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Grounding architecture
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nuckolls.bob(at)aeroelect
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PostPosted: Thu Jul 26, 2018 7:16 am    Post subject: Grounding architecture Reply with quote

Okay . . . the resistance of that wire is probably
100 times higher than the airframe. The wire doesn't
hurt anything but it adds no value . . .

Isn't the point of having a bus or 'field of tabs' grounded directly to the negative batt terminal to prevent ground loops through the airframe? If so, why then is the wire of no value, because of its length due to being run from the rear?

From the explanation above, it sounds like both ends (batt neg terminal and ground bus) are also grounded to the airframe, is that correct?

Could you specify which wire is 'adds no value' and how the planned system SHOULD be grounded then? Thanks!

We're talking two separate issues:

(1) Ground path integrity for DC power
distribution and . . .

(2) shared ground paths bet ween potential
antagonists [alternators, strobe supplies,
etc] and potential victims [audio systems,
some avitonics].

This thread is about issue #1. Yes, we'd
like to achieve the lowest practical path
resistance between the battery(-) and the
firewall ground block. For aircraft with the
battery forward, taking battery(-) directly
to the stud is ideal and practical.

For batteries mounted aft in a metal aircraft,
taking battery(-) to structure is the most
practical.

https://goo.gl/28exWU

Now, if one were to measure the airframe
resistance between the battery(-) grounding
location on the airframe and the firewall
ground block stud, one would measure some
exceedingly small resistance . . . generally
under 0.001 ohms (resistance from nose to
tailcone on a Beechjet is right at .001 ohms).

Enhancements to conductivity by adding some bit
of wire in PARALLEL with the structure would
be very difficult to measure.

GROUND LOOPS are a separate discussion unique
to managing grounds for potential victims
and is unrelated to management of DC power.


Bob . . .


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Rocketman1988



Joined: 21 Jun 2012
Posts: 57

PostPosted: Thu Jul 26, 2018 11:15 am    Post subject: Re: Grounding architecture Reply with quote

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

Similar to the Z-15 diagram...


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BARRY CHECK 6



Joined: 15 Mar 2011
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PostPosted: Thu Jul 26, 2018 6:13 pm    Post subject: Grounding architecture Reply with quote

Nothing beats a copper wire ground on a plane.
There is no reason why you can not do both...  A wire from the battery to the Firewall/Ground Buss and a short Ground wire to the airframe.  
Barry
On Thu, Jul 26, 2018 at 3:15 PM, Rocketman1988 <Rocketman(at)etczone.com (Rocketman(at)etczone.com)> wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com (Rocketman(at)etczone.com)>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan?  Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?




Read this topic online here:

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PostPosted: Thu Jul 26, 2018 6:57 pm    Post subject: Grounding architecture Reply with quote

On 7/26/2018 2:15 PM, Rocketman1988 wrote:
Quote:


So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

I think the idea is that running the extra ground wire forward is not a

*bad* idea; just an unnecessary  one, in a metal a/c. The airframe will
be a lower resistance ground path than any practically size wire.

Problems related to the ground loop issue are usually limited to audio
gear. I'm sure Bob can give you a better, more precise description of
what happens. But my layman's description is this: If a low level
signal, like audio, shares its ground return path with much stronger,
'noisy' electrical signals, like a strobe, the strobe noise can
effectively become part of the audio signal, and you get the noise in
the audio system. To prevent that, you use the 'forest of tabs' located
somewhere near the audio (and other low signal level) gear, and run all
low level signals to that spot instead of through the airframe. That
keeps the ground paths of the low level stuff & the 'noisy' stuff separate.

Charlie

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Rocketman1988



Joined: 21 Jun 2012
Posts: 57

PostPosted: Thu Jul 26, 2018 7:38 pm    Post subject: Re: Grounding architecture Reply with quote

If running a large wire ground isn't necessary, how does Z-15 fit in?

Just curious...


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PostPosted: Thu Jul 26, 2018 7:57 pm    Post subject: Grounding architecture Reply with quote

On 7/26/2018 10:38 PM, Rocketman1988 wrote:
Quote:


If running a large wire ground isn't necessary, how does Z-15 fit in?

Just curious...
Are you asking me? (no context for your question in the email version)


If so, did you read the text (pg z-4) that's associated with the drawing?

