I'm sorry but that's not correct. At least according to when I was taught
dive physics. One atmosphere of pressure is every 33 feet of sea water. At
sea level, above the surface of the water you are at one atmosphere of
pressure. Zero atmospheres of pressure would be a vacum. As you descend in
salt water (it's slightly different in fresh water but not by much) to a
depth of 33 feet you're at two atmospheres of pressure, 66 feet equals 3
atmospheres, 99 feet 4 atmospheres etc.... 1.5 atmospheres of pressure is
16.5 feet of sea water.


Jerry




"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

You guys don't seem to concieve the problem. We are NOT talking
absolute pressure here. Nitrogen absorption is not an issue. The
DIFFERENTIAL pressure is what we need to look at. The other end of the
hose is at one atmosphere not a vacuum and the lungs are at some higher
pressure. The lungs have to overcome the difference in pressure and
they will not be able to do so below about 40" of depth.

Debbie Griggs wrote:
I'm sorry but that's not correct. At least according to when I was taught
dive physics. One atmosphere of pressure is every 33 feet of sea water. At
sea level, above the surface of the water you are at one atmosphere of
pressure. Zero atmospheres of pressure would be a vacum. As you descend in
salt water (it's slightly different in fresh water but not by much) to a
depth of 33 feet you're at two atmospheres of pressure, 66 feet equals 3
atmospheres, 99 feet 4 atmospheres etc.... 1.5 atmospheres of pressure is
16.5 feet of sea water.


Jerry




"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





--
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

You guys don't seem to concieve the problem. We are NOT talking
absolute pressure here. Nitrogen absorption is not an issue. The
DIFFERENTIAL pressure is what we need to look at. The other end of the
hose is at one atmosphere not a vacuum and the lungs are at some higher
pressure. The lungs have to overcome the difference in pressure and
they will not be able to do so below about 40" of depth.

Debbie Griggs wrote:
I'm sorry but that's not correct. At least according to when I was taught
dive physics. One atmosphere of pressure is every 33 feet of sea water. At
sea level, above the surface of the water you are at one atmosphere of
pressure. Zero atmospheres of pressure would be a vacum. As you descend in
salt water (it's slightly different in fresh water but not by much) to a
depth of 33 feet you're at two atmospheres of pressure, 66 feet equals 3
atmospheres, 99 feet 4 atmospheres etc.... 1.5 atmospheres of pressure is
16.5 feet of sea water.


Jerry




"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





--
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

Glenn Ashmore wrote:

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.

One atm is 14.7 psia, it is a measure of absolute pressure. Itis the
pressure at the surface of the water. Pressure at 33 feet depth is 2
atmospheres absolute or 14.7 psig or guage pressure.

To obtain a pressure of 1.5 atmospheres (a measure of absolute pressure)
you would have to descend to around 16 feet. The guage pressure at that
depth is about 7 psig.

The pressure at 7 feet may be described as around 3 psig or 17.7 psia.
It is not by any measure 1.5 atm.

Rick

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

I'm sorry but that's not correct. At least according to when I was taught
dive physics. One atmosphere of pressure is every 33 feet of sea water. At
sea level, above the surface of the water you are at one atmosphere of
pressure. Zero atmospheres of pressure would be a vacum. As you descend in
salt water (it's slightly different in fresh water but not by much) to a
depth of 33 feet you're at two atmospheres of pressure, 66 feet equals 3
atmospheres, 99 feet 4 atmospheres etc.... 1.5 atmospheres of pressure is
16.5 feet of sea water.


Jerry




"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

Glenn Ashmore wrote:

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.

One atm is 14.7 psia, it is a measure of absolute pressure. Itis the
pressure at the surface of the water. Pressure at 33 feet depth is 2
atmospheres absolute or 14.7 psig or guage pressure.

To obtain a pressure of 1.5 atmospheres (a measure of absolute pressure)
you would have to descend to around 16 feet. The guage pressure at that
depth is about 7 psig.

The pressure at 7 feet may be described as around 3 psig or 17.7 psia.
It is not by any measure 1.5 atm.

Rick

Rick wrote in message link.net...
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

I do use a mask and snorkel to work on my prop. I even use it to work
on my keel and I just dive down and hold my breath. Its not a
problem. Sometimes when I dont want to dive down, I use a long
handled edging tool to reach the keel, works for the prop too.

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

Rick wrote in message link.net...
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

I do use a mask and snorkel to work on my prop. I even use it to work
on my keel and I just dive down and hold my breath. Its not a
problem. Sometimes when I dont want to dive down, I use a long
handled edging tool to reach the keel, works for the prop too.