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Grounding question

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Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Thu May 25, 2006 9:54 am Post subject: Grounding question

The RV-10 requires the battery to be mounted aft of the baggage area for 

CG purposes. I just got back from Bob's seminar and like the idea of a 

common ground buss on the firewall. (with the engine grounded on the 

forward side and everything else on the aft side) In Van's wiring 

harness  they have the battery grounded to the airframe close to where 

it's mounted. (way aft) I would prefer to not have to pull/run  two (pos 

& neg) 8-10 ft  #2 welding cables all the way from the battery forward. 

If I were to ground the battery close to it's mount on the airframe, 

whould this cause any problems using a 'common ground buss'?



Thanks for any illumination to this 'electron challenged' builder.



Deems Davis # 406

Fuse

http://deemsrv10.com/

rvbuilder(at)sausen.net
Guest

Posted: Thu May 25, 2006 11:23 am Post subject: Grounding question

Hey Deems,



   I gave this some thought too and decided to sacrifice the weight for =

a good solid electrical path.  For 95% of the stuff you would probably =

be fine.  The single item that comes to mind is the starter.  I also =

wanted to make sure I didn't have as much of a chance of corrosion =

between the joints at the tailcone attach point and the fuselage, or any =

place else the high currents need to travel to get to the starter.  The =

only way to get good bonding is with a bonding strap which would require =

some type of hole through the skin.



  Another thing is if you truly want to use the battery location as a =

common ground point you would then need to run all of your grounds back =

to there which will rapidly negate the benefit.



  I am going to be running #2 from the batteries to the firewall common =

ground point which will then have a through bolt to a mirror image =

engine side common ground point.  95% of my grounds will terminate at =

one of these two points.  The only exceptions will probably be the LED =

wingtip lights, HID landing light (Duckworks DS1 with the starter on the =

bulb), and other low current/noise incandescent type things.  My strobe =

pack and baggage lights are back by the batteries so they will be =

grounded right at the batteries which will still give the desired =

effect.  The whole point to this exercise is really to provide the best =

current handling for the weight, eliminate ground loops, and use the =

batteries as big filters.



  Hope this helps!



Michael Sausen

-10 #352 Fuselage

Do not archive



--

larry(at)macsmachine.com
Guest

Posted: Thu May 25, 2006 12:08 pm Post subject: Grounding question

Deems,

I did exactly as you suggest and have had no problems with it.  Note in 

the link below, the

positive side to each contactor and the negative sides bolt-connected to 

the battery tray with five A5 rivets

on the negative ground lug. It has good contact area being riveted to my 

rear spar and elsewhere.  The firewall ground

block and lug work really well, even considering the firewall, which is 

.015 stainless.



http://www.macsmachine.com/images/electrical/full/chargebatteryconnection.gif



I also used a #4 welding cable for positive going forward to the 

firewall, but my engine is also a 100 h.p. Subaru.



Larry McFarland - 601HDS at www.macsmachine.com



Deems Davis wrote:



 	  Quote: 	
		  



The RV-10 requires the battery to be mounted aft of the baggage area for 

CG purposes. I just got back from Bob's seminar and like the idea of a 

common ground buss on the firewall. (with the engine grounded on the 

forward side and everything else on the aft side) In Van's wiring 

harness  they have the battery grounded to the airframe close to where 

it's mounted. (way aft) I would prefer to not have to pull/run  two (pos 

& neg) 8-10 ft  #2 welding cables all the way from the battery forward. 

If I were to ground the battery close to it's mount on the airframe, 

whould this cause any problems using a 'common ground buss'?



Thanks for any illumination to this 'electron challenged' builder.



