Go try it in a swimming pool with a garden hose before you get yourself
hung up under your keel and get nominated for a Darwin Award. You will
find that it is impossible to breath if your lungs get more than about
3' deep.

Your prop is probably a foot or two deep minimum and if you are upright
your lungs will be a foot or two below that. You might be able to do it
upside down and sort of lay against the hull so your lungs are not as
deep. Hang your belly button on a barnicle to keep in place. Better
use red bottom paint so the blood stains won't show as bad. :-)

Movie cowboys hid from the indians with a reed by laying on their backs
so their body is just below the surface. About the same as normal
snorkling depth. It also helped to be solid muscle. Beer guts float. :-)


Lloyd Sumpter wrote:
Good point.

So you need to "in through the mouth out through the nose" or else get
a "proper" mouthpiece that expels the "out-breath" directly.

As for the pressure, that's a big question mark. At the prop, I'm only
under maybe a foot (depending on body position). I don't know if the
pressure would be too much for me to take a breath or not (it's easy for
me to create suction in my mouth at this depth, so...I donno.)

After all, look at all the Bad Movies that have Our Heros hiding
underwater with a reed in their mouths...

Lloyd


On Mon, 03 Nov 2003 20:37:27 +0000, Paul wrote:


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




--
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

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

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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"

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

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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

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

One atmosphere of pressure (14.7 psi) is 33 feet of seawater. THe .445
is correct but your math is wrong. 1.5 atmospheres would be about 50
feet. Regardless, the normal pressure differential that our lungs
produce is about 12 millibar or .17 psi. A person in very good health
can inhale at a maximum pressure differential of about 100 milibars or
1.45 psi. That is about 39 inches of seawater.

Just to verify the figures I went out to the boat shed, cranked up the
vacuum system and tried to breathe from the vacuum tube. I couldn't get
any air after 1.3 psi but I have probably inhaled more than my share of
Cabosil.



Rick wrote:

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


--
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

One atmosphere of pressure (14.7 psi) is 33 feet of seawater. THe .445
is correct but your math is wrong. 1.5 atmospheres would be about 50
feet. Regardless, the normal pressure differential that our lungs
produce is about 12 millibar or .17 psi. A person in very good health
can inhale at a maximum pressure differential of about 100 milibars or
1.45 psi. That is about 39 inches of seawater.

Just to verify the figures I went out to the boat shed, cranked up the
vacuum system and tried to breathe from the vacuum tube. I couldn't get
any air after 1.3 psi but I have probably inhaled more than my share of
Cabosil.



Rick wrote:

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


--
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

"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 .. .
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.

One atmosphere is sea level. Pressure of 14.7psi is the air pressure at sea
level. Kinda makes sense, if it was the pressure at 33 feet below sea level
then they wouldn't have called it an "atmosphere".

At 33 feet you are now subject to one additional atmosphere for a total of
two.

1.5 atmospheres is experienced at ~16 feet.


"Glenn Ashmore" wrote in message
news:F5Cpb.875$62.52@lakeread04...
One atmosphere of pressure (14.7 psi) is 33 feet of seawater. THe .445
is correct but your math is wrong. 1.5 atmospheres would be about 50
feet. Regardless, the normal pressure differential that our lungs
produce is about 12 millibar or .17 psi. A person in very good health
can inhale at a maximum pressure differential of about 100 milibars or
1.45 psi. That is about 39 inches of seawater.

Just to verify the figures I went out to the boat shed, cranked up the
vacuum system and tried to breathe from the vacuum tube. I couldn't get
any air after 1.3 psi but I have probably inhaled more than my share of
Cabosil.



Rick wrote:

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


--
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