Mailing List lml@lancaironline.net Message #59878
From: paul miller <paul@tbm700.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Re: Wick mechanical connection
Date: Sun, 02 Oct 2011 22:27:03 -0400
To: <lml@lancaironline.net>
I second Colyn's comments that non-conducting pieces should be prepared for static dissipation.   There are also many anti-static primers that can be used then finished with normal aircraft topcoats.   An important requirement if you do the painting yourself is to make the primer continue from the outside surface around the inside mating surfaces where it will further conduct to metal or other conductive primer or conductive composite.  The military aircraft shop here in Calgary explained that the static on the exterior paint will work through the topcoat layers easily to the primer and then migrate towards the wicks.  If a continuous large circuit is not available, charges build up until a gap can be jumped (100,000 volts is not unusual for p-static) and then you'll get unexplained  pitting in the paint, pinholes, burn marks, static in the radios that can render them completely unusable in snow, and flashes are night that look like BBQ igniters where charges are jumping gaps.   Of course, some climates like Florida don't get the same reaction in fair weather but up north here where it is dry, the conditions are magnified.   I had to have a new paint job stripped on all the fibreglass components to solve this issue (wingtips, cowls).  I found in my research that very few of the southern aircraft painters even knew about this issue so it is important to query the paint shops on how they will deal with static and how they ensure a continuous path from forward surfaces back to the wicks.

Paul Miller
Calgary
On 2011-10-02, at 8:08 AM, Colyn Case wrote:

> I didn't read this whole thread.  Did someone talk about connecting from the braid that comes from the hstab to the wick connection?  My conclusion was you need a wire from where the braid connects to the elevator to the wick socket(s) on the back of the elevator.   Most of the static will collect on the leading edge of the hstab, hopefully flow through the carbon to your amazingly low resistance (1 ohm?) braid connection, across the braid, through the connection to the wire, through the wire, into the socket, and out the wick.
>
> While you're there consider high resistance conductive paint on all fiberglas surfaces that contain a leading edge.   This will allow the charge to migrate to the back where hopefully you can figure out a way to get it to a wick.  This is the stuff they use on radomes in bigger airplanes.  Here's the info on the paint.  As far as I can tell, what you want is CA7870.

Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster