Octo/inflator in cold water?

[formula1mb@aol.com]

That's something I've thought about too, so far my uwatec air z though has been reliable and don't carry a regular spg. One thing you can do is bring along an spg for a trip in your save-a-dive kit, than if you do have problems you'll miss that one dive but can install the spg for the remainder of the trip. At least this way you're not carrying an unnecessary spg for the 99% of the time when you don't need it.

 

[charlesml3]

It reduces drag and it's one less failure point. However, the Air2 reg is going to produce more drag than a standard power inflator and arguably more than a power inflator + separate octopus if the octo is worn necklaced under the diver's chin. So dragwise, it's probably a wash.

Ha! ha! I love it when divers start talking about how they're "reducing drag." Please. A SCUBA diver is about as hydrodynamic as a cinder block. I wish this wasn't such an obscure myth. Maybe then Mythbusters would actually do some objective measurements.

Seriously? "...the AIR2 is going to produce more drag than a standard power inflator..." How did you come to this conclusion?

-Charles

 

[elmer fudd]

Ha! ha! I love it when divers start talking about how they're "reducing drag." Please. A SCUBA diver is about as hydrodynamic as a cinder block. I wish this wasn't such an obscure myth. Maybe then Mythbusters would actually do some objective measurements.

Seriously? "...the AIR2 is going to produce more drag than a standard power inflator..." How did you come to this conclusion?

-Charles

It's bigger, it's outside of your slipstream and it's generally mounted on a longer hose so that you can still breathe off of it when you turn your head. That certainly adds up to more drag than a power inflator by itself. My guess is that it also adds up to more drag than a power inflator and an octo tucked under your chin where drag is minimized, although certainly not more drag than an octo clipped to your chest or just left dangling.

As far as your implied question of why bother worrying about drag because our profile already sucks hind quarters; following that logic, why bother maintaining proper trim at all? Our hydrodynamics suck anyway, so why not just plow through the water at a 45 degree angle? Obviously, by minimizing drag we increase our efficiency and lower our SAC rates.

 

[charlesml3]

It's bigger, it's outside of your slipstream and it's generally mounted on a longer hose so that you can still breathe off of it when you turn your head. That certainly adds up to more drag than a power inflator by itself. My guess is that it also adds up to more drag than a power inflator and an octo tucked under your chin where drag is minimized, although certainly not more drag than an octo clipped to your chest or just left dangling.

You really cannot be serious about this. Tell you what, you come up with some objective way to measure this and demonstrate the "increased drag" and I'll buy you a brand new Zeagle Flathead or other similarly priced reg of your choice.

Drag produced by "plowing through at 45%" <> Drag produced by octo-inflator. It's not even close. My money says it isn't even measurable. How do you know that an octo under your chin is where "drag is minimized?" It's possible that it's just in the right location to setup turbulence and make it worse instead of better.

This stupid argument comes up out here all the time from the Octo/Inflator haters. They hate them, but don't even know why they do. Each discussion eventually ends up with "Well, CAVE DIVERS don't use them...." Yea, yea, blah, blah, blah. So the only compelling argument against them comes from a tiny fraction of divers worldwide in conditions that the vast majority of divers will never see. OK, I'll give you that. Yes, it takes different equipment to climb K2 as opposed to Pike's Peak.

Our hydrodynamics suck anyway,

Yep, they sure do. And if you're kicking around so fast that it's affecting your SAC rate then you really deserve the short bottom time. Slow down. The slower you go, the more you see.

-Charles

 

[elmer fudd]

Yep, they sure do. And if you're kicking around so fast that it's affecting your SAC rate then you really deserve the short bottom time. Slow down. The slower you go, the more you see.

If you slow down in current as often as not you get swept away, and I frequently dive in current. You can't fight strong currents for long, but currents of 1 knot or less are manageable. So I aim to minimize my drag in any practical manner. I also sometimes hunt and when doing so I might have a need to cover a lot of area or to chase down a fish or a crab.

