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View Full Version : Weight to add/subtract for Pony tanks?



thor
06-27-2008, 09:45
How much more weight, if any, do I need to add/subtract if I am carrying a pony tank?

awap
06-27-2008, 09:51
With my 13 cf pony, I could drop 2 lb. But, because it can be handed off in an emergency, I don't change my weighting.

cummings66
06-27-2008, 12:36
With my 40cf cylinder I don't change anything either. If you dropped weight, breathed your back gas down, breathed the pony down you'd be lighter than normal.

MSilvia
06-27-2008, 12:38
I don't change anything with an aluminium pony or stage, and I don't use steel because I'd have to drop weight if I did.

Sansho
06-27-2008, 12:57
You mighty want to shift 1 or 2 lbs, however, so whatever side the pony is on, your other side will offset it, leaving you more evenly balanced.

dive10killer
06-27-2008, 19:40
I use the same weight as well.

Grin
06-28-2008, 07:34
When you put a 13 or 19 on you could take off a couple lbs. But like stated by others, if you plan on handing it off, someday, you will then be underweighted around your safety stop depth.
I use my 13 pony every dive no matter what. Even on 20 ft dives. And virtually every dive is solo for me. So I am weighted including my pony. And my pony is not a hand off type mounting. But it could be.
I saw a situation where a guy on my boat had a 19 pony. He used it up, for extra bottom time, on his second dive. So he didn't rig it with him on his third dive, as it seemed uneccessary to carry a empty pony. He forgot that this changed his weighting, and didn't add a couple lbs to compensate. At the end of his dive I saw him pop up, kicking somewhat frantic, then go back down. I was in the boat thinking what the heck is going on there. I figured he dropped something and was going back down to get it or something? The real problem was, he was struggling to do his safety stop with too little weight, due to the pony not being part of his settup anymore. He popped right up to the surface uncontrolled and had to fin straight down to try to go back down and do a somewhat decent accent. I'm sure his accent to the safety stop was no beutiful logfile either.
I have to admit, I never thought about it until it happened to him.
And he did have some issues once in the boat. The issues were mild DCS symptoms IMO. He stated he thought the symptoms were due to something else (CO2 headache I think he said?). He puked, had a headache and we were done for the day.
Even if he was right about it not being DCS of some sort. A uncontrolled accent on your last dive of the day, and working extra hard, while being as NO2 loaded to the max, as you ever can be, is a recipe for DCS. And something as simple as this pony weight discussuion can get you in a not so great situation.

Rainer
06-28-2008, 08:09
You mighty want to shift 1 or 2 lbs, however, so whatever side the pony is on, your other side will offset it, leaving you more evenly balanced.

Yeah, a few pounds difference per side can really mess up your diving...

:smilie39:

Eddym67
06-28-2008, 08:54
No need to add or remove weight.

cummings66
06-28-2008, 14:47
To be honest I've never noticed the side to side difference, I'm sure it's real but I don't seem to be bothered by it and somehow compensate for it. When I have my can light on it's a non issue anyhow.

texdiveguy
06-28-2008, 15:10
I don't subtract any wt. either....and no issues with tilting as some might assume that have never dove slung cylinders.

Rockhound76
06-30-2008, 08:44
.......I saw a situation where a guy on my boat had a 19 pony. He used it up, for extra bottom time, on his second dive. So he didn't rig it with him on his third dive, as it seemed uneccessary to carry a empty pony. He forgot that this changed his weighting, and didn't add a couple lbs to compensate. At the end of his dive I saw him pop up, kicking somewhat frantic, then go back down. I was in the boat thinking what the heck is going on there. I figured he dropped something and was going back down to get it or something? The real problem was, he was struggling to do his safety stop with too little weight..

What he did wasn't very bright, for a number of reasons.

1) NEVER use your pony extend bottom time. It is for emergency use only.
2) He had signs of DCS and he had "extended" bottom time with supplemental air, so he was likely pushing things. He should have been put on oxygen and checked out by qualified medical personnel ASAP. Better to be safe than sorry.

Grin
07-01-2008, 09:18
You are not telling me anything I don't know.

It was what I call a case of denial. I claimed DCS. He had his own DAN oxygen kit in the boat. He claimed CNS or whatever? I agree even if it is CNS, why not breath some O2 for good measures.

I drank my end of the diving day celebration beer on the way in. He had a few advils.

Like it, or not, this is very common. Denial is huge in the diving / DSC department.