Deems Davis # 406

Fuse

http://deemsrv10.com/

Dan.Beadle(at)hq.inclines
Guest

Posted: Thu May 25, 2006 1:23 pm Post subject: Grounding question

Sounds like you are putting the battery in the rear.  Vans recommends a

frame ground instead of running a #2 ground back to the firewall.  I

need the battery aft for balance considerations. Light is great, but I

am concerned about grounding through the airframe. =20



=20



Also, I was figuring to ground the Duckworks HIDs back with a #18.  I do

want light weight, but I want trouble free.



=20



Any thoughts? =20



=20



--

nuckollsr(at)cox.net
Guest

Posted: Thu May 25, 2006 7:59 pm Post subject: Grounding question

Battery can be locally grounded as can other devices REMOTE

from the cockpit equipment like:



(1) Landing, taxi and recognition lights,



(2) nav lights,



(3) strobe power supply,



(4) most fuel pumps ground through their mounting bases,



(5) hydraulic landing gear pumps,



(6) pitot heaters,



(7) and of course antennas which always ground locally

     and are independent of power system grounding

     considerations.



The picture Larry posted is a good example of a technique

which I've amplified with captions on Larry's picture posted

at:



http://www.aeroelectric.com/Pictures/Grounding/Local_Battery_Grounds_1.jpg



Bob . . .



At 03:01 PM 5/25/2006 -0500, you wrote:



 	  Quote: 	
		  

<larry(at)macsmachine.com>



Deems,

I did exactly as you suggest and have had no problems with it.  Note in

the link below, the

positive side to each contactor and the negative sides bolt-connected to

the battery tray with five A5 rivets

on the negative ground lug. It has good contact area being riveted to my

rear spar and elsewhere.  The firewall ground

block and lug work really well, even considering the firewall, which is

.015 stainless.



http://www.macsmachine.com/images/electrical/full/chargebatteryconnection.gif



I also used a #4 welding cable for positive going forward to the

firewall, but my engine is also a 100 h.p. Subaru.



Larry McFarland - 601HDS at www.macsmachine.com



Deems Davis wrote:



 >

 >

 >The RV-10 requires the battery to be mounted aft of the baggage area for

 >CG purposes. I just got back from Bob's seminar and like the idea of a

 >common ground buss on the firewall. (with the engine grounded on the

 >forward side and everything else on the aft side) In Van's wiring

 >harness  they have the battery grounded to the airframe close to where

 >it's mounted. (way aft) I would prefer to not have to pull/run  two (pos

 >& neg) 8-10 ft  #2 welding cables all the way from the battery forward.

 >If I were to ground the battery close to it's mount on the airframe,

 >whould this cause any problems using a 'common ground buss'?

 >

 >Thanks for any illumination to this 'electron challenged' builder.

 >

 >Deems Davis # 406

 >Fuse

 >http://deemsrv10.com/

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >

 >





--



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Checked by AVG Anti-Virus.


	




        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

nuckollsr(at)cox.net
Guest

Posted: Thu May 25, 2006 8:00 pm Post subject: Grounding question

At 10:51 AM 5/25/2006 -0700, you wrote:



 	  Quote: 	
		  



The RV-10 requires the battery to be mounted aft of the baggage area for

CG purposes. I just got back from Bob's seminar and like the idea of a

common ground buss on the firewall. (with the engine grounded on the

forward side and everything else on the aft side) In Van's wiring

harness  they have the battery grounded to the airframe close to where

it's mounted. (way aft) I would prefer to not have to pull/run  two (pos

& neg) 8-10 ft  #2 welding cables all the way from the battery forward.

If I were to ground the battery close to it's mount on the airframe,

whould this cause any problems using a 'common ground buss'?



Thanks for any illumination to this 'electron challenged' builder.


	


    Batteries (and lots of other stuff) have been grounded locally

    to airframe structure since day-one. ALL of our aircraft at RAC

    ground batteries to local structure. This isn't an inherently

    evil thing to do as long as potential victims (generally stuff in

    cockpit and on panel) get the single-point ground treatment. See

    My response and amplification to Larry's photo cited in his

    reply to this thread.



