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Old 04-06-2014, 19:27   #61
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Re: Scuba Gear for Basic Boat Maintenance

If you don't have a way to refill a tank on board, then you've got a limited time to be underwater. So clearly the best is to have a dive compressor and some small tanks. A major expense here.

Holding your breath is still free.

The hooka setup looks cost-effective for basic boat maintenance,
and a little DIY is going to save a lot of money here with proper research.

Personally, my view is avoid the problem altogether,
and not have fixed props underwater, or even throughhulls, or heck in my case, even rudders.
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Old 04-06-2014, 19:29   #62
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Re: Scuba Gear for Basic Boat Maintenance

To answer the OP's original question,
Spare Air systems come in 2 sizes, small & smaller. They may be 1.5 & 3cf. I'm not sure about that. The larger size lasts me about 3 minutes when I'm trying to do something that is not overly strenuous. The big problem I have had with these things is that if they are not tuned properly, they leak down & are empty when you want to use them. You really need to fill them off of a real scuba tank just before you dive with them. They are a cute little compact system though & great for a quick look below.

The smallest real pony that I've seen is 6cf. It last's me about 5 minutes before it starts getting hard to breath off of using an old unbalanced regulator. That's what I keep on my boat in case of trouble below the water line.

There is a company out there that makes a front mounted tank pack that carries a larger pony (20ish cf?) & is very convenient for doing bottom work. I borrowed one several years ago & liked it. When I went to buy one, I got a case of sticker shock & went back to just using a small pony, sometimes with a 1" nylon web belt to hold it on my arm conveniently. Sometimes I just hold it in one hand. Sometimes I just let it float.

Before I had the little 6cf, I used to do this with another pony that was around 15 or 20cf. That worked OK too. I tried it once with a 40 & that was not OK loose without a backpack. I have sucessfully used that 40cf bottle set up like a stage rig, tied to the boat, with a weight attached to the tank to keep it from floating away.
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Old 04-06-2014, 19:33   #63
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Re: Scuba Gear for Basic Boat Maintenance

Quote:
Originally Posted by skipmac View Post
Aluminum tanks are at least if not more dangerous than steel. The two explosions I know of that happened in FL dive shops about 10-15 years back were both Al 80s.
I remember when Aluminum tanks first came out in the 1980s they had corrosion thread failures at the valve stem.

For a while they were recommending fewer VIPs until they sorted out that problem

Have not heard of any recent failures due to manufacturers defects.
As I have a home at a popular dive resort area.... All the dive operators use Al80s for years without problems.
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Old 04-06-2014, 19:33   #64
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Re: Scuba Gear for Basic Boat Maintenance

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When I was a kid, I got a little more creative. I put weights on a 2-liter soda bottle full of air & brought that down with me. Later, when I actually learned about diving, I realized how lucky I was not to have had a serious lung expansion injury.

You were on the way to making a rebreather. Add some caustic potash and maybe some other goodies and you could have stayed down for hours-and maybe not........
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Old 04-06-2014, 19:39   #65
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Re: Scuba Gear for Basic Boat Maintenance

Skipmac.... I am wrong! Just did a quick Google on Al tank failures.... Seems to be a problem. Thanks for the heads up!
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Old 04-06-2014, 19:44   #66
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Re: Scuba Gear for Basic Boat Maintenance

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Originally Posted by Pelagic View Post
I remember when Aluminum tanks first came out in the 1980s they had corrosion thread failures at the valve stem.

For a while they were recommending fewer VIPs until they sorted out that problem

Have not heard of any recent failures due to manufacturers defects.
As I have a home at a popular dive resort area.... All the dive operators use Al80s for years without problems.
Most likely these days little differences in life between Al and steel although I suspect possibly well maintained steel will outlast Al.

One real advantage with Al for dive resort operations is the flat bottom.

Personally I much prefer steel tanks because of their relative bouyancy as I am somewhat bouyant and always need weight belt even without wetsuit. Always hated the Al 's when neatly empty wanting to float on your back. I think its just a personal choice.

Really a tank setup will take up very little more space than a surfaced supplied unit.

cheers
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Old 04-06-2014, 19:46   #67
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Re: Scuba Gear for Basic Boat Maintenance

I used to do skip breathing and was usually the last to come up. In fact once there was panick on the boat and they thought I had drowned.
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Old 04-06-2014, 19:48   #68
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Re: Scuba Gear for Basic Boat Maintenance

Quote:
Originally Posted by Pelagic View Post
I remember when Aluminum tanks first came out in the 1980s they had corrosion thread failures at the valve stem.

For a while they were recommending fewer VIPs until they sorted out that problem

Have not heard of any recent failures due to manufacturers defects.
As I have a home at a popular dive resort area.... All the dive operators use Al80s for years without problems.
In addition to the failures at the threads in the neck there was a series of Al 80s that had a lot of problems due the use of a slightly different alloy that turned out to be brittle. It was only used for a couple of years before the makers changed alloys and those tanks were recalled. But same here, I haven't heard of any catastrophic failures in years.
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Old 04-06-2014, 19:48   #69
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pirate Re: Scuba Gear for Basic Boat Maintenance

LOOKING DOWN MY NOSE ALERT:

We've discussed age on here many times and many of us are old and I know from life experience that many of you oldsters are FAT too. 22 seconds might be a stretch for an old fat guy diving all the way down to say 4' underwater.

