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Author Topic:   Preventing condensation in the gas tank.

triblet posted 08-17-2001 04:05 PM ET (US)
Here's a crazy idea I just had for preventing
condensation in the gas tank.
Condensation happens because barometric
pressure and temperature changes cause the
tank to breathe in and out. When it
breathes in, it draws in moist air, which
then condenses when it gets colder. When
to warms up, it breathes out the now
slightly drier air. The cycle repeats each
day.
What if we put a flexible bag on the tank
vent. It breathes out and inflates the
bag a big. It breathes in and deflates the
bag a big. It's the same air and gas fumes,
so there's no new moisture getting in.
Obviously, the bag would have to be safe
for the gas fumes.
I'll try it the next time I store my Montauk.
Oooops, I forgot, I live in California and
we don't winterize. Oh well, maybe one of
the snowbirds on the list will run with the
idea.
Chuck
kingfish posted 08-17-2001 04:51 PM ET (US)
Snowbirds!!
Hey, I represent that remark!!
jcf
andygere posted 08-17-2001 05:44 PM ET (US)
Chuck,
To take the idea a step further, why not build the fuel tank like a hydropnuematic tank with bladder inside that seperates the liquid (fuel) from the air in a closed system? When it warms up, the bladder compresses, when it cools, it expands. Added benefit would be no need for a primer bulb anymore. Just add a little air to the bladder once a year and you're good to go. Could be tricky when adding fuel to the tank though.....
triblet posted 08-17-2001 06:02 PM ET (US)
You'll still need the primer bulb. That's
to fill the float bowls back up after
they dry up. Nothing to do with air in the
tank.
However, I never quite figured out why my
sports car de jour would fire right up after
sitting all winter when an outboard needs
a primer bulb. This includes a couple of
carbureted models with just a mechanical
fuel pump.
Chuck
Hank posted 08-17-2001 11:55 PM ET (US)
How about just filling the tank ? Very little air volume will mean little volume change during temperature cycling. Little volume change will result in very little moisture condensation.
Hank
Tom W Clark posted 08-18-2001 12:07 AM ET (US)
Hank,
Filling the tank is the convetional wisdom but I think triblet's post might be an extension of the query found here: http://continuouswave.com/ubb/Forum4/HTML/000422.html
Chuck,
Interesting idea. But the problem I see is that the tank and its filler, fuel outlet and vent all need to be sealed in order to withstand a certain small amount of pressure/vacuum. How do you envision sealing the tank on a Whaler?
triblet posted 08-18-2001 08:17 PM ET (US)
Using my Montauk as an example, there are
sealing caps. The bag would be on a separate
vent (the Pate has two places to attach the
tube, I could just use the second one for the
bag, Fuel outlet is probably not a problem,
the bulb has two check valves. Tank is
already sealed.
But again, we don't have to worry about
winterizing. I boat year round, conditions
permitting (admittedly I can get skunked
four weekends in a row in Jan/Feb, but I
don't know in adavance.
Macman posted 08-18-2001 08:21 PM ET (US)
Jeez...you engineers want to complicate everything! How about closing the vent and calling it good? Works for me!
Dick posted 08-18-2001 08:37 PM ET (US)
Macman
You beat me to it.
Closing the vent is the simple answer. It works on mine too.
Tom W Clark posted 08-18-2001 11:08 PM ET (US)
Closing the vent is fine for you Montauk and Sport owners but how about owners of boats with built in fuel tanks?
Dick posted 08-19-2001 10:36 AM ET (US)
Tom
Sorry about that, tunnel vision.
It is a real problem with built in tanks and I have never seen a solution. What about an inline shut off valve on the vent hose?

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Author	Topic: Preventing condensation in the gas tank.
triblet	posted 08-17-2001 04:05 PM ET (US) Here's a crazy idea I just had for preventing condensation in the gas tank. Condensation happens because barometric pressure and temperature changes cause the tank to breathe in and out. When it breathes in, it draws in moist air, which then condenses when it gets colder. When to warms up, it breathes out the now slightly drier air. The cycle repeats each day. What if we put a flexible bag on the tank vent. It breathes out and inflates the bag a big. It breathes in and deflates the bag a big. It's the same air and gas fumes, so there's no new moisture getting in. Obviously, the bag would have to be safe for the gas fumes. I'll try it the next time I store my Montauk. Oooops, I forgot, I live in California and we don't winterize. Oh well, maybe one of the snowbirds on the list will run with the idea. Chuck
kingfish	posted 08-17-2001 04:51 PM ET (US) Snowbirds!! Hey, I represent that remark!! jcf
andygere	posted 08-17-2001 05:44 PM ET (US) Chuck, To take the idea a step further, why not build the fuel tank like a hydropnuematic tank with bladder inside that seperates the liquid (fuel) from the air in a closed system? When it warms up, the bladder compresses, when it cools, it expands. Added benefit would be no need for a primer bulb anymore. Just add a little air to the bladder once a year and you're good to go. Could be tricky when adding fuel to the tank though.....
triblet	posted 08-17-2001 06:02 PM ET (US) You'll still need the primer bulb. That's to fill the float bowls back up after they dry up. Nothing to do with air in the tank. However, I never quite figured out why my sports car de jour would fire right up after sitting all winter when an outboard needs a primer bulb. This includes a couple of carbureted models with just a mechanical fuel pump. Chuck
Hank	posted 08-17-2001 11:55 PM ET (US) How about just filling the tank ? Very little air volume will mean little volume change during temperature cycling. Little volume change will result in very little moisture condensation. Hank
Tom W Clark	posted 08-18-2001 12:07 AM ET (US) Hank, Filling the tank is the convetional wisdom but I think triblet's post might be an extension of the query found here: http://continuouswave.com/ubb/Forum4/HTML/000422.html Chuck, Interesting idea. But the problem I see is that the tank and its filler, fuel outlet and vent all need to be sealed in order to withstand a certain small amount of pressure/vacuum. How do you envision sealing the tank on a Whaler?
triblet	posted 08-18-2001 08:17 PM ET (US) Using my Montauk as an example, there are sealing caps. The bag would be on a separate vent (the Pate has two places to attach the tube, I could just use the second one for the bag, Fuel outlet is probably not a problem, the bulb has two check valves. Tank is already sealed. But again, we don't have to worry about winterizing. I boat year round, conditions permitting (admittedly I can get skunked four weekends in a row in Jan/Feb, but I don't know in adavance.
Macman	posted 08-18-2001 08:21 PM ET (US) Jeez...you engineers want to complicate everything! How about closing the vent and calling it good? Works for me!
Dick	posted 08-18-2001 08:37 PM ET (US) Macman You beat me to it. Closing the vent is the simple answer. It works on mine too.
Tom W Clark	posted 08-18-2001 11:08 PM ET (US) Closing the vent is fine for you Montauk and Sport owners but how about owners of boats with built in fuel tanks?
Dick	posted 08-19-2001 10:36 AM ET (US) Tom Sorry about that, tunnel vision. It is a real problem with built in tanks and I have never seen a solution. What about an inline shut off valve on the vent hose?