    Bob . . .

Dick Sipp

Joined: 11 Jan 2006
Posts: 215
Location: Hope, MI

Posted: Thu May 25, 2006 8:26 pm Post subject: Grounding question

Deems,



I asked the exact same question about 6-8 months ago, answer: try it as the 

plans suggest and see if it works OK.



I still have not made up my mind.  Grounding the battery locally to the 

airframe will probably work fine, but on the other hand I would much rather 

run the ground cable now while it is easy rather than later after the 

airplane is flying.  I don't like the weight but will probably run the bat 

ground to the common ground at the firewall.  It may not be much of a factor 

but all of my structural parts were primed before assembly so there are 

numerous thin coats of paint in an airframe ground path.

Dick Sipp

40065

---

mstewart(at)iss.net
Guest

Posted: Fri May 26, 2006 4:30 am Post subject: Grounding question

In my case in my RV Super 8 with my Batt in the back, I grounded it

locally & ran a 12ga to the front, from the battery, for grounding of

all the 'stuff' to a single point. I have a perfectly quiet electrical

system. For all practical purposes, only the starter & alternator, are

using the airframe ground.

Mike

 



--

dennis.glaeser(at)eds.com
Guest

Posted: Fri May 26, 2006 5:05 am Post subject: Grounding question

Bob,



I'm also using rear mounted batteries (RV-7A - electrically dependent

engine) and I found a diagram somewhere on your site that showed rear

mounted batteries with a note NOT to ground them locally to the airframe

- it showed a ground going to a forward mounted grounding point (forest

of tabs).  So I'm curious: what circumstances would prompt this

recommendation?



2 questions to enhance my understanding:

   - In this situation, are there any considerations required for single

heavy power wire running forward (i.e. things to avoid running along the

same path)? =20

   - Are there any practical advantages to running a parallel ground as

well (which might balance the disadvantage of the added weight)?



Thanks,



Dennis Glaeser

nuckollsr(at)cox.net
Guest

Posted: Fri May 26, 2006 6:16 am Post subject: Grounding question

At 08:23 AM 5/26/2006 -0400, you wrote:



 	  Quote: 	
		  

<mstewart(at)iss.net>



In my case in my RV Super 8 with my Batt in the back, I grounded it

locally & ran a 12ga to the front, from the battery, for grounding of

all the 'stuff' to a single point. I have a perfectly quiet electrical

system. For all practical purposes, only the starter & alternator, are

using the airframe ground.

Mike


	


   Not a good deal. That long ground isn't really a ground. Please

   consider using the single point ground block mounted on the firewall

   as depicted in the Connection and making all cockpit and forward

   accessory grounds at that point limiting your local airframe grounds

   to the list cited in my posting of last night.

   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Fri May 26, 2006 6:23 am Post subject: Grounding question

At 09:02 AM 5/26/2006 -0400, you wrote:



 	  Quote: 	
		  

<dennis.glaeser(at)eds.com>



Bob,



I'm also using rear mounted batteries (RV-7A - electrically dependent

engine) and I found a diagram somewhere on your site that showed rear

mounted batteries with a note NOT to ground them locally to the airframe

- it showed a ground going to a forward mounted grounding point (forest

of tabs).  So I'm curious: what circumstances would prompt this

recommendation?


	


    The independent ground for battery minus leads is the electrically

    elegant technique. If I were building an airplane, I'd probably run

    the independent ground.



    Local grounding for batteries and the list of items in last night's

    posting poses no risks to those accessories because they are not

    particularly large contributors as antagonists nor are they potential

    victims.

 	  Quote: 	
		  2 questions to enhance my understanding:

    - In this situation, are there any considerations required for single

heavy power wire running forward (i.e. things to avoid running along the

same path)?