On the tank blowout issue, I've worked in several dive stores in FL and NC. This CF crowd of savvy divers know this stuff but I have personally run into several idiots who have doubled up their burst discs, and a couple of guys who restamped their big 2400 low pressure tanks in hope of running into some dumb cluck who'll will run them up to 3500 +. Over the years I have trained many young guys and gals on being alert to wot's wot on tank fills.

Oh the arguments I've heard! I almost had to kick a guy's ass at 0530 AM! when I refused to follow his fill "directions". I offered him free rentals but that wasn't good enough either so I just didn't let him get on board the dive boat. Tough titty as they say.

All these idiots say that the FL shops catering to cave divers routinely fill 2400s to 3500. I doubt it. For noobies, the very best way to extend yer bottom time is LOSE SOME WEIGHT. I've personally seen hundreds of divers who can't get up a dive ladder without assistance. How pathetic is that?

Getting old is no excuse for being grossly out of shape. Every serious dive accident/fatality I've seen, 5 or 6, the disabled or departed were overweights.
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Old 04-06-2014, 19:52   #70
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Re: Scuba Gear for Basic Boat Maintenance

EDIT Found this link.. NOT just Australian manufactured BUT worldwide?

Going to check my 4 tanks out today that are 10 years old

http://www.deir.qld.gov.au/workplace...ders/index.htm

http://www.deir.qld.gov.au/workplace...m#.U4_M9BmwrqA

Found this List of Tanks to check if you have one.
http://www.scubabomb.freeservers.com/List.htm
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Old 04-06-2014, 19:59   #71
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Re: Scuba Gear for Basic Boat Maintenance

[QUOTE=Blue Crab;1557231]LOOKING DOWN MY NOSE ALERT:
and a couple of guys who restamped their big 2400 low pressure tanks in hope of running into some dumb cluck who'll will run them up to 3500 +.


That's criminal and should be rewarded with jail time and revoked diving lic.
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Old 05-06-2014, 11:22   #72
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Re: Scuba Gear for Basic Boat Maintenance

I've saw burst disk in a tank blow out while it was filling and it pretty much emptied the water tank it was in, scared the crap out of everyone and certainly gave me new respect for a tank
Use to make my own beer and got the stuff for filling mini kegs including the CO2 cylinder. Got the cylinder filled once and laid it flat in my van while driving home. Big mistake. The liquid hit the burst disk and caused it to rupture while I was at a light. The tank emptied in less than a minute I think, filled the whole van and came out windows. I had to get out and just watch. People asked me if it was on fire. All funny now though.
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Old 05-06-2014, 11:36   #73
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Re: Scuba Gear for Basic Boat Maintenance

SCUBA burst discs are just thin pieces of copper, basically shim stock punched in a circle. And as sailors might know, copper in salt water, seated in a steel or aluminum fitting, it going to self-destruct. They are supposed to be replaced every year as part of the annual maintenance on the valve. There's no safety disc on a SCUBA tank, no burst disc on a SCUBA tank. The disc is on the valve.

But that's rarely done. Either it costs the shop time and money, or they have to explain why they're charging to do it, or, everyone can ignore it and then just charge the customer for a new disc and a fill when it fails, which is always more entertaining to watch. (ahem.)

I always used to maintain my own and I'd coat it with Krytox on both sides to ensure it couldn't corrode. And of course, rinse the valve after diving to get any salt water out of there. Krytox because it can be used on both sides, isn't a problem inside the tank, and it doesn't go anywhere or wash off the outside.

The early aluminum tanks were supposed to be "forever" but then there was the kerfuffle about faulty necks. Quickly "resolved" by "enhanced" VIPs using ultrasound to look for stress cracks in the necks. Except...Gungho, another $20 to add to the regular VIP and most shops didn't really know how to use them. The normal thread tappings in the neck were sometimes mistaken for flaws and perfectly good tanks sometimes condemned as a result.

Another sadly good reason that many shops, if not most shops, encourage mystic FUD instead of trying to educate divers. If you have ever had a tank hydro'd and VIP'd? Every dive shop insists on performing a VIP after the hydro. Which is most peculiar, since the US DOT regulations require the hydro shop to perform a VIP and only continue to do the hydro test if the tank passes that VIP. So if the tank has been hydro'd...it has just been VIP'd as well. The second VIP is totally redundant, a rip-off by the SCUBA shop.
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Old 05-06-2014, 11:42   #74
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Re: Scuba Gear for Basic Boat Maintenance

Hi folks
We have a mini B scuba on 'Norman James'. This comprises a rucksack which contains a 5l bottle, 1st & 2nd stage regs, BCD, and weight pouches. I haven't used it yet but seems easy & compact ( about the size of a largish day sack ), there is also a 3l version which presumably is lighter - the 5l set is 13Kg. Have a look on the web !
Regards
Rob
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Old 05-06-2014, 13:15   #75
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Re: Scuba Gear for Basic Boat Maintenance

[QUOTE=Adventurebound;1557247]
Quote:
Originally Posted by Blue Crab View Post
LOOKING DOWN MY NOSE ALERT:
and a couple of guys who restamped their big 2400 low pressure tanks in hope of running into some dumb cluck who'll will run them up to 3500 +.


That's criminal and should be rewarded with jail time and revoked diving lic.

It's extremely common in cave country (North Florida) to fill LP steel tanks to 3600, as it's been done continuously for the last twenty or more years with no failures it's apparently safe. Nobody stamps anything on them, it's called a "cave fill"

There is some argument that it may shorten the life, as in a tank may fail hydro sooner, but no data to support that either.

A well maintained steel tank will last forever.
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