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Bottom paint on prop

Dave wrote:
On Wed, 23 Nov 2005 15:26:17 GMT, Gary said:

Duh! Of course if the hose is reinforced and more rigid than your chest
walls the you could get squeezed if you are not smart enough to hold
your breath.

Take your "Duh" and shove it, schmuck. You're simply continuing to display
your own ignorance.

The 'squeeze' that

another poster has referred to. This limits me to a depth of about
4 - 5ft. Any deeper and I have a coughing fit after re-surfacing.
Apparently that's caused by bits of the lungs collapsing, and the
coughing is a reaction to the little subchambers unsticking again.
Nasty feeling.

The air needs to be pumped down at the ambient pressure of your lungs.
After a couple feet *most* people can't suck hard enough to get air.
You might be the exception.

That's what those of us who know something about diving physics have been
saying from the beginning, and what you've been totally oblivious to. Glad
you're beginning to catch on.
This schmuck is a Navy diver. How about you?

Bottom paint on prop

Dave wrote:
On Wed, 23 Nov 2005 23:16:08 GMT, Rosalie B.
said:

On Wed, 23 Nov 2005 21:12:09 GMT, Rosalie B.
said:

if I wear a wet suit, I am too buoyant
to stay down.

Everyone is. That's what weight belts are for.

But not when free diving.

Why not? The weight on the belt can be adjusted to provide neutral buoyancy
just as it can with tanks on. Only difference I can see is that you might
want to keep a very slight positive buoyancy rather than going for entirely
neutral.

At depth, you mean? If weighted neutral at surface, you will be
negative below 10 feet. With tanks and weights and a buoyancy vest
and pressure air in your lungs and available to your vest, you can
adjust your buoyancy, but free, the deeper you go, the less buoyancy
you have, because your lungs full of air get compressed, and occupy
less volume, displacing less water, so down you go. Without weights,
it is more directly dependant on your fat percentage, since fat
floats, but does not compress. Same compensation queerdom with
sponge rubber wet suits, and in dry suits with trapped air, but to
different degrees for each parameter.

Diving gets complicated.

I know just enough about diving to know I do not know enough. Take
a course if you intend to start screwing around with weights and
hookas and such like. If you start thinking you are Jaques Cousteau,
and want to invent diving stuff like he did, you will probably end
up married to Davey Jones, whatever you think about gay marriage.

Terry K

Bottom paint on prop

"Gary" wrote in message
news:tS%gf.578681$oW2.415490@pd7tw1no...
News f2s wrote:

What happens is that as you go deeper it becomes progressively
more difficult to breath in, because your lung pressure is at
atmospheric, whilst the water pressure is increasing at about
half a pound per square inch for each foot of depth.

Duh! Of course if the hose is reinforced and more rigid than
your chest walls the you could get squeezed if you are not smart
enough to hold your breath.

Gary, you also get squeezed if you hold your breath, though
slightly less.

This limits me to a depth of about 4 - 5ft. Any deeper and I
have a coughing fit after re-surfacing. Apparently that's
caused by bits of the lungs collapsing, and the coughing is a
reaction to the little subchambers unsticking again. Nasty
feeling.

The air needs to be pumped down at the ambient pressure of your
lungs. After a couple feet *most* people can't suck hard enough
to get air. You might be the exception.

We *were* talking about using a breathing pipe to inhale
uncompressed air. I've tried this, and found a technique that
allows me to breathe under a shallow hull, using a long pipe, just
a little deeper than with a snorkel. I don't recommend it. And
yes, I do have a tough rib cage. And yes, I hold my breath to go
temporarily deeper, and I do the breathing cycle at the shallowest
depth possible, and I usually work upside down - hands at 4ft and
lungs at 2ft. All of which makes it possible to work around a prop
wrapped with a fishing net without getting the tanks out.

However, there are serious hazards in playing this game without a
great deal of care, practice and preparation. Since you obviously
have enough under water experience to make rather patronising
comments, I'm sure you appreciate this.

JimB

Bottom paint on prop

Back to the topic:

If there is room between the propeller and the strut, put a donut zinc on the
shaft between the two. Nothing grows on the zinc, of course, since it is
constantly depleting. But it also seems to extend a zone of protection that
prevents or greatly reduces growth within a few inches of the zinc. That's
enough to keep the prop hub clean, which is where maximum growth occurs. A
frequently used prop won't have much growth beyond the hub in any case.

Rosalie B. wrote:

Some people can do quite well free-diving. My SIL does this for the
lobster season in FL, and can stay down for a considerable time. Even
I can dive on the prop and do some work on it if I wear fins. It is
not that hard if you practice and it makes a reasonable workout. The
only time I can't do too much is if the water is cold - I can't stay
in too long in cold water, and if I wear a wet suit, I am too buoyant
to stay down.

