firewall hardware

[Jimzim]

Does anyone have thoughts on what works best to seal firewall penetration points. I am beginning to run wires, and some new holes were drilled. The plans say insert a grommet and seal with pro-seal, but I'm not sure what type of grommet to use. Plastic or rubber doesn't seem adequate. Any thoughts or personal experience much appreciated.
Thanks, Jim

[flion]

The problem with firewall penetrations is the hole has to be big enough for the connector, which became a problem with the DB-9 plugs for my Lightspeed ignitions. Another approach is to make holes just big enough for the wires and attach the connectors after the wire has been run. There are several good approaches, including pass-through kits available from ACS or other suppliers. I went with rubber grommets to protect the wires from the firewall and stainless shields to protect the rubber.

But I've already had to replace the firewall after a nose-over and I can testify that it's a pain in the rectum to work with the penetrations. For that reason, I am springing for CPCs (Cannon Plug Connectors) specifically for the firewall. They are expensive but I think it will be worth it. Larger gauge wire for power will have marine-style bulkhead fittings. All fluid and pneumatic lines will have bulkhead fittings. All the major control cables will have eye-ball pass-throughs and I am working on a solution for the small bowden cables.

My goal is to thoroughly seal the firewall but make it easy to deal with penetrations for future work. It's way overkill, though, and I know it; many aircraft are flying with much simpler penetrations.

[mlwynn]

I am at the same step. I used rubber grommets through the stainless firewall. In Tony Bingellis book, he says to put an asbestos washer over the top before the stainless shield goes on. Obviously, the book is a little out of date because they ain't no asbestos washers no more.

I made a 1/4" thick fiberfrax insulation covered with .003 stainless foil as a heat shield (see the thread under safety for firewalls http://www.vansairforce.com/communit...all+insulation) on the engine side of the firewall as described here.

It looks from the thread on firewall sealants (http://www.vansairforce.com/communit...ad.php?t=72087) like I would be okay to seal with a big glob of 3M Firebarrier 2000 and cover with the stainless shield.

That same thread shows what Dan Horton has done, which is probably the single best approach to firewall penetrations I have seen. Read through these two threads and I think you questions will be well answered.

Regards,

Michael Wynn
RV 8 Finishing
San Ramon, CA