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Composite aircraft grounding systems.

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MikeDunlop

Joined: 02 Jan 2012
Posts: 15

Posted: Mon Jan 02, 2012 11:11 am Post subject: Composite aircraft grounding systems.

For Bob Nuckolls (or anyone else with knowledge of composite aircraft grounding systems),



I have recently bought your book, 'The AeroElectric Connection' (12th Edition) and have also looked at all the FAQ documents and archive posts such as 'Airframe Grounding' etc. Very, very interesting reading.



I'm starting the electrical system on a Rutan Long-EZ project (all composite as you will already know). The original builder had built in one copper 1/2 inch ID tube from front to back and I'm contemplating using it for possibly two purposes, a) a main earth rail. b) a conduit to carry the main power cable to the starter. The battery is in the nose and the distance from battery to starter (B&C light weight) is 14 ft (4.3 metre). Cable suppliers in the U.K. shows #4 as being suitable for starters but B&C responded to my question saying for a Long-EZ use #2, presumably for voltage drop reasons.



I've settled on the Z-12 setup with a automotive alternator and B&C LR-3 controller as primary power with a B&C SD-8 system for secondary power. I would like to seek valued opinions on the following:



Questions:



1. Would having a main power cable inside a copper ground tube generate unforseen problems (besides lots of sparks if shorted out!).

2. Can I use welding cable instead of the very heavy and very expensive #2 Tefzel coated aviation cable (circa $15 per foot in the U.K.)

3. Should the Starter solenoid be close to the battery or on the firewall (live power in the cable only at starting or all the time)



My main concern and objective at the moment is to establish a suitable and reliable earthing system before moving on to other matters.



Bob, many thanks for your excellent book and resources.



Regards



Mike Dunlop (U.K.)

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rparigoris

Joined: 24 Nov 2009
Posts: 780

Posted: Mon Jan 02, 2012 11:42 am Post subject: Re: Composite aircraft grounding systems.

Hi Mike



I'm building a composite Europa. There's a builder in Canada that put Eric Jones copper clad wire:

http://www.periheliondesign.com/fatwires.htm

inside a copper pipe as you suggest. I don't think he's flying yet, but here are a few pics:

http://www.europaowners.org/forums/gallery2.php?g2_itemId=78200

I think the yellow with green is heat shrink he added.

The aluminium wire is expensive but will save you some weight. It is not very flexable and fatugues more easily than thin stranded copper. If you need to make hard turns, best use welding cable for that area? I looked into welding cable and www.mcmaster is one resource. The #2 CCA is thicker in diameter compared to Tefzel, but has approx the same resistance.

Ron Parigoris

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jan 02, 2012 1:39 pm Post subject: Composite aircraft grounding systems.

M: Bob,



I've just joined the AeroElectric-List and will post the following 

when the acount is activated...



I have recently bought your book, 'The AeroElectric Connection' (12th 

Edition) and have also looked at all the FAQ documents and archive 

posts such as 'Airframe Grounding' etc. Very, very interesting reading.



   Thank you.



I'm starting the electrical system on a Rutan Long-EZ project (all 

composite as you will already know). The original builder had built 

in one copper 1/2 inch ID tube from front to back and I'm 

contemplating using it for possibly two purposes, a) a main earth 

rail. b) a conduit to carry the main power cable to the starter. The 

battery is in the nose and the distance from battery to starter (B&C 

light weight) is 14 ft (4.3 metre). Cable suppliers in the U.K. shows 

#4 as being suitable for starters but B&C responded to my question 

saying for a Long-EZ use #2, presumably for voltage drop reasons.



   Correct.



I've settled on the Z-12 setup with a automotive alternator and B&C 

LR-3 controler as primary power with a B&C SD-8 system for secondary 

power. I would like to seek your valued opinion on the following:



    Then you don't want Z-12 but Z-13/8.



Questions:



1. Would having a main power cable inside a copper ground tube 

generate unforseen problems.



   No, But you do want to craft your tube-to-wiring connections

   by soldering copper wrap-around flag terminals to the copper tube.



2. Can I use welding cable instead of the very heavy and expensive #2 

Tefzel coated aviation cable (circa $15 per foot in the U.K.)



   Absolutely. In fact I prefer it.



3. Should the Starter solinoid be close to the battery or on the 

firewall (live power in the cable only at starting or all the time)



    Close to the starter. Then use the same feeder

    to bring b-lead power up front from the main alternator.

    But a current limiter in the b-lead connecting right

    were it attaches to the hot-side of the starter contactor

    on the firewall.



