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Old 23-09-2007, 01:26   #76
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My boat has an 8 ft draft, so that's the deepest I need to go for hull cleaning, but it would be super nice to be able to dive a bit deeper anchored in an atoll somewhere.
I've been to 30' or so with no problems.
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Old 23-09-2007, 12:26   #77
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30 ft is great. I'm generally quite happy staying in 30 to 40 feet. Most of my concern is bottom cleaning or searching for something I just dropped overboard! I try to anchor with 10 to 20 feet under the keel, so 30 feet would do me most of the time. And I have my tanks on board for deeper/wider diving. I just don't have any way to recharge them.

I don't know what it costs to hire someone to clean the bottom, but I imagine with a 46ft boat a hookah system would pay for itself pretty quickly.

Thanks for your help. I'll go search for that Thomas compressor as soon as I get back to Hawaii.

Cheers,

Carl
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Old 23-09-2007, 13:02   #78
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The Thomas looks like a great way to go when diving from the boat, but can anyone recommend a 12 volt compressor suitable for floating hookah use? I could mount the Thomas in a float with an inverter and a battery, but the inverter will waste 20% of the battery capacity.
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Old 23-09-2007, 15:25   #79
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Thomas also make 12volt oilless compressors, search there website
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Old 23-09-2007, 20:57   #80
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With the proper compressor, a reserve tank and the associated plumbing that goes with it is unnecessary. My divers and I use the Thomas 1020, 110 volt oil-less compressors. They are nearly indestructable, run all day without needing to be shut down to cool and if any of the few moving parts does fail, the compressor can be rebuilt with parts from Grainger for less than $75.00. In fact, it is so inexpensive, I rebuild my compressors every year or two whether they require it or not.

Looks like a 1200W inverter would be required to run just this compressor. Definitely and interesting idea. How often do you have to run it at full blast?
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Old 23-09-2007, 21:24   #81
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I did a lot of research on this when i put together a unit last year, The best 12Vdc compressor i could find was the thomas TA5102DC
TA-2101-3101-4101-5102DC_Articulated__3215_1-07.pdf - pdf2html
puts out the best amount of air at 50psi, same unit as used by airline
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Old 24-09-2007, 09:55   #82
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Looks like a 1200W inverter would be required to run just this compressor. Definitely and interesting idea. How often do you have to run it at full blast?
It draws 10.5 amps, so yes, you do need to be able to produce some electricity onboard if you intend to use it that way. I only ever turn mine up all the way if I need to go deep. For hull cleaning, I run it at about 50-75%. However, the electric motor runs at full speed whenever it is switched on. The air flow is controlled by a needle valve at the output side of the compressor (if that's what you were getting at.)
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Old 24-09-2007, 10:27   #83
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It draws 10.5 amps, so yes, you do need to be able to produce some electricity onboard if you intend to use it that way. I only ever turn mine up all the way if I need to go deep. For hull cleaning, I run it at about 50-75%. However, the electric motor runs at full speed whenever it is switched on. The air flow is controlled by a needle valve at the output side of the compressor (if that's what you were getting at.)
If it is a magnetic drive motor, restricting the output CFM also decreases the amperage drawn... So, in your real-world example, it is possible that you usually only draw around 5-7 amps.

Thanks for the info!
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Old 24-09-2007, 10:52   #84
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The specs you provided show the 5102 draws 45 amps at rated load and 540 amp surge current. It also provides 1.6 cfm at 100 psi. That's a lot of air for a small compressor. If you're only drawing 10.5 amps I guess that's because you have the flow regulated with the needle valve.

Looks like a great compressor. The only downside I see is that there is no auto shutoff.

Thanks for the great info.

Carl
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Old 24-09-2007, 11:08   #85
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The specs you provided show the 5102 draws 45 amps at rated load and 540 amp surge current. It also provides 1.6 cfm at 100 psi. That's a lot of air for a small compressor. If you're only drawing 10.5 amps I guess that's because you have the flow regulated with the needle valve.
I think you're confusing my posts about the Thomas 1020 with that of Nauticatarcher, who posted info about the Thomas 5102 (the 12-volt unit.)
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Old 24-09-2007, 11:12   #86
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Gottcha! I see that now. Makes more sense with that distinction.

In any event, you both like the Thomas compressors. That's a good sign.

Carl
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Old 25-09-2007, 17:31   #87
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Any of you folks who've been using these to clean your hulls around marinas ever gotten shocked from ground fault problems? (I've been reviewing that section in Calder's book.) Do you do anything to check out this possibility before going into the water?

Frankly, the way Nigel describes it, it would be pretty easy to get a nasty -- and fatal -- dose of AC, and not even know it was waiting for you. Unless I've misunderstood him, due to the resistance properties of seawater, you could be "safe" at one distance from a poorly grounded boat; swim towards it, and get then get the shock.

Am I being a worry wort, or is this something you consider?

Thanks.

ID
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Old 25-09-2007, 18:56   #88
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I have read such warnings as well, though I do not recall 'twas in Calder's works or elsewhere. But, I've seen them more than once.


I've only cleaned my bottom in 3 marinas and haven't had any trouble. So far!

Your question is a good one, and I'd like a way to check for stray current before popping in the water too. It would also be good to know in terms of electrolysis risks since I have a steel hull.

Cheers,

Carl
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Old 25-09-2007, 23:14   #89
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Any of you folks who've been using these to clean your hulls around marinas ever gotten shocked from ground fault problems? (I've been reviewing that section in Calder's book.) Do you do anything to check out this possibility before going into the water?Am I being a worry wort, or is this something you consider?
I have been cleaning hulls professionally for 13 years and have zero firsthand knowledge of anybody having any serious problem with electricity underwater. I once heard a story about a diver who went to work and never made it back home. They found him the next day, clinging barehanded to the prop shaft of a powerboat. The story is that there was enough DC current going through the shaft that the diver couldn't let go, breathed down his tank and drowned.

True or not, I don't know. But after hearing it, I ALWAYS unplug any boat I'm diving on.
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Old 25-09-2007, 23:47   #90
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Electricity and water are a bad mix. There have been several verified reports in boating magazines of people electrocuted in the water, usually when a power line is in the water or a lightning strike occurs nearby.

The following info on AC current explains why you should never test a wire for current by grabbing it, but only by flicking it with the back of your hand so muscle contraction will make you jerk away.

The following is exerpted from Wikipedia:

The high voltage direct current (DC) electrocution tends to cause a single muscle contraction, throwing its victim from the source. These patients tend to have more blunt trauma. Direct current electrocution can also cause cardiac dysrrhythmias, depending on the phase of the cardiac cycle affected. This action is similar to the affect of a cardiac defibrillator.
Low voltage alternating current (AC) electrocution is three times more dangerous than DC current at the same voltage. The lowest frequency for electrical current in the United States is 60 Hertz (Hz) because this is the lowest frequency at which an incandescent light functions. With AC electrocution, continuous muscle contractions (tetany) may occur, since the muscle fibers are stimulated at between 40 to 110 times per second. With tetany, the victim tends to hold on to the source of current output, thereby increasing the duration of contact and worsening the injury.[2]
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