If you read my original post again, you'll notice that I only stated categorically that an inline octo would produce more drag than an inflator by itself. This is self-evident. An inflator is much smaller, hence less drag. I then went on to say that an inflator + octo could "arguably" produce less drag than an inline octo due when worn necklaced and I'll stand by that statement. I think it's a very arguable point. Does it produce less drag? I don't think anyone really knows, but the reason I brought it up was to make the point that just because an inline octo eliminated a hose didn't necessarily mean it would reduce drag. Eliminating the hose however, is also a self-evident reduction of drag. If you'll notice, I ended that post by saying, "dragwise, it's probably a wash." And what I meant by that is that I think an inline octo probably creates as much drag as it eliminates.

FWIW, I have done many dives with a SeaQuest inline octo. I didn't stop using it because of drag, but because I found it somewhat clumsy compared to an inflator on a short hose. It developed a leak one day, so I switched back to my inflator and after using them back to back I never put it back on.

If you like your inline octo, that's fine with me. I don't hate them or consider them inherently unsafe and I recognize that they also eliminate a failure point. I just view them as a compromise resulting in a mediocre inflator and a mediocre octopus.

 

[charlesml3]

Fair enough, Elmer. You don't like them and that's fine.

But what is a "mediocre inflator?" You push one button, air goes in. Push another, air goes out. I fail to see how one is any better than another.

I agree that my Octo-Z doesn't breathe as well as my primary. And I don't care. To quote another diver here : "I'd suck a fart out of a donkey's ass if it would get me to the surface alive."

-Charles

 

[charlesml3]

inline octo would produce more drag than an inflator by itself. This is self-evident.

No, I don't think it is. When it comes to fluid dynamics you really can just say that. Thousands of pickup truck owners were all leaving their tailgate down because "clearly letting the air flow through would reduce drag..." They thought it was self-evident. They were all wrong.

 

[elmer fudd]

Fair enough, Elmer. You don't like them and that's fine.

But what is a "mediocre inflator?" You push one button, air goes in. Push another, air goes out. I fail to see how one is any better than another.

I agree that my Octo-Z doesn't breathe as well as my primary. And I don't care. To quote another diver here : "I'd suck a fart out of a donkey's ass if it would get me to the surface alive."

-Charles

I consider it a mediocre inflator because I found it harder to locate and hit the right buttons when I wanted to. That longer hose means it can flop around more and I find that a bulkier inflator with both buttons in the same plane is harder to use. It's not that it's not functional, I just find that having a smaller inflator with the buttons at 90 degrees to each other makes things easier.

Your results may differ, but after about 30 dives with the Seaquest, when I should have developed some familiarity, I still found the standard inflator on my Ranger to be easier to use.

Edit: I'm going to have to take that part about the buttons being in same plane back. On most pictures of inline octos that I see that is indeed the case, but I went out to the garage and dug out my old SeaQuest and the buttons actually are 90 degrees off from each other. They're also awkward as hell. Just looking at it, I can't believe I dove with it for as long as I did.

 

[elmer fudd]

No, I don't think it is. When it comes to fluid dynamics you really can just say that. Thousands of pickup truck owners were all leaving their tailgate down because "clearly letting the air flow through would reduce drag..." They thought it was self-evident. They were all wrong.

On this I've got to disagree. C'mon, an inline octo is about twice the size and it's got a far less hydrodynamic shape, regardless of which way it faces. Sure there are aerodynamic/hydrodynamic quirks to things like tailgates and golf balls, but about 99.9% of the time smaller and more streamlined is better, and that other 0.1% results mainly from very good engineering and thorough testing. You can bet that car companies did a lot of wind tunnel testing to maximize their trucks efficiency with the tailgate up. I know GMC's even have a tapered bed which is wider up front and skinnier in back in order to get some small aerodynamic advantage.

 

[cmburch]

I am a hunter so I am as streamline as possible.

I normally freedive the rugged Northern California Coast near kelp beds when I hunt.

For SCUBA, I use a SS backplate with Oxycheq Mach V Extreme wing and full foot fins. About as streamline as one can get. Some divers in our area use no bladder with their backpacks, so they are even more streamline when on SCUBA.

The only reason I went with the inflator octo was to clean things up a little - one less hose.

The normal underarm hose Octo on my other Reg had minor issues as does any item when diving rocky shores with kelp or hiking cliff trails. It may get hung up on something. This is true for my Reg and SPG also.