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Bart
03-11-2008, 21:44
Im looking to buy a Spare Air and was wondering how reliable they are,and if anyone has anything negetive to say about them.
Also I was wondering, where is a handy place to mount them?

Thanks
Bart

texdiveguy
03-11-2008, 22:10
Im looking to buy a Spare Air and was wondering how reliable they are,and if anyone has anything negetive to say about them.
Also I was wondering, where is a handy place to mount them?

Thanks
Bart

Bart... you might do a search on this topic here and over at Scuba Board....there are many threads about just this subject.

I can't say anything good about the Spare Air system.....so I will just leave it at that.

PS--- get a pony bottle set-up!! :)

navyhmc
03-11-2008, 23:11
IMO, the spare air is a good bail out for less than 60'. It is intended for something to get you to the surface-that's about it. 6 cubic feet of air is not a lot of air. At 60' and a SAC of .75 cfm, if the diver is at 60' for 30 seconds getting things set and then starts to ascend, he/she will use about 3 cubic feet to get to the surface-good to go, right? Add a safety stop because the OOA incident happened at the NDL and you're down to literally 30 seconds of air left to ascend the last 15' after a safety stop.

Add additional depth to the scenario and you may have trouble. drop the depth to 90' with the same 30 seconds to get set for ascent. You used 1.5 cubic feet for that 30 seconds, 25% of your volume. the ascent to 15' for a SS will take roughly 1.5 min (Though in real life it would be faster, but bear with me.) that will use up 3 cubic feet of the spare air. Now you do not have enough for a safety stop if needed.

The good news is you will make the surface, the bad news is that you are at greater risk of DCS. This is also not taking into account that one's normal SAC rate is out the window when you figure that you will be a little paniced and without any PSI in your tank, you can't inflate your BC for aid in ascent if needed so there's additional work load as well.

I think that a spar air is good for shallower depth, but anything below 60' a pony will be better-13 cu ft minimum, 19 cu ft is better.

YMMV but that's my thought.

From what I have noted, the spare air system is reliable enough in it's own right, but the available air is the issue.

ETA: I was thinking that the spare air was 6 cu ft, halve the figures above and you can see why below 60' I wouldn't recommend it. The only thing it would be good for is to give you some breaths during your emergency ascent.

Crimediver
03-12-2008, 07:06
Navyhmc nailed it. I have a spare air. I don't use it for diving. Get a pony if you need a bailout.

MSilvia
03-12-2008, 07:23
If you need to bail out of a crashed helicopter or overturned kayak, Spare Air is the ticket. For diving, it isn't really an adequate backup, and I don't have much good to say about them as an emergency device for divers. I'd recommend a 19 cubic foot (or greater) pony tank too.

DarinMartell
03-12-2008, 10:28
I bought the Spare Air before I was even certified because I wanted a redundant Air source since I knew most of my buddies would be strangers assigned to me and I wouldn't know their dive styles. For the record my instructor / owner of the LDS said the same as what others have already said. I used it twice in open water and a handfull of times in the pool. I never had any problems with it. However after reading the many threads here about Spare Air vs. Ponies I sold my Spare Air on E-Bay.

On sale Spare Air in around $200. By doing my research, between price matching, our 10% discount, and the gift cards I earned on Scuba Toys I was able to get a 30CF pony, and Mares Regulator set for the same price.

charlesml3
03-12-2008, 12:11
I thought Spare-Air was only three cubic feet?

At any rate, I have two pony tanks. A 6 foot for shallow dive locations and a 13 for the deeper ones. I really don't want anything bigger than that because it gets to be a pain on the airplane.

-Charles

No Misses
03-12-2008, 12:14
Spare Air or Pony?
The question that you need to ask yourself is, "What do I need/want this for"?
IMHO, If you are worried about having an OOA (Out Of Air) situation in less than 60 fsw. You can easily do a CESA (Controlled Emergency Swimming Ascent). If, on the other hand, you are planning on doing dives where entanglement, overhead environments, and/or depth might be an issue; a spare air does not give you a lot of time to resolve these situations.

There is some simple math that you can use to figure out what capacity is needed for emergencies.

Let's say that your SAC (Surface Air Consumption) is .6 cf/min (cubic feet per minute)
Your planned dive is 66 fsw (3 ATA) on a wreck where entanglement in monofilament fishing line might be an issue. How many minutes of "Spare Air" will you need to get free of the entanglement and surface?