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PostPosted: Fri Jul 27, 2018 6:54 am    Post subject: Grounding architecture Reply with quote

At 09:13 PM 7/26/2018, you wrote:
Quote:
Nothing beats a copper wire ground on a plane.
There is no reason why you can not do both... A wire from the battery to the Firewall/Ground Buss and a short Ground wire to the airframe.

Can you support your assertion with an
analysis of the physics? Aluminum is not
a poor conductor. In fact, overhead transmission
lines for long distance power distribution are
aluminum over steel cables.

If the resistance between battery ground in
the tail and a firewall ground block is already
on the order of .001 ohms, how much of the
airframe current is shunted off onto a paralleled
wire? What benefit is realized by this 'sharing'
of battery current?

Except when cranking the engine, the
total current flowing through the battery
ground path will not exceed alternator capacity
and then only for the minutes needed to top
of the battery. Battery currents in normal
operations are essentially zero . . .





Bob . . .


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PostPosted: Fri Jul 27, 2018 6:59 am    Post subject: Grounding architecture Reply with quote

Bob's point is that it is completely unnecessary.  I have a robust battery to ground connection at the battery and at my firewall grounding bar:
Battery Mount and Ground (680s)
Firewall ground
You can see in the first link the 8AWG white wire going forward to the grounding bar.  If it is unnecessary then I consider a bad plan.  An error on my part that simply added weight.

On 7/26/2018 3:15 PM, Rocketman1988 wrote:

Quote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com> (Rocketman(at)etczone.com)

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=481866#481866





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Rocketman1988



Joined: 21 Jun 2012
Posts: 57

PostPosted: Fri Jul 27, 2018 7:01 am    Post subject: Re: Grounding architecture Reply with quote

Bob, so is there anything wrong with a grounding plan similar to the Z-15 for the Rv-10? It is simple enough to run that 2awg wire now, not so much later. For reference, the main 2awg wire running from the battery to the starter contactor is about 12 feet long. The ground would obviously be about the same.

Thanks in advance...


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PostPosted: Fri Jul 27, 2018 7:02 am    Post subject: Grounding architecture Reply with quote

At 02:15 PM 7/26/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

It's not 'bad' . . . just unnecessary when
a lighter alternative is available. Airplanes
like Beechjets and Hawkers have all manner
of airframe grounds that carry currents from
amps to thousands of amps (starter inrush).

There are NO wires installed to avoid running
ground returns through airframes. Well, almost
no wires . . . had a case on a T1 trainer (Beechjet)
in Mississippi where four strands of 2awg were
routed from tail to nose to carry power and
ground to a nose mounted air conditioning
compressor motor (3+ horsepower). This
antagonist was so profound that running
motor current over so much of the airframe
was a noise disaster. But that's another
story.



Bob . . .


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PostPosted: Fri Jul 27, 2018 7:07 am    Post subject: Grounding architecture Reply with quote

Charlie:
How can an aluminum - Riveted skin be a lower resistance than a straight run of copper wire?
It can't since aluminum has a higher resistance than copper.  To that add the poor connection of riveted panels.
Also remember aluminum sheeting is clear coat anodized.
Barry 
On Thu, Jul 26, 2018 at 10:58 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

On 7/26/2018 2:15 PM, Rocketman1988 wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com (Rocketman(at)etczone.com)>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan?  Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

I think the idea is that running the extra ground wire forward is not a *bad* idea; just an unnecessary  one, in a metal a/c. The airframe will be a lower resistance ground path than any practically size wire.

Problems related to the ground loop issue are usually limited to audio gear. I'm sure Bob can give you a better, more precise description of what happens. But my layman's description is this: If a low level signal, like audio, shares its ground return path with much stronger, 'noisy' electrical signals, like a strobe, the strobe noise can effectively become part of the audio signal, and you get the noise in the audio system. To prevent that, you use the 'forest of tabs' located somewhere near the audio (and other low signal level) gear, and run all low level signals to that spot instead of through the airframe. That keeps the ground paths of the low level stuff & the 'noisy' stuff separate.

Charlie

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PostPosted: Fri Jul 27, 2018 7:49 am    Post subject: Grounding architecture Reply with quote

Because the cross sectional area of the fuselage is many times greater than the cross section of the putative wire, and rivets are great conductors?

