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Copper braid

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#1 Posted: 1/16/2010 10:21:00

 Hi homebuilders,

I'm building an HN-700 Menestrel, a french project by Henry Nicollier (http://www.menestrel.org.uk)

It's a wood taildragger designed airplane, bi-place.

My actually matter is if I must install a copper braid inside the plane and connect at it every metal parts.

What is your experience about it? Is it absolutly necessary?

Thx.

 

Pella (...from Italy...)



Pella - EAA #844950 Felino - Parma - Italy
Ron Wanttaja
246
Posts
98
#2 Posted: 1/16/2010 11:02:08
Francesco Pellacini wrote:

 

 Hi homebuilders,

 

I'm building an HN-700 Menestrel, a french project by Henry Nicollier (http://www.menestrel.org.uk)

 

It's a wood taildragger designed airplane, bi-place.

 

My actually matter is if I must install a copper braid inside the plane and connect at it every metal parts.

 

What is your experience about it? Is it absolutly necessary?

 

I own a Bowers Fly Baby, a single-seat all-wood airplane, with a full electrical system.  No special effort was made to electrically connect the various metal parts, and the radios and electrical system work fine.

It's rather funny, sometimes, if I get gas at a place with an attendant.  They'll drag out the grounding wire and attach to the tiedown ring underneath the wing...and I have to point out that the tiedown ring is electrically isolated and thus the grounding strap isn't doing a thing.

One thing to remember is to ensure that all the antennas need a metal "ground plane"...basically, the antenna should be installed on a sheet of thin aluminum.  The ideal ground plane is circular with a radius equal to the length of the antenna, but for aircraft VHF, that's not really achievable most of the time.  Most wooden airplanes end up with some flat sheet metal on the exterior (like a metal pan on the belly) and you can install the antenna on that.

I've got some details on the ground plane I installed on my Fly Baby on my antenna web page . Scroll down about 3/4ths of the way to see the ground plane.

 

 



Ron Wanttaja
Lincoln Ross
53
Posts
5
#3 Posted: 2/26/2010 02:08:10

There's electrically isolated, and then there's electrically isolated. You probably need thousands of volts (but negligible amps) to get a good spark from static that might endanger the gas. Wood is just a tiny bit conductive, so if there's contact between the wood and the metal parts, that probably makes a spark less likely. Ever touch some wood thing after scuffing across a carpet so you wouldn't get zapped by a doorknob? Now, on a dry day in Arizona, this might not help.Plus, for all I know the amount of current from the refueling operation might overwhelm things, but I doubt it.

I have a bit of insight into this stuff because I made a van de Graaf generator some time ago. It's kaput now, but it was fun. BTW, according to hobbyist van de Graaf lore, india ink is very slightly conductive. But I think I'd rather use a 10 meg resistor in that case.

 

The copper braid might help if you were to be struck by lightning!



Joanne Palmer
Young Eagles Pilot or VolunteerHomebuilder or Craftsman
276
Posts
68
#4 Posted: 2/26/2010 10:45:27

Francesco:

Rather than running copper braid, just run a small wire Like MS22579/16-20 (20 AWG) though you could go as small as 26 AWG in which case it would be MS22579/16-26.  It doesn't matter what colour.  Attach each metal part to that and test with an ohmmeter.  You want less than .1 ohms so you need to make sure that your ohmmeter will measure that small.  Then attach that wire to a good ground like your battery negative or engine ground.

 

the purpose is to make all metal parts have the same electrical potential.  Whether you need to do this or not depends on wher and what the metal is for.  I'd just do the tie downs, major metal parts near the fuel tanks, and the control surface hinges, but that's just me.