How safe is it, really?

On Tue, 7 Dec 2004 06:26:57 -0600, "Dan Luke"
wrote:

I've been parking
my airplane under a shelter within a mile of Mobile Bay for five years.
I never top up the tanks after a flight. In that time, I don't recall
ever sumping a drop of water out of any of the drains. My tanks hold 32
gal. usable each.

That would be Mobile Bay Alabama, right? How much change in
temperature occurs overnight during the summers there? Here in New
England, we can, and often do, see a 30 to 40 degree swing from the
cold of night to the warmest part of the day.

Corky Scott

On Tue, 7 Dec 2004 06:26:57 -0600, "Dan Luke"
wrote in
::

I've been parking
my airplane under a shelter within a mile of Mobile Bay for five years.
I never top up the tanks after a flight. In that time, I don't recall
ever sumping a drop of water out of any of the drains.

That doesn't mean there is no water in your C-172RG's fuel system.
Are there rubber bladders in its fuel tanks?

As in the accident to which I included a link earlier in this message
thread, an uncoordinated bank on approach could be enough to cause
water trapped by the tanks folds to reach the carburetor (if so
equipped) at an altitude insufficient to facilitate a recovery.

"Larry Dighera" wrote in message
...
On Mon, 06 Dec 2004 14:21:10 -0000, Dylan Smith
wrote in
::

I have never discovered water condensing in half-full fuel
tanks.

Perhaps the laws of physics have been repealed on the Isle of Man. :-)


I guess that goes for Illinois also. Never a drop of water even with
partial tanks sitting in all seasons. Why don't other types of vehicles
have this supposed problem? Automobiles, boats, construction equipment?

"Larry Dighera" wrote:
I've been parking
my airplane under a shelter within a mile of Mobile Bay for five years.
I never top up the tanks after a flight. In that time, I don't recall
ever sumping a drop of water out of any of the drains.

That doesn't mean there is no water in your C-172RG's fuel system.

If there has been, I haven't seen--or felt--any evidence of it. While small
amounts might get stuck behind the fuel tank baffles, at least a *little*
should have shown up in the samples in all that time, don't you think? After
all, the airplane is parked in one of the most persistently humid locations
in the U. S. Day after day, warm, wet afternoons are followed by mornings
where the OAT falls to the dewpoint; you literally could wash my airplane
many mornings without using a hose. Those are perfect conditions for the
respiration/condensation scenario you fear, but they just don't seem to put
any detectable amount of water in my tanks. Why is that?

Are there rubber bladders in its fuel tanks?

No.

Now, how about some calculations showing that fuel tank respiration caused by
daily temperature fluctuations can cause enough air changes to produce
significant added condensation?

[snip]
--
Dan
C-172RG at BFM

"Dan Luke" wrote in message
...

"Roger" wrote:
Which is an old wives tale. The amount of water contained in 20-30
gallons of air is insignificant.

Just let those tanks inhale and exhale a few times. They do that
every morning and night so there is a *lot* more than 20-30 gallons
involved.

Another OWT, I'm afraid. Can you produce calculations to show how many
air exchanges/week occur in a half-full 40-gal. tank given a daily
temperature swing of 20 deg. F?

[snip]

I fly a Deb with about the same fuel capacity (not counting the tip
tanks). With half tanks and the plane hangered for two weeks in the
Spring, I drained over two full samplers of water out of one tank and
a half out of the other. None out of the auxiliaries as they were
full.

Since you bring up anecdotal evidence, I'll chip in: I've been parking my
airplane under a shelter within a mile of Mobile Bay for five years. I
never top up the tanks after a flight. In that time, I don't recall ever
sumping a drop of water out of any of the drains. My tanks hold 32 gal.
usable each.

[snip]
--
Dan
C172RG at BFM


To add another data point, when I had a Turbo Lance parked outside at Santa
Monica I never sumped a drop of water either. Same thing at Minden NV when
it was outside there. Never a drop.

Mike
MU-2

"Corky Scott" wrote:
I've been parking
my airplane under a shelter within a mile of Mobile Bay for five years.
I never top up the tanks after a flight. In that time, I don't recall
ever sumping a drop of water out of any of the drains. My tanks hold 32
gal. usable each.

That would be Mobile Bay Alabama, right? How much change in
temperature occurs overnight during the summers there?

16-20 deg. F. It falls to the dewpoint most mornings in summer.

Here in New
England, we can, and often do, see a 30 to 40 degree swing from the
cold of night to the warmest part of the day.

Overnight dry bulb temperatures, assuming no weather change, typically do not
fall below the dewpoint because of the heat of condensation. Therefore, if
there is that much swing, the dewpoint is mighty low; there is damned little
moisture in the air to begin with. Fuel tank respiration/condensation would
still not be a problem.
--
Dan
C-172RG at BFM

Corky Scott wrote:

...... How much change in
temperature occurs overnight during the summers there? Here in New
England, we can, and often do, see a 30 to 40 degree swing from the
cold of night to the warmest part of the day.

Another data point, as long as we're throwing them out - I park my COZY
MKIV outside at KFIT in MA. It lives outside throughout the whole year,
and sees large temperature swings (daily, usually). The fuel tanks are
integral with the strakes and made from fiberglass/epoxy - no bladders
or "wrinkles" in the bottom to trap water. The drains are at the lowest
point of the tanks. I rarely top up after a flight, and regularly leave
the tanks 1/10 - 1/2 full. I always sump the tanks first thing when
approaching the plane, before I move it or top it off. I have seen
water in the tanks exactly once, and that was after a very heavy rain.
I tightened the O-ring seal on the gas cap, and have never seen water
again in over 1.5 years.

The fiberglass is a good insulator, and as the temperature changes, I
see lots of condensation on the OUTSIDE - if it was going to condense on
the inside to any appreciable degree, it's got it's chance with the
materials at hand. It doesn't do so.

Personally, I think this condensation thing is a crock - if you've got
water in your tanks, it's because your caps leak in the rain.

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

"Marc J. Zeitlin" wrote:

Another data point, as long as we're throwing them out - I park my COZY
MKIV outside at KFIT in MA.

One more. My Maule has been parked outside since I bought it in 1995. Since the
venting system has no anti-syphon devices, it has a tendency to dump fuel if I
park it with the tanks near full, so I have not done so since shortly after I
bought it. I check the tanks during preflight, and, if they're down around 3/8,
I fill it back up before flying. I'm based now at Lakewood, which is a few miles
from an inlet of the Atlantic. I've never seen any water in the fuel.

George Patterson
The desire for safety stands against every great and noble enterprise.

"Marc J. Zeitlin" wrote:
Personally, I think this condensation thing is a crock...

Couldn't have said it better, myself.
--
Dan
non-condensing C-172RG at BFM

On Tue, 07 Dec 2004 16:31:27 GMT, "G.R. Patterson III"
wrote:

I'm based now at Lakewood


Do you know if a mechanic named Bob Hayes is still down there?

Just curious,
z