On Jul 27, 2018, at 16:07, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
Charlie:
How can an aluminum - Riveted skin be a lower resistance than a straight run of copper wire?
It can't since aluminum has a higher resistance than copper. To that add the poor connection of riveted panels.
Also remember aluminum sheeting is clear coat anodized.
Barry
On Thu, Jul 26, 2018 at 10:58 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

On 7/26/2018 2:15 PM, Rocketman1988 wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com (Rocketman(at)etczone.com)>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

I think the idea is that running the extra ground wire forward is not a *bad* idea; just an unnecessary one, in a metal a/c. The airframe will be a lower resistance ground path than any practically size wire.

Problems related to the ground loop issue are usually limited to audio gear. I'm sure Bob can give you a better, more precise description of what happens. But my layman's description is this: If a low level signal, like audio, shares its ground return path with much stronger, 'noisy' electrical signals, like a strobe, the strobe noise can effectively become part of the audio signal, and you get the noise in the audio system. To prevent that, you use the 'forest of tabs' located somewhere near the audio (and other low signal level) gear, and run all low level signals to that spot instead of through the airframe. That keeps the ground paths of the low level stuff & the 'noisy' stuff separate.

Charlie

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PostPosted: Fri Jul 27, 2018 8:48 am    Post subject: Grounding architecture Reply with quote

That, and the unrelated point that no aircraft grade aluminum sheet is anodized, clear or otherwise.
Barry, where are you getting your misinformation?
Charlie
Charlie
On Jul 27, 2018, at 10:55 AM, Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:
Quote:

Because the cross sectional area of the fuselage is many times greater than the cross section of the putative wire, and rivets are great conductors?

On Jul 27, 2018, at 16:07, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
Charlie:
How can an aluminum - Riveted skin be a lower resistance than a straight run of copper wire?
It can't since aluminum has a higher resistance than copper. To that add the poor connection of riveted panels.
Also remember aluminum sheeting is clear coat anodized.
Barry
On Thu, Jul 26, 2018 at 10:58 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

On 7/26/2018 2:15 PM, Rocketman1988 wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com (Rocketman(at)etczone.com)>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

I think the idea is that running the extra ground wire forward is not a *bad* idea; just an unnecessary one, in a metal a/c. The airframe will be a lower resistance ground path than any practically size wire.

Problems related to the ground loop issue are usually limited to audio gear. I'm sure Bob can give you a better, more precise description of what happens. But my layman's description is this: If a low level signal, like audio, shares its ground return path with much stronger, 'noisy' electrical signals, like a strobe, the strobe noise can effectively become part of the audio signal, and you get the noise in the audio system. To prevent that, you use the 'forest of tabs' located somewhere near the audio (and other low signal level) gear, and run all low level signals to that spot instead of through the airframe. That keeps the ground paths of the low level stuff & the 'noisy' stuff separate.

Charlie

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PostPosted: Fri Jul 27, 2018 9:16 am    Post subject: Grounding architecture Reply with quote

right... it’s a strong aluminium alloy clad in pure (soft, but corrosion resistant) aluminium. Hence “Alclad”.

On Jul 27, 2018, at 17:48, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
That, and the unrelated point that no aircraft grade aluminum sheet is anodized, clear or otherwise.
Barry, where are you getting your misinformation?
Charlie
Charlie
On Jul 27, 2018, at 10:55 AM, Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:
Quote:

Because the cross sectional area of the fuselage is many times greater than the cross section of the putative wire, and rivets are great conductors?

On Jul 27, 2018, at 16:07, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
Charlie:
How can an aluminum - Riveted skin be a lower resistance than a straight run of copper wire?
It can't since aluminum has a higher resistance than copper. To that add the poor connection of riveted panels.
Also remember aluminum sheeting is clear coat anodized.
Barry
On Thu, Jul 26, 2018 at 10:58 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

On 7/26/2018 2:15 PM, Rocketman1988 wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com (Rocketman(at)etczone.com)>

So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall stud a bad plan? Would a basic airframe ground be the better option,i.e. ground the batteries at their aft mounted location?

I think the idea is that running the extra ground wire forward is not a *bad* idea; just an unnecessary one, in a metal a/c. The airframe will be a lower resistance ground path than any practically size wire.

