Grounding Gas Tank - Curious

The answer to #4 is that you do have to run a separate ground wire from
the deck fill to ground. It is also a good idea to tap the fuel filler
nozzel against the deck fill before you open it to drain any built up
potential. Aircraft fuel trucks have a separate ground clip that is
attatched to the airplane before fueling to drain any charge.

Gary Warner wrote:

 > So yesterday we went up to see a boat restorer in upstate NY.
 > VERY nice guy. Anyway, while talking he reminded me that
 > I need to run a ground wire from my steel gas tank to the
 > engine or other ground point. ~ I'm sure this is a good idea
 > that can't hurt, but I'm just wondering:
 >
 > #1 - What exactly could happen without that. I assume it's that
 > a static electric charge could build up on the tank or on me...and
 > when I touch the gas cap a spark happens in the tank?
 >
 > #2 - Is the real purpose of the ground to the engine is because
 > the engine is grounded to the battery or is it because the engine
 > is connected to the drive shaft which is in the water (true ground).
 >
 > #3 - What happens when the boat is on the trailer? Then none of
 > the boat is grounded....It's setting on wooden bunks and on rubber
 > tires? Couldn't I still get a spark then? ~ It's like a car...that has a
 > gas tank, but it's not grounded since it all sets on rubber tires?
 >
 > #4 - Lastly, do the hoses at gas stations connect to ground? The
 > hoses appear to be rubber but I suppose maybe they are special
 > hoses with some ground wire embedded in the rubber to take
 > away any static charge ??
 >
 > THANKS
 > Gary
 >
 >
 >
 >
 >

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"Gary Warner" <jabadoodle.TakeThisOut@yahoo.com> wrote in message
news:bnr8pr$14mesm$1@ID-149710.news.uni-berlin.de...

 > #1 - What exactly could happen without that.

If you have a gas guage, the sending unit needs a ground in order to
operate. Since the sending unit frame is "ground" it will connect the tank
to ground at the same time. In many cases, it is the tank that is grounded
and the sending unit gets its ground from the tank.

 > I assume it's that
 > a static electric charge could build up on the tank or on me...and
 > when I touch the gas cap a spark happens in the tank?

Static discharge is a concern, not so much from you and/or fill nozzel but
from the fill plate to the tank. There isn't much you can do to equalize
the charge between the fill nozzel and the boat. As you pointed out, a car
is isolated from ground by the rubber tires. What you can protect against
is a buildup of charge between the fill plate and the tank The fill plate
and tank are generally connected via a rubber hose. If there is no other
electrical connection, it is possible for the gasoline running down the hose
to create a static buildup which create an arc at some point. Running a
ground wire between the two assures that this won't happen.


 > #2 - Is the real purpose of the ground to the engine is because
 > the engine is grounded to the battery or is it because the engine
 > is connected to the drive shaft which is in the water (true ground).

It is a good idea to have a "ground" bonding system that connects everything
together. The engine is usually the common connection point as it offers a
lot of opportunities to make such a connection, plus it is the source of 12
volt power when the engine is running. The battery would be a good spot
except that having too many wires connecting to the battery gets to be a
mess and is a real hassel when you have to change the battery.

There are several reasons why you want everything tied together with an
intended ground bond system. The primary reason is that if you don't
intentionally provide a ground path, you may end up with an unintentional
ground path that could cause problems. This is especially true of any
thru-hull fitting where the unintended ground path could be through the
water and result in electrolysis.

Rod<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Grounding Gas Tank - Curious 

The only gas gauge on this boat is going to be a stick.

And our filler pipe is a nipple screwed directly to the tank.

But thanks for all the comments anyway...the common ground
ideas apply just fine.
 >> Stay informed about: Grounding Gas Tank - Curious 

On Thu, 30 Oct 2003 09:55:53 -0500, "Gary Warner"
<jabadoodle.DeleteThis@yahoo.com> wrote:

 >
 >So yesterday we went up to see a boat restorer in upstate NY.
 >VERY nice guy. Anyway, while talking he reminded me that
 >I need to run a ground wire from my steel gas tank to the
 >engine or other ground point. ~ I'm sure this is a good idea
 >that can't hurt, but I'm just wondering:
 >
 >#1 - What exactly could happen without that. I assume it's that
 >a static electric charge could build up on the tank or on me...and
 >when I touch the gas cap a spark happens in the tank?

BOOOM!
 >
 >#2 - Is the real purpose of the ground to the engine is because
 >the engine is grounded to the battery or is it because the engine
 >is connected to the drive shaft which is in the water (true ground).

Static grounds don't have to handle major lightning strikes, just
provide a leakage path to bleed off the charge before it sparks. The
electrons don't produce BOOOOM!, the heat from the spark does. It's
the heat that sets it off.
 >
 >#3 - What happens when the boat is on the trailer? Then none of
 >the boat is grounded....It's setting on wooden bunks and on rubber
 >tires? Couldn't I still get a spark then? ~ It's like a car...that has a
 >gas tank, but it's not grounded since it all sets on rubber tires?

