Author Topic: Blue - small compressor system for snorkeling...anyone?  (Read 6424 times)

connector14

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #15 on: September 29, 2018, 01:44:58 PM »
The greatest change in water pressure occurs in the first 33ft. of descent. If your lungs are full of air and you suddenly ascend without continuously exhaling you will definitely be at risk of air embolism. Diving and snorkeling are great sports,  but can be fatal if not performed safely and with at least some basic training.
Side note but kind of similar topic: Been watching novice paddleboards take off up the beach at Makena in calm water with no wind...no leash or lifebelt or other safety equipment....then an hour later watching them try to battle hopelessly back to where they put in as the sudden strong North winds pick up. For some it will be a LONG walk home if they make it in ok. Even SUP can be dangerous.
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digger71

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #16 on: September 29, 2018, 02:19:14 PM »
The greatest change in water pressure occurs in the first 33ft. of descent.

I might be missing something here but it is my understanding that pressure increases by 1 atmosphere EVERY 33 ft.  Not sure what would make the first 33 ft special

Beasho

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #17 on: September 29, 2018, 02:39:00 PM »
The greatest change in water pressure occurs in the first 33ft. of descent. - INCORRECT

I might be missing something here but it is my understanding that pressure increases by 1 atmosphere EVERY 33 ft.  Not sure what would make the first 33 ft special - EXACTLY CORRECT

33 feet of water weighs as much as 20 miles of Atmosphere = 1 Atmosphere.  The next 33 feet of Water weighs as much as a SECOND atmosphere because water is in-compressible. 

From a pressure perspective it is all linear.  From a danger perspective - maybe the top 33 feet are worse because more people hang out in the 0 to 33 feet range.  Going deeper for longer timer periods involves nitrogen dissolving in your blood which can be a nasty problem.   
« Last Edit: September 29, 2018, 02:43:53 PM by Beasho »

Badger

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #18 on: September 29, 2018, 02:41:53 PM »
Badger--no. Both are dangerous and both require training. Go down 15 feet, breath compressed air from any source, hold your breath and shoot to the surface. The volume of air in your lungs just doubled--has to go somewhere. If you don't rupture the sack you'll likely blow out a bunch of Alvioli which are soft, gooshy, and have difficulty with a one pound change in pressure, never mind 16psi.


I thought so Bill. Thanks.
« Last Edit: September 29, 2018, 02:44:36 PM by Badger »
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PonoBill

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #19 on: September 29, 2018, 03:50:26 PM »
The greatest change in water pressure occurs in the first 33ft. of descent.

I might be missing something here but it is my understanding that pressure increases by 1 atmosphere EVERY 33 ft.  Not sure what would make the first 33 ft special

Mostly because diving instructors say that all the time, but there is also the volume difference of the gasses at say 66 feet vs. 33. At 33 feet the pressure is 2 atmospheres and the volume of the air filling your lungs is 1/2 as much as it would be on the surface. Ascending 33 feet doubles the volume. At 66 feet the pressure is 3atm which means the volume of the air is 1/3 of what it would be at the surface. Ascending from 66 to 33 feet changes the gas volume by 1/3. It's a difference, but it's really just fun with fractions. And it's true that the biggest volume change is from 2ATM to one.

It's more important when you're doing an emergency blow and go, which nobody practices anymore. With the crappy old gear we used to have the emergency blow and go was more like a normal ascent. So the deal is, at 150 feet you don't want to start blowing out much. For the first 33 feet you ascend the volume only changes by 1/5th. Blow too hard early on and your lungs get empty and you're too heavy--you'd need to start dropping stuff. At 100 feet to 66 feet the volume changes by 1/4. You still need to be blowing, and you might go a little harder, but really, you're going up wondering why air is still coming out of your mouth. 66 to 33, it's another third, and you're still blowing. From 33 to the surface--when you can start seeing ripples on the surface, you need to blow like hell because the volume of air remaining in your lungs is going to double.

Needless to say, that's a lot to remember when you're crapping your wetsuit because you ran out of air at 150 feet. So the rule of thumb is, don't go up any faster than your bubbles and yell all the way to the surface. Worked for me, way too many times. I dove with no pressure gauge for years, and the reserve valves NEVER work.
« Last Edit: September 29, 2018, 04:00:54 PM by PonoBill »
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connector14

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #20 on: September 29, 2018, 04:13:20 PM »
For liability and safety reasons,  most instructors do not make their students practice "free ascents".....probably a good thing.  But  back in the day when I was a NAUI instructor,  it was part of our training to teach free ascents and how to safely ascend if you ran out of air. I have done it from 150 ft. and it is not easy.
Amazing how diving gear has changed. My wife and I just had 4 awesome dives @ Molokini using dive regulators/computers supplied by the guides. Pretty cool technology.....but it still doesn't buy you any more downtime than playing by the old NAVY tables for repetitive no de-compression diving.
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stoneaxe

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #21 on: September 30, 2018, 04:48:14 AM »
If nothing else I'm glad I posted this so myself and others could be reminded of the potential danger. Despite forgetting about embolism being possible I still automatically exhale as I go to the surface even just snorkeling. But I was thinking about this for my granddaughter and grandson more than anything. Scary to think what might have happened.

