Submitted by Dace Kirk, Phoenix Composites, Mesa Arizona
At Phoenix Composites, Inc. we treat the problem of firewall grommets somewhat different. We find that there are generally three firewall pass-throughs for the wiring and control cables to the engine area.
Instead of using rubber grommets in the fiberglass firewall we wait until the firewall fire barrier is installed and then drill the typical hole size of 1” all the way through. We then install an aluminum sleeve that closes out the entire pass through and it has a rolled edge so no chafing occurs later. Once the wiring and control cables are all finally rigged, then we inject 3M Fire Barrier caulk to absolutely seal out all gases and heat from the cockpit area. It’s flexible and really seals well. It also final protects against all chaffing that may be present. Works great, give it a try, I think you will like the results.