	




    What we're trying to avoid is having MULTIPLE grounds to an airframe

    where heavy current accessories like landing lights, pitot heat, etc

    SHARE the airframe with multiply grounded potential victims like

    intercom and radios. It is 99.99% sufficient to pay attention to

    single point grounding of potential victims while letting the airframe

    go ahead and carry the ugly amps for devices which are not potential

    victims.



 	  Quote: 	
		      - Are there any practical advantages to running a parallel ground as

well (which might balance the disadvantage of the added weight)?


	




    Small and probably negligible as long as the victims remain "protected".



    Bob  . . .

rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Fri May 26, 2006 7:15 am Post subject: Grounding question

 	  Quote: 	
		  > In my case in my RV Super 8 with my Batt in the back, I grounded it

> locally & ran a 12ga to the front, from the battery, for grounding of

> all the 'stuff' to a single point. I have a perfectly quiet electrical

> system. For all practical purposes, only the starter & alternator, are

> using the airframe ground.

> Mike

 

    Not a good deal. That long ground isn't really a ground. Please

    consider using the single point ground block mounted on the firewall

    as depicted in the Connection and making all cockpit and forward

    accessory grounds at that point limiting your local airframe grounds

    to the list cited in my posting of last night.


	


I'm confused.  Why wouldn't Mike's 12ga wire extended to an

isolated forest of tabs be a ground?



I considered doing the same, but decided to ground the

forest of tabs to the front of the aircraft as well.



Here's how mine is set up:



http://www.rv8.ch/article.php?story=20060301215616213



I added the "fat" ground wire between the front forest

of tabs to the batteries in the back mainly to carry

starter currents a bit more efficiently.  I was afraid

that if I didn't, something between where I ground

the engine and the battery would get welded together

when I cranked the starter.



BTW, the engine cranks fine, but I have no idea about

noise, since I don't yet have my radio installed.



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

do not archive

_________________
Mickey Coggins
http://www.rv8.ch/

mstewart(at)iss.net
Guest

Posted: Fri May 26, 2006 7:15 am Post subject: Grounding question

Everything goes to a single point ground block up front. That block is

isolated from the airframe and gets it ground supply from the 12ga

coming directly from the battery in the back.

--

larry(at)ncproto.com
Guest

Posted: Fri May 26, 2006 8:58 am Post subject: Grounding Question

Hi All,

I too have an aft-mounted battery and semi-crucial 

starter requirement (high-compression pistons) and had 

been assuming a dedicated ground wire of the same size 

as the positive lead running forward.  After thinking 

about the posts on this; would it be reasonable to 

locally ground the battery and run a smaller-sized 

ground lead forward to a grounding-buss; with the 

reasoning that the starter load would use both this 

smaller ground lead and the airframe??  Or is this plain 

obvious   How then would one size this ground lead?? 

  If I had primed all (and bonded some) of my airframe 

parts before riveting - would this approach be 

not-a-good-idea??

-- 

Larry E. James

Bellevue, WA    HR2



-- 

This message has been scanned for viruses and

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steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Fri May 26, 2006 10:33 am Post subject: Re: Grounding question

Seems like everyone is talking in circles here. You can ground all your peripheral stuff (battery, landing lights, strobes etc) locally to the airframe (if it's not plastic), and use the common block on the firewall for your panel and engine stuff. Vans recommends it, Bob recommends it, Zenith/Zenair recommends it, and most certified small metal planes do it that way. You don't have to re-invent the wheel, you won't make it any better, you might make it worse, and you'll definitely add complexity to the system.

nuckollsr(at)cox.net
Guest

Posted: Sat May 27, 2006 7:05 am Post subject: Grounding question

At 05:12 PM 5/26/2006 +0200, you wrote:



 	  Quote: 	
		  

<mick-matronics(at)rv8.ch>



 >> In my case in my RV Super 8 with my Batt in the back, I grounded it

 >> locally & ran a 12ga to the front, from the battery, for grounding of

 >> all the 'stuff' to a single point. I have a perfectly quiet electrical

 >> system. For all practical purposes, only the starter & alternator, are

 >> using the airframe ground.

