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Brandon Belew
05-11-2008, 23:03
So here in the near future - i'm going to be buying a pony bottle.

Will someone take a look at my choices and make sure i'm not wasting money :D ?

Mares R2 Rebel Regulator, Regulators, Mares, Mares R2 Rebel Regulator (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=MaresR2Rebel)
40 Cubic Foot Pony Bottle, Scuba Tanks, Catalina, 40 Cubic Foot Pony Bottle (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=AL40)
HD Quick Draw Bracket for 30 or 40 cu. ft. Tanks, Scuba Tanks, Ultimate Products, HD Quick Draw Bracket for 30 or 40 cu. ft. Tanks (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=QuickDraw3040)
Pony Gauge With Hose, Hoses, H2Odyssey, Pony Gauge With Hose (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=H2odyssey_Pony_Gauge_With_Ho se)

What do you think? :smiley20:

Hope my bcd has enough lift for a 40cf tank + me + my al80 + lead. :)

Grin
05-12-2008, 08:22
I kind if wonder if you really need a 40 cf pony bottle. That's pretty big, and alot of gas for a normal no-deco diving pony. What type of depths and type of diving are you planning on?
As far as the equipment you picked: It should be fine. A no frills regulator is preferred, and the Quick draw brackett is real nice. I have a button gauge for my little pony bottle (13Cf). I can't see it while using it under water, and have contemplated getting something like what you chose there. My theory is the 13 is plenty enough air to do what I need (an emergency slow accent). My worst case, I run out of gas on my safety stop. I am very able to swim up from 20ft on a single breath, and can handle that no problem. My main goal of the pony is to not to get bent if my primary settup dies at depth.
A 40 strapped to a AL 80 seems a little awkward, but there could be reason for it. If you can get away with a 19, the difference would be much nicer and easier to wear.

Brandon Belew
05-12-2008, 08:29
I kind if wonder if you really need a 40 cf pony bottle. That's pretty big, and alot of gas for a normal no-deco diving pony. What type of depths and type of diving are you planning on?
As far as the equipment you picked: It should be fine. A no frills regulator is preferred, and the Quick draw brackett is real nice. I have a button gauge for my little pony bottle (13Cf). I can't see it while using it under water, and have contemplated getting something like what you chose there. My theory is the 13 is plenty enough air to do what I need (an emergency slow accent). My worst case, I run out of gas on my safety stop. I am very able to swim up from 20ft on a single breath, and can handle that no problem. My main goal of the pony is to not to get bent if my primary settup dies at depth.
A 40 strapped to a AL 80 seems a little awkward, but there could be reason for it. If you can get away with a 19, the difference would be much nicer and easier to wear.

Most of my dives are pretty deep, 100ft or deeper. Main reason I chose the 40 is because of the price - it's not much different then the 19cf in price - guess I just wanted more bang for my buck.

No Misses
05-12-2008, 09:13
I agree with Grin. A 40 is a large pony. In my experience, a large pony that is too big to carry on every dive does you no good if you leave it on the boat. You are better off with one that you will carry on every dive.

I have a AL19 w/Quick draw II bracket. I feel the difference in trim when it is there. I offset this by placing a 2lb weight opposite the pony.

Sizing pony bottle needs: Minutes of gas = Capacity/(SAC * ATA)

For an AL40, assuming your SAC is around .6 cf/min and you are diving to 99 fsw (4 ATA), you would have 12.5 minutes of breathing gas at that depth. An ascent from 99 fsw should take you a minimum of 3 minutes without a safety stop or 6 minutes with one.
12.5 minutes at depth = 30 cf / (.6 sac * 4 ATA)

I have attached a copy of a spreadsheet to do your calculations. There are a bunch of similar calculators on the web. Check out Rock Bottom Gas Management Rock Bottom and Gas Management for Recreational Divers (http://www.scriptkiddie.org/diving/rockbottom.html)

Good luck.

DOWNDEEP73
05-12-2008, 09:14
I kind if wonder if you really need a 40 cf pony bottle. That's pretty big, and alot of gas for a normal no-deco diving pony. What type of depths and type of diving are you planning on?
As far as the equipment you picked: It should be fine. A no frills regulator is preferred, and the Quick draw brackett is real nice. I have a button gauge for my little pony bottle (13Cf). I can't see it while using it under water, and have contemplated getting something like what you chose there. My theory is the 13 is plenty enough air to do what I need (an emergency slow accent). My worst case, I run out of gas on my safety stop. I am very able to swim up from 20ft on a single breath, and can handle that no problem. My main goal of the pony is to not to get bent if my primary settup dies at depth.
A 40 strapped to a AL 80 seems a little awkward, but there could be reason for it. If you can get away with a 19, the difference would be much nicer and easier to wear.

Most of my dives are pretty deep, 100ft or deeper. Main reason I chose the 40 is because of the price - it's not much different then the 19cf in price - guess I just wanted more bang for my buck.
That should work! When doing deep dives it is always good to have plenty of air. I myself will be purchasing a 19cf later on toward summer. Most of my dives are 40'-60' chasing flathead catfish in old river channels.