Naw....it leaks off quite nicely. My tank is polyethelene in my cheap
Sea Ray. It's just sitting in the bilge, held in with a couple of
little plastic angle brackets and some chewing gum. Polyethelene is
one of the finest insulators we know of. Take a poly bag and shuffle
it across the bed in the dark. It looks like a miniature thunder
storm!
 >
 >#4 - Lastly, do the hoses at gas stations connect to ground? The
 >hoses appear to be rubber but I suppose maybe they are special
 >hoses with some ground wire embedded in the rubber to take
 >away any static charge ??

Yes, these hoses are CONDUCTIVE back to the grounded pump. Conductive
rubber is used on airplanes for tires for the same reason, to bleed
off static buildup.



Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"<!-- ~MESSAGE_AFTER~ -->
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Larry W4CSC wrote:


 > Conductive rubber is used on airplanes for tires for
  > the same reason, to bleed off static buildup.

Larry, airplane tires are no more or less conductive than nearly any
other vehicle tire.

Do you have a book of wierd technical myths that you drag out every
couple of days or do these ideas just kind of jump off your fingertips
onto the keyboard?

Rick<!-- ~MESSAGE_AFTER~ -->
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On Thu, 30 Oct 2003 19:14:30 GMT, nospam.TakeThisOut@home.com (Larry W4CSC) wrote:

 >Take a poly bag and shuffle
 >it across the bed in the dark. It looks like a miniature thunder
 >storm!

Larry, what exactly do you do in the evening <!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Grounding Gas Tank - Curious 

Aircraft hangers generally have ground points to attach the aircraft to.

"Rick" <woodtugs RemoveThis @dearthlink.nyet> wrote in message
news:81fob.8501$Px2.929@newsread4.news.pas.earthlink.net...
 > Larry W4CSC wrote:
 >
 >
  > > Conductive rubber is used on airplanes for tires for
  > > the same reason, to bleed off static buildup.
 >
 > Larry, airplane tires are no more or less conductive than nearly any
 > other vehicle tire.
 >
 > Do you have a book of wierd technical myths that you drag out every
 > couple of days or do these ideas just kind of jump off your fingertips
 > onto the keyboard?
 >
 > Rick
 ><!-- ~MESSAGE_AFTER~ -->
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On Thu, 30 Oct 2003 09:55:53 -0500, "Gary Warner"
<jabadoodle.TakeThisOut@yahoo.com> wrote:

 >
 >So yesterday we went up to see a boat restorer in upstate NY.
 >VERY nice guy. Anyway, while talking he reminded me that
 >I need to run a ground wire from my steel gas tank to the
 >engine or other ground point. ~ I'm sure this is a good idea
 >that can't hurt, but I'm just wondering:
 >
 >#1 - What exactly could happen without that. I assume it's that
 >a static electric charge could build up on the tank or on me...and
 >when I touch the gas cap a spark happens in the tank?

Yes, sort of. Any positive static charge on you or the nozzle will
transfer to the filler hose or fitting. Most of the time, this is not
a problem. Sometimes it creates a spark, in the presence of fuel
vapor, which is a big problem.
 >
 >#2 - Is the real purpose of the ground to the engine is because
 >the engine is grounded to the battery or is it because the engine
 >is connected to the drive shaft which is in the water (true ground).
 >
Two different animals. The engine ground serves the electrical
operation of the engine and accesories. The fuel filler ground
attempts to dissipate any charge (electrical potential) difference
between you, the pump, and the boat. Static electrical charges occur
naturally. The problem arises when there is a *difference* in the
charges (potential=voltage). Contact will normally equalise the
potential.

 >#3 - What happens when the boat is on the trailer? Then none of
 >the boat is grounded....It's setting on wooden bunks and on rubber
 >tires? Couldn't I still get a spark then? ~ It's like a car...that has a
 >gas tank, but it's not grounded since it all sets on rubber tires?

Static charges can, and do, dissipate over the surface of
non-conductor materials. Contact is a primary ingredient in the
transfer. When you shuffle "sock feet" across the carpet and touch
the door knob, is the door knob grounded? No, not normally. Can you
get a spark? Absolutely, because you have built up a static
*difference* in potential (voltage). This spark is what can hurt you
while fueling.
 >
 >#4 - Lastly, do the hoses at gas stations connect to ground? The
 >hoses appear to be rubber but I suppose maybe they are special
 >hoses with some ground wire embedded in the rubber to take
 >away any static charge ??

Yes, gas station fuel hoses are grounded. This is good, but also
presents a possible problem. If you create a static potential while
filling (i.e. let go of the nozzle and get back in the vehicle), there
is a possibility of a transfer (spark) when you re-touch the nozzle,
or remove it from the filler on your boat. It is rare, but it does
happen. To eliminate this potential hazard, always touch the pump
nozzle to the filler cap before you open it (discharges any static
potential difference), then do not let go of the nozzle while filling
(keeps the static potential equal).

Yes, I know, some gas nozzles have a "hold open" tab for convenience.
If you are concerned about safety and potential explosion; don't use
them.
 >
 >THANKS
 >Gary
 >
 >
 >
 >

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