On Mon, 03 Nov 2003 13:36:10 +0000, Jim Richardson wrote:

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On Mon, 03 Nov 2003 11:48:30 -0800,
Lloyd Sumpter wrote:
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?


There are two problems.

1) Unless you have a seperate exhaust path (usually via a valve directly
into the water) you can't push the "bad" air, out of the snorkle very
far. If the volume of the snorkel tube is a significant fraction of your
lung volume, you just pusþ the air up the tube, and then draw that same
air, back into your lungs.

2) The pressure at say, 7 feet depth, is about 1.5 atmospheres, so you
will be drawing in 1 atmos air, against 1.5 atmos pressure on your
lungs. Try it. Take a garden hose down to 7 feet, with the other end in
the air, (of course, keeping the water out of it) and try taking a
breath through it. You will be able to do it, for a while, maybe a
minute, by exhaling through your nose, but you'll give your diaphram a
real workout.

The usual solution, is either a tank+reg with a really long hose in
between or a hookah setup. The tank's a lot cheaper, especially if
you allready have the tank and the regulator, the hose isn't too
expensive.


I'm guessing most of the respondents here have never "snorkel-dove" (ie
mask, fins, hold your breath) to do prop/rudder repairs, etc.

(long tube problem covered elsewhere - ie to exhale separately)

- A lungful of air pins you pretty tight onto the hull - there's NO
WAY you're "upright" or anywhere near 7 ft deep.

- (from another response) if you're gonna get hooked on the keel with an
"air tube", you will snorkel-diving as well, and in the latter case you
have NO air! Pinned to the hull, it's pretty easy to push off and get to
the surface.

- Um...if I had a tank and regulator, why not just put it on?

So I guess, Updated Question: How DO you do "maintenance" on your prop,
rudder, etc. underwater? "Snorkel-dive"? Scuba? Pay someone else? Survey
says...

Lloyd Sumpter
"Far Cove" Catalina 36 - put me down for "snorkel-dive"

Jim Richardson wrote:


2) The pressure at say, 7 feet depth, is about 1.5 atmospheres,

The pressure at say, 7 feet depth, (in seawater) is about 3 psig. It
would take another 9 feet to reach 1.5 ats.

Seawater pressure increases at around .445 psig per foot.

Rick

It would be extremely dificult if not impossible to breath through a
hose at surface pressure if your lungs get more than 2 or 3 feet under
water. The difference at 3' is only about 1.5 pounds per square inch
but the water is pressing on a couple thousand square inches of lung
surface.

Lloyd Sumpter wrote:

Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?

Lloyd Sumpter
"Far Cove" Catalina 36


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

That is a very dangerous idea but the reason why isn't immediately obvious.

When you exhale you will fill the long tube with your expelled air and then
breathe it all back in. I believe this would result in hypoxia (oxygen
deficiency) in which case you could drown without realizing what's
happening.

Snorkel tubes are short so most of the exhausted air is expelled and there
is enough of an influx of fresh air to avoid this problem.



"Lloyd Sumpter" wrote in message
news
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?

Lloyd Sumpter
"Far Cove" Catalina 36

"Lloyd Sumpter" wrote in message .. .
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?

Lloyd Sumpter
"Far Cove" Catalina 36

Because if water got into the top end, it would exert a pressure on
your lungs of about .5 psi/ft of depth. So if you are 10' down, it
would exert a pressure of 5 psi above atmospheric pressure.

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On Mon, 03 Nov 2003 11:48:30 -0800,
Lloyd Sumpter wrote:
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?


There are two problems.

1) Unless you have a seperate exhaust path (usually via a valve directly
into the water) you can't push the "bad" air, out of the snorkle very
far. If the volume of the snorkel tube is a significant fraction of your
lung volume, you just pusþ the air up the tube, and then draw that same
air, back into your lungs.

2) The pressure at say, 7 feet depth, is about 1.5 atmospheres, so you
will be drawing in 1 atmos air, against 1.5 atmos pressure on your
lungs. Try it. Take a garden hose down to 7 feet, with the other end in
the air, (of course, keeping the water out of it) and try taking a
breath through it. You will be able to do it, for a while, maybe a
minute, by exhaling through your nose, but you'll give your diaphram a
real workout.

The usual solution, is either a tank+reg with a really long hose in
between or a hookah setup. The tank's a lot cheaper, especially if
you allready have the tank and the regulator, the hose isn't too
expensive.


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--
Jim Richardson http://www.eskimo.com/~warlock
"What I look forward to is continued immaturity followed by death."
-- Dave Barry

"Lloyd Sumpter" wrote in message .. .
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?

Lloyd Sumpter
"Far Cove" Catalina 36

Because if water got into the top end, it would exert a pressure on
your lungs of about .5 psi/ft of depth. So if you are 10' down, it
would exert a pressure of 5 psi above atmospheric pressure.

"Lloyd Sumpter" wrote in message
news
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?


Take a look at the hookah equipment, cheap and cheerful, but recommend you
do a dive training course before use.

http://www.akmining.com/dive/systems.htm

garry

We met an interesting and inventive guy on our trip through the Panama Canal
who dealt with this by making his own electric hookah -- take one Jabsco
diaphragm bilge pump, attach hose and a SCUBA mouthpiece and presto, you
have cheap device that will work down a few feet. You want a diaphragm bilge
pump, not a pressure water pump, because the former is relatively high
volume, low pressure.

We used a "real" hookah from Brownie for work on the boat. Vast overkill.

For Fintry, I'm thinking about using a commercial oil-less compressor
(Porter Cable, for example) which will run air tools and, through a filter
(same filters we use on our tank-fill compressor) drive a low pressure hose
for use down to ten feet or so.


--
Jim Woodward
www.mvFintry.com



..
"Lloyd Sumpter" wrote in message
news
Hi,

Whenever I need to work on my prop, etc. underwater, I've just slapped
on the mask and fins and held my breath. But I've always wondered: why not
rig up a hose arrangement to be able to breathe? We're not talking 50-ft
depths here, so I'd think it would be pretty safe. Perhaps some kind of
non-collapsable hose on the end of a snorkel?

Does anyone do this? Why or why not?

Lloyd Sumpter
"Far Cove" Catalina 36

I put together a filter system for a remote source pressure demand face
mask that I use when spraying 2 part LPU. All from modular Speedair
filters from Grainger. It starts with a general purpose
separator/filter then a regulator, then a coalescing filter to remove
oil and another general purpose filter with a carbon element to grab any
remaining VOCs. Same series as used on a $2K MSA air source for a total
cost of about $120.

With a little oilless compressor on deck it would make a very acceptable
air source for bottom cleaning.

Jim Woodward wrote:

We met an interesting and inventive guy on our trip through the Panama Canal
who dealt with this by making his own electric hookah -- take one Jabsco
diaphragm bilge pump, attach hose and a SCUBA mouthpiece and presto, you
have cheap device that will work down a few feet. You want a diaphragm bilge
pump, not a pressure water pump, because the former is relatively high
volume, low pressure.

We used a "real" hookah from Brownie for work on the boat. Vast overkill.

For Fintry, I'm thinking about using a commercial oil-less compressor
(Porter Cable, for example) which will run air tools and, through a filter
(same filters we use on our tank-fill compressor) drive a low pressure hose
for use down to ten feet or so.



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com