5. Enter the water/soup and find the pipe. All by feel as vis is to the inside of your mask.
6. Evaluate the pipe for condition and amount of mud/sand/other blockage.
7. If needed, surface to get shovel, dredge or what ever is needed to clear the pipe.
8. Clean the pipe as needed.
9. Inspect the pipe to make sure that there is a good surface for the plug to seal and nothing to damage or puncture the plug.
10. Surface and get the plug.
11. Move the plug into place. This may be easy or hard depending on the location and size. Some of the plugs weigh several hundred pounds.
12. Surface and pump air into the plug. A motor driven air compressor is used and the tender usually does this job but the diver must be out of the water for safety. You don't want to be in the way if a plug bursts.
13. Depending on size and position, stop filling the plug and recheck the positioning.
14. When plug is at pressure (10 or 25 psi depending on the plug and job) go in and inspect to make sure plug is set properly and is not leaking.
15. Remove or otherwise secure hoses and ropes on the plug.
16. Surface.
17. Gear down, load equipment, go to next location or home.
18. Wash and dry gear as soon as possible.

Any ordinary DOPE might do this once. It takes a real PIPEDOPE to do it day after day.

Then there are fun jobs like a pipeline inspection under 18" of mud under Tampa Bay.

 

[pasley]

I have read a little about the DIR philosophy and agree with parts of it and disagree with other parts. In general it is simply not my cup of tea. I do not believe one size fits all.

I agree that the fancier the item, the more failure points it has. However in some cases, that fancy doodad does offer some advantages.

I also do not want anything wrapped around my neck, ever! I can see that having the second bungeed under my chin, could be a good thing, and I also agree that a panicked diver might steal my primary.

DIR is built around cave and wreck diving with their need for long hoses. I do have any desire to get into any confined space diving and so for me, this long hose is just an entanglement hazard waiting to happen.

I am also suspect of any system that gives the appearance, as IMHO DIR does of being built around a mfg product line. Kind of makes me wonder if it is not more about selling a specific brand than about diving. I prefer to pick and choose the best of any company’s product line for the type of diving I do, given the limitations of the old pocket book of course.

I currently dive a jacket style BC with integrated weights. My next BC will most likely be a back inflate model with integrated weights. I like integrated weights. With a 30 inch waist I like not having to worry about my weight belt slipping down past my hips. I will always dive integrated weights as that is the right choice for me.

I have dove with several DIR divers. Some were good, others were overweighed accidents waiting to happen.

Bottom line, there are more than one way to do things. What works well for you and your type of diving, may not be the best solution for me. So for me, I will use some of the DIR ideas and reject others.