SAC .6 cf = 1.8 cf at 66 fsw (Gas at depth of 3 ATA is more dense than at 1 ATA)

Small Spare Air is 1.7 cf
1.7/1.8= 0.9 minutes to get untangled and surface

Large Spare Air is 3 cf
3/1.8 = 1.7 minutes to get untangled and surface

13 cf pony bottle
13/1.8 = 7.2 minutes to get untangled and surface

19 cf pony bottle
19/1.8 = 10.5 minutes to get untangled and surface

How much time do you need/want?

Please note that I rounded off some of these numbers. Your Air Consumption will not stay at 1.8 cf/min. When you ascend to 33 fsw your consumption will be lowered to 1.2 cf/min. Also I used .6 SAC as a common reference. Your SAC may be higher or lower. Keep in mind that if you are stressed and strugling, your SAC will be higher than normal. I used 66 fsw for this example. You can put in any depth that you want. At 130 fsw your consumption will be ~5x SAC. SAC is calculated for the surface or 1 ATA - to calculate consumption at depth just multiply by your ATA.

I hope this helps with your decision.

MSilvia
03-12-2008, 12:39
I really don't want anything bigger than that because it gets to be a pain on the airplane.

Wow... if I lived in North Carolina, bringing my gear on a plane would be one of the last things I'd be worried about. Some of the best wreck diving in the world is right in your back yard!

No Misses
03-12-2008, 13:16
I am bored today. So, here is a graph showing minutes of air at different depths with different size cylinders. I still used .6 SAC for the calculations.

CompuDude
03-12-2008, 13:26
I am bored today. So, here is a graph showing minutes of air at different depths with different size cylinders. I still used .6 SAC for the calculations.

Nice job. :smiley20:

Might want to attach the .xls file instead of a PDF so people can experiment with it their own numbers more. Also, if you're still bored and looking for something to do, an interesting thing to add might be something showing how long it takes to ascend from that ATA level, with and/or without a safety stop.

No Misses
03-12-2008, 14:48
You asked for it. Here is the excel worksheet that you can input your own data (SAC, Pony cap, depth) into. Have Fun.

P.S. I feel the need to throw in a disclaimer here. This worksheet is for training purposes only. Please check the math for yourself before making life or death decisions.

Edit: I realized that I did not add a calculator for SAC Here is how to calculate SAC

CF Used = PSI used * (cap/wp) Note: capacity is in cubic feet and wp (working Pressure) is in PSI.
SAC = (time / CF used) / ((Average Depth/33)+1)

Here is a handy web link SAC Calculator (http://www.spearfishing.org/bruces_tips/java/sac.html)

navyhmc
03-12-2008, 16:24
Nice calculators! Thanks for posting No Misses.

Bart
03-12-2008, 21:30
Im moving on to ponys. High-O-Silver!

No Misses
03-12-2008, 22:09
Im moving on to ponys. High-O-Silver!

Good choice! I was trying to be as impartial as possible. It is amazing how persuasive empirical data can be. Now that you have decided to go with a pony, you just need to figure out what capacity and whether you will sling it or back mount it. There are advocates for every configuration. You will have to make the tough decisions for yourself.

Capacity; you want one big enough to get you out of trouble and back to the surface. The question is, how big is too big. Some people carry an AL80 as a stage/pony. Most of us can get by with a much smaller cylinder. A pony will do you no good if it is so big that you don’t dive with it. For my diving, I chose an AL19.

How to carry it; this is a really personal choice. If you sling it, it will be easy to deploy and you have the option of handing it off to another diver. The downside is that depending on your task loading, it may be in the way. I spearfish and lobster. Because of this I choose to back mount mine using the “Quick Draw II” bracket system. I mount it upside down with the hose and second stage bungeed to the pony. I dive with the valve turned off so that I know that a slow leak has not drained the pressure. When I want to deploy it, I just reach back and grab the second stage, pulling the hose free of the bungee. I then turn on the gas and viola, I am breathing again.

Good luck, with your decisions.
:smilie40:

navyhmc
03-12-2008, 22:31
I'm in favor of a 19 cu ft as a minimum for rec diving. It will get you to the surface with a safety stop and still ahve a little left over. Smalled and you will have volume issues as noted above and too much will be like hauling an extra bread truck through the water. There are many types of brackets that you can use to attach the tank to either your BC or tank. I have a stage strap on mine as well as a set of bands on the main tank to hold it-depends on what I'm doing and how I want to mount it.

