Don't know if this is the right forum but my question is about the increase in drag caused by using a pony bottle. I am a recreational diver and use a 30 cu. ft. pony bottle clipped to the front of my B.C.D. to add 37.5% to my air supply. On most of the Carribean Island diving I do they only have Aluminum 80 tanks available. Notwithstanding the usual comments I get about needing to learn to breath better, sip my air, relax more, skip breathe, breath through my nose etc... etc... etc... I was wondering if there was any truth to the divemaster's claim on my last trip. She said that I was probably adding so much drag by using the pony bottle that it negated the additional air from the pony bottle by increasing my air consumption. Anyone know if using a 30 cu. ft pony bottle on a leisurely paced recreational dive would increase air consumption by 38% or more?
Pony Bottle Drag?
- Thread starter searcher3
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Scott L
Contributor
38% doubtfull. 15-20%, probable. Having a pony or any peice of equipment underside/in your slipstream is the worst posiable place of attachment. Affixing to the AL 80 or slinging on a BP/wing rig is a much better way IMO. A lot of islands have tec operators for which you can rent steel cylinders even if you choose a more rec diving operator to dive with. If you are diving above 100ft I see little need for an additional gas source if you are utilizing your own properly serviced regulators...
XS Scuba Cylinder Accessories for Aluminum and Steel Scuba Cylinders
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searcher3
Are you actively using the 30 as a stage bottle on many dives?
If you are rigged so you are balanced and in trim I would not expect there to be any measurable consumption penalty. On the list of streamline offenses this is way down on the list past roto-tilling, arm flapping, fast swimming and bicycle kicking. If you're doing all the right things and are still a power breather then so be it. Bring your 30 and enjoy the dive.
Pete
Are you actively using the 30 as a stage bottle on many dives?
If you are rigged so you are balanced and in trim I would not expect there to be any measurable consumption penalty. On the list of streamline offenses this is way down on the list past roto-tilling, arm flapping, fast swimming and bicycle kicking. If you're doing all the right things and are still a power breather then so be it. Bring your 30 and enjoy the dive.
Pete
Scared Silly
Contributor
When you say clipped to the front of you BCD how so? Most tech divers clip a bottle to their shoulder strap and hip which makes it very low profile. I do not notice a 30/40 cuft bottle when doing so. Last time I did I was even shooting photos and did not notice even then.
If you really wanted to know how it affected your consumption go do a dive without it and then do the dive again with it. I bet your gas consumption will not change very much.
If you really wanted to know how it affected your consumption go do a dive without it and then do the dive again with it. I bet your gas consumption will not change very much.
Blackwood
Contributor
I made a rig for it as shown on this website:
http://dir-diver.com/en/equipment/stagebottle_rigging.html
Everything came from Home Depot.
I clip both clips to the rings on the end of my shoulder straps on my BCD. I have a separate regulator and gauge for it and usually breath 2000 PSI out of it near the beginning of the dive and leave 1000 PSI for emergencies or anyone who needs it (= to 375 PSI in my Aluminum 80 main tank). I cradle it under me pointed nose forward to be as streamlined as possible and I am in good trim. I have a little over 200 dives and got tired of my dives being cut short
Thanks to all for the advice.
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Heck, bring a stage-bottle kit, an extra reg and sling an 80. You'll be a really popular guy if there's a nearby OOA.
As was mentioned, if you're going nice and slow, it doesn't much matter what your drag is. In fact, if you want to really improve your consumption, get rid of the divemaster.
I'd be happy hanging out for the whole hour just watching a single area. For some reason, DMs want to chase you around.
Terry
During testing at the Tahoe Benchmark 2009, we tested several Technical configurations. Specifically, we tested a stage as:
The results were a surprise - the half full configuration, which tucks nicely into the armpit, was found to generate significantly more drag. This goes against common knowledge.
The full configuration, which "hangs", was found to have 12% less drag than the "float in the armpit" configuration.
Also, the Technical configuration (seen above) generated 26% to 30% more drag than the Tahoe Standard configuration of drysuit, BP/W, & single.
Hope this helps. Given the numbers we generated during testing, I can't see your pony creating more than 22% more drag.
All the best, James
- Luxfer Al 80, 3000 psi of 32%
- Luxfer Al 80, 1/2 full of 32%
The results were a surprise - the half full configuration, which tucks nicely into the armpit, was found to generate significantly more drag. This goes against common knowledge.
The full configuration, which "hangs", was found to have 12% less drag than the "float in the armpit" configuration.
Also, the Technical configuration (seen above) generated 26% to 30% more drag than the Tahoe Standard configuration of drysuit, BP/W, & single.
Hope this helps. Given the numbers we generated during testing, I can't see your pony creating more than 22% more drag.
All the best, James
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