I have been bent once. I carry a carefully thought out 100% oxygen settup now, on my boat. And I changed alot about my diving style. I have not had a issue since my one minor hit. I actually learned alot, and benefitted from my incident. I was not out of Padi stats when I got bent either. I atest my case to accending at 20-30fpm, like PADI recomends. I am thrilled at what I learned and enjoy diving more than ever. But you can only tell people what you think. If they have to learn the hard way, then so be it.
I drag my O2 with me every trip and havn't used it once.
My pony has never been used for extended bottom time. I have used it maybe twice to keep my accent within my personal accent guidlines(very slow/ 10fpm or less). Meaning I had to switch to my pony on my safety stop, a few times.
I see many people use their ponies for extended bottom time. That's their decision to make for themselves. There is no rule anywhere stating it is illegal. If they choose to do this, that's their decision and, I see no reason to try to claim it's completely wrong. I can't remember ever doing that myself. I actually have to remember to use my pony, to exerise it. That's my biggest problem. I always carry the thing, but I never use the thing and need to exercise it more often.
I also see many not take their pony down. They bring it, but it lays on the deck. Not mine. The pony debate is a pretty involved one. There are so many variables for different applications and expectations.
I'm not preaching. But if you ask me why I do what I do, I will tell you what I think. I don't expect compliance with my regiment though.

BouzoukiJoe A.K.A. wrecker130 AKA Chuck Norris AKA joeforbroke (banned)
07-01-2008, 09:50
Situation: Going to be diving the Spar for the last dive of the day. Depth 110 to the sand, deck at ~90 ft. Lot's of sand tiger sharks, so I'm really looking forward to this dive. Check my pressure - only 1900 psi. Damn! My tank valve had been slightly open so the tank leaked down during the day. I'm diving a 120cf tank so I have about 2/3 of an AL80. The Spar is small, intact and easy to navigate. We have some current, but not too bad. I decide that under the circumstances I'm going to make the dive and incorporate some of the the gas from my 40 cf pony into the dive plan. We are tied into the stern and for whatver reason the sharks like to school at the bow. Plan becomes this: I will touch the sand and then spend most of my time around 80 ft at the bow of the wreck. I wil not do any of the swim-throughs. At 1100 PSI I will mosey on back to within sight of the anchor. When I am within sight of the anchor I will switch over to my pony and explore the stern for a while, then switch back to the main tank for the ascent.

I know I'm never supposed to figure my pony in my dive plan, but in this case I thought it was a reasonable plan. I got a 30 minute dive. I could have stayed longer but I wanted to make a slow ascent and get back on the boat with a decent amount of gas in both tanks.

ianr33
07-01-2008, 10:44
It was what I call a case of denial. I claimed DCS. He had his own DAN oxygen kit in the boat. He claimed CNS or whatever? I agree even if it is CNS, why not breath some O2 for good measures.


What do you mean by "CNS" ?

crpntr133
07-01-2008, 10:53
It was what I call a case of denial. I claimed DCS. He had his own DAN oxygen kit in the boat. He claimed CNS or whatever? I agree even if it is CNS, why not breath some O2 for good measures.


What do you mean by "CNS" ?

Central nervous system? If I am thinking right he doesn't want more O2 with CNS.

wmspdi
07-01-2008, 11:03
I don't change my weights when I add a pony, or carry extra lights. If I dropped a light, or handed off the tank I might be underweighted. I do clip the extra lights off on the opposite side of the pony for balance.

LRDWILDER
07-01-2008, 11:21
I don't change my weight...I keep it the same, that way I know exactly what would happen if I handed off my pony or lost it ect ect.

in_cavediver
07-01-2008, 11:28
It was what I call a case of denial. I claimed DCS. He had his own DAN oxygen kit in the boat. He claimed CNS or whatever? I agree even if it is CNS, why not breath some O2 for good measures.


What do you mean by "CNS" ?

Central nervous system? If I am thinking right he doesn't want more O2 with CNS.

On the surface, O2 is ALWAYS GOOD. What you describe is an CNS Oxtox issue where you might sieze underwater due to O2 toxicity. It doesn't hold on the surface. When in doubt, use O2. I will not hurt and it very well may help. Heck, if even mildy questioning something - goto O2.

ianr33
07-01-2008, 12:14
CNS oxygen toxicity is not really an issue with recreational diving. It is almost impossible to exceed the O2 limits provided a PO2 of 1.4 is not exceeded.

Even if you were to seize while breathing O2 on a boat its not the end of the world. Certainly MUCH better than getting bent badly. Also the chance of seizing at a PO2 of 1.0 (and probably less than that in reality) is pretty much zero.

cummings66
07-01-2008, 12:19
I was taught that on the surface to use O2. It won't hurt there and may perhaps help.