I am also a fan of having the pony turned off to decrease the risk of an unnoticed leak. I will turn the pony on to check it before the diving as part of my safety check and then turn it off, leaving the system pressured to help keep water out of where it shouldn't be.

anvil
03-13-2008, 01:39
All good advice, I use a 13 attached to my tank. Motto I live by is
PREPARE FOR IT AND IT NEVER HAPPENS!!!! You always have a backup plan.

russp
03-13-2008, 08:49
I'm kind of new to diving but I've noticed the majority of recreational divers carry no secondary air tank. Compared to an emergency ascent with only the air in your lungs, I would think the dozen or so breathes from a SpareAir unit (depending on whether the 1.7 or 3 cu ft) would be a blessing. With the small size and easy mounting options, more divers may be willing to carry SpareAir. Sure bigger is better but a pony is a little harder to rig and carry depending on the size.

skdvr
03-13-2008, 10:45
I'm kind of new to diving but I've noticed the majority of recreational divers carry no secondary air tank. Compared to an emergency ascent with only the air in your lungs, I would think the dozen or so breathes from a SpareAir unit (depending on whether the 1.7 or 3 cu ft) would be a blessing. With the small size and easy mounting options, more divers may be willing to carry SpareAir. Sure bigger is better but a pony is a little harder to rig and carry depending on the size.


Yeah the pony does take some time to rig (about 30 min the first time I did it, and about 10 min the second). I have mine (al 40) slung on my left side and I hardly notice the thing is there. I had a friend of mine that thought that the 40 would get in the way a lot, but after he tried it he felt the same way that I do.

Spare Air is better than No Air but if someone is going to spend the money anyway I reccomend to get a pony and a reg.

Phil

skdvr
03-13-2008, 10:48
PREPARE FOR IT AND IT NEVER HAPPENS!!!!

Great advice. Just like if you are working on a project at home and you buy some extra supplies just incase you break something you will never use the extra, but I guarantee that if you do not buy the extra you will be making a another trip to the store...

Phil

CompuDude
03-14-2008, 15:44
You asked for it. Here is the excel worksheet that you can input your own data (SAC, Pony cap, depth) into. Have Fun.

P.S. I feel the need to throw in a disclaimer here. This worksheet is for training purposes only. Please check the math for yourself before making life or death decisions.

Edit: I realized that I did not add a calculator for SAC Here is how to calculate SAC

CF Used = PSI used * (cap/wp) Note: capacity is in cubic feet and wp (working Pressure) is in PSI.
SAC = (time / CF used) / ((Average Depth/33)+1)

Here is a handy web link SAC Calculator (http://www.spearfishing.org/bruces_tips/java/sac.html)

Very nice spreadsheet... one more small thing that it may be a good idea to add. (Since you're the official ST secretary now LOL)

An adjustable field for "time spent at depth dealing with issue before starting ascent". Most standard bock-bottom-style calculations assume 1 minute, but some people like to add a little extra time to pad their calculations (could take longer if you're dealing with entanglement, etc.. Even 30 seconds spent at 90' adds a very measurable amount of extra gas needed from the pony.

WD8CDH
03-17-2008, 07:14
The units are reliable, in fact, I am using a couple of them on a rebreather. One filled with Nitrox and the other filled with O2. 2 plus hours at 100 feet on 2 spare airs. :D

The reason why I used them on the rebreather was I got them cheap from a couple of diver that found them almost useless for emergency air due to their limited capacity.

By the way, you can put them on larger tanks. Fit one to a 19 to 40 and you have a nice pony.

russp
03-18-2008, 11:47
The units are reliable, in fact, I am using a couple of them on a rebreather. One filled with Nitrox and the other filled with O2. 2 plus hours at 100 feet on 2 spare airs. :D

The reason why I used them on the rebreather was I got them cheap from a couple of diver that found them almost useless for emergency air due to their limited capacity.

By the way, you can put them on larger tanks. Fit one to a 19 to 40 and you have a nice pony.

This brings up an interesting idea, are there all in 1 first and second stages that mount directly to an air tank to create a slightly larger version of SpareAir? A 6 or 9 CF tank is still pretty small so would be easy to mount and still not add a hose.

LiteHedded
03-18-2008, 11:59
I recommend a dive buddy instead :D

charlesml3
03-18-2008, 12:36
Wow... if I lived in North Carolina, bringing my gear on a plane would be one of the last things I'd be worried about. Some of the best wreck diving in the world is right in your back yard!

