Mailing List lml@lancaironline.net Message #65234
From: Frederick Moreno <frederickmoreno@bigpond.com>
Subject: Re: [LML] Fw: Static Wicks
Date: Tue, 9 Apr 2013 18:53:08 +0800
To: Lancair Mail (lml@lancaironline.net) <lml@lancaironline.net>, Colyn Case <colyncase@earthlink.net>
Sorry ofr ambiguity.  Use wicks.  The question is - attach them to what?  PReferred but not mandatory answer: a dedicated grounding system dedicated to handlin static discharge and other electrical nastiness.
 
Bonding static wicks to a grounding net that is independent of the ship's grounding wiring, but meets ship's grounding system at the battery buss will keep any spikes off the ship's ground wiring and provide the best place to mate the two networks together - all at the one place with a big capacitor (battery) at that point. 
 
Reasoning: in the event of a big discharge or lightning strike (small one), the WIcks and associated ground net will more likely take the hit due to their physical positioning out to the extremities of the aircraft (where the wicks stick out at the control surfaces) which will hopefully permit the electrical spike to bypass all the essential ship's wiring.   Hopefully.  This means for more extreme events, if you are in the build process, route the big static discharge wires physically away from other wires if possible. 
 
It is all a bit of belt plus suspenders reasoning that attempts to increase the margin of safety.
 
In the event of a big lightning hit......
 
Good luck.
 
Fred 
 
 
 
-------Original Message-------
 
Date: 8/04/2013 10:15:33 PM
Subject: Re: [LML] Fw: Static Wicks
 
Fred,

Wasn't sure how to read your last paragraph. 
Does this mean static wicks are not required if you bond everything into the battery?
...or that static wicks work better if you bond everything into the battery?

Colyn

On Apr 8, 2013, at 6:24 AM, Frederick Moreno wrote:

Static develops based on the impact of precip and ice crystals on the front (forward facing surfaces) of the airplane, that is, what you see if you stand way in front of the airplane and view it front on with a telescope.  This includes all the cowl, the front of the wings up to the thickest point of the wings, windshield, etc.  Behind the line where the curvature of wing, tail, and such hide the surface from impacting particles, static is not formed.  The rudder is in this region.
 
The number of static wicks required it dissipate static is based on a calculation of the frontal areas as described above (some percentage of thewing area, for example, like 30-50%) and the speed of the aircraft. 
 
Normal Lancair procedure is to put static wicks on the trailing edge of ailerons, elevators, rudder with number as calculated by the wick maker.  These must be connected to a conductive surface or wire, and this means wires in the rudder.  Ideally, all carbon surfaces are bonded together with straps using conductive epoxy bonded to the bare carbon fibers exposed by sanding, and wires that go from control surface in parallel to the hinges so that there is a continuous electrical path to be followed via wire (not hinge) in the event of a big discharge that may pit a bearing.   Anti static radome paint works on the fiberglass cowl and vertical stabilizer carrying charge (letting it leak away) to the carbon fiber or local ground and thence into the ships ground.
 
In the end, a group of us concluded that it was best to run 10 gage ground wires to each corner of the airplane, bond all carbon surfaces to this ground net (that means top and bottom skins, control surfaces, etc.) and take the ground net to the main battery ground at the firewall so that the battery serves as a pulse absorber which it does well.  This level of connective bonding has eliminated static discharge problems on aircraft previously affected.
 
Fred Moreno
 
 
 
 
-------Original Message-------
 
Date: 7/04/2013 11:02:53 PM
Subject: Static Wicks
 

This question has to do with the rudder in the IVP.  It’s written that because the rudder is fiberglass, wicks aren’t effective due to non conductivity. 

 

A build shop installed wicks on my rudder and they ran ground wires to those wicks from a/c ground.  It seemed logical that this would make them useful, but last night I had a discussion with Dan Newland who got involved in static discharge problems on a satellite project in his working days and he scratched his head at the notion.  Said he wasn’t sure but would guess that the wicks are not going to be useful in that configuration. 

 

Anyone on the LML have knowledge that bears on the subject?  I would like to learn more.

 

Thanks

 

John Barrett, CEO

Leading Edge Composites

PO Box 428

Port Hadlock, WA 98339

 

www.carbinge.com

 

 

 
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