BSea
05-12-2008, 09:38
I agree with the Grin & No Misses. A 19 should do even with the deeper dives. And a 40 is really more of a deco bottle than a bail out bottle. Plus, that 40 is going to be as long as the 80. If you go with a 19 or larger, I'd sling it vrs using a quick draw bracket. After a few dives, you hardly know it's there. Plus it makes it easier to change tanks since it isn't attached.

EDIT: A potential problem with the quick draw bracket is using it on charter boats. It can get in the way of tank holders. However, if you don't intend to travel with it, then it shouldn't matter. I do take my pony on driving trips, but not on plane trips.

Brandon Belew
05-12-2008, 11:23
Thanks for all the tips - one more thing.

I also plan on doing quite a bit of cavern, thats another reason why I was looking at such a big bottle. So I have plenty of air, even if I have to come out then make an ascent.

mike_s
05-12-2008, 12:30
So here in the near future - i'm going to be buying a pony bottle.



go ahead and spend a few extra bucks and get a convertible thermo pro valve (3442psi). It might cost $15 to $25 bucks more, but if you ever go DIN, you won't have to change the valve. Or if you ever sell it, it will sell much better.

ST or any shop can change the valve out for you when you buy it as an 'upgrade'. It might not be on their webpage as 'point and click', but if you call them they can do it.


or... as "option 2", since you've got to buy a new tank and a new pony reg, consider the h20dyssey or Zeagle valve that is integrated with the first stage. It won't have the huge yoke on it that could snag hanging cut fishing lines.





I have attached a copy of a spreadsheet to do your calculations. .


Nice little chart you've got there...

I might try to take that add add a variable for ascent rate and do a total time, including a 3min stop at 20ft, of a bottle as you ascend to the surface.




Thanks for all the tips - one more thing.

I also plan on doing quite a bit of cavern, thats another reason why I was looking at such a big bottle. So I have plenty of air, even if I have to come out then make an ascent.

in cavern you dive "rule of thirds". In theory if you have an AL80 (77cf) then would never need more than 25cf for your exit on a pony for that tank (AL80). a 40cf is adequate for that, but a 30cf you'll find might be easy to use in a cavern. ( a 30cf I think is about 3" shorter).

MSilvia
05-12-2008, 13:58
I personally like a slung AL40, and don't find it interferes with my trim much at all. Tank mounting may give different results, but I don't ever do that.

ChrisA
05-12-2008, 14:16
Main reason I chose the 40 is because of the price - it's not much different then the 19cf in price - guess I just wanted more bang for my buck.If price is it than why not simply use a second AL80? and then get some bands and a manifold. Doubles is better then a pony. Seriously if you are going to mount a 40 cu ft tank to your main tank you may as well just mount an 80, that 40 is huge.

I dove with a very experianced diver who used "twins". twins are not like doubles. With doubles you have a manifold and an isolation valve but twins are just two AL80 tanks each with a standard valve and regulator. each reg has only one 2nd stage. What you do is turn both on and breath from one reg for five minutes then switch regs and keep the tanks even. You get the same safty as with your huge pony but with twins you get to breath the gas. The point about twins i that is is very non-complex and there are no "valve drils" to learn. In the worst case of a blown tank o-ring there is nothing to do as the tanks are always isolated.

But really if you are only going to just below 100 feet a 19cu ft pony will get you to the surface and you can put it on a sling. It will be much more managable. If biger then that I'd just used two full size tanks.

MSilvia
05-12-2008, 16:34
The point about twins i that is is very non-complex and there are no "valve drils" to learn.
The equipment may be very non-complex, but the management of that gear is not.

Since there isn't a manifold, using twins means you'll be breathing out of only one of the cylinders at a time. As a result, the more you breathe, the more your trim goes out of equilibrium. You tend to roll toward the side with the tank that's heavier due to the greater quantity of gas it contains.

In order to maintain proper balance, you need to switch regulators periodically so that neither cylinder is significantly lighter than the other. This can add a bit of task loading, and naturally requires you to stow the reg you were using previously, which can potentially create challenges related to gas sharing. That aside, IMHO you still ought to be able to shut down your valves if there's a problem, and switching regs like this can also make it unnecessarily challenging to remember which tank it is that you're actually breathing from at any given time.

Suffice it to say it's not quite as straightforward as using a slung AL40 as a backup, unless you're content to finish your dives sideways.

Brandon Belew
05-12-2008, 16:44
I thought about just running doubles, but I don't think my BC ( Scuba Pro Knighthawk ) will really support double 80's. I don't need a manifold, would have no problem switching between regs - and when it came time to get a manifold they aren't too expensive.

I think the knighthawk only has like 46lb of lift, and it doesn't appear that I can change out the bladder.

plot
05-12-2008, 16:48
46lbs should be enough for 2 al80's.

MSilvia
05-12-2008, 17:03
No doubt. I dive Asahi HP100s with a 40# wing, and they're like 26 lbs negative when full.

beperkins
10-17-2008, 08:01
Thanks for the spreadsheet no misses, isn't it funny, when you are done with your classes that's when the learning really begins.