Agreed, but I don't dive off the coast of NC anymore. I used to. I just had too many trips cancelled at the last minute or diverted to a closer (lame) site due to weather. Then there were the very occasional days where we would have good visibility.

I can go down to Cozumel or Roatan and get great visibility every day and hardly ever worry about weather.

-Charles

ianr33
03-18-2008, 14:04
This brings up an interesting idea, are there all in 1 first and second stages that mount directly to an air tank to create a slightly larger version of SpareAir? A 6 or 9 CF tank is still pretty small so would be easy to mount and still not add a hose.

Yes such a thing exists although I have no idea why !

http://scubatoys.com/store/Scuba_Alt_Air.asp?PAGE=2

russp
03-18-2008, 17:15
This brings up an interesting idea, are there all in 1 first and second stages that mount directly to an air tank to create a slightly larger version of SpareAir? A 6 or 9 CF tank is still pretty small so would be easy to mount and still not add a hose.

Yes such a thing exists although I have no idea why !

http://scubatoys.com/store/Scuba_Alt_Air.asp?PAGE=2

Well, since everyone seems to agree the problem with SpareAir is that it is too small, the larger Odyssey system seems like the perfect comprimise between SpareAir and a full size pony system.

ianr33
03-18-2008, 21:56
What advantage do you see in the Odyssey compared to a regular pony?

russp
03-19-2008, 08:24
Since most recreational divers seem not to carry any alternate air tank, the ease of a small tank next to the standard 80cf seems like a better alternative than a larger tank slung under the arm with a seperate set of hoses if the diver wanted something that didn't change his dive style. This is why the SpareAir may have sold so well despite its limitations.

Sound Man
04-10-2008, 20:00
so if you get a pony tank or the odyysey, say a 13 or 19 cf tank what do you do for filling when you are out of town say jamaica or cozumel when the dive operator doesn't have a fill station?

CompuDude
04-10-2008, 20:15
so if you get a pony tank or the odyysey, say a 13 or 19 cf tank what do you do for filling when you are out of town say jamaica or cozumel when the dive operator doesn't have a fill station?

What dive operator doesn't have a fill station?

awap
04-10-2008, 20:41
so if you get a pony tank or the odyysey, say a 13 or 19 cf tank what do you do for filling when you are out of town say jamaica or cozumel when the dive operator doesn't have a fill station?

What dive operator doesn't have a fill station?

In Cozumel, many of the operations use a central fill station so it could take a day or more to get your pony filled. In some cases the op may have an equalizer hose or may be able to rent you a pony. It's one of those things you may have to address when you make your arrangements.

CompuDude
04-10-2008, 20:45
so if you get a pony tank or the odyysey, say a 13 or 19 cf tank what do you do for filling when you are out of town say jamaica or cozumel when the dive operator doesn't have a fill station?

What dive operator doesn't have a fill station?

In Cozumel, many of the operations use a central fill station so it could take a day or more to get your pony filled. In some cases the op may have an equalizer hose or may be able to rent you a pony. It's one of those things you may have to address when you make your arrangements.

Ah, I see what you're saying.

Solution = transfill whip.

cummings66
04-10-2008, 21:24
If it could take a day or more to get a pony filled, it'd take the same to fill a normal cylinder. If you drain the one you have to fill the pony you don't have the air to dive with, so the transfill might not work there.

Unless, you go to the beach and wait for returning divers and ask to borrow their air they won't be using. I've done that on dives for a buddy and got enough extra air to let him do one more dive.

CompuDude
04-10-2008, 23:55
If it could take a day or more to get a pony filled, it'd take the same to fill a normal cylinder. If you drain the one you have to fill the pony you don't have the air to dive with, so the transfill might not work there.

Unless, you go to the beach and wait for returning divers and ask to borrow their air they won't be using. I've done that on dives for a buddy and got enough extra air to let him do one more dive.

Just rent an extra tank to fill from, then. I'm not seeing any big issue here. The same issues apply with a spare air, it's just that you're stealing less air from the big tank.

diver-wife
05-29-2008, 14:46
:smilie40: just curious, has anyone heard a diver recommend spare air?

Rainer
05-29-2008, 15:43
Solution = transfill whip.

Depends on the size of the pony. For anything of decent capacity, trying to fill it with a transfill whip from an AL80 would be an exercise in futility.

MSilvia
05-29-2008, 15:58
:smilie40: just curious, has anyone heard a diver recommend spare air?
I recommended one once... to a kayaker.

Rainer
05-29-2008, 15:59
They're also great for helicopter pilots...