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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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 Posted: Mon Apr 03, 2006 5:00 am Post subject: Top Gun Dave/Fueling the Kitfox |
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I am using a Mr. Funnel to direct the fuel/filter the fuel into the
tank. This funnel is supposed to be the conducting model...that is, it
is made with carbon black as I understand it. Now I guess I'll have to
make a resistance check of the funnel. It's gonna seem strange to hook
up an ohmmeter to a piece of plastic, but what the heck?!
So if I make sure the spout of the plastic fuel can contacts the rim of
the (conductive) Mr. Funnel, which is in contact with the metal neck of
the Kitfox's fuel tank, which has (in my case) a bonding strap soldered
to it, and the bonding strap is electrically attached to the exhaust
pipe, and I attach a grounding jumper to the earth's ground (piece of
pipe driven into the dirt floor of the hangar, or any suitable ground
if fueling somewhere other than my hangar), I am safe?
Lynn
On Sunday, April 2, 2006, at 11:50 PM, James Shumaker wrote:
| Quote: |
<jimshumaker(at)sbcglobal.net>
Lynn
6 ohms is plenty low. In fact anything below 100 ohms is fine.
Because the voltage (think pressure) must be very high in order to get
a spark to jump a gap (normal static sparks are on the order of 10,000
volts) high resistances can drain off the charge before enough voltage
builds up. Where you need to be careful is that you use a
semiconducting funnel or a metal fuel spout when pouring into the
tank. When the fuel falls into the tank and the little drops seperate
from the main stream they each carry a charge which can build up a
differential potential (another way of saying voltage). Thus if you
had an insulating funnel then the charge differential would be between
the planes fuel tank and the filling can. A conducting funnel has a
high resitance that lets the charge leak slowly back to the can.
Jim Shumaker
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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wingnut
Joined: 11 Jan 2006
Posts: 356
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| Posted: Mon Apr 03, 2006 7:32 am Post subject: Re: Top Gun Dave/Fueling the Kitfox |
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Don't you need to ground the gas can first? If there's a charge in the gas can (or the gas in the can) and the first opportunity for that electricity to dissipate is through contact with the funnel, wouldn't that be the most likely place for a spark to occur?
| Quote: | So if I make sure the spout of the plastic fuel can contacts the rim of the (conductive) Mr. Funnel, which is in contact with the metal neck of
the Kitfox's fuel tank, which has (in my case) a bonding strap soldered
to it, and the bonding strap is electrically attached to the exhaust
pipe, and I attach a grounding jumper to the earth's ground (piece of
pipe driven into the dirt floor of the hangar, or any suitable ground
if fueling somewhere other than my hangar), I am safe?
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mike
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| Posted: Mon Apr 03, 2006 9:07 am Post subject: Re: Top Gun Dave/Fueling the Kitfox |
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put the gas can on the cement floor.
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pwmac(at)sisna.com
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| Posted: Mon Apr 03, 2006 9:20 am Post subject: Top Gun Dave/Fueling the Kitfox |
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Yes ground the items before doing a fuel transfer. Having said that I doubt
if a static charge would be present on a non flowing tank. Its the flow of
liquid in the air that creates a static charge. I assume you filled the
portable can when it was properly grounded. If it has been sitting on the
ground then I would expect no charge to be present.
The sequence is probably not significant. If you have grounded your filler
neck to the spar then I would connect the wing spar to ground. (Connect the
ground to wherever you terminated the ground strap leading from the filler
neck on the tank). And connect the fuel source to ground. Then proceed with
the transfer process making sure all the items are in contact with each
other. A conductive hose, jerry can, or funnel are good for reduced risk.
I would intuitively think that connecting the plane filler neck to ground
would be a risky thing to do.
Paul
===================
At 08:32 AM 4/3/2006, you wrote:
| Quote: |
Don't you need to ground the gas can first? If there's a charge in the gas
can (or the gas in the can) and the first opportunity for that electricity
to dissipate is through contact with the funnel, wouldn't that be the most
likely place for a spark to occur?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=26252#26252
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pwmac(at)sisna.com
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| Posted: Mon Apr 03, 2006 9:26 am Post subject: Top Gun Dave/Fueling the Kitfox |
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Cement floor like a sidewalk or the concrete at the gas station. But not
the elastomer coated hanger floor.
Paul
==============
At 10:07 AM 4/3/2006, you wrote:
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rexjan(at)bigpond.com
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| Posted: Tue Apr 04, 2006 5:54 pm Post subject: Top Gun Dave/Fueling the Kitfox |
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Lynn,
I think re measuring the conductivity of the funnel you will find no reading on an ordinary multimeter reading ohms. You will need an instrument called a megger. This actually measures the ohms resistance using about 500 volts whereas a multimeter is between 1.5 and 9 volts. The 500 volts needed to get your reading is OK as you are aren't going to get a spark at low voltage occuring in your filling situation. Also be prepared that the reading will probaly be fairly high ohms. Again this is ok as it only needs to bleed, fairly quickly, off the voltage. [ static build up ]
I just thought I'd point this out before everyone meaured their conducting funnels with a multimeter and got no reading and worried about it.
Rex Shaw
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Wed Apr 05, 2006 3:47 am Post subject: Top Gun Dave/Fueling the Kitfox |
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Thanks for reminding me, Rex, that I took the readings the other day
and wrote them down on a scrap of paper and promptly shuffled the paper
under other scraps near my computer station. : )
My readings were somewhat scrambled on my Craftsman AutoRanging
MultiMeter (digital...about $80)....one of these days I'll get a
Fluke..I won't know what to do with it, but it'll look impressive to
those that know.
Anyway, the readings I got were in the neighborhood of 22K-150K ohms,
and occasionally bounced up to 1.3M ohms. I was going to report this
and became distracted by helping out on another project, and forgot.
Kitfox IV...Jabiru 2200
On Wednesday, April 5, 2006, at 02:25 PM, Rex Shaw wrote:
| Quote: |
Lynn,
I think re measuring the conductivity of the funnel you will
find no reading on an ordinary multimeter reading ohms. You will need
an instrument called a megger. This actually measures the ohms
resistance using about 500 volts whereas a multimeter is between 1.5
and 9 volts. The 500 volts needed to get your reading is OK as you are
aren't going to get a spark at low voltage occuring in your filling
situation. Also be prepared that the reading will probaly be fairly
high ohms. Again this is ok as it only needs to bleed, fairly quickly,
off the voltage. [ static build up ]
I just thought I'd point this out before everyone meaured their
conducting funnels with a multimeter and got no reading and worried
about it.
Rex Shaw
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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