Problems related to the ground loop issue are usually limited to audio gear. I'm sure Bob can give you a better, more precise description of what happens. But my layman's description is this: If a low level signal, like audio, shares its ground return path with much stronger, 'noisy' electrical signals, like a strobe, the strobe noise can effectively become part of the audio signal, and you get the noise in the audio system. To prevent that, you use the 'forest of tabs' located somewhere near the audio (and other low signal level) gear, and run all low level signals to that spot instead of through the airframe. That keeps the ground paths of the low level stuff & the 'noisy' stuff separate.

Charlie

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PostPosted: Fri Jul 27, 2018 12:57 pm    Post subject: Grounding architecture Reply with quote

At 10:07 AM 7/27/2018, you wrote:
Quote:
Charlie:

How can an aluminum - Riveted skin be a lower resistance than a straight run of copper wire?

It's a 'cross section' thing. The square inches of conductor
cross-section from nose to tail of a metal airplane is
a whole lot bigger than any practical chunk of wire
you might choose to run.

Quote:
It can't since aluminum has a higher resistance than copper.

Depending on the alloy, aluminum will present
a volume resistivity on the order of 2.82x10^-8
while copper will be about 1.68x10^-8 or 67%
higher. Given that the cross section of wire
goes up with the square of diameter, an aluminum
wire only needs to be about 30% larger. This
speaks to the success of Eric's offer for copper-
clad, fine-strand FAT wires.

https://goo.gl/8HTqEV

In spite of being larger wires, they are lighter
for the same electrical performance. This also
speaks to the preference for using aluminum in
long distance transmission lines . . . the lighter
wire makes for a smaller steel core in the makeup
of the strands.


Quote:
To that add the poor connection of riveted panels.


A properly sized rivet SWELLS up in the hole
with such force that a gas-tight connection
is achieved even when the sheet is coated with
corrosion preventatives.

Quote:
Also remember aluminum sheeting is clear coat anodized.

Yes, there are come chemical passivation processes
offered for aluminum sheet . . . which has zero
influence on the electrical integrity of riveted
joints.


Bob . . .


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PostPosted: Fri Jul 27, 2018 1:12 pm    Post subject: Grounding architecture Reply with quote

At 10:01 AM 7/27/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "Rocketman1988" <Rocketman(at)etczone.com>

Bob, so is there anything wrong with a grounding plan similar to the Z-15 for the Rv-10? It is simple enough to run that 2awg wire now, not so much later. For reference, the main 2awg wire running from the battery to the starter contactor is about 12 feet long. The ground would obviously be about the same.

If you don't mind the weight penalty and cost
of installation, no . . . it will perform as
advertised.

I've updated View -A- to Z-15 to add a note on
the battery(-) connection to (1) suggest it
be used as shown on forward/rear mounted batteries
in plastic and forward mounted batteries in
metal airplanes. It can be replaced with local
grounding of the battery on a metal airplane.

https://goo.gl/NtQT1P

We've discussed this on several occasions over
the years but the conclusions didn't get
carried over to Z-15.




Bob . . .


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Kellym



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Posts: 1545
Location: Sun Lakes AZ

PostPosted: Fri Jul 27, 2018 5:20 pm    Post subject: Grounding architecture Reply with quote

You are comparing 2AWG copper or lesser, to almost infinite size
aluminum, which is NOT clear coat anodized, never has been, as far as
the common varieties such as 2024T3 or 5056. The 2024 in fact has a thin
layer of pure aluminum at the surface, known as alclad. Rivets are in
fact gas tight metal to metal connections.
Have you any data to assert that the copper has less resistance?
Kelly

On 7/27/2018 10:07 AM, FLYaDIVE wrote:
Quote:
Charlie:

How can an aluminum - Riveted skin be a lower resistance than a straight
run of copper wire?
It can't since aluminum has a higher resistance than copper.  To that
add the poor connection of riveted panels.
Also remember aluminum sheeting is clear coat anodized.

Barry

On Thu, Jul 26, 2018 at 10:58 PM, Charlie England <ceengland7(at)gmail.com
<mailto:ceengland7(at)gmail.com>> wrote:


<ceengland7(at)gmail.com <mailto:ceengland7(at)gmail.com>>

On 7/26/2018 2:15 PM, Rocketman1988 wrote:


<Rocketman(at)etczone.com <mailto:Rocketman(at)etczone.com>>

So is running a 2 AWG cable from the aft mounted batteries on an
RV 10 to a firewall stud a bad plan?  Would a basic airframe
ground be the better option,i.e. ground the batteries at their
aft mounted location?

