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 pusū 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"