It's weird....I turned my back to the ocean when I found I couldn't dive.  It felt like everything I wanted was gone. I was SO %$#^ing mad. I didn't want to be reminded of what I couldn't do. It took years, still played some on the surface but didn't even snorkel again until years later when my kids were young.
Bob

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PonoBill

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #22 on: September 30, 2018, 09:08:02 AM »
Connector, I have always considered PADI to be the weenie version of NAUI. Reliance on buddy breathing for emergency ascents and an assumption that the gear is always working. If you ask a PADI diver what his dive profile was for the dive they just completed they couldn't tell you without looking at their wrist. It made diving a lot more accessible, and the better gear makes it less dangerous--until it doesn't. The old stuff is good to know when the new stuff breaks.

The notion of resort dives where someone with virtually no training dives with a divemaster is beyond nuts. I've watched the panicked reactions of untrained divers, blowing air like a bubble machine, unable to control their buoyancy, thrashing around and banging into everything. Not good.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

connector14

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #23 on: September 30, 2018, 01:22:17 PM »
"I have always considered PADI to be the weenie version of NAUI. "
I
I taught back in the early 70's and PADI was just coming on the scene. I think their goal was to sell a ton of equipment and promote diving as a sport that ANYONE could do...even if you were not a swimmer.
As a water safety instructor long before I became a dive instructor,  I liked the fact that NAUI put heavy emphasis on "watermanship". Most of our pool training was to weed out the poor swimmers and folks that would not make very safe divers. My NAUI instructor course was a week long grueling event of many pool exercises designed to weed out weak swimmers. I was already a very strong swimmer and I really enjoyed some of the tests they put us through to try and "break" us. Kind of like NAVY Seal training. Some of the group washed out. So yea,  I guess we early NAUI instructors felt we were superior to the NASDAQ and PADI instructors.
But I am guessing that may have changed. The divemasters and shop owners of the outfit we use on MAUI seem very experienced and have thousands of hours of experience and they seem VERY safety conscious without making the experience uncomfortable. We have used B & B Scuba out of Kihei for 5 years in a row and they have always given us a great dive experience.
"never leave the dock without your paddle"
Imagine Rocket 14 ...my new favorite, smooth and fast and lite
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Zooport

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #24 on: September 30, 2018, 01:31:08 PM »
"I have always considered PADI to be the weenie version of NAUI. "
 

Probably true, but I'll expect it varies from shop to shop.  The PADI guys I certified with grilled me in every possible way.  They were very serious about safety and thorough in their training.
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PonoBill

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #25 on: October 01, 2018, 02:42:18 PM »
Ultimately it's all about the instructors or divemasters.  I've done certification with both. I got good instruction both times, but PADI seemed to put a lot more emphasis on the equipment working properly, NAUI seemed a lot more aimed at preparing divers for equipment failure. PADI focused closely on a level of buddy diving that I've never experienced in the wild. Naui seemed to assume you should have a buddy, but you should be prepared to take care of yourself in an emergency.  That's probably as much a sign of the times that I did the certification as it is a function of the organizations. I never saw a tank pressure gauge until the late 80's, never saw a computer until the 90's, and never saw an air-integrated computer until hmmm, I'm not sure when.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

stoneaxe

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #26 on: October 01, 2018, 03:12:29 PM »
I got my NAUI cert the same summer I got my Life saving cert and both from the same guy at the Boys Club in Allston. He was a real nice guy but an absolute prick in the water. I choked more times on regulators getting ripped from my face unexpectedly and other nasty shit. He absolutely had no qualms about trying to bring on panic. He loved playing the drowning victim in life saving classes too....panicked and trying to climb your head. He was not going to have anyone making it through that couldn't cut it. I was 6-4 220lbs of lean muscle when I was 15 and could hold my breath for an easy couple of minutes so I nailed him and wrapped him up in a cross chest carry so tight I almost broke his ribs....he wasn't too happy but I passed..... :)
Bob

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connector14

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #27 on: October 02, 2018, 10:46:31 AM »
Yes,  I remember those days.  When I was aquatics director for the City of Salem, Oregon,  I interviewed and tested all of my lifeguards personally. I could make myself pretty "heavy" on the bottom of the pool and they had to recover and then haul me out. We had some pretty awesome lifeguards......I ended up marrying one of them :)........
"never leave the dock without your paddle"
Imagine Rocket 14 ...my new favorite, smooth and fast and lite
2018 Red Paddle 14 x 27 Elite
2014 Bark Dominator 14....smooth and quiet
2014 Imagine Connector 14...the "barge"

Zooport

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #28 on: October 09, 2018, 04:18:34 AM »
I can't imagine making an emergency ascent from extremely deep waters.  Never did one from that deep, but the instructors made me practice several from 35ft.  After I got my certs,  I always carried a "Spare Air" emergency air bottle on my BC when I dove alone.  That way, should equipment ever fail, I had enough air to get to the surface.  Practiced with it a few times and it worked great.  No time to dawdle with it, but you can make a safe ascent breathing normally.   
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PonoBill

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Re: Blue - small compressor system for snorkeling...anyone?
« Reply #29 on: October 09, 2018, 06:24:38 AM »
I've got a spare air. Nice to have, but gear fails. And the backup to the backup is rarely maintained. Divemasters glare at me when I start talking about emergency ascents (or anything really). I never became a divemaster because the certification looks like it's mostly about teaching divers. I wouldn't mind doing ride-alongs on a six pac again, but I wore out my welcome with the dive company on Maui that knows me. Opinionated assholes tend to do that.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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