 >> Mike

 >

 >    Not a good deal. That long ground isn't really a ground. Please

 >    consider using the single point ground block mounted on the firewall

 >    as depicted in the Connection and making all cockpit and forward

 >    accessory grounds at that point limiting your local airframe grounds

 >    to the list cited in my posting of last night.



I'm confused.  Why wouldn't Mike's 12ga wire extended to an

isolated forest of tabs be a ground?



I considered doing the same, but decided to ground the

forest of tabs to the front of the aircraft as well.



Here's how mine is set up:



http://www.rv8.ch/article.php?story=20060301215616213



I added the "fat" ground wire between the front forest

of tabs to the batteries in the back mainly to carry

starter currents a bit more efficiently.  I was afraid

that if I didn't, something between where I ground

the engine and the battery would get welded together

when I cranked the starter.



BTW, the engine cranks fine, but I have no idea about

noise, since I don't yet have my radio installed.


	


    "Ground" systems are much more than multiple systems

    simply sharing a common conductor to satisfy their

    individual needs for conductivity. The dynamic nature

    of "ground" is dependent on its conductivity, geometry

    and discontinuities. The ideal vehicular "ground" conductor

    would probably be a welded joint, relatively thick sheet

    of highly conductive material . . . say copper or silver

    and have the minimum possible surface area to enclose

    a given volume . . . hence a sphere.



    Spheres and copper do not lend themselves well to

    the fabrication of vehicular structures so instead

    we find ourselves dealing with a variety of materials

    ranging from excellent insulators (epoxy/glass) to

    pretty good conductors (stir-welded aluminum) and all

    technologies in between. Further, they're not spherical.

    To make matters more interesting, the conduction pathways

    for systems that share "ground" in any vehicle are never

    straightest lines between two points on the system.



    Just to make matters still more interesting, the

    prudent designer has to consider the effectiveness

    and cross coupling of signals for frequencies ranging

    from DC to microwave. There's a condition in the

    RAC Hawker 800 series aircraft where an antenna system

    using airframe for part of the antenna's RF 'ground'

    excites spaces in the hell-hole to the tune of over

    100 volts/meter at various HF frequencies when the

    transmitter is keyed. It varies from airplane to airplane

    and is not a "problem" for most airplanes. But the effects

    are present on every airplane and from time to time,

    rise up and halt delivery of a multi-million dollar

    machine because the ground system was not properly

    configured for this application. Worse yet, it

    would cost staggering amounts of money to fix it

    now. Instead, we craft individual Band-Aids

    on an airplane-by-airplane basis when a particular

    combination of circumstances rise to intolerable

    interference levels.



    This dissonant array of conditions that never

    approach the ideal ground system is NEVER a problem

    for any one system operating by itself . . . nor is

    it a problem for systems that are generally not vulnerable

    to ground induced coupling of noises from a potential

    antagonist to a potential victim system.



    This gives rise to many builder's assertions that

    their particular version of a ground system "works

    just fine" . . . and he's not wrong. Just as I've cited

    for the Hawkers above, there are ground system issues

    that while they are predictable and even measurable,

    the magnitude of the 'interference' is below the

    threshold of deleterious effects. This is why

    99.9% of all airplanes crafted over the last

    100 years are considered by their owners to be

    'satisfactory' performers. Only the occasional

    machine comes to the attention of some poor

    avionics tech who now has to figure out how to

    work around a noise problem that would have best

    been designed out in the first place.



    Ladies and gentlemen, to offer a comprehensive

    course in ground system design features and effects

    of poor science is beyond the scope of activities

    we can offer in this venue. You folks need to concentrate

    on getting first-light-under-the-wheels with a minimum

    of $time$ and lowest practical cost of ownership later.