My main concern and objective at the moment is to establish a 

suitable earthing system before moving on to other matters. I could 

go on asking questions like this all day but I'm sure you have other 

things to do and I need to concentrate on getting this bit sorted first.



   The conduit ground system is fine.



Many thanks for your excellent book and resources.



   I'm pleased that you find it a good value . . .



   Bob . . .

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steve(at)tomasara.com
Guest

Posted: Tue Jan 03, 2012 6:36 am Post subject: Composite aircraft grounding systems.

Mike and the group:



Regarding the the placement of the starter solenoid there is, as usual, 

more than one way to skin this cat.  There are some trade-offs.  Bob's 

recommendation to put the solenoid back by the starter and use the one 

big feed line for both the starter supply and Alternator B lead, which I 

think is a good one for many people, eliminates an otherwise needed 

additional wire (#8 in my case) for the alternator B lead running from 

the alternator back to the bus and thus saves it's weight.



My LongEz was flying when purchased but I immediately grounded it and 

spent ~4 years reworking it before putting it back in the air again.  

It's been flying it since August '11.  When I totally replaced the 

electrical system in the my LongEz, I read the book, considered all the 

options, posted lots of question on the forum and I ended up with the 

planned location for the starter solenoid up front.  Here's why:



My goal, in recognition that I was new to experimentals in general and 

LongEzs in particular, was to stick pretty close to the plans and owners 

manual authored by Burt unless they had been superseded by CPs, or a 

perceived (and well reasoned) consensus on the yahoo group 

canardaviators.  With that in mind, I wanted all my initial flight 

testing without a starter (even though it had one when I bought it) to 

keep the CG as far forward as I could and keep it as light as possible.  

I haven't yet installed the heavy feed or return cables back to the 

firewall that will be required if I later reinstall the starter.



I did, keeping a future installation in mind, reserve space up front for 

the starter solenoid and I kept the #8 firewall return (i.e. ground) 

wire separate from the laced bundle going back to the firewall so that 

it would be easy to replace it with welding wire (or CCA) later if required.



The two biggest reasons I went this route is that, when I am running 

without the starter as I am now, I'm not carrying around the heavier 

wire and it allowed me to protect the #8 B-wire with an ANL up near the 

master relay and battery so that I didn't have an unprotected 

high-current feed running from the master relay (or buss) all the way 

back to the firewall.  As I understand it (and Bob is the authority 

here, not me) there is nothing wrong with having the unprotected feed 

from the buss  going all the way back to the firewall but I was more 

comfortable not doing so.  Another benefit was that I could keep all 

this stuff together up in the nose (which is also where I moved the 

regulator) rather than back on the firewall (which is already crowded 

enough on a LongEz, esp. if you have electronic ignition as I do).



If and when I do re-install the starter, the downside for going the 

route that I did is that I'll be carrying around a single extra #8 wire 

running from back to front.  That wasn't a problem for me given that 

I'll also be adding two long lines of welding wire and a starter at that 

time as well...  A purest might reconfigure at that time to the 

configuration Bob recommended to save the weight of the #8 wire.  I won't.



btw: I recommend both the canardaviators forum and Central States 

Association.  There is a lot of good information out there on LongEzs 

beyond the plans and CPs but it takes some digging to get to it.



In completing your LongEz be sure to be more concerned about "completion 

drag" than "aerodynamic drag".  Anything you do that hasn't already been 

done before, and been well documented in the process, will cost you more 

time (i.e. be a drag on getting your bird flying) than you imagine...



Steve Stearns

Boulder/Longmont, Colorado

CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less)

Restoring (since 1/07) and flying again (8/11!): N45FC O235 Longeze 

Cothern/Friling CF1 (~1000 Hrs)

Flying (since 9/86): N43732 A65 Taylorcraft BC12D

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Tue Jan 03, 2012 8:40 am Post subject: Re: Composite aircraft grounding systems.

I sell lots of Copper-Clad Aluminum cable to 300 mph fuel dragster and racecar builders, weird groups doing strange things where the weight is important. I even sell the stuff to the companies building remote-controlled drones. Predator drones and the more advance secret stuff...



Airbus and Boeing use similar CCA configurations. 



I sell Super-2-CCA, Super-4-CCA, AWG-6-CCA (same dimensions as AWG-6 but CCA with Tefzel insulation), and Super-CCA RG+142  



See my website. CCA is 60% the weight of copper for the same conductivity.



If you have the battery on the firewall, you are okay. Otherwise, use CCA.



Also see Bob's most excellent article, http://www.aeroelectric.com/articles/economics_of_weight_reduction.html



and on my website: http://www.periheliondesign.com/fatwires_files/Coppercables.pdf

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

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