I think the idea is that running the extra ground wire forward is
not a *bad* idea; just an unnecessary  one, in a metal a/c. The
airframe will be a lower resistance ground path than any practically
size wire.

Problems related to the ground loop issue are usually limited to
audio gear. I'm sure Bob can give you a better, more precise
description of what happens. But my layman's description is this: If
a low level signal, like audio, shares its ground return path with
much stronger, 'noisy' electrical signals, like a strobe, the strobe
noise can effectively become part of the audio signal, and you get
the noise in the audio system. To prevent that, you use the 'forest
of tabs' located somewhere near the audio (and other low signal
level) gear, and run all low level signals to that spot instead of
through the airframe. That keeps the ground paths of the low level
stuff & the 'noisy' stuff separate.

Charlie

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PostPosted: Fri Jul 27, 2018 6:49 pm    Post subject: Grounding architecture Reply with quote

At 08:19 PM 7/27/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com>

You are comparing 2AWG copper or lesser, to almost infinite size aluminum, which is NOT clear coat anodized, never has been, as far as the common varieties such as 2024T3 or 5056. The 2024 in fact has a thin layer of pure aluminum at the surface, known as alclad. Rivets are in fact gas tight metal to metal connections.
Have you any data to assert that the copper has less resistance?

It's a fact of physics that copper is
a better conductor than aluminum in the
same cross section. The harder thing to
wrap your arms around is to consider the
effective cross section of a fuselage
structure covered in a relatively thin
layer of aluminum. The path traveled by
current flows through the airframe do not
move is straight lines but will concentrate
over the areas of least resistance.

There have been studies and experiments
run for effects of direct lightning strikes.
Intuitively we can assert that small aircraft
will have higher resistance between similar
locations on the airframe . . . but for this
thread, it's sufficient to assert that adding
an extra wire between battery(-) in the tail
and firewall ground stud will produce no
demonstrable benefit.

A 12' run of 22759 2AWG at ~0.28 pounds/ft
adds about 3.4 pounds to the aircraft's
empty weight.



Bob . . .


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Joined: 10 Jan 2006
Posts: 559
Location: Massachusetts

PostPosted: Sat Jul 28, 2018 6:50 am    Post subject: Re: Grounding architecture Reply with quote

Years ago Bob N. put togther a little collection called the "Economics of Weight Reduction", in which he had a piece I had written. It is still on the Aeroelectric Connection, but I attach it here. Good reading.

I too, wonder about using the aluminum skin for a ground conductor...Not that it doesn't work in most cases (it does work), but as the structure ages, and in some special cases, it gives me pause. The rivets could grow weak any you wouldn't even know it.

My guess is that steel airframes are best not used as ground due to magnetization.

Also to be sure, Aluminum is a far better conductor than copper per weight. I also include my piece on the subject.

I sell a lot of Copper Clad Aluminum cable to people who are extremely careful with weight. Drones, NASCAR, EAA aircraft, NASA,Aerovironment, TOP FUEL DRAGSTERS!, Searey, many others. There has never been a problem history with CCA.


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PostPosted: Sat Jul 28, 2018 7:11 am    Post subject: Grounding architecture Reply with quote

On 7/28/2018 9:50 AM, Eric M. Jones wrote:
Quote:


Years ago Bob N. put togther a little collection called the "Economics of Weight Reduction", in which he had a piece I had written. It is still on the Aeroelectric Connection, but I attach it here. Good reading.

I too, wonder about using the aluminum skin for a ground conductor...Not that it doesn't work in most cases (it does work), but as the structure ages, and in some special cases, it gives me pause. The rivets could grow weak any you wouldn't even know it.

My guess is that steel airframes are best not used as ground due to magnetization.

Also to be sure, Aluminum is a far better conductor than copper per weight. I also include my piece on the subject.

I sell a lot of Copper Clad Aluminum cable to people who are extremely careful with weight. Drones, NASCAR, EAA aircraft, NASA,Aerovironment, TOP FUEL DRAGSTERS!, Searey, many others. There has never been a problem history with CCA.

--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net


The obvious solution to the unlikely resistance growth issue would be to
use a longeron. Obviously won't apply to every a/c design, but the RVs
have a continuous longeron from firewall to tail. Tying to a longeron
(1/8 thick x 3/4 x 3/4 inches)  would give an unbroken path.

Charlie

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