It sounds to me like the guy in Costa Rica didn't have a dive flag or
take appropriate safety measures - like having someone watching.

It was reported in Lat 38's Electronic Latitude that he was
the victim of shallow water blackout, not having a boat
above him.

Shallow water blackout occurs when you hyperventilate too
much before a freedive, and then when down, you run out of
O2. Your body uses increasing levels of CO2 to tell you
when to breathe, and hyperventilating reduces blood CO2. So
you don't get the urge to breathe, and pass out underwater.

I've come close a few times (black spots as I come up).
Now I only ever hyperventilate 3 deep breaths before a dive.
Diving with a buddy close by might save you, but by the
time they notice a problem you might be 20' deep and sinking...

It reduces my bottom time slightly but I feel a lot safer

Evan Gatehouse

"Evan Gatehouse" wrote in message
...

Shallow water blackout occurs when you hyperventilate too much
before a freedive, and then when down, you run out of O2. Your
body uses increasing levels of CO2 to tell you when to breathe,
and hyperventilating reduces blood CO2. So you don't get the
urge to breathe, and pass out underwater.

Thanks for that one Evan. I wasn't aware. I've had a dizzy spell
or two, and hadn't thought through the cause too carefully.

JimB

Bottom paint on prop

Desitin. Baby bottoms and props.
Tom
"Garland Gray II" wrote in message
news:fOsgf.12766$ih5.6397@dukeread11...
Thanks !

"Bil" wrote in message
...
On Sun, 20 Nov 2005 19:08:32 -0500, "Garland Gray II"
wrote:

"Bil" wrote in
On 20 Nov 2005 08:46:07 -0800, "beaufortnc"
wrote:

Hi,

I'm prepping the bottom of my sailboat for barrier coat then ablative
bottom paint.

I'm thinking, however, that it might be a good idea to paint the prop
with something like Trinidad instead of ablative. It seems to me that
the ablative won't last long on the prop.

What's the conventional wisdom here?

What you use on your prop depends on your pattern of boating. Regular
boat use, eg once or more a week, can mean no special treatment
(depending on your local level of fouling). And on your prop: whether
bronze or stainless steel or plastic etc. And on other characteristics
of your prop, eg whether it's a surface prop, such as a Levi drive; or
a deep prop; whether it's spinning at around 1,000 rpm or two or three
times faster.

If you have a new bronze prop, waxes applied during the polishing
process can mean that no permanent treatment works until that wax is
removed and, perhaps, an etch primer is used.

Some treatments that do work:

* Grease the prop: if you are cruising, but anchor or berth for up to
a month, coating the prop with a salt-water resistant grease works
(for about a month). I use a German-made grease, Bechem SW2, and send
the cook over the side after taking a berth or anchorage. The grease
spins off, taking any slime etc with it. No chance that it can change
the balance of the prop.

* Bagging the prop: a physical barrier, such as a plastic bag, works.
But you have to send the cook (or the cook's assistant) over the side
twice, once to install the bag, once to remove it.

* Painting with an antifouling. Whether you use a hard or ablative
antifouling matters little; the problem is getting the paint to
adhere. New props are a problem, because of the waxes. Older props
work better. And the primer/paint combination is important.

One technique that works is to use an epoxy primer and to follow,
within the prescribed recoating time (usually about an hour, before
the epoxy primer has completely hardened) with antifouling. The next
step is important: then leave to harden completely (ie about one week
- any sooner and the primer will spin off).

I've also used a zinc chromate primer, with some -but not complete -
success.

* Commercially applied silicon coatings. Expensive (applying yourself
is not a good as paying the experts to apply). But works in many
conditions, especially if the boat is used fairly often.

Bil,
This was very informative.
Regarding your suggestion of epoxy primer followed by antifouling, which
expoxy primer do you recommend, and what kind of antifouling ?
I have saildrives with folding props. At last haulout I followed each of
the
many steps (Interlux Primecom as one layer comes to mind) required, but
this
seems simpler.
Thanks.

Garland:

I always beg epoxy primer from the yard which has hauled me out - the
prop does not need much and I usually have no other use for it. So I
take whatever the yard has in terms of left over epoxy primer.

My sailboat is currently wearing International Micron Extran
(International is called Interlux stateside), so that's the antifoul I
use.

To reiterate, the important steps a 1. to apply the antifouling
onto the epoxy primer before the epoxy has dried (usually the
manufacturer will detail the timing on the package); and 2. to leave
the epoxy/antifoul to harden for at least a week.

I have two props, a 2-blade and a 3-blade, so I antifoul whichever is
not on the prop shaft (because I am usually on the hard for only 3
days - and that is not long enough for the primer/antifoul coatings to
harden).