    Be wary of variations on a theme for ground system

    features that depart from those suggested in the

    'Connection and in the considered words of the

    grey-beards on the List. Virtually every variation

    offered to you by some builder you met at a fly-in

    will be touted as a 'solution' to some unfounded

    concern or a desire to cut a corner . . . and since

    the airplane flew to that gathering, no doubt the

    owner will report "it works fine".  The grounding

    philosophies offered in this venue are a prophylactic

    effort designed to avoid that 0.1%, pain-in-the-arse

    airplane that's going to be expensive in $time$

    at some point in the future. These same philosophies

    also attenuate the 10-20% of the airplanes that have

    some degree of noise issue which the owner is willing

    to accept as below his personal threshold of deleterious

    performance.



    The double-grounding architecture described above is

    generally not a significant improvement in ground

    system performance and opens the doors for new issues.

    In another time, I'll tell you the saga of a "double

    ground" issue that rose up in a Beechjet a year or

    so ago that had a very expensive airplane down for

    months (at taxpayer expense) and took hundreds of

    hours to find and fix.



    "Extending" ground busses for major chunks of system

    hardware on the end of a 12AWG wire makes everything

    'grounded' by that wire subject to single point failure

    of one wire. Further, the resistance/inductance

    contributed to the system by the wire length makes

    it less than ideal ground.



    These are 'experimental' airplanes and one can certainly

    do as he/she wishes in terms of personalizing the

    electrical system architecture. Most variations will

    be found to function in a 'satisfactory' manner.



    Just be aware that departures from architectures

    configured with use of well considered science and experience

    tosses out the $time$ invested in crafting those architectures.

    They also elevate the risk for added expense and aggravation

    at some later date. The fruits of those investments are being

    shared with you at virtually zero expense so as to minimize

    $time$ to first-light and $time$ needed to fix something later

    when you'd rather be flying.



    Bob . . .

larry(at)ncproto.com
Guest

Posted: Mon May 29, 2006 1:50 pm Post subject: Grounding Question

Bob,

I appreciate your sentiments to the effect that our 

focus needs to be to "get light under the wheels" ..... 

boy do I agree !!

But you went over my head.  Is the short version that 

one big Ground wire the same size as the main Positive 

lead (2awg) should run forward to a combo 

thru-the-firewall-lug / Gound "forest" ??  In other 

words; one ground wire to one ground block and 

continuing to the starter??  I'm after just the simple 

answer 

-- 

Larry E. James

Bellevue,  WA    HR2



-- 

This message has been scanned for viruses and

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lhelming(at)sigecom.net
Guest

Posted: Tue May 30, 2006 3:03 am Post subject: Grounding Question

---

nuckollsr(at)cox.net
Guest

Posted: Tue May 30, 2006 5:30 am Post subject: Grounding Question

At 02:44 PM 5/29/2006 -0700, you wrote:



 	  Quote: 	
		  



Bob,

I appreciate your sentiments to the effect that our

focus needs to be to "get light under the wheels" .....

boy do I agree !!

But you went over my head.  Is the short version that

one big Ground wire the same size as the main Positive

lead (2awg) should run forward to a combo

thru-the-firewall-lug / Gound "forest" ??  In other

words; one ground wire to one ground block and

continuing to the starter??  I'm after just the simple

answer 


	


   Yes, the ground lead should be the same size as the

   (+) lead and 2AWG is a good size for a remotely

   mounted battery.



   2AWG other than nice, soft welding cable should

   not be bolted directly to a battery. If you run

   22759 or copper clad aluminum wire from batteries

   to the firewall ground stud, I'd recommend

   a short (6") 4AWG welding cable jumper be used to

   make the leap from battery(-) to the end of the

   battery ground feeder.



   You could bolt the two wires together with ring

   terminals and cover with heatshrink.



   For local airframe grounding of batteries, I've

   published a new Shop Notes at:



http://aeroelectric.com/articles/Battery_Grounds/Battery_Grounds.html



        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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