Cheers

Bottom paint on prop

As I said to begin with - Bob has used all those methods and none have
worked - that includes Desitin, anhydrous lanolin, and various kinds
and formulations of paint. The only thing that works is regular use.

"Tom R." wrote:

Desitin. Baby bottoms and props.
Tom
"Garland Gray II" wrote in message
news:fOsgf.12766$ih5.6397@dukeread11...
Thanks !

"Bil" wrote in message
...
On Sun, 20 Nov 2005 19:08:32 -0500, "Garland Gray II"
wrote:

"Bil" wrote in
On 20 Nov 2005 08:46:07 -0800, "beaufortnc"
wrote:

Hi,

I'm prepping the bottom of my sailboat for barrier coat then ablative
bottom paint.

I'm thinking, however, that it might be a good idea to paint the prop
with something like Trinidad instead of ablative. It seems to me that
the ablative won't last long on the prop.

What's the conventional wisdom here?

What you use on your prop depends on your pattern of boating. Regular
boat use, eg once or more a week, can mean no special treatment
(depending on your local level of fouling). And on your prop: whether
bronze or stainless steel or plastic etc. And on other characteristics
of your prop, eg whether it's a surface prop, such as a Levi drive; or
a deep prop; whether it's spinning at around 1,000 rpm or two or three
times faster.

If you have a new bronze prop, waxes applied during the polishing
process can mean that no permanent treatment works until that wax is
removed and, perhaps, an etch primer is used.

Some treatments that do work:

* Grease the prop: if you are cruising, but anchor or berth for up to
a month, coating the prop with a salt-water resistant grease works
(for about a month). I use a German-made grease, Bechem SW2, and send
the cook over the side after taking a berth or anchorage. The grease
spins off, taking any slime etc with it. No chance that it can change
the balance of the prop.

* Bagging the prop: a physical barrier, such as a plastic bag, works.
But you have to send the cook (or the cook's assistant) over the side
twice, once to install the bag, once to remove it.

* Painting with an antifouling. Whether you use a hard or ablative
antifouling matters little; the problem is getting the paint to
adhere. New props are a problem, because of the waxes. Older props
work better. And the primer/paint combination is important.

One technique that works is to use an epoxy primer and to follow,
within the prescribed recoating time (usually about an hour, before
the epoxy primer has completely hardened) with antifouling. The next
step is important: then leave to harden completely (ie about one week
- any sooner and the primer will spin off).

I've also used a zinc chromate primer, with some -but not complete -
success.

* Commercially applied silicon coatings. Expensive (applying yourself
is not a good as paying the experts to apply). But works in many
conditions, especially if the boat is used fairly often.

Bil,
This was very informative.
Regarding your suggestion of epoxy primer followed by antifouling, which
expoxy primer do you recommend, and what kind of antifouling ?
I have saildrives with folding props. At last haulout I followed each of
the
many steps (Interlux Primecom as one layer comes to mind) required, but
this
seems simpler.
Thanks.

Garland:

I always beg epoxy primer from the yard which has hauled me out - the
prop does not need much and I usually have no other use for it. So I
take whatever the yard has in terms of left over epoxy primer.

My sailboat is currently wearing International Micron Extran
(International is called Interlux stateside), so that's the antifoul I
use.

To reiterate, the important steps a 1. to apply the antifouling
onto the epoxy primer before the epoxy has dried (usually the
manufacturer will detail the timing on the package); and 2. to leave
the epoxy/antifoul to harden for at least a week.

I have two props, a 2-blade and a 3-blade, so I antifoul whichever is
not on the prop shaft (because I am usually on the hard for only 3
days - and that is not long enough for the primer/antifoul coatings to
harden).

Cheers

grandma Rosalie

Bottom paint on prop

In article . com,
"beaufortnc" wrote:

I'm prepping the bottom of my sailboat for barrier coat then ablative
bottom paint.

I'm thinking, however, that it might be a good idea to paint the prop
with something like Trinidad instead of ablative. It seems to me that
the ablative won't last long on the prop.

What's the conventional wisdom here?

I suspect something came up in the replies, but gave up when the thread
took a strange turn.

I've tried ablative, hard, "outboard" (TNT) and other options over the
years and have yet to find something that actually kept our prop clean
throughout the season.

I'm about to try something that scares the living dickens out of me, but
was recommended by the shop that installed our engine: NOTHING. No zinc,
no copper or tin-based paints. The theory is that the slight electrical
imbalance between the SS shaft and bronze prop will be sufficient to
keep both clean.

Since our shaft is isolated from everything else in the boat, the only
thing eating away half of our zincs each year is the SS/Bronze imbalance.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/